Picture Comparison Code Not Working Properly


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I am still very much a beginner in programming and am facing a problem with a Java code. I would be very thankful for suggestions and comments. The problem is as following:

I found a Java code online that is designed to compare two pictures and highlight the differences between them. However, the way the code works is by using a loop that compares the RGB value of each pixel of the two pictures and highlights it in a certain color if the value is equal. This however results in a problem that even the slightest shift in camera angle or lighting conditions between the two pictures leads to a different RGB value of the pixels making the code highlight them as a difference even though the pictures are mostly identical. The code is written below and i have added the link to photos showing examples of the outcome of the code. What would you suggest i change in the code? Thank you for your help in advance.

The code:

Code:
import java.awt.image.BufferedImage;
    import java.io.File;
    import java.io.IOException;
    
    import javax.imageio.ImageIO;
public class PictureOverlayTest {
    /*
     * Four variables, three for the wanted BufferedImages, one String for the
     * Path of the third Image, which does not already exist.
     */
 
    private BufferedImage image1;
    private BufferedImage image2;
    private BufferedImage image3;
 
    private String pathImage3;
 
    public PictureOverlayTest(String filePathAndName1, String filePathAndName2,
            String filePathAndName3) throws IOException {
        /*
         * Constructor in order to keep this method reusable and clean. Needs
         * three Strings. The paths and Filenames of all three images. Image 1
         * and 2 should exist already, Image 3 will be created if all
         * requirements are met. Constructor creates the first two buffered
         * images, sets all needed variables and starts the checkAndCompare()
         * method
         */
 
        File file = new File(filePathAndName1);
        this.image1 = ImageIO.read(file);
 
        file = new File(filePathAndName2);
        this.image2 = ImageIO.read(file);
 
        this.pathImage3 = filePathAndName3;
        checkAndCompare();
    }
 
    private void checkAndCompare() throws IOException {
        /*
         * This function creates the Color blue, compares the sizes of both
         * pictures and if they are the same, creates a third image. Then it
         * loops through the two images and compares each pixel. If the pixels
         * are the same, the third image gets a blue pixel at that point
         */
 
        Color blue = Color.blue;
        Color yellow = Color.yellow;
 
        if (image1.getHeight() == image2.getHeight()
                && image1.getWidth() == image2.getWidth()) {
 
            image3 = new BufferedImage(image1.getWidth(), image1.getHeight(),
                    image1.getType());
            for (int y = 0; y < image1.getHeight(); y++) {
                for (int x = 0; x < image1.getWidth(); x++) {
 
                    int colorImage1 = image1.getRGB(x, y);
                    int colorImage2 = image2.getRGB(x, y);
 
                    if (colorImage1 == colorImage2) {
 
                        image3.setRGB(x, y, blue.getRGB());
 
                    } else {
                              image3.setRGB(x, y, yellow.getRGB());
                        // Whatever Color you want. By default it is black.
 
                    }
 
                }
            }
            savePicture3();
            System.out.println("Message: Image comparison is done");
 
        } else {
 
            System.out.println("Error: Image dimensions do not match");
 
        }
 
    }
 
    private void savePicture3() throws IOException {
        /*
         * This method saves the created Image into a file onto your computer.
         * The if() statement is used to check if the file was successfully
         * created, in order to avoid unwanted errors. Keep in mind, that you
         * have to change the "bmp" in ImageIO.write() to whatever format you
         * actually want
         */
 
        File file = new File(pathImage3);
        if (file.createNewFile()) {
            ImageIO.write(image3, "bmp", file);
        }
    }
 
}

import java.io.IOException;
 
public class Main {
 
    public static void main(String[] args) {
        // TODO Auto-generated method stub
 
        try {
            PictureOverlayTest test = new PictureOverlayTest(
                    "C:\\Users\\Rabee Taha\\Desktop\\Java Test Pics\\test1.png",
                    "C:\\Users\\Rabee Taha\\Desktop\\Java Test Pics\\test2.png",
                    "C:\\Users\\Rabee Taha\\Desktop\\Java Test Pics\\test3.png");
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
 
}

Here is the link to example images of the outcome ( https://postimg.cc/gallery/rkXfPr7 )
 
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Joined
Mar 3, 2021
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That is far easier said than done, especially when it's the angle that changes and it's not just shifted. The concept you're looking for is "feature matching" (related to "feature detection"). OpenCV has some good plugins for it, but I'm not sure about its Java bindings.
 

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