I have nothing against bumping up a thread, but don't forget people sleep, eat, work... This is not a chat room, but a forum, where people are around the world.

You also have the brightness() function that should help you.

You can take, for example, the http://processing.org/learning/topics/brightness.html sketch which shows how to load the pixels of an image. Then, in the inner loop, just put:

1. int loc = x + y*img.width;
2. color c = brightness(img.pixels[loc]);
3. pixels[y*width + x] = c;

and it might work (untested).

Sorry I delete the extra messages

What is wrong with the code I point to?
Or, to adapt to what you show, use:

1. color c = brightness(pixels[i]);
2. pixels[i] = c;

Just put the two lines I give in place of your pixels[i] = pink; line.

Just replace
  pixels[i] = color(c);
with
  pixels[i] = color(255, c, c);