Looking for a method to replace a PNG's transparent background with any other color in Linux without using ImageMagick

When given a png with a transparent background, even without any of it being visible it causes problems with the rest of my code, so I'm looking for a way to remove the transparent background either using an open source solution or the default libpng library - preferably in linux.

I have tried using ImageMagick and it's how I've verified that converting the transparent background to that of any color solves my issues. I'm just looking for a different solution than ImageMagick.

You can do that in many ways. Here's an example using the NetPBM suite and using this red image with a transparent circular hole in the centre:

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The steps are as follows:

• make a blue background image over which to composite
• convert your PNG to PAM
• composite your image over the background
• convert resulting PPM back to PNG

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ppmmake blue 200 100 > background.ppm
pngtopam -alphapam YOURIMAGE.png > foreground.pam
pamcomp foreground.pam background.ppm > result.ppm
pamtopng result.ppm > result.png

TL;DR

That's all a bit of a palaver, so leverage the power of Unix to chain lots of things done well together and you get:

pamcomp <(pngtopam -alphapam YOURIMAGE.png) <(ppmmake blue 200 100) | pamtopng - > result.png

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Depending on how your PNG is actually constructed, and at the loss of flexibility in the colour replacing the transparency, you may find this command, which just ditches the alpa channel, is enough:

pngtopam YOURIMAGE.png | pamtopng - > result.png

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Other ways of approaching this might be:

• PIL/Pillow and 3-4 lines of Python
• OpenCV and 3-4 lines of Python
• gd and 4-5 lines of PHP
• CImg and 10-11 lines of C++

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With PIL/Pillow, that might look like this:

from PIL import Image

im = Image.open('YOURIMAGE.png')          # open image
bg = Image.new('RGB',im.size, 'yellow')   # make yellow background, same size
bg.paste(im, mask=im)                     # composite your image over background
bg.save('result.png')                     # save result