CanvasRenderingContext2D对象

说明： 从API version 4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。

使用CanvasRenderingContext2D在canvas画布组件上进行绘制，绘制对象可以是矩形、文本、图片等。

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas1" style="width: 200px; height: 150px; background-color: #ffff00;"></canvas>
  <input type="button" style="width: 180px; height: 60px;" value="handleClick" onclick="handleClick" />
  <input type="button" style="width: 180px; height: 60px;" value="antialias" onclick="antialias" />
</div>

// xxx.js
export default {
  handleClick() {
    const el = this.$refs.canvas1;
    const ctx = el.getContext('2d');
    ctx.beginPath();
    ctx.arc(100, 75, 50, 0, 6.28);
    ctx.stroke();
  },
  antialias() {
    const el = this.$refs.canvas1;
    const ctx = el.getContext('2d', { antialias: true });
    ctx.beginPath();   
    ctx.arc(100, 75, 50, 0, 6.28);
    ctx.stroke(); 
    }
  }

• 示意图（关闭抗锯齿）

  

• 示意图（开启抗锯齿）

  

属性

fillStyle

<!-- xxx.hml -->
<div>
<canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.fillStyle = '#0000ff';
    ctx.fillRect(20, 20, 150, 100);
  }
}

lineWidth

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.lineWidth = 5;
    ctx.strokeRect(25, 25, 85, 105);
  }
}

strokeStyle

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.lineWidth = 10;
    ctx.strokeStyle = '#0000ff';
    ctx.strokeRect(25, 25, 155, 105);
  }
}

lineCap

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.lineWidth = 8;
    ctx.beginPath();
    ctx.lineCap = 'round';
    ctx.moveTo(30, 50);
    ctx.lineTo(220, 50);
    ctx.stroke();
  }
}

lineJoin

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.beginPath();
    ctx.lineWidth = 8;
    ctx.lineJoin = 'miter';
    ctx.moveTo(30, 30);
    ctx.lineTo(120, 60);
    ctx.lineTo(30, 110);
    ctx.stroke();
  }
}

miterLimit

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 500px; height: 500px; "></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.lineWidth =14;
    ctx.lineJoin = 'miter';
    ctx.miterLimit = 3;
    ctx.moveTo(30, 30);
    ctx.lineTo(120, 60);
    ctx.lineTo(30, 70);
    ctx.stroke();
  }
}

font

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.font = '30px sans-serif';
    ctx.fillText("Hello World", 20, 60);
  }
}

textAlign

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.strokeStyle = '#0000ff';
    ctx.moveTo(140, 10);
    ctx.lineTo(140, 160);
    ctx.stroke();
    ctx.font = '18px sans-serif'; 
    // Show the different textAlign values
    ctx.textAlign = 'start'; 
    ctx.fillText('textAlign=start', 140, 60);
    ctx.textAlign = 'end';
    ctx.fillText('textAlign=end', 140, 80);
    ctx.textAlign = 'left'; 
    ctx.fillText('textAlign=left', 140, 100);
    ctx.textAlign = 'center'; 
    ctx.fillText('textAlign=center',140, 120);
    ctx.textAlign = 'right';
    ctx.fillText('textAlign=right',140, 140);
  }
}

textBaseline

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 500px; height: 500px; "></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.strokeStyle = '#0000ff';
    ctx.moveTo(0, 120);
    ctx.lineTo(400, 120);
    ctx.stroke();
    ctx.font = '20px sans-serif';
    ctx.textBaseline = 'top'; 
    ctx.fillText('Top', 10, 120); 
    ctx.textBaseline = 'bottom'; 
    ctx.fillText('Bottom', 55, 120); 
    ctx.textBaseline = 'middle'; 
    ctx.fillText('Middle', 125, 120); 
    ctx.textBaseline = 'alphabetic'; 
    ctx.fillText('Alphabetic', 195, 120); 
    ctx.textBaseline = 'hanging'; 
    ctx.fillText('Hanging', 295, 120);
  }
}

globalAlpha

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.fillStyle = 'rgb(255,0,0)';
    ctx.fillRect(0, 0, 50, 50);
    ctx.globalAlpha = 0.4;
    ctx.fillStyle = 'rgb(0,0,255)'; 
    ctx.fillRect(50, 50, 50, 50);

