The createImage() function provides a fresh buffer of pixels to play with. This example creates an image gradient.
Original Processing.org Example: CreateImage
// All Examples Written by Casey Reas and Ben Fry
// unless otherwise stated.
PImage img;
void setup()
{
size(200, 200);
img = createImage(120, 120, RGB);
for(int i=0; i < img.pixels.length; i++) {
img.pixels[i] = color(0, 90, 102, i%img.width * 2);
}
}
void draw()
{
background(204);
image(img, 33, 33);
image(img, mouseX-60, mouseY-60);
}