OffscreenCanvasRenderingContext2D

使用OffscreenCanvasRenderingContext2D在Canvas上进行离屏绘制，绘制对象可以是矩形、文本、图片等。离屏绘制是指将需要绘制的内容先绘制在缓存区，然后将其转换成图片，一次性绘制到canvas上，加快了绘制速度。

说明：

从 API Version 8 开始支持。后续版本如有新增内容，则采用上角标单独标记该内容的起始版本。

接口

OffscreenCanvasRenderingContext2D(width: number, height: number, settings?: RenderingContextSettings)

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

属性

说明： fillStyle、shadowColor与 strokeStyle 中string类型格式为 'rgb(255, 255, 255)'，'rgba(255, 255, 255, 1.0)'，'#FFFFFF'。

fillStyle

// xxx.ets
@Entry
@Component
struct FillStyleExample {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.fillStyle = '#0000ff'
          offContext.fillRect(20, 20, 150, 100)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

// xxx.ets
@Entry
@Component
struct FillStyleExample {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.fillStyle = 0x0000FF
          offContext.fillRect(20, 20, 150, 100)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

lineWidth

// xxx.ets
@Entry
@Component
struct LineWidthExample {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.lineWidth = 5
          offContext.strokeRect(25, 25, 85, 105)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

strokeStyle

// xxx.ets
@Entry
@Component
struct StrokeStyleExample {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.lineWidth = 10
          offContext.strokeStyle = '#0000ff'
          offContext.strokeRect(25, 25, 155, 105)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

// xxx.ets
@Entry
@Component
struct StrokeStyleExample {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.lineWidth = 10
          offContext.strokeStyle = 0x0000ff
          offContext.strokeRect(25, 25, 155, 105)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

lineCap

// xxx.ets
@Entry
@Component
struct LineCapExample {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.lineWidth = 8
          offContext.beginPath()
          offContext.lineCap = 'round'
          offContext.moveTo(30, 50)
          offContext.lineTo(220, 50)
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

lineJoin

// xxx.ets
@Entry
@Component
struct LineJoinExample {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.beginPath()
          offContext.lineWidth = 8
          offContext.lineJoin = 'miter'
          offContext.moveTo(30, 30)
          offContext.lineTo(120, 60)
          offContext.lineTo(30, 110)
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

miterLimit

// xxx.ets
@Entry
@Component
struct MiterLimit {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.lineWidth = 8
          offContext.lineJoin = 'miter'
          offContext.miterLimit = 3
          offContext.moveTo(30, 30)
          offContext.lineTo(60, 35)
          offContext.lineTo(30, 37)
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

font

// xxx.ets
@Entry
@Component
struct Fonts {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.font = '30px sans-serif'
          offContext.fillText("Hello px", 20, 60)
          offContext.font = '30vp sans-serif'
          offContext.fillText("Hello vp", 20, 100)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

textAlign

// xxx.ets
@Entry
@Component
struct CanvasExample {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
        let offContext = this.offCanvas.getContext("2d", this.settings)
        offContext.strokeStyle = '#0000ff'
        offContext.moveTo(140, 10)
        offContext.lineTo(140, 160)
        offContext.stroke()

        offContext.font = '18px sans-serif'

        offContext.textAlign = 'start'
        offContext.fillText('textAlign=start', 140, 60)
        offContext.textAlign = 'end'
        offContext.fillText('textAlign=end', 140, 80)
        offContext.textAlign = 'left'
        offContext.fillText('textAlign=left', 140, 100)
        offContext.textAlign = 'center'
        offContext.fillText('textAlign=center',140, 120)
        offContext.textAlign = 'right'
        offContext.fillText('textAlign=right',140, 140)
        let image = this.offCanvas.transferToImageBitmap()
        this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

textBaseline

// xxx.ets
@Entry
@Component
struct TextBaseline {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.strokeStyle = '#0000ff'
          offContext.moveTo(0, 120)
          offContext.lineTo(400, 120)
          offContext.stroke()

          offContext.font = '20px sans-serif'

          offContext.textBaseline = 'top'
          offContext.fillText('Top', 10, 120)
          offContext.textBaseline = 'bottom'
          offContext.fillText('Bottom', 55, 120)
          offContext.textBaseline = 'middle'
          offContext.fillText('Middle', 125, 120)
          offContext.textBaseline = 'alphabetic'
          offContext.fillText('Alphabetic', 195, 120)
          offContext.textBaseline = 'hanging'
          offContext.fillText('Hanging', 295, 120)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

