Re: Compare images in Cocoa
Re: Compare images in Cocoa
- Subject: Re: Compare images in Cocoa
- From: Jean-Daniel Dupas <email@hidden>
- Date: Fri, 31 Oct 2008 17:09:42 +0100
Le 31 oct. 08 à 16:56, Brian Stern a écrit :
On Oct 30, 2008, at 11:21 PM, Pierce Freeman wrote:
Hi everyone. I am wondering if there is some way to compare two
images in
Cocoa, and then somehow spit out a percent of how similar they are.
The only
way I could think of is comparing every pixel, but this seems like
it would
take a long time, and even so I have no idea how to go about doing
that.
Thanks for your help.
You don't say what you want this number for. Are you trying to tell
if two images of faces are of the same person? Two images of
buildings are of the same building? Two images have similar colors
in them?
FWIW, iterating over all the pixels in an image and doing some kind
of simple math on the pixel values will not be very time-consuming.
There are lots of Photoshop filters that do this and are very fast.
One thought that comes to mind is to calculate the histogram for the
two images and compare them. This could give a kind of simplistic %
difference.
One usage of image comparaison is "cut detection" in movie. There's an
article about it on wikipedia that presents some image comparaison
technics (histogram is one of them):
http://en.wikipedia.org/wiki/Cut_detection
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