finding the RGB value of a pixel

[drewvy]

Is there a way to ask for the RGB values of a pixel at location X, Y?

[magick]

Is there a way to ask for the RGB values of a pixel at location X, Y?

What are you using? The command-line, PerlMagick, MagickCore, MagickWand, Magick++, iMagick? The answer depends on your interface to ImageMagick.

[drewvy]

The command line.

[fmw42]

convert rose.png[1x1+10+10] txt:
# ImageMagick pixel enumeration: 1,1,65535,rgb
0,0: (18504,16448,14649) #484840403939 rgb(72,64,57)

or

convert rose.png[1x1+10+10] -format "%[fx:int(255*r)],%[fx:int(255*g)],%[fx:int(255*b)]" info:
72,64,57

[drewvy]

I don't understand this [1x1+10+10]

What does this mean?

[fmw42]

It is a subsection of the image that is 1x1 pixel at offset x=10 and y=10 from the upper left corner.

see
http://www.imagemagick.org/script/comma ... essing.php
http://www.imagemagick.org/Usage/files/#read_mods

you can also do it this way:

convert rose.png -format "%[fx:int(255*p{10,10}.r)],%[fx:int(255*p{10,10}.g)],%[fx:int(255*p{10,10}.b)]" info:
72,64,57

see
http://www.imagemagick.org/script/fx.php
http://www.imagemagick.org/Usage/transform/#fx_escapes

If you are on Windows, see
http://www.imagemagick.org/Usage/windows/

[anthony]

I don't understand this [1x1+10+10]

Its a crop done immediateally after reading, before the image is added to the current image sequence in memory.

Equivelent to

Code: Select all

 convert rose.png  -crop 1x1+10+10  txt:-

just faster.

NOTE you may have to quote the square brackets as it is a 'shell meta-charcater'
so the original command should have been...

Code: Select all

convert rose.png'[1x1+10+10]' txt:-

Another alternative is

Code: Select all

  convert rose.png -format "%[pixel:p{10,10}]" info:

Though that may produce a color name, instead of the pixels RGB values. For a 16 bit image it may also use percent values in the RGB value it returns. Fred's more complex method gurantees the return of a the 8bit RGB values.

For more methdos and information see
IM Examples, Color Quantization and Dithering, Extracting Colors
http://www.imagemagick.org/Usage/quantize/#extract