globalAlpha

// xxx.ets
@Entry
@Component
struct GlobalAlpha {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.fillStyle = 'rgb(0,0,255)'
          offContext.fillRect(0, 0, 50, 50)
          offContext.globalAlpha = 0.4
          offContext.fillStyle = 'rgb(0,0,255)'
          offContext.fillRect(50, 50, 50, 50)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

lineDashOffset

// xxx.ets
@Entry
@Component
struct LineDashOffset {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.arc(100, 75, 50, 0, 6.28)
          offContext.setLineDash([10,20])
          offContext.lineDashOffset = 10.0
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

globalCompositeOperation

// xxx.ets
@Entry
@Component
struct GlobalCompositeOperation {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.fillStyle = 'rgb(255,0,0)'
          offContext.fillRect(20, 20, 50, 50)
          offContext.globalCompositeOperation = 'source-over'
          offContext.fillStyle = 'rgb(0,0,255)'
          offContext.fillRect(50, 50, 50, 50)
          offContext.fillStyle = 'rgb(255,0,0)'
          offContext.fillRect(120, 20, 50, 50)
          offContext.globalCompositeOperation = 'destination-over'
          offContext.fillStyle = 'rgb(0,0,255)'
          offContext.fillRect(150, 50, 50, 50)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

shadowBlur

// xxx.ets
@Entry
@Component
struct ShadowBlur {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.shadowBlur = 30
          offContext.shadowColor = 'rgb(0,0,0)'
          offContext.fillStyle = 'rgb(255,0,0)'
          offContext.fillRect(20, 20, 100, 80)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

shadowColor

// xxx.ets
@Entry
@Component
struct ShadowColor {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.shadowBlur = 30
          offContext.shadowColor = 'rgb(0,0,255)'
          offContext.fillStyle = 'rgb(255,0,0)'
          offContext.fillRect(30, 30, 100, 100)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

shadowOffsetX

// xxx.ets
@Entry
@Component
struct ShadowOffsetX {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.shadowBlur = 10
          offContext.shadowOffsetX = 20
          offContext.shadowColor = 'rgb(0,0,0)'
          offContext.fillStyle = 'rgb(255,0,0)'
          offContext.fillRect(20, 20, 100, 80)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

shadowOffsetY

// xxx.ets
@Entry
@Component
struct ShadowOffsetY {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.shadowBlur = 10
          offContext.shadowOffsetY = 20
          offContext.shadowColor = 'rgb(0,0,0)'
          offContext.fillStyle = 'rgb(255,0,0)'
          offContext.fillRect(30, 30, 100, 100)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

imageSmoothingEnabled

// xxx.ets
@Entry
@Component
struct ImageSmoothingEnabled {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private img:ImageBitmap = new ImageBitmap("common/images/icon.jpg")
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.imageSmoothingEnabled = false
          offContext.drawImage(this.img,0,0,400,200)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

imageSmoothingQuality

  // xxx.ets
  @Entry
  @Component
  struct ImageSmoothingQualityDemoOff {
    private settings: RenderingContextSettings = new RenderingContextSettings(true);
    private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.
settings);
    private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
    private img:ImageBitmap = new ImageBitmap("common/images/example.jpg");

    build() {
      Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, 
justifyContent: FlexAlign.Center }) {
        Canvas(this.context)
          .width('100%')
          .height('100%')
          .backgroundColor('#ffff00')
          .onReady(() =>{
            let offContext = this.offCanvas.getContext("2d", this.settings)
            let offctx = offContext
            offctx.imageSmoothingEnabled = true
            offctx.imageSmoothingQuality = 'high'
            offctx.drawImage(this.img, 0, 0, 400, 200)

            let image = this.offCanvas.transferToImageBitmap()
            this.context.transferFromImageBitmap(image)
          })
      }
      .width('100%')
      .height('100%')
    }
  }

direction

  // xxx.ets
  @Entry
  @Component
  struct DirectionDemoOff {
    private settings: RenderingContextSettings = new RenderingContextSettings(true);
    private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.
settings);
    private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

