[vox-tech] count pixels

[Wade Pinkston]

I made this image with gimp as a test image.  The image is 100% #ff0000 
no matter what I convert the image to I don't get a pixel count.

$ identify -verbose red1.tiff
Image: red1.tiff
   Format: TIFF (Tagged Image File Format)
   Geometry: 256x256
   Class: DirectClass
   Colorspace: RGB
   Type: Palette
   Depth: 1 bits
   Endianess: MSB
   Channel depth:
     Red: 1-bits
     Green: 1-bits
     Blue: 1-bits
   Channel statistics:
     Red:
       Min: 1
       Max: 1
       Mean: 1
       Standard deviation: 0
     Green:
       Min: 0
       Max: 0
       Mean: 0
       Standard deviation: 0
     Blue:
       Min: 0
       Max: 0
       Mean: 0
       Standard deviation: 0
   Colors: 1
   Histogram:
   Rendering-intent: Undefined
   Resolution: 72x72
   Units: PixelsPerInch
   Filesize: 192kb
   Interlace: None
   Background Color: white
   Border Color: #DFDFDF
   Matte Color: grey74
   Dispose: Undefined
   Iterations: 0
   Compression: None
   Orientation: TopLeft
   document: /home/blata/red1.tiff
   comment: Created with The GIMP
   signature: 
d764b5e26d0f9155ebf131dcbf35ecaae5b3508c4b7d240173f5fe85b406ae64
   Tainted: False
   User Time: 0.000u
   Elapsed Time: 0:01

This image is the same with three white ovals cut out of the red.  Again 
no pixel count.  If I could get a simple pixel count per color then I 
can do the math and all is good.

identify -verbose red2.tiff
Image: red2.tiff
   Format: TIFF (Tagged Image File Format)
   Geometry: 256x256
   Class: DirectClass
   Colorspace: RGB
   Type: Palette
   Depth: 8 bits
   Endianess: MSB
   Channel depth:
     Red: 1-bits
     Green: 8-bits
     Blue: 8-bits
   Channel statistics:
     Red:
       Min: 255
       Max: 255
       Mean: 255
       Standard deviation: 0
     Green:
       Min: 0
       Max: 255
       Mean: 32.4795
       Standard deviation: 84.5242
     Blue:
       Min: 0
       Max: 255
       Mean: 32.4795
       Standard deviation: 84.5242
   Colors: 105
   Histogram:
   Rendering-intent: Undefined
   Resolution: 72x72
   Units: PixelsPerInch
   Filesize: 192kb
   Interlace: None
   Background Color: white
   Border Color: #DFDFDF
   Matte Color: grey74
   Dispose: Undefined
   Iterations: 0
   Compression: None
   Orientation: TopLeft
   document: /home/blata/red2.tiff
   comment: Created with The GIMP
   signature: 
1e69860505dfe98ecbede60074549452546deb485ce49723f2feb62ab73b40c9
   Tainted: False
   User Time: 0.000u
   Elapsed Time: 0:01



Troy Arnold wrote:
> On Wed, Feb 21, 2007 at 07:27:20PM -0800, Wade Pinkston 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.
> 
> 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
> 
> 
> 
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> 

-- 
Wade Pinkston

Ipsa scientia potestas est

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