Replace all occurrences of one image inside another image

Question

In Java, I'm trying to replace one BufferedImage inside another BufferedImage.

For example, could be replaced with inside , so that is produced as a result.

Would it be possible to write a function that would replace one BufferedImage inside another BufferedImage, and return the resulting BufferedImage?

public static BufferedImage replaceInsideBufferedImage(BufferedImage containingImage, BufferedImage toBeReplaced, BufferedImage replaceWithThis){
//In containingImage, replace all occurrences of toBeReplaced with replaceWithThis    
}

Answer 1

The method below does the trick. Pseudo-code:

• (1) For every pixel of containingImage :
  • Begin matching the toBeReplaced (pixel by pixel)
    • If it finds it (all pixels matched), it goes and replaces all of them with replaceWithThis
    • If not, goes back to (1)

As all patterns will be found, finally, it will return returnImage .

replaceInsideBufferedImage() code:

public static BufferedImage replaceInsideBufferedImage(BufferedImage containingImage, BufferedImage toBeReplaced, BufferedImage replaceWithThis) {
    BufferedImage returnImage = deepCopyImage(containingImage);
    for (int x = 0; x+toBeReplaced.getWidth() < containingImage.getWidth(); x++) {
        for (int y = 0; y+toBeReplaced.getHeight() < containingImage.getHeight(); y++) {
            BufferedImage subImg = containingImage.getSubimage(x, y, toBeReplaced.getWidth(), toBeReplaced.getHeight());
            if (imageEquals(subImg,toBeReplaced)) {
                for (int sx = 0; sx < replaceWithThis.getWidth(); sx++) {
                    for (int sy = 0; sy < replaceWithThis.getHeight(); sy++) {
                        returnImage.setRGB(x+sx, y+sy, replaceWithThis.getRGB(sx, sy));
                    }
                }
            }
        }
    }
    return returnImage;
}

Full working code:

import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.WritableRaster;
import java.io.File;

import javax.imageio.ImageIO;

public class ReplacePattern {

    public static void main(String[] args) throws Exception {
        BufferedImage containingImage = ImageIO.read(new File("fourWhites.png"));
        BufferedImage toBeReplaced = ImageIO.read(new File("oneWhite.png"));
        BufferedImage replaceWithThis = ImageIO.read(new File("oneRed.png"));
        BufferedImage replaced = replaceInsideBufferedImage(containingImage, toBeReplaced, replaceWithThis);
        ImageIO.write(replaced, "png", new File("fourReds.png"));
    }

    public static BufferedImage replaceInsideBufferedImage(BufferedImage containingImage, BufferedImage toBeReplaced, BufferedImage replaceWithThis) {
        BufferedImage returnImage = deepCopyImage(containingImage);
        for (int x = 0; x+toBeReplaced.getWidth() < containingImage.getWidth(); x++) {
            for (int y = 0; y+toBeReplaced.getHeight() < containingImage.getHeight(); y++) {
                BufferedImage subImg = containingImage.getSubimage(x, y, toBeReplaced.getWidth(), toBeReplaced.getHeight());
                if (imageEquals(subImg,toBeReplaced)) {
                    for (int sx = 0; sx < replaceWithThis.getWidth(); sx++) {
                        for (int sy = 0; sy < replaceWithThis.getHeight(); sy++) {
                            returnImage.setRGB(x+sx, y+sy, replaceWithThis.getRGB(sx, sy));
                        }
                    }
                }
            }
        }
        return returnImage;
    }

    // http://stackoverflow.com/a/3514297/1850609
    public static BufferedImage deepCopyImage(BufferedImage bi) {
        ColorModel cm = bi.getColorModel();
        boolean isAlphaPremultiplied = cm.isAlphaPremultiplied();
        WritableRaster raster = bi.copyData(null);
        return new BufferedImage(cm, raster, isAlphaPremultiplied, null);
    }

    // http://stackoverflow.com/a/11006474/1850609
    private static boolean imageEquals(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;
    }
}

Answer 2

It would be possible, however I would not suggest doing that.

Detecting whether an image is present within another image will be very slow.

Moreover, due to possible encoding artifacts, it is possible that an image will never be detected in another image. In such case you would have to implement a more flexible detection function, which will take even longer and may lead to false positives.

Most likely, you have the data to rebuild the image from scratch. Instead of operating on images simply get the data used to generate the initial image and create a new one based on it.

But if you really need to do it, you will have to loop over both images and compare pixels. Use getRGB() function and compare the images pixel by pixel.