    build() {
      Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, 
justifyContent: FlexAlign.Center }) {
        Canvas(this.context)
          .width('100%')
          .height('100%')
          .backgroundColor('#ffff00')
          .onReady(() =>{
            let offContext = this.offCanvas.getContext("2d", this.settings)
            let offctx = offContext
            offctx.font = '48px serif';
            offctx.textAlign = 'start'
            offctx.fillText("Hi ltr!", 200, 50);

            offctx.direction = "rtl";
            offctx.fillText("Hi rtl!", 200, 100);

            let image = offctx.transferToImageBitmap()
            this.context.transferFromImageBitmap(image)
          })
      }
      .width('100%')
      .height('100%')
    }
  }

filter

  // xxx.ets
  @Entry
  @Component
  struct FilterDemoOff {
    private settings: RenderingContextSettings = new RenderingContextSettings(true);
    private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings);
    private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
    private img:ImageBitmap = new ImageBitmap("common/images/example.jpg");

    build() {
      Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.
Center }) {
        Canvas(this.context)
          .width('100%')
          .height('100%')
          .backgroundColor('#ffff00')
          .onReady(() =>{
            let offContext = this.offCanvas.getContext("2d", this.settings)
            let offctx = offContext
            let img = this.img

            offctx.drawImage(img, 0, 0, 100, 100);

            offctx.filter = 'grayscale(50%)';
            offctx.drawImage(img, 100, 0, 100, 100);

            offctx.filter = 'sepia(60%)';
            offctx.drawImage(img, 200, 0, 100, 100);

            offctx.filter = 'saturate(30%)';
            offctx.drawImage(img, 0, 100, 100, 100);

            offctx.filter = 'hue-rotate(90degree)';
            offctx.drawImage(img, 100, 100, 100, 100);

            offctx.filter = 'invert(100%)';
            offctx.drawImage(img, 200, 100, 100, 100);

            offctx.filter = 'opacity(25%)';
            offctx.drawImage(img, 0, 200, 100, 100);

            offctx.filter = 'brightness(0.4)';
            offctx.drawImage(img, 100, 200, 100, 100);

            offctx.filter = 'contrast(200%)';
            offctx.drawImage(img, 200, 200, 100, 100);

            offctx.filter = 'blur(5px)';
            offctx.drawImage(img, 0, 300, 100, 100);

            let image = this.offCanvas.transferToImageBitmap()
            this.context.transferFromImageBitmap(image)
          })
      }
      .width('100%')
      .height('100%')
    }
  }

方法

fillRect

fillRect(x: number, y: number, w: number, h: number): void

填充一个矩形。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct FillRect {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.fillRect(30,30,100,100)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
       })
      }
    .width('100%')
    .height('100%')
  }
}

strokeRect

strokeRect(x: number, y: number, w: number, h: number): void

绘制具有边框的矩形，矩形内部不填充。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct StrokeRect {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.strokeRect(30, 30, 200, 150)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

clearRect

clearRect(x: number, y: number, w: number, h: number): void

删除指定区域内的绘制内容。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct ClearRect {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.fillStyle = 'rgb(0,0,255)'
          offContext.fillRect(20,20,200,200)
          offContext.clearRect(30,30,150,100)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

fillText

fillText(text: string, x: number, y: number, maxWidth?: number): void

绘制填充类文本。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct FillText {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.font = '30px sans-serif'
          offContext.fillText("Hello World!", 20, 100)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

strokeText

strokeText(text: string, x: number, y: number): void

绘制描边类文本。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct StrokeText {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.font = '55px sans-serif'
          offContext.strokeText("Hello World!", 20, 60)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

measureText

measureText(text: string): TextMetrics

该方法返回一个文本测算的对象，通过该对象可以获取指定文本的宽度值。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