  }
}

lineDashOffset

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; background-color: #ffff00;"></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.arc(100, 75, 50, 0, 6.28);
    ctx.setLineDash([10,20]);
    ctx.lineDashOffset = 10.0;
    ctx.stroke();
  }
}

globalCompositeOperation

类型字段说明

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

// xxx.js
export default {
onShow() {
  const el =this.$refs.canvas;
  const ctx = el.getContext('2d');
  ctx.fillStyle = 'rgb(255,0,0)';
  ctx.fillRect(20, 20, 50, 50);
  ctx.globalCompositeOperation = 'source-over';
  ctx.fillStyle = 'rgb(0,0,255)';
  ctx.fillRect(50, 50, 50, 50);
  // Start drawing second example
  ctx.fillStyle = 'rgb(255,0,0)';
  ctx.fillRect(120, 20, 50, 50);
  ctx.globalCompositeOperation = 'destination-over';
  ctx.fillStyle = 'rgb(0,0,255)';
  ctx.fillRect(150, 50, 50, 50);
}
}

示例中，新绘制内容是蓝色矩形，现有绘制内容是红色矩形。

shadowBlur

<!-- xxx.hml -->
<div>
<canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.shadowBlur = 30;
    ctx.shadowColor = 'rgb(0,0,0)';
    ctx.fillStyle = 'rgb(255,0,0)';
    ctx.fillRect(20, 20, 100, 80);
  }
}

shadowColor

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px;"></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.shadowBlur = 30;
    ctx.shadowColor = 'rgb(0,0,255)';
    ctx.fillStyle = 'rgb(255,0,0)';
    ctx.fillRect(30, 30, 100, 100);
  }
}

shadowOffsetX

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px;"></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.shadowBlur = 10;
    ctx.shadowOffsetX = 20;
    ctx.shadowColor = 'rgb(0,0,0)';
    ctx.fillStyle = 'rgb(255,0,0)';
    ctx.fillRect(20, 20, 100, 80);
  }
}

shadowOffsetY

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.shadowBlur = 10;
    ctx.shadowOffsetY = 20;
    ctx.shadowColor = 'rgb(0,0,0)';
    ctx.fillStyle = 'rgb(255,0,0)';
    ctx.fillRect(30, 30, 100, 100);
 }
}

imageSmoothingEnabled⁶⁺

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

// xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    var img = new Image();
    img.src = 'common/image/example.jpg';
    img.onload = function() {
    ctx.imageSmoothingEnabled = false;
    ctx.drawImage(img, 0, 0, 400, 200);
    };
  }
}

方法

fillRect

fillRect(x: number, y: number, width:number, height: number): void

填充一个矩形。

参数：

示例：

  <!-- xxx.hml -->
  <div>
    <canvas ref="canvas" style="width: 500px; height: 500px; background-color: #ffff00;"></canvas>
  </div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.fillRect(20, 20, 200, 150);
  }
}

clearRect

clearRect(x: number, y: number, width:number, height: number): void

删除指定区域内的绘制内容。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 500px; height: 500px; background-color: #ffff00;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.fillStyle = 'rgb(0,0,255)';
    ctx.fillRect(0, 0, 400, 200);
    ctx.clearRect(20, 20, 150, 100);
  }
}

strokeRect

strokeRect(x: number, y: number, width:number, height: number): void

绘制具有边框的矩形，矩形内部不填充。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.strokeRect(30, 30, 200, 150);
  }
}

fillText

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

绘制填充类文本。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.font = '35px sans-serif';
    ctx.fillText("Hello World!", 10, 60);
  }
}

strokeText

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

绘制描边类文本。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.font = '25px sans-serif';
    ctx.strokeText("Hello World!", 10, 60);
  }
}

