Bad thing about open source – everyone sees your mistakes.
Good thing about open source – nice folks correct them for you.

I just pinched the colourSample code, but it looks like it only samples the top line rather than the whole picture because the step size is 1 pixel. I’ve changed mine to:

void sampleColour() {
PImage img = loadImage(”data/bottles.jpg”);
image(img,0,0);
int count = 0;
int stepX = img.width / floor(sqrt(numcols));
int stepY = img.height / floor(sqrt(numcols));
for (int x=0; x < img.width; x+=stepX){
for (int y=0; y < img.height; y+=stepY) {
if (count < numcols) {
color c = get(x,y);
colArr[count] = c;
}
count++;
}
}
}