返回值：

示例：

// xxx.ets
@Entry
@Component
struct MeasureText {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.font = '50px sans-serif'
          offContext.fillText("Hello World!", 20, 100)
          offContext.fillText("width:" + this.context.measureText("Hello World!").width, 20, 200)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

stroke

stroke(path?: Path2D): void

进行边框绘制操作。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct Stroke {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.moveTo(25, 25)
          offContext.lineTo(25, 105)
          offContext.lineTo(75, 105)
          offContext.lineTo(75, 25)
          offContext.strokeStyle = 'rgb(0,0,255)'
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

beginPath

beginPath(): void

创建一个新的绘制路径。

从API version 9开始，该接口支持在ArkTS卡片中使用。

示例：

// xxx.ets
@Entry
@Component
struct BeginPath {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.beginPath()
          offContext.lineWidth = 6
          offContext.strokeStyle = '#0000ff'
          offContext.moveTo(15, 80)
          offContext.lineTo(280, 160)
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

moveTo

moveTo(x: number, y: number): void

路径从当前点移动到指定点。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct MoveTo {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.beginPath()
          offContext.moveTo(10, 10)
          offContext.lineTo(280, 160)
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

lineTo

lineTo(x: number, y: number): void

从当前点到指定点进行路径连接。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct LineTo {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.beginPath()
          offContext.moveTo(10, 10)
          offContext.lineTo(280, 160)
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

closePath

closePath(): void

结束当前路径形成一个封闭路径。

从API version 9开始，该接口支持在ArkTS卡片中使用。

示例：

// xxx.ets
@Entry
@Component
struct ClosePath {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
            let offContext = this.offCanvas.getContext("2d", this.settings)
            offContext.beginPath()
            offContext.moveTo(30, 30)
            offContext.lineTo(110, 30)
            offContext.lineTo(70, 90)
            offContext.closePath()
            offContext.stroke()
            let image = this.offCanvas.transferToImageBitmap()
            this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

createPattern

createPattern(image: ImageBitmap, repetition: string | null): CanvasPattern | null

通过指定图像和重复方式创建图片填充的模板。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

返回值：

示例：

// xxx.ets
@Entry
@Component
struct CreatePattern {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private img:ImageBitmap = new ImageBitmap("common/images/icon.jpg")
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          let pattern = offContext.createPattern(this.img, 'repeat')
          offContext.fillStyle = pattern as CanvasPattern
          offContext.fillRect(0, 0, 200, 200)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

bezierCurveTo

bezierCurveTo(cp1x: number, cp1y: number, cp2x: number, cp2y: number, x: number, y: number): void

创建三次贝赛尔曲线的路径。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct BezierCurveTo {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.beginPath()
          offContext.moveTo(10, 10)
          offContext.bezierCurveTo(20, 100, 200, 100, 200, 20)
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

quadraticCurveTo

quadraticCurveTo(cpx: number, cpy: number, x: number, y: number): void

创建二次贝赛尔曲线的路径。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct QuadraticCurveTo {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.beginPath()
          offContext.moveTo(20, 20)
          offContext.quadraticCurveTo(100, 100, 200, 20)
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

arc

arc(x: number, y: number, radius: number, startAngle: number, endAngle: number, counterclockwise?: boolean): void

绘制弧线路径。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct Arc {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.beginPath()
          offContext.arc(100, 75, 50, 0, 6.28)
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

arcTo

arcTo(x1: number, y1: number, x2: number, y2: number, radius: number): void

依据圆弧经过的点和圆弧半径创建圆弧路径。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct ArcTo {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.moveTo(100, 20)
          offContext.arcTo(150, 20, 150, 70, 50)
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

ellipse

ellipse(x: number, y: number, radiusX: number, radiusY: number, rotation: number, startAngle: number, endAngle: number, counterclockwise?: boolean): void

在规定的矩形区域绘制一个椭圆。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct CanvasExample {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.beginPath()
          offContext.ellipse(200, 200, 50, 100, Math.PI * 0.25, Math.PI * 0.5, Math.PI * 2, false)
          offContext.stroke()
          offContext.beginPath()
          offContext.ellipse(200, 300, 50, 100, Math.PI * 0.25, Math.PI * 0.5, Math.PI * 2, true)
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

rect

rect(x: number, y: number, w: number, h: number): void

创建矩形路径。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct CanvasExample {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.rect(20, 20, 100, 100) // Create a 100*100 rectangle at (20, 20)
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

fill

fill(fillRule?: CanvasFillRule): void

对封闭路径进行填充。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数:

// xxx.ets
@Entry
@Component
struct Fill {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.fillStyle = '#000000'
          offContext.rect(20, 20, 100, 100) // Create a 100*100 rectangle at (20, 20)
          offContext.fill()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

fill(path: Path2D, fillRule?: CanvasFillRule): void

对封闭路径进行填充。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数:

示例:

