ColorMatrixFilter documentation ?

[bali33]

Hi guys,

 

I can't find any documentation about the ColorMatrixFilter - It's a 4x4 Matrix but what represent each value inside it ?

 

Thank you

[pongstylin]

I've stared at that thing for a long time.  It's similar to the flash documentation on their 4x5 matrix.  But it's missing the 5th column (offset), which is a source of frustration for me.

http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/filters/ColorMatrixFilter.html

 

Every pixel's color and alpha values are multiplied in the matrix.  The following matrix produces no change in the pixel.

  R G B AR 1 0 0 0G 0 1 0 0B 0 0 1 0A 0 0 0 1 

So let's say I have a pixel with the following color: 0x010203 and alpha of 1 and pass it through a matrix like this:

2.0  0.0  1.0  00.0  0.5  0.0  00.0  0.0  0.0  00.0  0.0  0.0  1

The pixel's new value will be calculated as follows:

R = 2*1 + 0*2 + 1*3 + 0*1;

G = 0*1 + 0.5*2 + 0*3 + 0*1;

B = 0*1 + 0*2 + 0*3 + 0*1;

A = 0*1 + 0*2 + 0*3 + 1*1;

 

Which is 0x050100 with an alpha of 1.  Essentially, we removed all the blue and doubled the red and added even more redness where there used to be blue.  The green was reduced by half.

 

Common use cases include brightening/darkening an image (multiply all colors by an equal amount above/below 1) and grayscale an image (multiply all colors together).

 

And if that is still confusing I defer to a random article I found:

http://code.tutsplus.com/tutorials/manipulate-visual-effects-with-the-colormatrixfilter-and-convolutionfilter--active-3221

[bali33]

That all make sense now, thank you !