import ij.IJ;
import ij.ImagePlus;
import ij.gui.ImageWindow;
import ij.plugin.PlugIn;
import ij.process.ImageProcessor;

import java.awt.Frame;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import java.nio.IntBuffer;
import javax.media.opengl.*;
import javax.media.opengl.glu.GLU;

// Note that a GLCanvas is not a window component ImageJ knows about,
// so it will not appear in the ImageJ window menu.
// Also, even though it extends Canvas, its paint and update methods can't
// be used to draw on it, or the Graphics object be used to get at pixel values

public class OpenGLExample2_ implements PlugIn, GLEventListener {

	public OpenGLExample2_() { }

	IntBuffer buffer = null;
	ImagePlus implus = null;

	public void run (String arg) {
		implus = ij.WindowManager.getCurrentImage();
		if (implus == null) {
			IJ.showMessage("No image is open.");
			return;
		}
		if (implus.getType() != ImagePlus.COLOR_RGB) {
			IJ.showMessage("This plugin works with RGB images only.");
			return;
		}

		int width = implus.getWidth();
		int height = implus.getHeight();
		buffer = IntBuffer.allocate(3 * width * height);
		ImageProcessor proc = (ImageProcessor) implus.getProcessor();

		for (int h=0; h<height; h++)
			for (int w=0; w<width; w++) {
				int pixel = proc.getPixel(w, height-h-1);
				int r = ((pixel >> 16) & 255) << 23;
				int g = ((pixel >> 8) & 255) << 23;
				int b = ((pixel & 255) << 23);
					// if these bit operations look strange, it's because I don't fully
					// understand how OpenGL stores R, G and B values in integers
				buffer.put(r);
				buffer.put(g);
				buffer.put(b);
			}

		final Frame f = new Frame("OpenGL Canvas 2");
		f.addWindowListener(new WindowAdapter() {
			public void windowClosing (WindowEvent evt) {
				f.dispose();
			}
		});
		GLCanvas canvas =  new GLCanvas();
		canvas.addGLEventListener(this);
		canvas.setSize(width, height);
		f.add(canvas);
		f.pack();
		f.setVisible(true);
	}

// The following methods implement the GLEventListener interface

	public void init (GLAutoDrawable drawable) {
		GL gl = drawable.getGL();
	}

	public void reshape (GLAutoDrawable drawable, int x, int y, int width, int height) {
		GL gl = drawable.getGL();
		gl.glViewport(0, 0, width, height);
		gl.glLoadIdentity();
	}

	public void display (GLAutoDrawable drawable) {
		buffer.rewind();
		GL gl = drawable.getGL();
		gl.glDrawPixels(implus.getWidth(), implus.getHeight(), GL.GL_RGB, GL.GL_INT, buffer);
		gl.glFinish();
		IJ.showStatus("OpenGL image copied");
	}

	public void displayChanged (GLAutoDrawable drawable, boolean modeChanged, boolean deviceChanged) { }
}