How to compare images for similarity using java

Question

Recently I got an opportunity to work with Image Processing Technologies as a part of one of my projects and my task was to find matching images from an image store when a new image is given. I started my project with googling "How to compare images using java" and I got some good articles on finding the similarity of two images. Almost all of them were based on four basic steps, they are:

1.Locating the Region of Interest (Where the Objects appear in the given image),
2.Re-sizing the ROIs in to a common size,
3.Substracting ROIs,
4.Calculating the Black and White Ratio of the resultant image after subtraction.

Though this sounds as a good algorithm to compare images, it takes a considerable amount of time after implementing it using JAI in my project. Therefore I have to find an alternate method of doing it.

Any suggestions?

Answer 1

    **// This API will compare two image file //
// return true if both image files are equal else return false//**
public static boolean compareImage(File fileA, File fileB) {        
    try {
        // take buffer data from botm image files //
        BufferedImage biA = ImageIO.read(fileA);
        DataBuffer dbA = biA.getData().getDataBuffer();
        int sizeA = dbA.getSize();                      
        BufferedImage biB = ImageIO.read(fileB);
        DataBuffer dbB = biB.getData().getDataBuffer();
        int sizeB = dbB.getSize();
        // compare data-buffer objects //
        if(sizeA == sizeB) {
            for(int i=0; i<sizeA; i++) { 
                if(dbA.getElem(i) != dbB.getElem(i)) {
                    return false;
                }
            }
            return true;
        }
        else {
            return false;
        }
    } 
    catch (Exception e) { 
        System.out.println("Failed to compare image files ...");
        return  false;
    }
}

Answer 2

Depending on how different the images are, you could do something like this (pseudocode). It's very primitive, but should be pretty efficient. You could speed it up by taking random or patterned pixels instead of every one.

for x = 0 to image.size:
    for y = 0 to image.size:
        diff += abs(image1.get(x,y).red - image2.get(x,y).red)
        diff += abs(image1.get(x,y).blue - image2.get(x,y).blue)
        diff += abs(image1.get(x,y).green - image2.get(x,y).green)
    end
end

return ((float)(diff)) / ( x * y * 3)

Answer 3

This API will compare two image file and return the percentage of similarity

public float compareImage(File fileA, File fileB) {

    float percentage = 0;
    try {
        // take buffer data from both image files //
        BufferedImage biA = ImageIO.read(fileA);
        DataBuffer dbA = biA.getData().getDataBuffer();
        int sizeA = dbA.getSize();
        BufferedImage biB = ImageIO.read(fileB);
        DataBuffer dbB = biB.getData().getDataBuffer();
        int sizeB = dbB.getSize();
        int count = 0;
        // compare data-buffer objects //
        if (sizeA == sizeB) {

            for (int i = 0; i < sizeA; i++) {

                if (dbA.getElem(i) == dbB.getElem(i)) {
                    count = count + 1;
                }

            }
            percentage = (count * 100) / sizeA;
        } else {
            System.out.println("Both the images are not of same size");
        }

    } catch (Exception e) {
        System.out.println("Failed to compare image files ...");
    }
    return percentage;
}