harmony 鸿蒙CanvasRenderingContext2D

  • 2023-06-24
  • 浏览 (467)

CanvasRenderingContext2D

CanvasRenderingContext2D allows you to draw rectangles and text on a canvas.

Example

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


// 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();
  },
}

en-us_image_0000001431548113

fillRect()

Fills a rectangle on the canvas.

Parameters

Parameter Type Description
x number X-coordinate of the upper left corner of the rectangle.
y number Y-coordinate of the upper left corner of the rectangle.
width number Width of the rectangle.
height number Height of the rectangle.

Example

en-us_image_0000001431388525

  ctx.fillRect(20, 20, 200, 150);

fillStyle

Sets the style to fill an area.

Parameters

Parameter Type Description
color &lt;color&gt; Color used to fill the area

Example

en-us_image_0000001431388505

  ctx.fillStyle = '#0000ff';
  ctx.fillRect(20, 20, 150, 100);

strokeRect()

Draws a rectangle stroke on the canvas.

Parameters

Parameter Type Description
x number X-coordinate of the upper left corner of the rectangle.
y number Y-coordinate of the upper left corner of the rectangle.
width number Width of the rectangle.
height number Height of the rectangle.

Example

en-us_image_0000001381268264

  ctx.strokeRect(30, 30, 200, 150);

fillText()

Draws filled text on the canvas.

Parameters

Parameter Type Description
text string Text to draw.
x number X-coordinate of the lower left corner of the text.
y number Y-coordinate of the lower left corner of the text.

Example

en-us_image_0000001431548109

  ctx.font = '35px sans-serif';
  ctx.fillText("Hello World!", 20, 60);

lineWidth

Sets the width of a line.

Parameters

Parameter Type Description
lineWidth number Line width.

Example

en-us_image_0000001431548121

  ctx.lineWidth = 5;
  ctx.strokeRect(25, 25, 85, 105);

strokeStyle

Sets the stroke style.

Parameters

Parameter Type Description
color &lt;color&gt; Color of the stroke.

Example

en-us_image_0000001380789172

  ctx.lineWidth = 10;
  ctx.strokeStyle = '#0000ff';
  ctx.strokeRect(25, 25, 155, 105);

stroke()5+

Draws a stroke.

Example

en-us_image_0000001431388513

  ctx.moveTo(25, 25);
  ctx.lineTo(25, 105);
  ctx.strokeStyle = 'rgb(0,0,255)';
  ctx.stroke();

beginPath()5+

Creates a drawing path.

Example

en-us_image_0000001431548125

  ctx.beginPath();              
  ctx.lineWidth = '6';
  ctx.strokeStyle = '#0000ff';
  ctx.moveTo(15, 80); 
  ctx.lineTo(280, 160);
  ctx.stroke();

moveTo()5+

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

Parameters

Parameter Type Description
x number X-coordinate of the target position.
y number Y-coordinate of the target position.

Example

en-us_image_0000001431388529

  ctx.beginPath();
  ctx.moveTo(10, 10);
  ctx.lineTo(280, 160);
  ctx.stroke();

lineTo()5+

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

Parameters

Parameter Type Description
x number X-coordinate of the target position.
y number Y-coordinate of the target position.

Example

en-us_image_0000001431148365

  ctx.beginPath();
  ctx.moveTo(10, 10);
  ctx.lineTo(280, 160);
  ctx.stroke();

closePath()5+

Draws a closed path.

Example

en-us_image_0000001381268284

  ctx.beginPath();
  ctx.moveTo(30, 30);
  ctx.lineTo(110, 30);
  ctx.lineTo(70, 90);
  ctx.closePath();
  ctx.stroke();

font

Sets the font style.

Parameters

Parameter Type Description
value string Font style. sans-serif, serif, and monospace are supported. The default value is 30px HYQiHei-65S.

Example

en-us_image_0000001381108328

  ctx.font = '30px sans-serif';
  ctx.fillText("Hello World", 20, 60);

textAlign

Sets the text alignment mode.

Parameters

Parameter Type Description
align string Available values are as follows:
- left (default): The text is left-aligned.
- right: The text is right-aligned.
- center: The text is center-aligned.

Example

en-us_image_0000001431388517

  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 = '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);

arc()5+

Draws an arc on the canvas.

Parameters

Parameter Type Description
x number X-coordinate of the center point of the arc.
y number Y-coordinate of the center point of the arc.
radius number Radius of the arc.
startAngle number Start radian of the arc.
endAngle number End radian of the arc.
anticlockwise boolean Whether to draw the arc counterclockwise.

Example

en-us_image_0000001381108320

  ctx.beginPath();
  ctx.arc(100, 75, 50, 0, 6.28);
  ctx.stroke();

rect()5+

Creates a rectangle on the canvas.

Parameters

Parameter Type Description
x number X-coordinate of the upper left corner of the rectangle.
y number Y-coordinate of the upper left corner of the rectangle.
width number Width of the rectangle.
height number Height of the rectangle.

Example

en-us_image_0000001381108312

  ctx.rect(20, 20, 100, 100); // Create a 100*100 rectangle at (20, 20)
  ctx.stroke(); // Draw it

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