Image Thinning using JAVA

[sumera]

Hi!
I have written some code in java to convert a colored image into black and white image and then tried to perform thinning on that gray-scale image. Black and white conversion is done successfully, but image thinning is still not giving correct output. Kindly help me in fixing my problem. My code is as follows:

//colored image to black and white conversion; black and white image to thinned image.

public static void main(String[] args)
{
try
{
//colored image path
BufferedImage colored_image = ImageIO.read(new File("D:\\logo.jpg"));
//getting width and height of image
double image_width = colored_image.getWidth();
double image_height = colored_image.getHeight();
BufferedImage img = colored_image;

//drawing a new image
BufferedImage bimg = new BufferedImage((int)image_width, (int)image_height, BufferedImage.TYPE_BYTE_GRAY);
Graphics2D gg = bimg.createGraphics();
gg.drawImage(img, 0, 0, img.getWidth(null), img.getHeight(null), null);

//saving black and white image onto drive
String temp = "logo in blackAndwhite.jpeg";
File fi = new File("D:\\" + temp);
ImageIO.write(bimg, "jpg", fi);

//thinning by resizing gray scale image to desired eight and width
BufferedImage bimg2 = new BufferedImage((int)image_width, (int)image_height, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2 = bimg2.createGraphics();

// Perform your drawing here
g2.setColor(Color.BLACK);
g2.drawLine(0, 0, 200, 200);

//saving thinned image onto drive
String temp2 = "logo thinned.jpeg";
File fi2 = new File("D:\\" + temp2);
ImageIO.write(bimg2, "jpg", fi2);
//g2.dispose();
}
catch (Exception e)
{
System.out.println(e);
}
}

[markspace]

On 6/26/2012 9:50 AM, sumera wrote:
> Hi! I have written some code in java to convert a colored image into
> black and white image and then tried to perform thinning on that
> gray-scale image. Black and white conversion is done successfully,
> but image thinning is still not giving correct output.

What would you consider correct output, if the conversion is successful?

[John B. Matthews]

In article <csqdnUsK6PaldXTS...@giganews.com>,

sumera <kanwal...@yahoo.com> wrote:

> I have written some code in java to convert a colored image into
> black and white image and then tried to perform thinning on that
> gray-scale image. Black and white conversion is done successfully,
> but image thinning is still not giving correct output. Kindly help me
> in fixing my problem. My code is as follows:

AffineTransformOp works well for scaling an image, as it allows control
over the interpolation type. There's an example here:

<https://sites.google.com/site/trashgod/scaled>

--
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>

[Knute Johnson]

On 6/26/2012 9:50 AM, sumera wrote:

public static BufferedImage convertToGray(BufferedImage image) {
BufferedImage gray = new BufferedImage(image.getWidth(),
image.getHeight(),BufferedImage.TYPE_BYTE_GRAY);
ColorConvertOp op = new ColorConvertOp(
image.getColorModel().getColorSpace(),
gray.getColorModel().getColorSpace(),null);
op.filter(image,gray);
return gray;
}

You can use the same technique as above with an AffineTransformOp, as
John Matthews mentioned, to scale an image.

--

Knute Johnson

[John B. Matthews]

In article <jsd9em$hur$1...@dont-email.me>,

Knute Johnson <nos...@knutejohnson.com> wrote:

> public static BufferedImage convertToGray(BufferedImage image) {
> BufferedImage gray = new BufferedImage(image.getWidth(),
> image.getHeight(), BufferedImage.TYPE_BYTE_GRAY);
> ColorConvertOp op = new ColorConvertOp(
> image.getColorModel().getColorSpace(),
> gray.getColorModel().getColorSpace(), null);
> op.filter(image, gray);
> return gray;
> }

Thanks for weighing in on this. Your approach has always worked
flawlessly on JPG images, but I had trouble with a PNG file: the result
was unusually dark, and a subsequent call to gray.getGrapics() failed.
I'd welcome any insight you can offer.

> You can use the same technique as above with an AffineTransformOp, as
> John Matthews mentioned, to scale an image.

I had good results with AffineTransformOp.TYPE_NEAREST_NEIGHBOR for
down sampling:

<https://sites.google.com/site/trashgod/scaled>

As recently suggested by BGB:

<https://groups.google.com/d/msg/comp.lang.java.programmer/zH_xK85o2mA/V--P6ruObwUJ>

[Knute Johnson]

You got me interested on that one. I made a really simple test program
because of time constraints.

What I found was that if you just did a ColorConvertOP to a PNG or a
JPEG image, the image was in fact fairly dark. But if you then convert
that image to a compatible image it looks really good in gray scale.

