Image Histogram ImageJ Plugin

[Sunshineserene]

Hi all, I am having some problem writing an ImageJ plugin for display image histogram.

import ij.ImagePlus;
import ij.plugin.filter.PlugInFilter;
import ij.process.ByteProcessor;
import ij.process.ImageProcessor;

public class Create_New_Image implements PlugInFilter {
	String title = null;

	public int setup(String arg, ImagePlus im) {
		title = im.getTitle();
		return DOES_8G + NO_CHANGES;
	}

	public void run(ImageProcessor ip) {
		int[] hist = ip.getHistogram();
                int w = 256; 
		int h = ???; 
		
		
		ImageProcessor histIp = new ByteProcessor(w, h);
		histIp.setValue(255);	// white = 255
		histIp.fill();

		for (int v = 0; v < h; v++) {
			for (int u = 0; u < w; u++) {
				ip.getPixel(u, v);
				histIp.putPixel(u, v, 0);

			}
		}
		
		// display histogram:
		String hTitle = "Histogram of " + title;
		ImagePlus histIm = new ImagePlus(hTitle, histIp);
		histIm.show();
		// histIm.updateAndDraw();
	}
}

I don't know how to get the height of the histogram. I know it's actually the largest frequency in the histogram, but I don't know how to get it and equate to my variable h (line 17). And I'm not sure if line 24-27 is correct for drawing the histogram values as black bars.