Gradient Map Filter - Pixel Bender for AS3

Question

i need some help to create a filter in Pixel Bender for AS3 to make this effect in the right side in this image:

http://a.imageshack.us/img829/1488/gradientmap.jpg

Can you help me?

Thank you.

Answer 1

A little late, but this seems to do the trick:

<languageVersion : 1.0;>

kernel Darken
<   namespace : "omino";
    vendor : "omino";
    version : 1;
    description : "darken the right part of an image";
>
{
    input image4 src;
    output pixel4 dst;

    parameter float leftEdgeOfEffect <minValue: 0.0 ; maxValue: 2000.0; defaultValue: 200.0;>;
    parameter float darkness <minValue: 0.0 ; maxValue: 1.0; defaultValue: 0.75;>;

    void
    evaluatePixel()
    {
        float2 co = outCoord();
        pixel4 p = sampleNearest(src,co);
        if(co.x >= leftEdgeOfEffect)
            p.rgb = p.rgb * (1.0 - darkness);
        dst = p;
    }
}

The actual pixel manipulation happens here: p.rgb = p.rgb * (1.0 - darkness);

It's just darkening the R, G, and B. You could get trickier here for more interesting effects.

Answer 2

Is there any reason it needs to be done in Pixel Bender? You could probably get the same effect by covering half of the image with a black rectangle set to about 80% opacity. If you need any additional tweaking of the effect, applying a blend mode to the fill would probably work.