Chromatic Aberration with blueScaler and yellowDecrease

ChromaticAberration.pde

#define PROCESSING_TEXTURE_SHADER
uniform sampler2D texture;
varying vec4 vertTexCoord;

//downscale the blue channel to correct 
//for chromatic aberration of fish eye lens
const float blueScaler = 1 - (1 / 600.); 

void main() {
  //also decrease the amount of yellow towards outside
  const float yellowDecrease = .3 * length(vertTexCoord.st-.5);

  gl_FragColor.rg = texture2D(texture, vertTexCoord.st).rg - yellowDecrease;
  gl_FragColor.b = texture2D(texture, ((vertTexCoord.st-.5)*blueScaler)+.5).b;
}