Histogram

/**
 * Histogram Viewer derived from the "Histogram" built-in example sketch.
 *
 * Calculates the histogram based on the image from the camera feed.
 */

import gohai.glvideo.*;
GLCapture video;

void setup() {
  size(640, 480, P2D);

  String[] devices = GLCapture.list();
  println("Devices:");
  printArray(devices);

  // Use camera resolution of 640x480 pixels at 24 frames per second
  video = new GLCapture(this, devices[0], 640, 480, 24);
  video.start();
}

void draw() {
  background(0);
  if (video.available()) {
    video.read();
  }

  image(video, 0, 0);
  int[] hist = new int[256];

  // Calculate the histogram
  for (int i = 0; i < video.width; i++) {
    for (int j = 0; j < video.height; j++) {
      int bright = int(brightness(get(i, j)));
      hist[bright]++;
    }
  }

  // Find the largest value in the histogram
  int histMax = max(hist);

  stroke(255);
  // Draw half of the histogram (skip every second value)
  for (int i = 0; i < video.width; i += 2) {
    // Map i (from 0..img.width) to a location in the histogram (0..255)
    int which = int(map(i, 0, video.width, 0, 255));
    // Convert the histogram value to a location between
    // the bottom and the top of the picture
    int y = int(map(hist[which], 0, histMax, video.height, 0));
    line(i, video.height, i, y);
  }
}