Processing: Creative Coding and Computational Art

the book that a primitive type is directly assigned a specific value (e.g., int i = 1;), but a
reference type is internally assigned an address in the computer’s memory where the
object is stored. Thus, the syntax array1 = array2 makes the two array variables point to
the same place in the computer’s memory (where the array is stored)—generally not what
you want to do. This is a fairly advanced topic, but something you do need to be aware of.
I cover variables in detail in Chapter 3.
There are a lot of other interesting things you can do using bitwise operations. Here’s a
sketch, shown in Figure 10-32, that changes the contrast of an image (I used a 400 ✕ 400
pixel image for the example).
/* Contrast (using bitwise operations)
created January 18, 2006
updated December 4, 2006 */
size(800, 400);
PImage img = loadImage("harbor.jpg");
PImage img2 = createImage(img.width, img.height, RGB);
arraycopy(img.pixels, img2.pixels);
float threshold = 127.5;
float contrast = .5; // pos or neg values
loadPixels();
for(int i=0; i> 16 & 0xFF;
int g = img2.pixels[i] >> 8 & 0xFF;
int b = img2.pixels[i] & 0xFF;
int a = img2.pixels[i] >> 24 & 0xFF;
// red
r = int(r*(1.0 + (contrast)*((r-threshold)*.01)));
r = constrain(r, 0, 255);
// green
g = int(g*(1.0 + (contrast)*((g-threshold)*.01)));
g = constrain(g, 0, 255);
// blue
b = int(b*(1.0 + (contrast)*((b-threshold))*.01));
b = constrain(b, 0, 255);
// combine components back into a 32-bit integer
img2.pixels[i] = (a