Legacy ImageMagick Discussions Archive

Dear Qins：
which command can judge whether a png pic has alpha channel ？

My favorite is "pngcheck", which you can get fromhttp://www.libpng.org/pub/png/apps/pngcheck.html

pngcheck file.png

On *nix, you have "file" and can type

file file.png

(although this will miss PNG files where the alpha is conveyed via the tRNS chunk).

If you prefer to use ImageMagick, type

identify -verbose file.png

and look for lines containing "png:IHDR.color_type:" and "png:tRNS"

see string format %[channels] or %[opaque] at http://www.imagemagick.org/script/escape.php

convert image -format " %[channels]" info:

convert image -format " %[opaque]" info:

which command can judge whether a png pic has alpha channel ？