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# Image Processing in Java | Set 14 ( Comparison of two images )

• Last Updated : 22 Jun, 2017

We strongly recommend to refer below posts as a prerequisite of this.

In this article we will learn how to compare two given images (must be of same dimensions) and print the percentage of difference between them.

Algorithm:

Step 1 – Check if dimensions of both the image match.
Step 2 – Get the RGB values of both images.
Step 3 – Calculate the difference in two corresponding pixel of three color components.
Step 4 – Repeat Step 2-3 for each pixel of the images.
Step 5 – Calculate the percentage by dividing the sum of differences with:

• Number of pixels, to obtain the average difference per pixel
• 3, to obtain the average difference per color component
• 255, to obtain a value between 0.0 and 1.0 which can be converted into a percent value

Implementation:

 `// Java Program to compare two images``import` `java.awt.image.BufferedImage;``import` `javax.imageio.ImageIO;``import` `java.io.File;``import` `java.io.IOException;`` ` `class` `ImageComparision``{``    ``public` `static` `void` `main(String[] args)``    ``{``        ``BufferedImage imgA = ``null``;``        ``BufferedImage imgB = ``null``;`` ` `        ``try``        ``{``            ``File fileA = ``new` `File(``"/home / pratik /"``+``                             ``" Desktop / image1.jpg"``);``            ``File fileB = ``new` `File(``"/home / pratik /"``+``                             ``" Desktop / image2.jpg"``);`` ` `            ``imgA = ImageIO.read(fileA);``            ``imgB = ImageIO.read(fileB);``        ``}``        ``catch` `(IOException e)``        ``{``            ``System.out.println(e);``        ``}``        ``int` `width1 = imgA.getWidth();``        ``int` `width2 = imgB.getWidth();``        ``int` `height1 = imgA.getHeight();``        ``int` `height2 = imgB.getHeight();`` ` `        ``if` `((width1 != width2) || (height1 != height2))``            ``System.out.println(``"Error: Images dimensions"``+``                                             ``" mismatch"``);``        ``else``        ``{``            ``long` `difference = ``0``;``            ``for` `(``int` `y = ``0``; y < height1; y++)``            ``{``                ``for` `(``int` `x = ``0``; x < width1; x++)``                ``{``                    ``int` `rgbA = imgA.getRGB(x, y);``                    ``int` `rgbB = imgB.getRGB(x, y);``                    ``int` `redA = (rgbA >> ``16``) & ``0xff``;``                    ``int` `greenA = (rgbA >> ``8``) & ``0xff``;``                    ``int` `blueA = (rgbA) & ``0xff``;``                    ``int` `redB = (rgbB >> ``16``) & ``0xff``;``                    ``int` `greenB = (rgbB >> ``8``) & ``0xff``;``                    ``int` `blueB = (rgbB) & ``0xff``;``                    ``difference += Math.abs(redA - redB);``                    ``difference += Math.abs(greenA - greenB);``                    ``difference += Math.abs(blueA - blueB);``                ``}``            ``}`` ` `            ``// Total number of red pixels = width * height``            ``// Total number of blue pixels = width * height``            ``// Total number of green pixels = width * height``            ``// So total number of pixels = width * height * 3``            ``double` `total_pixels = width1 * height1 * ``3``;`` ` `            ``// Normalizing the value of different pixels``            ``// for accuracy(average pixels per color``            ``// component)``            ``double` `avg_different_pixels = difference /``                                          ``total_pixels;`` ` `            ``// There are 255 values of pixels in total``            ``double` `percentage = (avg_different_pixels /``                                            ``255``) * ``100``;`` ` `            ``System.out.println(``"Difference Percentage-->"` `+``                                                ``percentage);``        ``}``    ``}``}`

NOTE:Code will not run on online ide since it requires image in drive.

Output:

Input images:

Output : Difference Percentage–>2.843600130405922

Input images:

Output : Difference Percentage–>6.471412648669786

Input images:

Output : Difference Percentage–>0.0

This article is contributed by Pratik Agarwal. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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