Legacy ImageMagick Discussions Archive

Hi all,
I have a transparent png file and I want to replace an existing opaque colour (eg. #000) with a transparent rgba colour (eg. rgba(255, 0, 0, 50.0)). Is it possible?
I spent days without result.
Here the command I use:

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convert -fuzz 100% img_black.png -alpha on -fill 'rgba(255, 0, 0, 50.0)' -opaque '#000' image_red.png

Please, anyone can help me?
Thanks in advance

try reading the input first, then use opaque black. Also alpha is specified in the range of 0 to 1, not 0 to 100 or 0 to 255. So if you want 50% transparent use 0.5

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convert img_black.png -fuzz 100% -alpha on -fill 'rgba(255, 0, 0, 0.5)' -opaque '#000' image_red.png

or if that does not work, then

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convert img_black.png -fuzz 100% -alpha on -fill 'rgba(255,0,0,0.5)' -opaque '#000000FF' image_red.png

Please always provide your IM version and platform when asking questions on this forum.

Hi,
thanks for your reply.
First of all, sorry for my forgetfulness.

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$ convert -version
Version: ImageMagick 6.8.9-9 Q16 x86_64 2017-07-31 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2014 ImageMagick Studio LLC
Features: DPC Modules OpenMP
Delegates: bzlib cairo djvu fftw fontconfig freetype jbig jng jpeg lcms lqr ltdl lzma openexr pangocairo png rsvg tiff wmf x xml zlib

My OS is Ubuntu Linux 16.04

I tried your commands simply by copy-paste but without success.
This is the black image:

This is the output of the fist command:

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convert img_black.png -fuzz 100% -alpha on -fill 'rgba(255, 0, 0, 0.5)' -opaque '#000' image_red.png

And this is the output of the second command:

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convert img_black.png -fuzz 100% -alpha on -fill 'rgba(255,0,0,0.5)' -opaque '#000000FF' image_red.png

I expecting something like this:

Important: I opened the output image with Gimp and the color profile is "indexed...". Is it possible to assign an RGB color profile to the output?

Thanks

Your image is totally black with a binary alpha channel. So one way is to make it totally red with an alpha channel reduced by 50%. This works for me on IM 6.9.9.8 Q16 Mac OSX. Change my path to your path to your sRGB.icc profile

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convert img_black.png -alpha off -fill red -opaque black -alpha on -channel a -evaluate multiply 0.5 +channel -profile /Users/fred/images/profiles/sRGB.icc image_red_half_alpha.png

This also works. Add -channel rgba from my earlier suggested command.

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convert img_black.png -alpha on -channel rgba -fill 'rgba(255,0,0,0.5)' -opaque '#000000FF' -profile /Users/fred/images/profiles/sRGB.icc image_red_half_alpha.png

Thanks!
The first command works as well.
The colour profile is downloadable from here: http://archive.ubuntu.com/ubuntu/pool/m ... ig.tar.bz2

Thanks a lot.
Gubi

Legacy ImageMagick Discussions Archive

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