[vox-tech] count pixels

[Troy Arnold]

On Wed, Feb 21, 2007 at 07:27:20PM -0800, Wade Pinkston wrote:
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> Hello,  I need to process some images and count the number of pixes of a
> given color.
> 
> A little background.  I want to take pix of leaves against a mat
> background.  The leaves are then subjected to damage.  I'll then take a
> duplicate photo.  Now what I want to do is subtract out the colors of the
> leaf leaving only a two tone image.
> 
> I was hoping to find a way to then use ImageMagick or Gimp to count the
> pixels of color so I can then get a percent change between the two images.
> 
> Does anybody know how to get ether of these two programs to give this type
> of information.  Actually any software would be help full.

If the image is in an indexed format, you can use identify from the
imagemagick suite:

$ identify -verbose some.gif
[...]
       155: (238,238,238,  0)   #EEEEEE00
       244: (245,245,242,  0)   #F5F5F200
       264: (249,249,249,  0)   #F9F9F900
       139: (252,252,252,  0)   grey99
      3885: (255,255,255,  0)   white
      3197: (235,235,217,255)   #EBEBD9FF

[...]
This shows that this image has 3,885 white pixels.


-troy