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Re: Compare image levels?
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Re: Compare image levels?


  • Subject: Re: Compare image levels?
  • From: Chris Williams <email@hidden>
  • Date: Mon, 26 Nov 2007 16:45:04 -0800
  • Thread-topic: Compare image levels?

Poop, accidentally hit send...

Check out the Perceptual Image Difference project on sourceforge at:

http://sourceforge.net/projects/pdiff/


> From: Chris Williams <email@hidden>
> Date: Mon, 26 Nov 2007 16:43:59 -0800
> To: Brendan Wilde <email@hidden>, <email@hidden>
> Conversation: Compare image levels?
> Subject: Re: Compare image levels?
>
> Image comparison is a very, very complex subject.  It has been the subject of
> more than a few CompSci PhD theses.  So, a short answer is difficult.
>
> However, picture data is just data.  A byte (more or less) for Red, one for
> Green, one for Blue, etc. (if in RGB).  You can access the data in an
> NSBitmapImageRep and have at it.
>
> You will soon, however, realize that this is really hard.  Compression
> algorithms mess with the data "just a little bit" to get better results, and
> that throws off comparisons.  Pictures get cropped and that makes them just a
> bit different.  And so on.  Comparing strictly numerically almost never works.
>
> However, as a starting point, you might consider looking at the project:
>
>
>
>> From: Brendan Wilde <email@hidden>
>> Date: Tue, 27 Nov 2007 11:23:26 +1100
>> To: <email@hidden>
>> Subject: Compare image levels?
>>
>> I am trying to find a way to compare images based on colour etc.
>> If I am using Photoshop I can use it doing the levels or historyogram
>> and then visually compare the information. I am wondering if I can
>> somehow do this programmatically?
>>
>> The idea is compare two images and check if they are the same or
>> similiar
>> based on their levels possibly comparing to a range of levels to find
>> a match.
>>
>> Can anyone give me a starting point?
>> Thanks
>> Brendan
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 >Re: Compare image levels? (From: Chris Williams <email@hidden>)

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