I am trying to convert an entire folder to grayscale, using image magick.
convert *.jpg -colorspace Gray -separate -average
is met with this error :
convert: `-average' @ error/convert.c/ConvertImageCommand/3290.
What is the correct command for this?
If you have lots of files to process, use mogrify:
magick mogrify -colorspace gray *.jpg
If you have tens of thousands of images and a multi-core CPU, you can get them all done in parallel with GNU Parallel:
parallel -X magick mogrify -colorspace gray ::: *.jpg
来源：https://stackoverflow.com/questions/53262968/convert-entire-folder-to-greyscale-using-image-magick