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Re: [vox-tech] count pixels
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Re: [vox-tech] count pixels



Wade Pinkston wrote:
I put a webpage up with an example.

http://bugs.osu.edu/wade
JPEG is a poor choice for this since the compression messes with colors
near edges. If you are stuck with it though, you may want to play with ppmquant.

As you can see its the same image but the first has no damage. The second has damage. So what I need it the percent difference.
$ RED5=`jpegtopnm red5.jpg 2>/dev/null | ppmhist \
| egrep '^[ ]*254[ ]+0[ ]+0' \
| perl -ne 'if ( /^\s*[0-9]+\s+[0-9+]+\s+[0-9+]+\s+[0-9+]+\s+([0-9]+)/ ) { print $1 };'`

$ RED4=`jpegtopnm red4.jpg 2>/dev/null | ppmhist | \
egrep '^[ ]*254[ ]+0[ ]+0' | \
perl -ne 'if ( /^\s*[0-9]+\s+[0-9+]+\s+[0-9+]+\s+[0-9+]+\s+([0-9]+)/ ) { print $1 };'`

$ perl -e "print (100*$RED5)/$RED4-100, \"\\n\";"

Jim Angstadt wrote:

--- Wade Pinkston <blata@bugs.osu.edu> wrote:

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

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.

Here is an example of using IM to compare 2 images, in
this case, images from a webcam:

 http://www.notbig.org/bin/webcam.sh.txt

Note the command that begins with
  differ=$(composite
which first compares 2 images, then ignores minor
color variations, converts the pixel comparison to
text, and then manipulates the text as needed.

I don't really understand what you are trying to do,
but this sample of IM make be helpful for image
comparisons.

Jim
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