AlphaMapFilter Class
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
Parameters:
-
alphaMapHTMLImageElement | HTMLCanvasElementThe greyscale image (or canvas) to use as the alpha value for the result. This should be exactly the same dimensions as the target.
Item Index
Properties
Methods
_applyFilter
-
imageData
Parameters:
-
imageDataImageDataTarget ImageData instance.
Returns:
_prepAlphaMap
()
protected
applyFilter
-
ctx -
x -
y -
width -
height -
[targetCtx] -
[targetX] -
[targetY]
Applies the filter to the specified context.
Parameters:
-
ctxCanvasRenderingContext2DThe 2D context to use as the source.
-
xNumberThe x position to use for the source rect.
-
yNumberThe y position to use for the source rect.
-
widthNumberThe width to use for the source rect.
-
heightNumberThe height to use for the source rect.
-
[targetCtx]CanvasRenderingContext2D optionalThe 2D context to draw the result to. Defaults to the context passed to ctx.
-
[targetX]Number optionalThe x position to draw the result to. Defaults to the value passed to x.
-
[targetY]Number optionalThe y position to draw the result to. Defaults to the value passed to y.
Returns:
If the filter was applied successfully.
clone
()
Filter
Returns a clone of this Filter instance.
Returns:
A clone of the current Filter instance.
getBounds
-
[rect]
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 optionalIf specified, the provided Rectangle instance will be expanded by the padding amounts and returned.
Returns:
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
Assign any unique uniforms or other setup functionality here.
Parameters:
-
glWebGLContextThe context associated with the stage performing the render.
-
stageStageGLThe stage instance that will be rendering.
-
shaderProgramShaderProgramThe compiled shader that is going to be used to perform the render.
Properties
_alphaMap
HTMLImageElement | HTMLCanvasElement
protected
_mapData
Uint8ClampedArray
protected
_multiPass
Filter
private
Another filter that is required to act as part of this filter and created and managed under the hood.
Default: null
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.
FRAG_SHADER
String
readonly
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
A flag stating that this filter uses a context draw mode and cannot be batched into imageData processing.
Default: false
VTX_SHADER
String
readonly
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