import ij.*;
import ij.process.*;
import ij.plugin.filter.*;

/** This plugin counts the number of unique colors in an RGB image. It does not do anything else. This is merely Wayne Rasband's  Color Counter https://imagej.nih.gov/ij/plugins/color-counter.html plugin with the output of color values stripped out so that it is 2-3 times faster
Peter J. Lee 5/31/2016 */
public class Color_Count_Only implements PlugInFilter {
	ImagePlus imp;
	int colors;
	static final int MAX_COLORS = 16777216;
	int[] counts = new int[MAX_COLORS];
	int slice;

	public int setup(String arg, ImagePlus imp) {
		this.imp = imp;
		return DOES_RGB+NO_UNDO+NO_CHANGES+DOES_STACKS;
	}

	public void run(ImageProcessor ip) {
		int[] pixels = (int[])ip.getPixels();
		for (int i=0; i<pixels.length; i++)
			counts[pixels[i]&0xffffff]++;
		if (++slice==imp.getStackSize()) {
			for (int i=0; i<MAX_COLORS; i++) {
				if (counts[i]>0) colors++;
			}
			IJ.log("Unique colors: "+colors);
		}
	}
}