Cómo realizar la comparación de 2 imágenes y determinar si son iguales o similares

Esta entrada contiene el código para determinar si 2 imagenes son iguales, si puede variar los parámetros para que dos imágenes que tienen similitud los reconozca como similares.

Está realizado en Netbeans en un proyecto en consola para ello se debe crear un nuevo proyecto Java Aplication, para mi caso el nombre es ComparacionImagen.

A continuación crear una nueva clase, dar clic sobre el paquete y luego crear la Clase ImageCompare.

package comparacionimagen;
import javax.swing.*;
import java.io.*;
import java.util.*;
import java.awt.*;
import java.awt.image.*;
import com.sun.image.codec.jpeg.*;

 public class ImageCompare {

 protected BufferedImage img1 = null;
 protected BufferedImage img2 = null;
 protected BufferedImage imgc = null;
 protected int comparex = 0;
 protected int comparey = 0;
 protected int factorA = 0;
 protected int factorD = 10;
 protected boolean match = false;
 protected int debugMode = 0; // 1: textual indication of change, 2: difference of factors

 // constructor 1. use filenames
 public ImageCompare(String file1, String file2) {
  this(loadJPG(file1), loadJPG(file2));
 }

 // constructor 2. use awt images.
 public ImageCompare(Image img1, Image img2) {
  this(imageToBufferedImage(img1), imageToBufferedImage(img2));
 }

 // constructor 3. use buffered images. all roads lead to the same place. this place.
 public ImageCompare(BufferedImage img1, BufferedImage img2) {
  this.img1 = img1;
  this.img2 = img2;
  autoSetParameters();
 }

 // like this to perhaps be upgraded to something more heuristic in the future.
 protected void autoSetParameters() {
  comparex = 10;
  comparey = 10;
  factorA = 10;
  factorD = 10;
 }

 // set the parameters for use during change detection.
 public void setParameters(int x, int y, int factorA, int factorD) {
  this.comparex = x;
  this.comparey = y;
  this.factorA = factorA;
  this.factorD = factorD;
 }

 // want to see some stuff in the console as the comparison is happening?
 public void setDebugMode(int m) {
  this.debugMode = m;
 }

 // compare the two images in this object.
 public void compare() {
  // setup change display image
  imgc = imageToBufferedImage(img2);
  Graphics2D gc = imgc.createGraphics();
  gc.setColor(Color.RED);
  // convert to gray images.
  img1 = imageToBufferedImage(GrayFilter.createDisabledImage(img1));
  img2 = imageToBufferedImage(GrayFilter.createDisabledImage(img2));
  // how big are each section
  int blocksx = (int)(img1.getWidth() / comparex);
  int blocksy = (int)(img1.getHeight() / comparey);
  // set to a match by default, if a change is found then flag non-match
  this.match = true;
  // loop through whole image and compare individual blocks of images
  for (int y = 0; y < comparey; y++) {
   if (debugMode > 0) System.out.print("|");
   for (int x = 0; x < comparex; x++) {
    int b1 = getAverageBrightness(img1.getSubimage(x*blocksx, y*blocksy, blocksx - 1, blocksy - 1));
    int b2 = getAverageBrightness(img2.getSubimage(x*blocksx, y*blocksy, blocksx - 1, blocksy - 1));
    int diff = Math.abs(b1 - b2);
    if (diff > factorA) { // the difference in a certain region has passed the threshold value of factorA
     // draw an indicator on the change image to show where change was detected.
     gc.drawRect(x*blocksx, y*blocksy, blocksx - 1, blocksy - 1);
     this.match = false;
    }
    if (debugMode == 1) System.out.print((diff > factorA ? "X" : " "));
    if (debugMode == 2) System.out.print(diff + (x < comparex - 1 ? "," : ""));
   }
   if (debugMode > 0) System.out.println("|");
  }
 }

 // return the image that indicates the regions where changes where detected.
 public BufferedImage getChangeIndicator() {
  return imgc;
 }

 // returns a value specifying some kind of average brightness in the image.
 protected int getAverageBrightness(BufferedImage img) {
  Raster r = img.getData();
  int total = 0;
  for (int y = 0; y < r.getHeight(); y++) {
   for (int x = 0; x < r.getWidth(); x++) {
    total += r.getSample(r.getMinX() + x, r.getMinY() + y, 0);
   }
  }
  return (int)(total / ((r.getWidth()/factorD)*(r.getHeight()/factorD)));
 }


 // returns true if image pair is considered a match
 public boolean match() {
  return this.match;
 }

 // buffered images are just better.
 protected static BufferedImage imageToBufferedImage(Image img) {
  BufferedImage bi = new BufferedImage(img.getWidth(null), img.getHeight(null), BufferedImage.TYPE_INT_RGB);
  Graphics2D g2 = bi.createGraphics();
  g2.drawImage(img, null, null);
  return bi;
 }

 // write a buffered image to a jpeg file.
 protected static void saveJPG(Image img, String filename) {
  BufferedImage bi = imageToBufferedImage(img);
  FileOutputStream out = null;
  try {
   out = new FileOutputStream(filename);
  } catch (java.io.FileNotFoundException io) {
   System.out.println("File Not Found");
  }
  JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
  JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(bi);
  param.setQuality(0.8f,false);
  encoder.setJPEGEncodeParam(param);
  try {
   encoder.encode(bi);
   out.close();
  } catch (java.io.IOException io) {
   System.out.println("IOException");
  }
 }

 // read a jpeg file into a buffered image
 protected static Image loadJPG(String filename) {
  FileInputStream in = null;
  try {
   in = new FileInputStream(filename);
  } catch (java.io.FileNotFoundException io) {
   System.out.println("File Not Found");
  }
  JPEGImageDecoder decoder = JPEGCodec.createJPEGDecoder(in);
  BufferedImage bi = null;
  try {
   bi = decoder.decodeAsBufferedImage();
   in.close();
  } catch (java.io.IOException io) {
   System.out.println("IOException");
  }
  return bi;
 }

}

En el método main debemos ir calibrando a nuestras necesidades

package comparacionimagen;


/**
 *
 * @author Paulo
 */
public class Main {

  

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
       // Especificamos las imagenes que deseamos comparar, cada imagene debe tener una dimension de 300 x 225.
  ImageCompare ic = new ImageCompare("e:\\test1.jpg", "e:\\test5.jpg");
  // Set the comparison parameters.
  //   (numero de regiones verticales, numero de regiones horizontales, sensibilidad, stabilizer)
  ic.setParameters(12, 12, 15, 10); 
                 // Display some indication of the differences in the image.
  ic.setDebugMode(2);
  // Compare.
  ic.compare();
  // Display if these images are considered a match according to our parameters.
  System.out.println("Match: " + ic.match());
  // si las imagenes son distintas se creará una nueva imagen con nombre changes.jpg en la que se muestre las regiones que son distintas pues sobrepasan la sensibilidad.
  if (!ic.match()) {
   ImageCompare.saveJPG(ic.getChangeIndicator(), "e:\\changes.jpg");
  }
 }

}

Información tomada de http://mindmeat.blogspot.com/2008/07/java-image-comparison.html