import java.awt.image.BufferedImage;
public class Motor {
int[] findSubimage(BufferedImage im1, BufferedImage im2){
int w1 = im1.getWidth(); int h1 = im1.getHeight();
int w2 = im2.getWidth(); int h2 = im2.getHeight();
assert(w2 <= w1 && h2 <= h1);
// will keep track of best position found
int bestX = 0; int bestY = 0; double lowestDiff = Double.POSITIVE_INFINITY;
// brute-force search through whole image (slow...)
for(int x = 0;x < w1-w2;x++){
for(int y = 0;y < h1-h2;y++){
double comp = compareImages(im1.getSubimage(x,y,w2,h2),im2);
if(comp < lowestDiff){
bestX = x; bestY = y; lowestDiff = comp;
}
}
}
// output similarity measure from 0 to 1, with 0 being identical
System.out.println(lowestDiff);
System.out.println(bestX+" "+bestY);
// return best location
return new int[]{bestX,bestY};
}
/**
* Determines how different two identically sized regions are.
*/
private double compareImages(BufferedImage im1, BufferedImage im2) {
assert(im1.getHeight() == im2.getHeight() && im1.getWidth() == im2.getWidth());
double variation = 0.0;
for(int x = 0;x < im1.getWidth();x++){
for(int y = 0;y < im1.getHeight();y++){
variation += compareARGB(im1.getRGB(x,y),im2.getRGB(x,y))/Math.sqrt(3);
}
}
return variation/(im1.getWidth()*im1.getHeight());
}
/**
* Calculates the difference between two ARGB colours (BufferedImage.TYPE_INT_ARGB).
*/
private double compareARGB(int rgb1, int rgb2) {
double r1 = ((rgb1 >> 16) & 0xFF)/255.0; double r2 = ((rgb2 >> 16) & 0xFF)/255.0;
double g1 = ((rgb1 >> 8) & 0xFF)/255.0; double g2 = ((rgb2 >> 8) & 0xFF)/255.0;
double b1 = (rgb1 & 0xFF)/255.0; double b2 = (rgb2 & 0xFF)/255.0;
double a1 = ((rgb1 >> 24) & 0xFF)/255.0; double a2 = ((rgb2 >> 24) & 0xFF)/255.0;
// if there is transparency, the alpha values will make difference smaller
return a1*a2*Math.sqrt((r1-r2)*(r1-r2) + (g1-g2)*(g1-g2) + (b1-b2)*(b1-b2));
}
}
