# Compare bitmaps

**URL:** <https://www.ruby-forum.com/t/compare-bitmaps/68287>\
**Category:** Ruby\
**Created:** [September 11, 2006, 2:06pm UTC](https://www.ruby-forum.com/t/compare-bitmaps/68287 "2006-09-11T14:06:07Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Junkone](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e274bd/32.png) [@Junkone](https://www.ruby-forum.com/u/Junkone)\
**Post date:** [September 11, 2006, 2:06pm UTC](https://www.ruby-forum.com/t/compare-bitmaps/68287/1 "2006-09-11T14:06:07Z")

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hi  
i am looking for libraries to compare bitmap images in png format. can  
it be done in ruby?  
seede

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**Author:** ![Junkone](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e274bd/32.png) [@Junkone](https://www.ruby-forum.com/u/Junkone)\
**Post date:** [September 11, 2006, 2:10pm UTC](https://www.ruby-forum.com/t/compare-bitmaps/68287/2 "2006-09-11T14:10:07Z")

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try RMagick the ruby interface to the ImageMagik libs

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**Author:** ![Junkone](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e274bd/32.png) [@Junkone](https://www.ruby-forum.com/u/Junkone)\
**Post date:** [September 11, 2006, 2:10pm UTC](https://www.ruby-forum.com/t/compare-bitmaps/68287/3 "2006-09-11T14:10:07Z")

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Junkone wrote:

> hi  
> i am looking for libraries to compare bitmap images in png format. can  
> it be done in ruby?  
> seede

Yes. You want to look at the RMagick library - specifically, if you’re  
trying to do a pixel-wise difference, you’ll want to look at the  
Image#composite method, and the DifferenceCompositeOp CompositeOperator.

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<div class="post-metadata">

**Author:** ![Junkone](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e274bd/32.png) [@Junkone](https://www.ruby-forum.com/u/Junkone)\
**Post date:** [September 11, 2006, 2:16pm UTC](https://www.ruby-forum.com/t/compare-bitmaps/68287/4 "2006-09-11T14:16:08Z")

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On 11/09/06, Junkone [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> hi  
> i am looking for libraries to compare bitmap images in png format. can  
> it be done in ruby?  
> seede

It’s probably easiest to generate MD5 hashes for each file and compare  
those.

Farrel