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:
-
alphaMap
Image | HTMLCanvasElementThe 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
-
ctx
-
x
-
y
-
width
-
height
-
[targetCtx]
-
[targetX]
-
[targetY]
Applies the filter to the specified context.
Parameters:
-
ctx
CanvasRenderingContext2DThe 2D context to use as the source.
-
x
NumberThe x position to use for the source rect.
-
y
NumberThe y position to use for the source rect.
-
width
NumberThe width to use for the source rect.
-
height
NumberThe 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
()
Rectangle
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:
a rectangle object indicating the margins required to draw the filter or null if the filter does not effect bounds.
initialize
()
protected
Initialization method.
Properties
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.