CanvasRenderingContext2D

NOTE

This component is supported since API version 4. Updates will be marked with a superscript to indicate their earliest API version.

CanvasRenderingContext2D allows you to draw rectangles, text, images, and other objects on a canvas.

Example

<!-- 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(); 
    }
  }

• Anti-aliasing disabled

  

• Anti-aliasing enabled

  

Attributes

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

Enumerates the operation types.

Example

<!-- 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);
}
}

In the above example, the blue rectangle represents the new drawing, and the red rectangle represents the existing drawing.

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);
    };
  }
}

Methods

fillRect

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

Fills a rectangle on the canvas.

Parameters

Example

  <!-- 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

Clears the content in a rectangle on the canvas.

Parameters

Example

<!-- 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

Draws a rectangle stroke on the canvas.

Parameters

Example

<!-- 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

Draws filled text on the canvas.

Parameters

Example

<!-- 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

Draws a text stroke on the canvas.

Parameters

Example

<!-- 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

Returns a TextMetrics object used to obtain the width of specified text.

Parameters

Return value

Example

<!-- 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

Draws a stroke.

Example

<!-- 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

Creates a drawing path.

Example

<!-- 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

Moves a drawing path to a target position on the canvas.

Parameters

Example

<!-- 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

Connects the current point to a target position using a straight line.

Parameters

Example

<!-- 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

Draws a closed path.

Example

<!-- 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

Creates a pattern for image filling based on a specified source image and repetition mode.

Parameters

Return value

Example

<!-- 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

Draws a cubic bezier curve on the canvas.

Parameters

Example

<!-- 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.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

Draws a quadratic curve on the canvas.

Parameters

Example

<!-- 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

Draws an arc on the canvas.

Parameters

Example

<!-- 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

Draws an arc based on the radius and points on the arc.

Parameters

Example

<!-- 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

Draws an ellipse in the specified rectangular region on the canvas.

Parameters

Example

<!-- 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

Creates a rectangle on the canvas.

Parameters

Example

<!-- 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

Fills the area inside a closed path on the canvas.

Example

<!-- 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

Sets the current path to a clipping path.

Example

<!-- 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

Rotates a canvas clockwise around its coordinate axes.

Parameters

Example

<!-- 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

Scales the canvas based on scale factors.

Parameters

Example

<!-- 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

Defines a transformation matrix. To transform a graph, you only need to set parameters of the matrix. The coordinates of the graph are multiplied by the matrix values to obtain new coordinates of the transformed graph. You can use the matrix to implement multiple transform effects.

NOTE
The following formulas calculate coordinates of the transformed graph. x and y represent coordinates before transformation, and x' and y' represent coordinates after transformation.

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

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

Parameters

Example

<!-- 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

Resets the existing transformation matrix and creates a new transformation matrix by using the same parameters as the transform() API.

Parameters

Example

<!-- 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

Moves the origin of the coordinate system.

Parameters

Example

<!-- 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

Creates a Path2D object.

Parameters

Return value

Path2D object

Example

<!-- 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

Draws an image on the canvas.

Parameters

Example

<!-- 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

Restores the saved drawing context.

Example

<!-- 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

Saves the current drawing context.

Example

<!-- 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

Creates a linear gradient and returns a CanvasGradient object. For details, see CanvasGradient.

Parameters

Return value

Example

<!-- 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

Creates a radial gradient and returns a CanvasGradient object.

Parameters

Return value

Example

<!-- 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

Creates an ImageData object. For details, see ImageData.

Parameters

Return value

Example

<!-- 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

Obtains the ImageData object created with the pixels within the specified area on the canvas.

Parameters

Return value

Example

<!-- 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

Puts the ImageData onto a rectangular area on the canvas.

Parameters

Example

<!-- 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

Obtains the PixelMap object created with the pixels within the specified area on the canvas.

Parameters

Return value

Example

<!-- 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

Sets the dash line style.

Parameters

Example

<!-- 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

Obtains the dash line style.

Return value

Example

<!-- 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

Displays the specified ImageBitmap object.

Parameters

Example

<!-- 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);
  }
}