This example is for Processing 2+. If you have a previous version, use the examples included with your software. If you see any errors or have suggestions, please let us know.

Noise2D by Daniel Shiffman.

Using 2D noise to create simple texture.

 
float increment = 0.02;

void setup() {
  size(640, 360);
}

void draw() {
  
  loadPixels();

  float xoff = 0.0; // Start xoff at 0
  float detail = map(mouseX, 0, width, 0.1, 0.6);
  noiseDetail(8, detail);
  
  // For every x,y coordinate in a 2D space, calculate a noise value and produce a brightness value
  for (int x = 0; x < width; x++) {
    xoff += increment;   // Increment xoff 
    float yoff = 0.0;   // For every xoff, start yoff at 0
    for (int y = 0; y < height; y++) {
      yoff += increment; // Increment yoff
      
      // Calculate noise and scale by 255
      float bright = noise(xoff, yoff) * 255;

      // Try using this line instead
      //float bright = random(0,255);
      
      // Set each pixel onscreen to a grayscale value
      pixels[x+y*width] = color(bright);
    }
  }
  
  updatePixels();
}