User Guide

506 ActionScript classes

To apply filters to movie clips at runtime, use the filters property. Setting the filters

property of an object does not modify the object and can be undone by clearing the

filters

property.

To a p ply fil te r s t o Bi tm a pData instances, use the

BitmapData.applyFilter() method.

Calling

applyFilter() on a BitmapData object modifies that BitmapData object and

cannot be undone.

You can also apply filter effects to images and video at authoring time. For more information,

see your authoring documentation.

If you apply a filter to a movie clip or button, the

cacheAsBitmap property of the movie clip

or button is set to

true. If you clear all filters, the original value of cacheAsBitmap is

restored.

The filter uses the following formula:

dstPixel[x, y] = srcPixel[x + ((componentX(x, y) - 128) * scaleX) / 256, y +

((componentY(x, y) - 128) * scaleY) / 256]

where componentX(x, y) gets the componentX color value from the mapBitmap property at

(x - mapPoint.x ,y - mapPoint.y).

The map image used by the filter is scaled to match the Stage scaling. It is not scaled in any

way when the object itself is scaled.

This filter supports Stage scaling, but not general scaling, rotation, or skewing. If the object

itself is scaled (if x-scale and y-scale are not 100%), the filter effect is not scaled. It is scaled

only when the Stage is zoomed in.

Here is how the DisplacementMapFilter class works. For each pixel (x,y) in the destination

bitmap, the DisplacementMapFilter class does the following:

■ Gets the color from (x,y) in the map bitmap

■ Calculates an offset based on that color

■ Looks up that offset location (x+dx,y+dy) in the source bitmap

■ Writes that pixel to the destination(x,y), if boundary conditions permit

A filter is not applied if the resulting image would exceed 2880 pixels in width or height. For

example, if you zoom in on a large movie clip with a filter applied, the filter is turned off if the

resulting image reaches the 2880-pixel limit.

Availability: ActionScript 1.0; Flash Player 8