Halftone hydra filter
From Adobe Labs
[edit]
Source
// Filter by Justin Everett-Church
// http://justin.everett-church.com
// October 2007
kernel halftone
{
parameter int radius
< minValue:int(0);
maxValue:int(50);
defaultValue:int(4); >;
parameter int offset
< minValue:int(0);
maxValue:int(10);
defaultValue:int(2); >;
const pixel4 blank = pixel4(0,0,0,0);
void evaluatePixel(in image4 src, out pixel4 outputPixel)
{
int fullOffset = offset*radius;
//what color should go out?
float2 gridWidth = float2((radius)*2 +offset);
float2 sampledPixelLocation = floor(float2(outCoord().x,outCoord().y+float(offset)) / gridWidth) * gridWidth;
pixel4 sampledPixel = sampleNearest(src, sampledPixelLocation);
//find center
float2 centerPixel = floor(outCoord() / gridWidth) * gridWidth + (gridWidth/2.0);
centerPixel.y-=float(offset)*.5;
//how far from center?
float dist = distance(centerPixel, outCoord());
//halftoning
pixel4 white = pixel4(1,1,1,1);
float radius2 = float(radius)*(sampledPixel.r+sampledPixel.g+sampledPixel.b+sampledPixel.a)/4.0;
white.a =1.0-(dist-radius2);
outputPixel = white;
}
}