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。

参数：

返回值：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.font = '20px sans-serif';
    var txt = 'Hello World';
    ctx.fillText("width:" + ctx.measureText(txt).width, 20, 60);
    ctx.fillText(txt, 20, 110);
  }
}

stroke

stroke(): void

进行边框绘制操作。

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.moveTo(25, 25);
    ctx.lineTo(25, 250);
    ctx.lineWidth = '6';
    ctx.strokeStyle = 'rgb(0,0,255)';
    ctx.stroke();
  }
}

beginPath

beginPath(): void

创建一个新的绘制路径。

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 500px; height: 500px; "></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.beginPath();              
    ctx.lineWidth = '6';
    ctx.strokeStyle = '#0000ff';
    ctx.moveTo(15, 80); 
    ctx.lineTo(280, 80);
    ctx.stroke();
  }
}

moveTo

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

路径从当前点移动到指定点。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.beginPath();
    ctx.moveTo(10, 10);
    ctx.lineTo(280, 160);
    ctx.stroke();
  }
}

lineTo

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

从当前点到指定点进行路径连接。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.beginPath();
    ctx.moveTo(10, 10);
    ctx.lineTo(280, 160);
    ctx.stroke();
  }
}

closePath

closePath(): void

结束当前路径形成一个封闭路径。

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.beginPath();
    ctx.moveTo(30, 30);
    ctx.lineTo(110, 30);
    ctx.lineTo(70, 90);
    ctx.closePath();
    ctx.stroke();
  }
}

createPattern

createPattern(image: Image, repetition: string): Object

通过指定图像和重复方式创建图片填充的模板。

参数：

返回值：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 1000px; height: 1000px;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    var img = new Image();
    img.src = 'common/images/example.jpg';
    var pat = ctx.createPattern(img, 'repeat');
    ctx.fillStyle = pat;
    ctx.fillRect(0, 0, 500, 500);
  }
}

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。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.beginPath();
    ctx.moveTo(10, 10);
    ctx.bezierCurveTo(20, 100, 200, 100, 200, 20);
    ctx.stroke();
  }
}

quadraticCurveTo

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

创建二次贝赛尔曲线的路径。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.beginPath();
    ctx.moveTo(20, 20);
    ctx.quadraticCurveTo(100, 100, 200, 20);
    ctx.stroke();
  }
}

arc

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

绘制弧线路径。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.beginPath();
    ctx.arc(100, 75, 50, 0, 6.28);
    ctx.stroke();
  }
}

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。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.moveTo(100, 20);
    ctx.arcTo(150, 20, 150, 70, 50); // Create an arc
    ctx.stroke();
  }
}

ellipse⁶⁺

ellipse(x: number, y: number, radiusX: number, radiusY: number, rotation: number, startAngle: number, endAngle: number, anticlockwise: number): void

在规定的矩形区域绘制一个椭圆。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 500px; height: 500px; background-color: #ffff00;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.beginPath();
    ctx.ellipse(200, 200, 50, 100, Math.PI * 0.25, Math.PI * 0.5, Math.PI, 1);
    ctx.stroke();
  }
}

rect

rect(x: number, y: number, width: number, height: number): void

创建矩形路径。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.rect(20, 20, 100, 100); // Create a 100*100 rectangle at (20, 20)
    ctx.stroke(); // Draw it
  }
}

fill

fill(): void

对封闭路径进行填充。

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.rect(20, 20, 100, 100); // Create a 100*100 rectangle at (20, 20)
    ctx.fill(); // Draw it in default setting
  }
}

clip

clip(): void

设置当前路径为剪切路径。

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.rect(0, 0, 200, 200);
    ctx.stroke();
    ctx.clip();
    // Draw red rectangle after clip
    ctx.fillStyle = "rgb(255,0,0)";
    ctx.fillRect(0, 0, 150, 150);
  }
}

rotate

rotate(rotate: number): void

针对当前坐标轴进行顺时针旋转。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.rotate(45 * Math.PI / 180); // Rotate the rectangle 45 degrees
    ctx.fillRect(70, 20, 50, 50);
  }
}

