#

API Documentation for: NEXT
Show: Inherited Protected Private Deprecated

# AlphaMaskFilter Class

Extends Filter
Defined in: `AlphaMaskFilter:39`
Module: EaselJS

Applies the alpha from the mask image (or canvas) to the target, such that the alpha channel of the result will be derived from the mask, and the RGB channels will be copied from the target. This can be used, for example, to apply an alpha mask to a display object. This can also be used to combine a JPG compressed RGB image with a PNG32 alpha mask, which can result in a much smaller file size than a single PNG32 containing ARGB.

IMPORTANT NOTE: This filter currently does not support the targetCtx, or targetX/Y parameters correctly.

#### Example

This example draws a gradient box, then caches it and uses the "cacheCanvas" as the alpha mask on a 100x100 image.

     var box = new createjs.Shape();
     box.graphics.beginLinearGradientFill(["#000000", "rgba(0, 0, 0, 0)"], [0, 1], 0, 0, 100, 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.AlphaMaskFilter(box.cacheCanvas)
     ];
     bmp.cache(0, 0, 100, 100);

See Filter for more information on applying filters.

## Constructor

### `AlphaMaskFilter`

(

- `mask`

)

Defined in `AlphaMaskFilter:39`

#### Parameters:

- `mask` Image

- Index
- Methods
- Properties

## Item Index

### Methods

- applyFilter
- clone
- getBounds
- initialize
- toString

### Properties

- mask

## Methods

### `applyFilter`

(

- `ctx`
- `x`
- `y`
- `width`
- `height`
- `[targetCtx]`
- `[targetX]`
- `[targetY]`

)
Boolean

Inherited from Filter but overwritten in `applyFilter:89`

Applies the filter to the specified context.

IMPORTANT NOTE: This filter currently does not support the targetCtx, or targetX/Y parameters correctly.

#### 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`

() AlphaMaskFilter

Inherited from Filter but overwritten in `clone:129`

Returns a clone of this object.

#### Returns:

AlphaMaskFilter:

### `getBounds`

() Rectangle

Inherited from Filter: `getBounds:83`

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: `initialize:75`

Initialization method.

### `toString`

() String

Inherited from Filter: `toString:109`

Returns a string representation of this object.

#### Returns:

String:

a string representation of the instance.

## Properties

### `mask`

Image

Defined in `mask:80`

The image (or canvas) to use as the mask.