Code:
C:\Users\JB>magick convert path/to/input/wizard.jpg -quality 80 -colorspace gray /path/to/output/wizard.jpg
convert: unable to open image 'path/to/input/wizard.jpg': No such file or directory @ error/blob.c/OpenBlob/3569.
convert: no images defined `/path/to/output/wizard.jpg' @ error/convert.c/ConvertImageCommand/3354.
Instead with this one:
Code:
C:\Users\JB>magick convert wizard.jpg -quality 80 -colorspace gray wizard.jpg
It has worked perfectly.