int     stageW     = 1920;
int     stageH     = 1080;
color   clrBG      = #CCCCCC;
String  pathDATA   = "../../data/";

// ********************************************************************************************************************

import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

PImage  mySourceImg;
IntList usedColors = new IntList();
int     swatchSize = 40;

// ********************************************************************************************************************

void settings() {
	size(stageW, stageH, P3D);
}

void setup() {
	background(clrBG);
	mySourceImg = loadImage(pathDATA + "source.gif"); // load in image
	mySourceImg.loadPixels(); // load in all the pixels of the image in this case, 1,166,400 pixels
	removeDuplicateColors(); // grab all the color pixels in the image and remove duplicates, build a new array
}

void draw() {
	background(clrBG);

	image(mySourceImg, 0, 0, stageW, stageH); // show image on screen

	// show swatches of ONLY unique colors
	for (int i = 0; i < usedColors.size(); ++i) {
		strokeWeight(0);
		noStroke();
		fill(usedColors.get(i));
		rect(i*swatchSize, 0, (swatchSize-1), 100);
	}
}

// ********************************************************************************************************************

void removeDuplicateColors() {
	List<Integer> colors = new ArrayList<Integer>();
	for (int i = 0; i < mySourceImg.pixels.length; ++i) colors.add(mySourceImg.pixels[i]);

	Set<Integer> colorsWithoutDuplicates = new LinkedHashSet<Integer>(colors);
	colors.clear();
	colors.addAll(colorsWithoutDuplicates);

	for (int j = 0; j < colors.size(); ++j) usedColors.append( colors.get(j) );

	println( usedColors );
}