// Dartmouth CS 2, Winter 2009, Chris Bailey-Kellogg
// Notes 18 | Sketch 6
// Based on Greenberg 10-41

size(800,600);
PImage baker = loadImage("baker.jpg");

loadPixels();
float invert = 0;  // subtract pixel value from this, which varies from top to bottom
for (int y=0; y<height; y++) {
  for (int x=0; x<width; x++) {
    color p=baker.pixels[x+y*baker.width];
    float r=red(p), g=green(p), b=blue(p);
    pixels[x+y*width] = color(abs(invert-r), abs(invert-g), abs(invert-b));
  }
  invert += 255.0/height;
}
updatePixels();