Processing: Creative Coding and Computational Art

separate out and invert component color values
float r = abs(red(pixels[i])-invertFactor);
float g = abs(green(pixels[i])-invertFactor);
float b = abs(blue(pixels[i])-invertFactor);
// put pixel back together
pixels[i] = color(r, g, b);
// each row interval decrements invertFactor
if (i>0 && i% width==0){
invertFactor-=(255.0/height);
}
}
updatePixels();
Figure 10-37. From Neg to Pos sketch
Besides showcasing a custom invert filter, this last sketch demonstrated another example
of the usefulness of the modulus operator:
if (i>0 && i% width==0){
By dividing i by the display window width and checking for a 0 remainder, I ensured that
the variable invertFactor would only be decremented per each row of pixels, giving me
a smooth gradation down the image.
COLOR AND IMAGING
455
10