API Documentation for: 1.0.0
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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 HTMLImageElement | 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:180

Parameters:

  • imageData ImageData

    Target ImageData instance.

Returns:

_prepAlphaMap

() protected

Defined in _prepAlphaMap:161

applyFilter

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

Inherited from Filter: applyFilter:131

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:

Boolean:

If the filter was applied successfully.

clone

() Filter

Inherited from Filter: clone:170

Returns a clone of this Filter instance.

Returns:

Filter:

A clone of the current Filter instance.

getBounds

(
  • [rect]
)
Rectangle

Inherited from Filter: getBounds:111

Provides padding values for this filter. That is, how much the filter will extend the visual bounds of an object it is applied to.

Parameters:

  • [rect] Rectangle optional

    If specified, the provided Rectangle instance will be expanded by the padding amounts and returned.

Returns:

Rectangle:

If a rect param was provided, it is returned. If not, either a new rectangle with the padding values, or null if no padding is required for this filter.

shaderParamSetup

(
  • gl
  • stage
  • shaderProgram
)

Inherited from Filter: shaderParamSetup:121

Assign any unique uniforms or other setup functionality here.

Parameters:

  • gl WebGLContext

    The context associated with the stage performing the render.

  • stage StageGL

    The stage instance that will be rendering.

  • shaderProgram ShaderProgram

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

toString

() String

Inherited from Filter: toString:161

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

_multiPass

Filter private

Inherited from Filter: _multiPass:79

Another filter that is required to act as part of this filter and created and managed under the hood.

Default: null

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 readonly

Inherited from Filter: FRAG_SHADER:98

Pre-processed template shader code. It will be parsed before being fed in into the shader compiler. This should be based upon StageGL.SHADER_FRAGMENT_BODY_REGULAR

usesContext

Boolean

Inherited from Filter: usesContext:71

A flag stating that this filter uses a context draw mode and cannot be batched into imageData processing.

Default: false

VTX_SHADER

String readonly

Inherited from Filter: VTX_SHADER:88

Pre-processed template shader code. It will be parsed before being fed in into the shader compiler. This should be based upon StageGL.SHADER_VERTEX_BODY_REGULAR