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

Questions and postings pertaining to the usage of ImageMagick regardless of the interface. This includes the command-line utilities, as well as the C and C++ APIs. Usage questions are like "How do I use ImageMagick to create drop shadows?".
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zxsz4084
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which command can judge whether a png pic has alpha channel ?

Post by zxsz4084 »

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

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

Post by glennrp »

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

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pngcheck file.png
On *nix, you have "file" and can type

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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

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identify -verbose file.png
and look for lines containing "png:IHDR.color_type:" and "png:tRNS"

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fmw42
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Re: which command can judge whether a png pic has alpha channel ?

Post by fmw42 »

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

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

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

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