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。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.strokeRect(10, 10, 25, 25);
    ctx.scale(2, 2);// Scale to 200%
    ctx.strokeRect(10, 10, 25, 25);
  }
}

transform

transform(scaleX: number, skewX: number, skewY: number, scale: number, translateX: number, translateY: 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。

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.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.fillStyle = 'rgb(0,0,0)';
    ctx.fillRect(0, 0, 100, 100)
    ctx.transform(1, 0.5, -0.5, 1, 10, 10);
    ctx.fillStyle = 'rgb(255,0,0)';
    ctx.fillRect(0, 0, 100, 100);
    ctx.transform(1, 0.5, -0.5, 1, 10, 10);
    ctx.fillStyle = 'rgb(0,0,255)';
    ctx.fillRect(0, 0, 100, 100);
  }
}

setTransform

setTransform(scaleX: number, skewX: number, skewY: number, scale: number, translateX: number, translateY: 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。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.fillStyle = 'rgb(255,0,0)';
    ctx.fillRect(0, 0, 100, 100)
    ctx.setTransform(1,0.5, -0.5, 1, 10, 10);
    ctx.fillStyle = 'rgb(0,0,255)';
    ctx.fillRect(0, 0, 100, 100);
  }
}

translate

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

移动当前坐标系的原点。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.fillRect(10, 10, 50, 50);
    ctx.translate(70, 70);
    ctx.fillRect(10, 10, 50, 50);
  }
}

createPath2D⁶⁺

createPath2D(path: Path2D, cmds: string): Path2D

创建一个Path2D对象。

参数：

返回值：

Path2D对象

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 500px; height: 500px; background-color: #ffff00;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    var path1 = ctx.createPath2D();
    path1.moveTo(100, 100);
    path1.lineTo(200, 100);
    path1.lineTo(100, 200);
    path1.closePath();
    ctx.stroke(path1);
    var path2 = ctx.createPath2D("M150 150 L50 250 L250 250 Z");
    ctx.stroke(path2);
    var path3 = ctx.createPath2D(path2);
    ctx.stroke(path3);
  }
}

drawImage

drawImage(image: Image | PixelMap, sx: number, sy: number, sWidth: number, sHeight: number, dx: number, dy: number, dWidth: number, dHeight: number):void

进行图像绘制。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 500px; height: 500px; background-color: #ffff00;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    var test = this.$refs.canvas;
    var ctx = test.getContext('2d');
    var img = new Image();
    img.src = 'common/image/test.jpg';
    ctx.drawImage(img, 0, 0, 200, 200, 10, 10, 200, 200);
  }
}

restore

restore(): void

对保存的绘图上下文进行恢复。

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; background-color: #ffff00;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.restore();
  }
}

save

save(): void

对当前的绘图上下文进行保存。

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; background-color: #ffff00;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.save();
  }
}

createLinearGradient⁶⁺

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

创建一个线性渐变色，返回CanvasGradient对象，请参考CanvasGradient对象。

参数：

返回值：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 500px; height: 500px; background-color: #ffff00;"></canvas>
  <input type="button" style="width: 180px; height: 60px;" value="fillStyle" onclick="handleClick" />
</div>

// xxx.js
export default {
  handleClick() {
    const el = this.$refs.canvas;
    const ctx = el.getContext('2d');
    // Linear gradient: start(50,0) end(300,100)
    var gradient = ctx.createLinearGradient(50,0, 300,100);
    // Add three color stops
    gradient.addColorStop(0.0, '#ff0000');
    gradient.addColorStop(0.5, '#ffffff');
    gradient.addColorStop(1.0, '#00ff00');
    // Set the fill style and draw a rectangle
    ctx.fillStyle = gradient;
    ctx.fillRect(0, 0, 500, 500);
  }
}

createRadialGradient⁶⁺

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

创建一个径向渐变色，返回CanvasGradient对象，请参考CanvasGradient

参数：

返回值：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 500px; height: 500px; background-color: #ffff00;"></canvas>
  <input type="button" style="width: 180px; height: 60px;" value="fillStyle" onclick="handleClick" />
</div>

