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I'm working on a project and quiet new to java. I want to scan an image pixel by pixel for a certain color, i.e. cyan and then print the coordinates of that pixel color. The code runs, creates an output file but doesn't write anything to it. Can somebody please help me with it to find the errors. I also want to know how to read a .tiff file in java while using the same code.

Java Code:

import java.awt.Color;
import java.awt.image.BufferedImage;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import javax.imageio.ImageIO;

public class GetPixelColor {

    //int y, x, tofind, col;
    /**
     * @param args the command line arguments
     * @throws IOException  
     */
    public static void main(String args[]) throws IOException {
        try {
            //read image file
            File file1 = new File("E:\\birds.jpg");
            BufferedImage image1 = ImageIO.read(file1);

            //write file
            FileWriter fstream = new FileWriter("E:\\pixellog1.txt");
            BufferedWriter out = new BufferedWriter(fstream);

            //color object
            //Color cyan = new Color(0, 255, 255);

            //find cyan pixels
            for (int y = 0; y < image1.getHeight(); y++) {
                for (int x = 0; x < image1.getWidth(); x++) {

                  int c = image1.getRGB(x,y);
                  Color color = new Color(c);

                  //int  red = (c & 0x0000FFFF) >> 16;
                  //int  green = (c & 0x0000FFFF) >> 8;
                  //int  blue = c & 0x0000FFFF;

                   //if (cyan.equals(image1.getRGB(x, y)){

                   if (color.getRed() < 30 && color.getGreen() > 255 && color.getBlue() > 255) {
                        out.write("CyanPixel found at=" + x + "," + y);
                        out.newLine();

                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
me erum
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  • Are you sure that your image has a cyan pixel? By the way, if you're going to close the file after finding the first pixel, then you should stop looping. If you find a second pixel, you will generate an IOException because `out` will already be closed when you try to write.) – Ted Hopp Feb 05 '12 at 07:26
  • You can use [`Zoom`](http://stackoverflow.com/a/3742841/230513) to see the RGB components of any pixel on your desktop. – trashgod Feb 05 '12 at 08:57
  • You should look for colors _like cyan_ and not exactly _cyan_ – Jose Garrido Feb 05 '12 at 12:44

2 Answers2

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The problem is probably that your birds.jpg image doesn't contain a pixel that is exactly r=0, g=255, b=255 (i.e. cyan). Even if you open the image in Paint and draw a cyan pixel, the color may get slightly altered when you save because JPEG is a lossy format.

You could try testing for pixels that are close to cyan by replacing your if statement with this:

Color c = new Color(image1.getRGB());
if (c.getRed() < 30 && c.getGreen() > 225 && c.getBlue() > 225) {
Joe Daley
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  • okay i got this to work but not with >255, as colors are only 0-255. Can you please tell me the range for cyan.. from where it starts upto 255..??? – me erum Feb 06 '12 at 06:21
  • Note my answer says >225, not >255. I chose 30 as the tolerance (255-30=225) but the tolerance is up to you! There is no official range for cyan. – Joe Daley Feb 06 '12 at 09:29
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I think another problem is in your if statement. You have the image looking for something GREATER than 255. However, in java, 255 is the max value you can have for red, blue, or green. If you are looking for exactly 255, change it from color.getBlue() > 255 to color.getRed() == 255 Hope this helps!

Josh Heaps
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