Processing: Creative Coding and Computational Art

PROCESSING: CREATIVE CODING AND COMPUTATIONAL ART
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The pixels[] array stores each pixel as Processing’s color data type, structured in consecutive
rows. For example, if the sketch size is 100 ✕ 100, then the 5,050th pixel
(pixels[5049]) will be close to the center point in the display window. Here’s an example
that directly changes the color of that pixel:
size(100, 100);
background(0);
loadPixels();
pixels[5050] = color(255);
updatePixels();
The Processing reference includes a very simple mathematical expression to help you target
a pixel in the pixels[] array of the display window: pixels[y*width+x]. Based on this
expression, the last little sketch (shown in Figure 10-20) could be rewritten as follows:
size(100, 100);
background(0);
loadPixels();
pixels[height/2*width+width/2] = color(255);
updatePixels();
Figure 10-20. Pixels array (single white pixel) sketch
To change more than 1 pixel, a loop will help. The next example divides the display window
in horizontal bands, assigning a different color to each band (see Figure 10-21):
// Color Banding with pixels[]
size(400, 400);
loadPixels();
int px = pixels.length;
int bands = 20; // should be a factor of px
color c;