ADDITIONAL SYSTEM INFORMATION :
Tested on several computers and operating systems

A DESCRIPTION OF THE PROBLEM :
I encountered some weird behavior while experimenting with `java.awt.Robot`. If I use it to take two screenshots, one of the entire screen and one of just a subsection of the screen, the subsection of the screen has different pixels than a subimage of the original screenshot with the same coordinates as the subsection screenshot. Here is my code:

```
import java.awt.AWTException;
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;

public class ScreenCapTest {
    public static void main(String[] args) throws AWTException, IOException {
        // Construct Robot
        Robot r = new Robot();
        
        // Get dimensions of screen
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        
        // Take screenshot
        BufferedImage screen = r.createScreenCapture(new Rectangle(0,0, (int)screenSize.getWidth(), (int)screenSize.getHeight()));
        
        // Take screenshot of small section of screen
        int x = 5;
        int y = 5;
        int w = 50;
        int h = 50;
        BufferedImage subscreen = r.createScreenCapture(new Rectangle(x,y,w,h));
        
        // Create a subimage of the same section of the screen from the original screenshot
        BufferedImage subimageOfScreen = screen.getSubimage(x,y,w,h);
        
        // Are they equal?
        System.out.println(imgEqual(subimageOfScreen, subscreen));
        
        // Output images for comparison
        ImageIO.write(subimageOfScreen, "png", new File("subimage.png"));
        ImageIO.write(subscreen, "png", new File("subscreen.png"));
    }
    
    public static boolean imgEqual(BufferedImage image1, BufferedImage image2) {
        int width;
        int height;
        boolean imagesEqual = true;

        if( image1.getWidth() == ( width = image2.getWidth() ) &&
            image1.getHeight() == ( height = image2.getHeight() ) ){

            for(int x = 0;imagesEqual == true && x < width; x++){
                for(int y = 0;imagesEqual == true && y < height; y++){
                    if( image1.getRGB(x, y) != image2.getRGB(x, y) ){
                        imagesEqual = false;
                    }
                }
            }
        } else {
            imagesEqual = false;
        }
        return imagesEqual;
    }
}
```

Most of the time, it reports false, meaning that the subimage of a full screenshot from (5,5) to (55,55) is different from the screenshot of the screen from (5,5) to (55,55). Weirdly, for some values of x, y, w, and h, it prints true.

I can see that the saved images are slightly different, but I don't understand why this behavior exists. What's going on?

This question is currently being discussed on StackOverflow at https://stackoverflow.com/questions/77727691/java-awt-robot-why-doesnt-a-smaller-screen-capture-equal-a-subimage-of-a-captu

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile and run the code in the description with a static window

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Console reads "true"
ACTUAL -
Console reads "false"

---------- BEGIN SOURCE ----------
import java.awt.AWTException;
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;

public class ScreenCapTest {
    public static void main(String[] args) throws AWTException, IOException {
        // Construct Robot
        Robot r = new Robot();
        
        // Get dimensions of screen
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        
        // Take screenshot
        BufferedImage screen = r.createScreenCapture(new Rectangle(0,0, (int)screenSize.getWidth(), (int)screenSize.getHeight()));
        
        // Take screenshot of small section of screen
        int x = 5;
        int y = 5;
        int w = 50;
        int h = 50;
        BufferedImage subscreen = r.createScreenCapture(new Rectangle(x,y,w,h));
        
        // Create a subimage of the same section of the screen from the original screenshot
        BufferedImage subimageOfScreen = screen.getSubimage(x,y,w,h);
        
        // Are they equal?
        System.out.println(imgEqual(subimageOfScreen, subscreen));
        
        // Output images for comparison
        ImageIO.write(subimageOfScreen, "png", new File("subimage.png"));
        ImageIO.write(subscreen, "png", new File("subscreen.png"));
    }
    
    public static boolean imgEqual(BufferedImage image1, BufferedImage image2) {
        int width;
        int height;
        boolean imagesEqual = true;

        if( image1.getWidth() == ( width = image2.getWidth() ) &&
            image1.getHeight() == ( height = image2.getHeight() ) ){

            for(int x = 0;imagesEqual == true && x < width; x++){
                for(int y = 0;imagesEqual == true && y < height; y++){
                    if( image1.getRGB(x, y) != image2.getRGB(x, y) ){
                        imagesEqual = false;
                    }
                }
            }
        } else {
            imagesEqual = false;
        }
        return imagesEqual;
    }
}
---------- END SOURCE ----------

FREQUENCY : always