Core Image Conundrum

cybero's picture

I wonder why this Core Image kernel code isn't working for me. It was found on the fromaremotevillage blog.

A Core Image kernel routine that computes a convolution effect.
The code looks up the source pixel in the sampler and then multiplies it by the value passed to the routine.
kernel vec4 Convolution3by3(sampler image,
float r00, float r01, float r02,
float r10, float r11, float r12,
float r20, float r21, float r22)
  vec2 loc;
  vec4 result = vec4(0,0,0,0);
  //0,0 in my mind is left and up.
  loc = vec2(1.0,0.0);
  vec4 p12 = unpremultiply(sample(image, (samplerCoord(image) + loc) ));
  result.rgb += p12.rgb * r12;
  loc = vec2(-1.0,-1.0);
  vec4 p20 = unpremultiply(sample(image, (samplerCoord(image) + loc) ));
  result.rgb += p20.rgb * r20;
  loc = vec2(0.0,-1.0);
  vec4 p21 = unpremultiply(sample(image, (samplerCoord(image) + loc) ));
  result.rgb += p21.rgb * r21;
  loc = vec2(1.0,-1.0);
  vec4 p22 = unpremultiply(sample(image, (samplerCoord(image) + loc) ));
  result.rgb += p22.rgb * r22;
  result = premultiply( result );
  return result;

Currently produces nothing more than blank empty space when run in QC 4.5 on Lion. Haven't tried it in Snow or earlier as yet.

CoreImageConundrumConvolution3by3.qtz35.26 KB

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gtoledo3's picture
Re: Core Image Conundrum

Try twiddling:

vec4 result = vec4(0,0,0,0);


vec4 result = vec4(0,0,0,1);

cybero's picture
Re: Core Image Conundrum

Cheers, gtoledo.

That, in all probability, is it, will give that a try shortly.

That 4 lane channel escaped my increasingly tired attention.

Just tried it and it works beautifully.