Java Loop through pixels in an image?

Question

I\'m trying to find a way to make maps for my 2D java game, and I thought of one Idea in which I would loop through each pixel of an image and depends on what color the pixe

Answer 1

I think Pixelgrabber is what you looking for. If you have problems with the code please write a comment. Here is the link to the javadoc: [Pixelgrabber][1] and another short examples: [Get the color of a specific pixel][2], Java program to get the color of pixel

The following example is from the last link. Thanks to roseindia.net

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

public class ImageTest
{
    public static void main(final String args[])
        throws IOException
    {
        final File file = new File("c:\\example.bmp");
        final BufferedImage image = ImageIO.read(file);

        for (int x = 0; x < image.getWidth(); x++) {
            for (int y = 0; y < image.getHeight(); y++) {
                final int clr = image.getRGB(x, y);
                final int red = (clr & 0x00ff0000) >> 16;
                final int green = (clr & 0x0000ff00) >> 8;
                final int blue = clr & 0x000000ff;

                // Color Red get cordinates
                if (red == 255) {
                    System.out.println(String.format("Coordinate %d %d", x, y));
                } else {
                    System.out.println("Red Color value = " + red);
                    System.out.println("Green Color value = " + green);
                    System.out.println("Blue Color value = " + blue);
                }
            }
        }
    }
}

[1]: https://docs.oracle.com/javase/7/docs/api/java/awt/image/PixelGrabber.html [2]: http://www.rgagnon.com/javadetails/java-0257.html

Answer 2

Note that if you want to loop over all pixels in an image, make sure to make the outer loop over the y-coordinate, like so:

for (int y = 0; y < image.getHeight(); y++) {
    for (int x = 0; x < image.getWidth(); x++) {
          int  clr   = image.getRGB(x, y); 
          int  red   = (clr & 0x00ff0000) >> 16;
          int  green = (clr & 0x0000ff00) >> 8;
          int  blue  =  clr & 0x000000ff;
          image.setRGB(x, y, clr);
    }
}

This will likely make your code much faster, as you'll be accessing the image data in the order it's stored in memory. (As rows of pixels.)