// xxx.ets
@Entry
@Component
struct Fill {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          let region = new Path2D()
          region.moveTo(30, 90)
          region.lineTo(110, 20)
          region.lineTo(240, 130)
          region.lineTo(60, 130)
          region.lineTo(190, 20)
          region.lineTo(270, 90)
          region.closePath()
          // Fill path
          offContext.fillStyle = '#00ff00'
          offContext.fill(region, "evenodd")
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

clip

clip(fillRule?: CanvasFillRule): void

设置当前路径为剪切路径。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数:

示例：

// xxx.ets
@Entry
@Component
struct Clip {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.rect(0, 0, 100, 200)
          offContext.stroke()
          offContext.clip()
          offContext.fillStyle = "rgb(255,0,0)"
          offContext.fillRect(0, 0, 200, 200)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

clip(path:Path2D, fillRule?: CanvasFillRule): void

设置封闭路径为剪切路径。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数:

示例：

// xxx.ets
@Entry
@Component
struct Clip {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          let region = new Path2D()
          region.moveTo(30, 90)
          region.lineTo(110, 20)
          region.lineTo(240, 130)
          region.lineTo(60, 130)
          region.lineTo(190, 20)
          region.lineTo(270, 90)
          region.closePath()
          offContext.clip(region,"evenodd")
          offContext.fillStyle = "rgb(0,255,0)"
          offContext.fillRect(0, 0, 600, 600)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

resetTransform

resetTransform(): void

使用单位矩阵重新设置当前矩阵。该接口为空接口。

从API version 9开始，该接口支持在ArkTS卡片中使用。

rotate

rotate(angle: number): void

针对当前坐标轴进行顺时针旋转。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct Rotate {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.rotate(45 * Math.PI / 180)
          offContext.fillRect(70, 20, 50, 50)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

scale

scale(x: number, y: number): void

设置canvas画布的缩放变换属性，后续的绘制操作将按照缩放比例进行缩放。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct Scale {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.lineWidth = 3
          offContext.strokeRect(30, 30, 50, 50)
          offContext.scale(2, 2) // Scale to 200%
          offContext.strokeRect(30, 30, 50, 50)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

transform

transform(a: number, b: number, c: number, d: number, e: number, f: number): void

transform方法对应一个变换矩阵，想对一个图形进行变化的时候，只要设置此变换矩阵相应的参数，对图形的各个定点的坐标分别乘以这个矩阵，就能得到新的定点的坐标。矩阵变换效果可叠加。

从API version 9开始，该接口支持在ArkTS卡片中使用。

说明： 变换后的坐标计算方式（x和y为变换前坐标，x'和y'为变换后坐标)：

• x' = scaleX * x + skewY * y + translateX

• y' = skewX * x + scaleY * y + translateY

参数：

示例：

// xxx.ets
@Entry
@Component
struct Transform {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.fillStyle = 'rgb(0,0,0)'
          offContext.fillRect(0, 0, 100, 100)
          offContext.transform(1, 0.5, -0.5, 1, 10, 10)
          offContext.fillStyle = 'rgb(255,0,0)'
          offContext.fillRect(0, 0, 100, 100)
          offContext.transform(1, 0.5, -0.5, 1, 10, 10)
          offContext.fillStyle = 'rgb(0,0,255)'
          offContext.fillRect(0, 0, 100, 100)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

setTransform

setTransform(a: number, b: number, c: number, d: number, e: number, f: number): void

setTransform方法使用的参数和transform()方法相同，但setTransform()方法会重置现有的变换矩阵并创建新的变换矩阵。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct SetTransform {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.fillStyle = 'rgb(255,0,0)'
          offContext.fillRect(0, 0, 100, 100)
          offContext.setTransform(1,0.5, -0.5, 1, 10, 10)
          offContext.fillStyle = 'rgb(0,0,255)'
          offContext.fillRect(0, 0, 100, 100)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

setTransform

setTransform(transform?: Matrix2D): void

以Matrix2D对象为模板重置现有的变换矩阵并创建新的变换矩阵。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
 @Entry
 @Component
 struct TransFormDemo {
   private settings: RenderingContextSettings = new RenderingContextSettings(true);
   private context1: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings);
   private offcontext1: OffscreenCanvasRenderingContext2D = new OffscreenCanvasRenderingContext2D(600, 200, this.settings);
   private context2: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings);
   private offcontext2: OffscreenCanvasRenderingContext2D = new OffscreenCanvasRenderingContext2D(600, 200, this.settings);

