Hi,
I have loaded an image, but before doing anyother processing I want to greyscale it. I have read the api but can't find a clear example:
File file =new File(fLoci);
loadImage = ImageIO.read(file);
greyscale loadImage?
I know you can use BufferedImage.TYPE_BYTE_GRAY for a bufferedimage, I am just not sure how to apply it in this situation.
Many thanks, Ron
Message was edited by:
cake
Here's a small, simple method I found online.
public static BufferedImage convertToGrayscale(BufferedImage source) {
BufferedImageOp op = new ColorConvertOp(
ColorSpace.getInstance(ColorSpace.CS_GRAY), null);
return op.filter(source, null);
}
Here's the link.
http://www.jguru.com/faq/view.jsp?EID=221919
Here's two ways. I don't know why they produce different results.
import java.awt.*;
import java.awt.color.*;
import java.awt.image.*;
import java.io.*;
import java.net.*;
import javax.imageio.*;
import javax.swing.*;
public class BWExample implements Runnable {
public void run() {
BufferedImage im1 = getImage();
JPanel p = new JPanel();
p.add(new JLabel(new ImageIcon(im1)));
p.add(new JLabel(new ImageIcon(toBW1(im1))));
p.add(new JLabel(new ImageIcon(toBW2(im1))));
JFrame f = new JFrame("BWExample");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setContentPane(p);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
BufferedImage getImage() {
try {
URL url = new URL("http://blogs.sun.com/jag/resource/JagHeadshot-small.jpg");
return ImageIO.read(url);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
BufferedImage toBW1(BufferedImage im) {
int w = im.getWidth();
int h = im.getHeight();
BufferedImage result = new BufferedImage(w, h, BufferedImage.TYPE_BYTE_GRAY);
Graphics2D g = result.createGraphics();
g.drawRenderedImage(im, null);
g.dispose();
return result;
}
BufferedImage toBW2(BufferedImage im) {
ColorSpace cs = ColorSpace.getInstance(ColorSpace.CS_GRAY);
return new ColorConvertOp(cs, null).filter(im, null);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new BWExample());
}
}
Hi,
I tried thi:
int w = im.getWidth();
int h = im.getHeight();
BufferedImage result = new BufferedImage(w, h, BufferedImage.TYPE_BYTE_GRAY);
and i ended up with a black image?!
i'll try the other, i wonder if it was the downsample that was doing it!
Thanks, Ron
Hi, yes I did, and I still ended up with a black image.
entryImage = new BufferedImage(w, h, BufferedImage.TYPE_BYTE_GRAY);
Graphics2D g = entryImage.createGraphics();
g.drawRenderedImage(entryImage, null);
g.dispose();
The convertToGrayscale function works though.
I will try with img2 now.
One other question, what is the accepted cutoff point for 'white' background. So if a pixel is ? int value it is considered white, and > than that and you would say it is black, this is obviously thinking in monochrome now?
Thanks, Ron
Message was edited by:
cake
Your code:
entryImage = new BufferedImage(w, h, BufferedImage.TYPE_BYTE_GRAY);
Graphics2D g = entryImage.createGraphics();
g.drawRenderedImage(entryImage, null);
g.dispose();
My code:
BufferedImage result = new BufferedImage(w, h, BufferedImage.TYPE_BYTE_GRAY);
Graphics2D g = result.createGraphics();
g.drawRenderedImage(im, null);
g.dispose();
Do you see your mistake? I am rendering the original im onto result.
You are rendering the new entryImage onto entryImage -- black on black!
> One other question, what is the accepted cutoff point for 'white' background.
That sounds like a judgment call to me.