// xxx.js
export default {
  handleClick() {
    const el = this.$refs.canvas;
    const ctx = el.getContext('2d');
    // Radial gradient: inner circle(200,200,r:50) outer circle(200,200,r:200)
    var gradient = ctx.createRadialGradient(200,200,50, 200,200,200);
    // Add three color stops
    gradient.addColorStop(0.0, '#ff0000');
    gradient.addColorStop(0.5, '#ffffff');
    gradient.addColorStop(1.0, '#00ff00');
    // Set the fill style and draw a rectangle
    ctx.fillStyle = gradient;
    ctx.fillRect(0, 0, 500, 500);
  }
}

createImageData

createImageData(width: number, height: number, imageData: Object): Object

创建新的ImageData 对象，请参考ImageData对象。

参数：

返回值：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; background-color: #ffff00;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    var imageData = ctx.createImageData(50, 100);  // Create ImageData with 50px width and 100px height
    var newImageData = ctx.createImageData(imageData);  // Create ImageData using the input imageData
  }
}

getImageData

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

以当前canvas指定区域内的像素创建ImageData对象。

参数：

返回值：

示例：

<!-- xxx.hml -->
<div>
  <canvas id="getImageData" style="width: 200px; height: 150px; background-color: #ffff00;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const test = this.$element('getImageData')
    const ctx = test.getContext('2d');
    var imageData = ctx.getImageData(0, 0, 280, 300);
  }
}

putImageData

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

使用ImageData数据填充新的矩形区域。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas id="getImageData" style="width: 200px; height: 150px; background-color: #ffff00;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const test = this.$element('getImageData')
    const ctx = test.getContext('2d');
    var imgData = ctx.createImageData(100, 100);
    for (var i = 0; i < imgData.data.length; i += 4) {
      imgData.data[i + 0] = 255;
      imgData.data[i + 1] = 0;
      imgData.data[i + 2] = 0;
      imgData.data[i + 3] = 255;
  }
    ctx.putImageData(imgData, 10, 10);
  }
}

getPixelMap⁹⁺

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

获取用当前canvas指定区域内的像素创建的PixelMap对象。

参数：

返回值：

示例：

<!-- xxx.hml -->
<div>
  <canvas id="canvasId" style="width: 200px; height: 150px; background-color: #ffff00;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const test = this.$element('canvasId')
    const ctx = test.getContext('2d');
    var pixelMap = ctx.getPixelMap(0, 0, 280, 300);
  }
}

setLineDash

setLineDash(segments: Array): void

设置画布的虚线样式。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; background-color: #ffff00;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    ctx.arc(100, 75, 50, 0, 6.28);
    ctx.setLineDash([10,20]);
    ctx.stroke();
  }
}

getLineDash

getLineDash(): Array

获得当前画布的虚线样式。

返回值：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 200px; height: 150px; "></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    var info = ctx.getLineDash();
  }
}

transferFromImageBitmap⁷⁺

transferFromImageBitmap(bitmap: ImageBitmap): void

显示给定的ImageBitmap对象。

参数：

示例：

<!-- xxx.hml -->
<div>
  <canvas ref="canvas" style="width: 500px; height: 500px; background-color: #ffff00;"></canvas>
</div>

//xxx.js
export default {
  onShow() {
    const el =this.$refs.canvas;
    const ctx = el.getContext('2d');
    var canvas = this.$refs.canvas.getContext('2d');
    var offscreen = new OffscreenCanvas(500,500);
    var offscreenCanvasCtx = offscreen.getContext("2d");
    offscreenCanvasCtx.fillRect(0, 0, 200, 200); 

    var bitmap = offscreen.transferToImageBitmap();
    canvas.transferFromImageBitmap(bitmap);
  }
}