   build() {
     Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
       Text('context1');
       Canvas(this.context1)
         .width('230vp')
         .height('160vp')
         .backgroundColor('#ffff00')
         .onReady(() =>{
           this.offcontext1.fillRect(100, 20, 50, 50);
           this.offcontext1.setTransform(1, 0.5, -0.5, 1, 10, 10);
           this.offcontext1.fillRect(100, 20, 50, 50);
           let image = this.offcontext1.transferToImageBitmap();
           this.context1.transferFromImageBitmap(image);
         })
       Text('context2');
       Canvas(this.context2)
         .width('230vp')
         .height('160vp')
         .backgroundColor('#0ffff0')
         .onReady(() =>{
           this.offcontext2.fillRect(100, 20, 50, 50);
           let storedTransform = this.offcontext1.getTransform();
           this.offcontext2.setTransform(storedTransform);
           this.offcontext2.fillRect(100, 20, 50, 50);
           let image = this.offcontext2.transferToImageBitmap();
           this.context2.transferFromImageBitmap(image);
         })
     }
     .width('100%')
     .height('100%')
   }
 }

getTransform

getTransform(): Matrix2D

获取当前被应用到上下文的转换矩阵。

从API version 9开始，该接口支持在ArkTS卡片中使用。

返回值：

示例：

// xxx.ets
@Entry
@Component
struct TransFormDemo {
  private settings: RenderingContextSettings = new RenderingContextSettings(true);
  private context1: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings);
  private offcontext1: OffscreenCanvasRenderingContext2D = new OffscreenCanvasRenderingContext2D(600, 100, this.settings);
  private context2: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings);
  private offcontext2: OffscreenCanvasRenderingContext2D = new OffscreenCanvasRenderingContext2D(600, 100, this.settings);

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Text('context1');
      Canvas(this.context1)
        .width('230vp')
        .height('120vp')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          this.offcontext1.fillRect(50, 50, 50, 50);
          this.offcontext1.setTransform(1.2, Math.PI/8, Math.PI/6, 0.5, 30, -25);
          this.offcontext1.fillRect(50, 50, 50, 50);
          let image = this.offcontext1.transferToImageBitmap();
          this.context1.transferFromImageBitmap(image);
        })
      Text('context2');
      Canvas(this.context2)
        .width('230vp')
        .height('120vp')
        .backgroundColor('#0ffff0')
        .onReady(() =>{
          this.offcontext2.fillRect(50, 50, 50, 50);
          let storedTransform = this.offcontext1.getTransform();
          console.log("Matrix [scaleX = " + storedTransform.scaleX + ", scaleY = " + storedTransform.scaleY +
          ", rotateX = " + storedTransform.rotateX + ", rotateY = " + storedTransform.rotateY +
          ", translateX = " + storedTransform.translateX + ", translateY = " + storedTransform.translateY + "]")
          this.offcontext2.setTransform(storedTransform);
          this.offcontext2.fillRect(50,50,50,50);
          let image = this.offcontext2.transferToImageBitmap();
          this.context2.transferFromImageBitmap(image);
        })
    }
    .width('100%')
    .height('100%')
  }
}

translate

translate(x: number, y: number): void

移动当前坐标系的原点。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct Translate {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.fillRect(10, 10, 50, 50)
          offContext.translate(70, 70)
          offContext.fillRect(10, 10, 50, 50)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

drawImage

drawImage(image: ImageBitmap | PixelMap, dx: number, dy: number): void

drawImage(image: ImageBitmap | PixelMap, dx: number, dy: number, dw: number, dh: number): void

drawImage(image: ImageBitmap | PixelMap, sx: number, sy: number, sw: number, sh: number, dx: number, dy: number, dw: number, dh: number):void

