why do my white and black pixels come out red and grey?

[Ralph Cook]

I have the following program; it is meant to read a JPG file, create a buffered image of that file, compare each pixel to a cutoff value, and write either a black or white pixel in its place depending on whether it is above or below the cutoff.

It mostly works, except that the pixels it ends up writing appear to be either red or grey.

Clearly there's something about the pixel format I don't understand here. I'd appreciate it if someone could help me figure out what it is.

I am on a Windows system, using msPaint and Windows Picture and Fax Viewer to edit and look at the completed JPGs. I don't *think* those are affecting what I see, but then I don't understand what is happening, either.

package example;

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Scanner;

import javax.imageio.ImageIO;

public class Cleanup
{
	public static void say(String msg) { System.out.println(msg); }
	
	public static void main(String[] args)
	{
	  System.out.println("CLEANUP: input file, then output ");
	  
	  Scanner scanner = new Scanner(System.in);

		String inputFilename = scanner.nextLine();
		String outputFilename = scanner.nextLine();
		scanner.close();
		
		new Cleanup().go(inputFilename, outputFilename);
	}
	public void go(String sourceFilename, String destinationFilename)
	{
		// create a buffered image copy of our input file
	  BufferedImage sourceImage = loadImage(sourceFilename);
	  BufferedImage destImage = new BufferedImage(sourceImage.getWidth(), sourceImage.getHeight(), BufferedImage.TYPE_INT_ARGB);
	  Graphics2D graphics = destImage.createGraphics();
	  graphics.setComposite(AlphaComposite.Src);
	  graphics.drawImage(sourceImage, null, 0, 0);
	  graphics.dispose();
	  
	  // for every pixel in this file, if the rgb value is less than the cutoff,
	  // write out the value for black, otherwise write out the value for white.
	  // the intent is to leave us with nothing but black and white pixels.
	  int cutoff = 0x800000;
	  say("cutoff " + cutoff);
	  for(int i=0; i<destImage.getHeight(); i++)
	  {
	  	for (int j=0; j><destImage.getWidth(); j++)
	  	{
	  		int colorValue = destImage.getRGB(j, i);
	  		// remove the alpha value from the color value.
	  		colorValue = colorValue & 0xffffff;
	  		if (colorValue >< cutoff)
	  				 { colorValue = Color.black.getRGB(); }
	  		else { colorValue = Color.white.getRGB(); }
	  		destImage.setRGB(j, i, colorValue);
	  	}
	  }
		saveImage(destImage, destinationFilename);
	}
	
	public BufferedImage loadImage(String filename)
	{
		BufferedImage image = null;
		try
		{
			image = ImageIO.read(new File(filename));
		}
		catch (Exception e)
		{
			e.printStackTrace();
		}
		return image;
	}
	
	private void saveImage(BufferedImage img, String ref)
	{
		try
		{
			String format = (ref.endsWith(".png")) ? "png" : "jpg";
			ImageIO.write(img,  format, new File(ref));
		}
		catch (IOException e) { e.printStackTrace(); }
	}
}

[Tina Smith]

After replacing the >< comparisons with <, I ran it and it output a black and white image...when I saved as a PNG. Saving as a JPEG on the other hand...well let's just say that pink and turquoise aren't my favorite colors. It's a transparency problem; it can be fixed by changing this:

BufferedImage destImage = new BufferedImage(sourceImage.getWidth(), sourceImage.getHeight(), BufferedImage.TYPE_INT_ARGB); 

to this:

BufferedImage destImage = new BufferedImage(sourceImage.getWidth(), sourceImage.getHeight(), BufferedImage.TYPE_INT_RGB); 

Yes, that's a one-character change (not including the changes to get it to compile).

[Campbell Ritchie]

Tina Smith wrote:After replacing the >< comparisons with < . . .

There is a fault in the software changing < to >< inside code tags. I don’t know what it is.

[Tina Smith]

Didn't realize that, sorry.

[Ralph Cook]

Thanks for the help -- this simple fix solved my immediate problem.

I wish I could find a mid-level tutorial on dealing with graphics at this level; it would be nice to know what the "transparency" issue actually was, instead of just removing the letter to bypass it. If someone can point me to such a beast, I'd appreciate it.

rc