Canvas

wx.createCanvas

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The API usage is as follows:wx.createCanvas()

• Functional description: Create a canvas object. The first call creates a canvas displayed on the screen, and subsequent calls create off-screen canvases.
• Return value: Canvas , Canvas object.

Canvas

Properties

• number width：Canvas width.
• number height：Canvas height.

Method

Canvas.getContext

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The API usage is as follows:Canvas.getContext(string contextType, Object contextAttributes)

• Functional description: Get the drawing context of the canvas object.

• Parameters and descriptions:

  • string contextType, Context type, legal values ​​are as follows:

    Legal value	Description
    2d	2d drawing context
    webgl	webgl drawing context
    webgl2	webgl2 drawing context

    • Object contextAttributeswebgl context attribute, valid only when contextType is webgl.

    Properties	Type	Default value	Required	Description
    antialias	boolean	false	No	Indicates whether anti-aliasing is used
    preserveDrawingBuffer	boolean	false	No	Indicates whether the drawing buffer is retained after drawing is completed
    antialiasSamples	number	2	No	Number of anti-aliasing samples. The minimum value is 2, and the maximum value does not exceed the system limit. Only iOS supports

• Return value: RenderingContext Drawing context.

Canvas.toDataURL

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The API usage is as follows:Canvas.toDataURL()

• Functional description: Return the drawing content on the canvas in the format of a data URI.
• Return value: string A string in data URI format.

RenderingContext

• Functional description: The drawing context of the canvas object.

  • The CanvasRenderingContext2D object can be obtained through the Canvas.getContext('2d') interface, which implements most of the properties and methods defined by the HTML Canvas 2D Context.
  • The WebGLRenderingContext object can be obtained through the Canvas.getContext('webgl') interface, which implements all the properties, methods, and constants defined in WebGL 1.0.
  • The WebGL2RenderingContext object can be obtained through the Canvas.getContext('webgl2') interface, which implements all the properties, methods, and constants defined in WebGL 2.0.

• 2D interface support

  2D attributes and interfaces not supported by iOS/Android

  • GlobalCompositeOperation does not support the following values: source-in source-out destination-atop lighter copy. If used, no error will be reported, but the result will not be consistent with the expectation.
  • isPointInPath
  • isPointInStroke
  • setLineDash
  • getLineDash
  • lineDashOffset
  • shadowColor
  • shadowBlur
  • shadowOffsetX
  • shadowOffsetY

• WebGL interface support

  Compressed texture support

  • iOS supports pvr format
  • Android supports etc1 format