API Documentation for: 0.8.2
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AlphaMapFilter Class

Extends Filter
Defined in: AlphaMapFilter:41
Module: EaselJS

Applies a greyscale alpha map image (or canvas) to the target, such that the alpha channel of the result will be copied from the red channel of the map, and the RGB channels will be copied from the target.

Generally, it is recommended that you use AlphaMaskFilter, because it has much better performance.

Example

This example draws a red->blue box, caches it, and then uses the cache canvas as an alpha map on a 100x100 image.

  var box = new createjs.Shape();
  box.graphics.beginLinearGradientFill(["#ff0000", "#0000ff"], [0, 1], 0, 0, 0, 100)
  box.graphics.drawRect(0, 0, 100, 100);
  box.cache(0, 0, 100, 100);

  var bmp = new createjs.Bitmap("path/to/image.jpg");
  bmp.filters = [
      new createjs.AlphaMapFilter(box.cacheCanvas)
  ];
  bmp.cache(0, 0, 100, 100);
  stage.addChild(bmp);

See Filter for more information on applying filters.

Constructor

AlphaMapFilter

(
  • alphaMap
)

Defined in AlphaMapFilter:41

Parameters:

  • alphaMap Image | HTMLCanvasElement

    The greyscale image (or canvas) to use as the alpha value for the result. This should be exactly the same dimensions as the target.

Methods

_applyFilter

(
  • imageData
)
Boolean

Inherited from Filter: _applyFilter:177

Parameters:

  • imageData ImageData

    Target ImageData instance.

Returns:

_createWebGLRenderer

() protected

Attempt to creates a WebGLContextRenderer for fast, efficient filter rendering. Used during filter initialization. If it cannot be done, or this.useGL is set to false, then the filter is rendered normally using a Context2D.

_getFragmentShader Get fragment shader code in GLSL.

() String protected

Returns:

_getFragmentShader Get fragment shader code in GLSL. Filters are responsible for their own fragment shaders.

() String protected

Returns:

_getVertexShader Get vertex shader in GLSL code. This sets the positions of each point on the context in 3D space.

() String protected

Returns:

_initBuffers

(
  • ctx
)
protected

Inherited from Filter: _initBuffers:213

Setup the buffers and camera for the object. In this case, just create a rectangle that occupies the full stage.

Parameters:

_initShaders

(
  • ctx
)
protected

Inherited from Filter: _initShaders:156

Setup the shaders for WebGL rendering. Each filter is responsible for its own fragment shader.

Parameters:

_initUniforms

(
  • ctx
)
protected

Inherited from Filter but overwritten in _initUniforms:248

Setup the uniforms for the fragment shader. Each filter is responsible for its own fragment shader uniforms, as they are responsible for their own fragment shaders.

Parameters:

_prepAlphaMap

() protected

Defined in _prepAlphaMap:133

applyFilter

(
  • ctx
  • x
  • y
  • width
  • height
  • targetCtx
  • targetX
  • targetY
)
Boolean

Inherited from Filter but overwritten in applyFilter:98

Applies the filter to the specified context.

Parameters:

  • ctx CanvasRenderingContext2D

    The 2D context to use as the source.

  • x Number

    The x position to use for the source rect.

  • y Number

    The y position to use for the source rect.

  • width Number

    The width to use for the source rect.

  • height Number

    The height to use for the source rect.

  • targetCtx CanvasRenderingContext2D

    Optional. The 2D context to draw the result to. Defaults to the context passed to ctx.

  • targetX Number

    Optional. The x position to draw the result to. Defaults to the value passed to x.

  • targetY Number

    Optional. The y position to draw the result to. Defaults to the value passed to y.

Returns:

clone

() AlphaMapFilter

Inherited from Filter but overwritten in clone:161

Returns a clone of this object.

Returns:

AlphaMapFilter:

A clone of the current AlphaMapFilter instance.

getBounds

() Rectangle

Inherited from Filter but overwritten in getBounds:88

Returns a rectangle with values indicating the margins required to draw the filter or null. For example, a filter that will extend the drawing area 4 pixels to the left, and 7 pixels to the right (but no pixels up or down) would return a rectangle with (x=-4, y=0, width=11, height=0).

Returns:

Rectangle:

a rectangle object indicating the margins required to draw the filter or null if the filter does not effect bounds.

initialize

() protected

Inherited from Filter but overwritten in initialize:80

Initialization method.

shaderParamSetup

(
  • gl
  • stage
  • shaderProgram
)

Inherited from Filter: shaderParamSetup:118

Assign any unique uniforms or other setup functionality here.

Parameters:

  • gl WebGLContext

    The context associated with the stage performing the render.

  • stage SpriteStage

    The stage instance that will be rendering.

  • shaderProgram ShaderProgram

    The compiled shader that is going to be sued to perform the render.

toString

() String

Inherited from Filter but overwritten in toString:114

Returns a string representation of this object.

Returns:

String:

a string representation of the instance.

Properties

_alphaMap

HTMLImageElement | HTMLCanvasElement protected

Defined in _alphaMap:84

_mapData

Uint8ClampedArray protected

Defined in _mapData:91

alphaMap

Image | HTMLCanvasElement

Defined in alphaMap:83

The greyscale image (or canvas) to use as the alpha value for the result. This should be exactly the same dimensions as the target.

alphaMap

HTMLImageElement | HTMLCanvasElement

Defined in alphaMap:74

The greyscale image (or canvas) to use as the alpha value for the result. This should be exactly the same dimensions as the target.

FRAG_SHADER

String

Inherited from Filter: FRAG_SHADER:81

Pre-processing shader code, will be parsed before being fed in. This should be based upon SpriteStage.SHADER_FRAGMENT_BODY_REGULAR

VTX_SHADER

String

Inherited from Filter: VTX_SHADER:71

Pre-processing shader code, will be parsed before being fed in. This should be based upon SpriteStage.SHADER_VERTEX_BODY_REGULAR