If you have the command-line tool imagemagick installed, you can use the following command in *nix or OSX terminal:

convert <filename> txt:- | cut -d " " -f 4 | uniq -c

replacing <filename> with the name of your file. This will print a list of counts and hex colors, like:

   10 #4A413F
   14 #483E3C

This works by using the convert tool to convert the file to "txt" format, which is made up of lines like:

 9,0: (75,74,76)  #4B4A4C  srgb(75,74,76)

Which is the x, y coords, then the decimal RGB values, the hex value, and then the srgb value of the pixel. Obviously, this format is not very efficient :)

Then, we use the built-in cut command to grab the fourth (-f 4) column, delimited on spaces (-d " "), which here is the hex value (interestingly, there are two spaces between the decimal RGB and the hex value).

Finally, we use the built-in uniq command to count -c the unique lines, and print it to standard out (the terminal).

If you have the command-line tool imagemagick installed, you can use the following command in *nix or OSX terminal:

convert <filename> txt:- | cut -d " " -f 4 | uniq -c

replacing <filename> with the name of your file. This will print a list of counts and hex colors, like:

   10 #4A413F
   14 #483E3C

This works by using the convert tool to convert the file to "txt" format, which is made up of lines like:

 9,0: (75,74,76)  #4B4A4C  srgb(75,74,76)

Which is the x, y coords, then the decimal RGB values, the hex value, and then the srgb value of the pixel. Obviously, this format is not very efficient :). We write this to standard out (txt:- means "write txt format to stdout").

Then, we use the built-in cut command to grab the fourth (-f 4) column, delimited on spaces (-d " "), which here is the hex value (interestingly, there are two spaces between the decimal RGB and the hex value, so if you want the decimal RGB, use -f 2).

Finally, we use the built-in uniq command to count -c the unique lines, and print it to standard out (the terminal).