进行图像绘制。

从API version 9开始，该接口支持在ArkTS卡片中使用，卡片中不支持PixelMap对象。

参数：

示例：

// xxx.ets
@Entry
@Component
struct DrawImage {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private img:ImageBitmap = new ImageBitmap("common/images/icon.jpg")
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
      .width('100%')
      .height('100%')
      .backgroundColor('#ffff00')
      .onReady(() => {
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.drawImage( this.img,0,0,400,200)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

createImageData

createImageData(sw: number, sh: number): ImageData

根据当前ImageData对象重新创建一个宽、高相同的ImageData对象，请参考ImageData。createImageData示例同putImageData。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

createImageData(imageData: ImageData): ImageData

根据已创建的ImageData对象创建新的ImageData对象，请参考ImageData。createImageData示例同putImageData。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

返回值：

getPixelMap

getPixelMap(sx: number, sy: number, sw: number, sh: number): PixelMap

以当前canvas指定区域内的像素创建PixelMap对象，该接口存在内存拷贝行为，高耗时，应避免频繁使用。

参数：

返回值：

示例：

// xxx.ets
@Entry
@Component
struct GetPixelMap {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  private img:ImageBitmap = new ImageBitmap("/images/star.png")

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
           let offContext = this.offCanvas.getContext("2d", this.settings)
           offContext.drawImage(this.img, 100, 100, 130, 130)
           let pixelmap = offContext.getPixelMap(150, 150, 130, 130)
           offContext.setPixelMap(pixelmap)
           let image = this.offCanvas.transferToImageBitmap()
           this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

setPixelMap

setPixelMap(value?: PixelMap): void

将当前传入PixelMap对象绘制在画布上。setPixelMap示例同getPixelMap。

参数：

getImageData

getImageData(sx: number, sy: number, sw: number, sh: number): ImageData

以当前canvas指定区域内的像素创建ImageData对象，该接口存在内存拷贝行为，高耗时，应避免频繁使用。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

返回值：

示例：

// xxx.ets
@Entry
@Component
struct GetImageData {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  private img:ImageBitmap = new ImageBitmap("/common/images/1234.png")

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.drawImage(this.img,0,0,130,130)
          let imagedata = offContext.getImageData(50,50,130,130)
          offContext.putImageData(imagedata,150,150)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

putImageData

putImageData(imageData: Object, dx: number | string, dy: number | string): void

putImageData(imageData: Object, dx: number | string, dy: number | string, dirtyX: number | string, dirtyY: number | string, dirtyWidth?: number | string, dirtyHeight: number | string): void

使用ImageData数据填充新的矩形区域。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

// xxx.ets
@Entry
@Component
struct PutImageData {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          let imageDataNum = offContext.createImageData(100, 100)
          for (let i = 0; i < imageDataNum.data.length; i += 4) {
            imageDataNum.data[i + 0] = 255
            imageDataNum.data[i + 1] = 0
            imageDataNum.data[i + 2] = 255
            imageDataNum.data[i + 3] = 255
          }
          let imageData = this.context.createImageData(imageDataNum)
          offContext.putImageData(imageData, 10, 10)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

setLineDash

setLineDash(segments: number[]): void

设置画布的虚线样式。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

示例：

@Entry
@Component
struct SetLineDash {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.arc(100, 75, 50, 0, 6.28)
          offContext.setLineDash([10,20])
          offContext.stroke()
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
      })
    }
    .width('100%')
    .height('100%')
  }
}

getLineDash

getLineDash(): number[]

获得当前画布的虚线样式。

从API version 9开始，该接口支持在ArkTS卡片中使用。

返回值：

示例：

// xxx.ets
@Entry
@Component
struct OffscreenCanvasGetLineDash {
  @State message: string = 'Hello World'
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  build() {
    Row() {
      Column() {
        Text(this.message)
          .fontSize(50)
          .fontWeight(FontWeight.Bold)
          .onClick(()=>{
            console.error('before getlinedash clicked')
            let offContext = this.offCanvas.getContext("2d", this.settings)
            let res = offContext.getLineDash()
            console.error(JSON.stringify(res))
          })
        Canvas(this.context)
          .width('100%')
          .height('100%')
          .backgroundColor('#ffff00')
          .onReady(() => {
            let offContext = this.offCanvas.getContext("2d", this.settings)
            offContext.arc(100, 75, 50, 0, 6.28)
            offContext.setLineDash([10,20])
            offContext.stroke()
            let res = offContext.getLineDash()
            let image = this.offCanvas.transferToImageBitmap()
            this.context.transferFromImageBitmap(image)
          })
      }
      .width('100%')
    }
    .height('100%')
  }
}