Here's the simple code.

package com.knutejohnson.test;

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.io.*;
import javax.imageio.*;
import javax.swing.*;

import com.knutejohnson.classes.ImageUtilities;

public class PNGtoGray extends JPanel implements ActionListener {
private BufferedImage bi;

public PNGtoGray(BufferedImage bi) {
this.bi = bi;

setPreferredSize(new Dimension(bi.getWidth(),bi.getHeight()));
}

public void actionPerformed(ActionEvent ae) {
bi = ImageUtilities.convertToGray(bi);
bi = ImageUtilities.convertToCompatible(bi);
repaint();
}

public void paintComponent(Graphics g) {
g.drawImage(bi,0,0,null);
}

public static void main(final String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
BufferedImage bi = ImageIO.read(new File(args[0]));
JFrame f = new JFrame("PNGtoGray");
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
PNGtoGray ptg = new PNGtoGray(bi);
f.add(ptg,BorderLayout.CENTER);
JButton b = new JButton("Conver to Gray");
b.addActionListener(ptg);
f.add(b,BorderLayout.SOUTH);
f.pack();
f.setVisible(true);
} catch (IOException ioe) {
System.out.println(ioe);
}
}
});
}
}

package com.knutejohnson.classes;

import java.awt.*;
import java.awt.geom.*;
import java.awt.image.*;
import java.io.*;
import java.util.*;
import javax.imageio.*;
import javax.imageio.stream.*;
import javax.imageio.plugins.jpeg.*;

public class ImageUtilities {
public static void writeJPEG(RenderedImage image, float quality,
File file)
throws IOException {
if (quality < 0.0f || quality > 1.0f)
throw new IllegalArgumentException("0.0 < Quality < 1.0");
ImageWriter writer = null;
Iterator iter = ImageIO.getImageWritersByFormatName("JPEG");
if (!iter.hasNext())
throw new IOException("No Writers Available");
writer = (ImageWriter)iter.next();
if (file.exists())
file.delete();
ImageOutputStream ios = ImageIO.createImageOutputStream(file);
writer.setOutput(ios);
JPEGImageWriteParam iwp = new JPEGImageWriteParam(null);
iwp.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
iwp.setCompressionQuality(quality);
writer.write(null,new IIOImage(image,null,null),iwp);
ios.flush();
writer.dispose();
ios.close();

}

public static BufferedImage convertToGray(BufferedImage image) {
BufferedImage gray = new BufferedImage(image.getWidth(),
image.getHeight(),BufferedImage.TYPE_BYTE_GRAY);
ColorConvertOp op = new ColorConvertOp(
image.getColorModel().getColorSpace(),
gray.getColorModel().getColorSpace(),null);
op.filter(image,gray);
return gray;
}

public static BufferedImage scaleImage(BufferedImage src, double sx,
double sy, int interpolationType) {
AffineTransformOp op = new AffineTransformOp(
AffineTransform.getScaleInstance(sx,sy),interpolationType);
return op.filter(src,null);
}

public static BufferedImage scaleImage(BufferedImage src, double sx,
double sy, RenderingHints hints) {
AffineTransformOp op = new AffineTransformOp(
AffineTransform.getScaleInstance(sx,sy),hints);
return op.filter(src,null);
}

public static BufferedImage convertToCompatible(BufferedImage image) {
GraphicsEnvironment ge =
GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice gd = ge.getDefaultScreenDevice();
GraphicsConfiguration gc = gd.getDefaultConfiguration();

BufferedImage compatible =
gc.createCompatibleImage(image.getWidth(),
image.getHeight());

if (compatible.getType() == image.getType())
return image;

ColorConvertOp op = new ColorConvertOp(
image.getColorModel().getColorSpace(),

compatible.getColorModel().getColorSpace(),null);

return op.filter(image,compatible);
}
}


--

Knute Johnson

[Roedy Green]

On Tue, 26 Jun 2012 11:50:00 -0500, sumera <kanwal...@yahoo.com>
wrote, quoted or indirectly quoted someone who said :

>Hi!
>I have written some code in java to convert a colored image into
black and white image and then tried to perform thinning on that
gray-scale image. Black and white conversion is done successfully, but
image thinning is still not giving correct output. Kindly help me in
fixing my problem. My code is as follows:

How do you define thinning? Shrinking the image by deleting every
second pixel? Trying to make a JPG smaller?

--
Roedy Green Canadian Mind Products
http://mindprod.com
When you get stuck trying to solve a computer program:
1. Go into the kitchen and make coffee.
2. If that fails, go for a walk.
3. If that fails, take a nap.
Why? To avoid being swamped with details, to see the big picture,
to allow in some random noise to kick you out of your thinking rut.

[John B. Matthews]

In article <jse48p$pku$1...@dont-email.me>,

Knute Johnson <nos...@knutejohnson.com> wrote:

> What I found was that if you just did a ColorConvertOP to a PNG or a
> JPEG image, the image was in fact fairly dark. But if you then convert
> that image to a compatible image it looks really good in gray scale.

Having a compatible image was the key; thank you.