Informaticus

Sometimes single color-channels are needed for further processing and therefore we have to grab a graphic tool of our choice to accomplish that task. If you have a stack of images it can get very tedious. So why not use a handy script? I've written a short bash script that extracts red, green and blue channel from all images in the current directory storing each channel with postfixes _red|_green|_blue. Again you can change the output format at line 16, 18 and 20 to your desired format. If your input images are not PNG files then you have to change the input format at line 7 (e.g. .png -> .jpg).

#/bin/bash
# RGB splitter
#

#set debug

find . -type f | /bin/grep .png$ |while read file
do
 filenoext=${file%%.png}
 filenameout=$filenoext.png #change filetype here
 echo "Processing $file"
 echo "Output R=$filenoext""_red.png"
 echo "Output G=$filenoext""_green.png"
 echo "Output B=$filenoext""_blue.png"
 echo "Processing R"
convert "$file" -channel R -separate "$filenoext"_red.png
 echo "Processing G"
convert "$file" -channel G -separate "$filenoext"_green.png
 echo "Processing B"
convert "$file" -channel B -separate "$filenoext"_blue.png
done