toDataURL

toDataURL(type?: string, quality?: number): string

生成一个包含图片展示的URL。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

返回值：

示例：

// xxx.ets  
@Entry
@Component
struct ToDataURL {
    private settings: RenderingContextSettings = new RenderingContextSettings(true)
    private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
    private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          let dataURL = offContext.toDataURL()
        })
    }
    .width('100%')
    .height('100%')
  }
}

transferToImageBitmap

transferToImageBitmap(): ImageBitmap

在离屏画布最近渲染的图像上创建一个ImageBitmap对象。

返回值：

示例：

// xxx.ets
@Entry
@Component
struct PutImageData {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          let imageData = offContext.createImageData(100, 100)
          for (let i = 0; i < imageData.data.length; i += 4) {
            imageData.data[i + 0] = 255
            imageData.data[i + 1] = 0
            imageData.data[i + 2] = 255
            imageData.data[i + 3] = 255
          }
          offContext.putImageData(imageData, 10, 10)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

restore

restore(): void

对保存的绘图上下文进行恢复。

从API version 9开始，该接口支持在ArkTS卡片中使用。

示例：

// xxx.ets
@Entry
@Component
struct CanvasExample {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.save() // save the default state
          offContext.fillStyle = "#00ff00"
          offContext.fillRect(20, 20, 100, 100)
          offContext.restore() // restore to the default state
          offContext.fillRect(150, 75, 100, 100)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

save

save(): void

对当前的绘图上下文进行保存。

从API version 9开始，该接口支持在ArkTS卡片中使用。

示例：

// xxx.ets
@Entry
@Component
struct CanvasExample {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          offContext.save() // save the default state
          offContext.fillStyle = "#00ff00"
          offContext.fillRect(20, 20, 100, 100)
          offContext.restore() // restore to the default state
          offContext.fillRect(150, 75, 100, 100)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

createLinearGradient

createLinearGradient(x0: number, y0: number, x1: number, y1: number): CanvasGradient

创建一个线性渐变色。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

返回值：

示例：

// xxx.ets
@Entry
@Component
struct CreateLinearGradient {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          let grad = offContext.createLinearGradient(50,0, 300,100)
          grad.addColorStop(0.0, '#ff0000')
          grad.addColorStop(0.5, '#ffffff')
          grad.addColorStop(1.0, '#00ff00')
          offContext.fillStyle = grad
          offContext.fillRect(0, 0, 400, 400)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

createRadialGradient

createRadialGradient(x0: number, y0: number, r0: number, x1: number, y1: number, r1: number): CanvasGradient

创建一个径向渐变色。

从API version 9开始，该接口支持在ArkTS卡片中使用。

参数：

返回值：

示例：

// xxx.ets
@Entry
@Component
struct CreateRadialGradient {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)
  
  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffff00')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          let grad = offContext.createRadialGradient(200,200,50, 200,200,200)
          grad.addColorStop(0.0, '#ff0000')
          grad.addColorStop(0.5, '#ffffff')
          grad.addColorStop(1.0, '#00ff00')
          offContext.fillStyle = grad
          offContext.fillRect(0, 0, 440, 440)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}

createConicGradient¹⁰⁺

createConicGradient(startAngle: number, x: number, y: number): CanvasGradient

创建一个圆锥渐变色。

参数：

返回值：

示例：

// xxx.ets
@Entry
@Component
struct OffscreenCanvasConicGradientPage {
  private settings: RenderingContextSettings = new RenderingContextSettings(true)
  private context: CanvasRenderingContext2D = new CanvasRenderingContext2D(this.settings)
  private offCanvas: OffscreenCanvas = new OffscreenCanvas(600, 600)

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Canvas(this.context)
        .width('100%')
        .height('100%')
        .backgroundColor('#ffffff')
        .onReady(() =>{
          let offContext = this.offCanvas.getContext("2d", this.settings)
          let grad = offContext.createConicGradient(0, 50, 80)
          grad.addColorStop(0.0, '#ff0000')
          grad.addColorStop(0.5, '#ffffff')
          grad.addColorStop(1.0, '#00ff00')
          offContext.fillStyle = grad
          offContext.fillRect(0, 30, 100, 100)
          let image = this.offCanvas.transferToImageBitmap()
          this.context.transferFromImageBitmap(image)
        })
    }
    .width('100%')
    .height('100%')
  }
}