5 Ways to Compare the Difference Between Two Identical Looking Images

Photo hunt is a popular spot the difference type of game where two nearly matching images are given and you are required to find the differences before the time runs out. Even if the photos are placed next to each other, sometimes it is nearly impossible to find all the differences in a given time. A way to have a better chance of winning is to get more people to play together with you so that the chances of spotting the difference are much higher. However, you might find it really difficult especially when you are playing it alone.

An easy way to automatically find the difference between two images is by using computer software to do it for you. Software such as Adobe Photoshop has the ability to analyze an image to accurately find the difference but it is unsuitable for users not involved in graphic design since Photoshop is expensive and not so user friendly. Here we have 5 free tools that can compare and find the differences between two nearly identical looking images.

To use any of the image comparison programs below on the Photo Hunt game, you should first save the two images as different files either using a screenshot capturing software or by pressing the Print Screen button and paste it to Paint. Then use the crop function to cut out areas that are out of the photo.

1. ImageMagick

ImageMagick comes with a few command line utilities to manipulate images. Although the utilities are command line based, the Windows binary package is currently at over 75MB in size and you only need the single compare.exe tool that is found in the ImageMagick archive. The command line below will use ImageMagick’s compare.exe tool to compare between the firstimage.png and secondimage.png file, and the difference will be saved to new file called outputdifference.png.

compare.exe firstimage.png secondimage.png outputdifference.png

The difference is highlighted in red color.

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2. PerceptualDiff

PerceptualDiff is an open source command line image comparison tool hosted on SourceForge. It is only 20KB in file size and supports a very limited number of image formats, which are TIFF and PNG. This is not really a problem because the image format can be easily converted through online web services or even Microsoft Paint that is built in to the Windows operating system.

The command line is to compare between images is quite similar to the ImageMagick’s compare tool except you need to include the -output option.

perceptualdiff.exe firstimage.png secondimage.png -output outputdifference.png

The default options for the output file will only show a black background with the difference highlighted in blue.

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3. Image Comparer

If you prefer an easier to use graphical user interfaced based program to compare between images, you can give Image Comparer a try. Image Comparer is a single portable executable file, so just run it and browse the first and second image, then click the Compare button.

If you see “False” in the “Is Same?” box, click at the View Differences link and go to the Differences tab to see the highlighted location of the differences.

Do take note that Image Comparer requires .NET Framework 3.5 to run.

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4. imageDiff

imageDiff is another GUI based image comparison freeware tool that is easy to use. After installation, run the program, click on the “Left” button to select the first image followed by clicking on the “Right” button to select the second image. Optionally, you can increase the threshold level if the images contain a lot of small differences which you’d like imageDiff to ignore. Click the Compare button and the differences can be shown in either 4 different modes (Monochrome, X-Ray, Predator, Thermal).

imageDiff requires MSVCR71.dll which is a Microsoft Visual C Runtime library to run. The DLL file is not included in the installer but can be easily downloaded from the Internet.

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5. Resemble.js

Resemble.js is a web based image analysis and comparison tool that uses HTML5 canvas and Javascript to compare between 2 images and show the areas that are mismatched. All you need to do is drag the 2 different photos into the boxes and the diff image will instantly show up at the right hand side. You have the options to ignore colors and antialiasing, changing the diff color from pink to yellow, and displaying the background as opaque or transparent.

There is a small problem with Resemble.js where the images to be compared must be a square shape. If the images are rectangular, the lower part will be automatically cut off which means you won’t get a full comparison between the pictures.

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