> Does any one know how to compare pixels in a picture, or a dll that
will allow me to do so. I need to be able to find objects in a
picture. Like a table, chair, car etc. Compare a given picture say of
a car, and scan another picture for same type of car?
I don't know of this functionality is nice-to-have or required, but let me
outline a few of the issues you'll have to deal with and then you can decide
wether it's worth it:
A pixel-by-pixel comparison will not handle:
- variations in lightsource
- variations in size
- minor differences like a pixel here and there off by a minute amount of
color
- color differences
- rotation
- scale
- mirrored versions
Let's take an example of comparing two whole images to see if they're the
same image, as is a typical example of what a news agency or ad agency would
like to do. You'd have to cope with:
- cropped versions of the image (to get rid of black/white border after scanning
for instance)
- mirrored versions of the image
- scale differences (one image is 800x600, the other 1280x1024)
- minor editing, like removing red-eyes or just enhancing contrast and the
likes
The particular algorithm you need to pick depends heavily on your exact needs
and you'll not find a fits-everything algorithm that can handle all the cases.
If you need to look at a photograph and extract objects like "car", "chair",
"person", etc. then you need to find a neural-net or similar algorithm with
heavily image analysis procedures to get those objects. If you put a person
up against a light wall you have no problems seeing what is a person and
what is a wall, but the computer needs explicit instructions.
If this is a nice-to-have project/module then my advise would be to either
buy it or forget it.
--
Lasse Vågsæther Karlsen
http://usinglvkblog.blogspot.com/
mailto:la***@vkarlsen.no
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