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Comparing two images

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Comparing two images

Postby bimbalas » Mon Sep 19, 2016 10:36 am

Hi guys,

I'm trying to compare two images and evaluate the difference numerically (not sure if this is a proper term though :) )

Challenges that I encounter:
- Images are browser screenshots, containing quite a lot of text. These are rendered a little bit differently on different instances- aliasing stuff. So this generates a little threshold that needs to be ignored (somehow...)
- Meantime, I want quite small changes in those two images (button gone, additional text appearing, drastic color change or so) to be detected and treated as high impact having issues

I've tried using ExhaustiveBlockMatching, but it serves a bit different purpose. It's matching images very well indeed, but even such a change in an image as disappearing button is generating too little decrease in a match % value (0,996 "perfect" match, 0,993 with the button removed). On the other hand, it was veeery promising and tempting to use it as it is ignoring pixel shifting and other similar stuff.

Was thinking about AForge.Imaging.Filters.ThresholdedDifference class, counting black/white ratio after applying it, but again without much luck- had to increase treshold a bit to get font aliasing ignored, and while doing that, real changes got lost...

I do understand those two challenges I mentioned are kind of crossing each other, but hell, maybe you got the idea :)

So... Guys, do you have any ideas or suggestions how I might proceed with it?
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