ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Filtering display objects
Color matrix filter
Flash Player 9 and later, Adobe AIR 1.0 and later
The ColorMatrixFilter class is used to manipulate the color and alpha values of the filtered object. This allows you to
create saturation changes, hue rotation (shifting a palette from one range of colors to another), luminance-to-alpha
changes, and other color manipulation effects using values from one color channel and potentially applying them to
other channels.
Conceptually, the filter goes through the pixels in the source image one by one and separates each pixel into its red,
green, blue, and alpha components. It then multiplies values provided in the color matrix by each of these values,
adding the results together to determine the resulting color value that will be displayed on the screen for that pixel. The
matrix property of the filter is an array of 20 numbers that are used in calculating the final color. For details of the
specific algorithm used to calculate the color values, see the entry describing the ColorMatrixFilter class’s matrix
property in the ActionScript 3.0 Reference for the Adobe Flash Platform.
Convolution filter
Flash Player 9 and later, Adobe AIR 1.0 and later
The ConvolutionFilter class can be used to apply a wide range of imaging transformations to BitmapData objects or
display objects, such as blurring, edge detection, sharpening, embossing, and beveling.
The convolution filter conceptually goes through each pixel in the source image one by one and determines the final
color of that pixel using the value of the pixel and its surrounding pixels. A matrix, specified as an array of numeric
values, indicates to what degree the value of each particular neighboring pixel affects the final resulting value.
Consider the most commonly used type of matrix, which is a three by three matrix. The matrix includes nine values:
N N N
N P N
N N N
When the convolution filter is applied to a certain pixel, it will look at the color value of the pixel itself (“P” in the
example), as well as the values of the surrounding pixels (labeled “N” in the example). However, by setting values in
the matrix, you specify how much priority certain pixels have in affecting the resulting image.
For example, the following matrix, applied using a convolution filter, will leave an image exactly as it was:
0 0 0
0 1 0
0 0 0
The reason the image is unchanged is because the original pixel’s value has a relative strength of 1 in determining the
final pixel color, while the surrounding pixels’ values have relative strength of 0—meaning their colors don’t affect the
final image.
Similarly, this matrix will cause the pixels of an image to shift one pixel to the left:
0 0 0
0 0 1
0 0 0
Notice that in this case, the pixel itself has no effect on the final value of the pixel displayed in that location on the final
image—only the value of the pixel to the right is used to determine the pixel’s resulting value.
Last updated 6/6/2012
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