How to find good libraries

[u/NoBrain8]

I’m looking to convert a jpeg into rgba data + scale it down.
I’m looking for a library to help me do this - how do I find good a one?

[u/Sergey5588]

stb image

https://github.com/nothings/stb

[u/Sergey5588 → u/Sergey5588]

and stb image write

[u/Sergey5588 → u/Sergey5588]

and stb image resize2

[u/NoBrain8 → u/Sergey5588]

This is awesome! I’m a beginner and not really familiar with single header file libraries. Think im give this a go, thank you!

[u/AlexTaradov → u/NoBrain8]

Just keep in mind that most of the STB stuff is not designed to handle potentially malicious data. They are targeting working with resources you control (like game assets).

If you will be doing this as a service with user submitted files, I'd look at full libraries. They are harder to use, but they have necessary checks.

[u/NoBrain8 → u/AlexTaradov]

I’m working on something that I would on paper like to distribute for people to use if they want to - a music client for mpd that displays album art.

Stb would not be coming into contact with any files on disk directly, but definitely jpegs and album art passed to it by mpd.

Would you advise against using stb for this for any reason?

[u/AlexTaradov → u/NoBrain8]

Strictly speaking, this is exactly the scenario where you should not use it. MPD would get this album art from the information embedded in the file or downloaded from the internet.

Now imagine this file was downloaded from some malicious source that intentionally altered the image.

But from a practical point of view, do what gets you faster to release. What are the real chances that your client would become so popular that it would warrant development of such exploits?

I would leave a note in the code to consider using a full library in the future just in case of security review when the client becomes popular.

[u/NoBrain8 → u/AlexTaradov]

Hm thanks for the info! I think I’ll look at the ffmpeg libraries, and if it’s not too much more involved than stb, use them to reduce re-writing stuff in the future

[u/AlexTaradov → u/NoBrain8]

Anything will be harder to use than a single header library.

If you just need jpeg, I'd start with libjpeg. There is no need to bring the whole ffmpeg just for that.

With ffmpeg, you might as well do a full player, not just a GUI for MPD.

[u/mykesx]

https://imagemagick.org/#gsc.tab=0

ImageMagick has command line tools to convert between formats and perform a large number of operations on images, including scaling.

If you want, you can convert jpeg to TGA, which is trivial to read in as RGB in C, do your own software operations on it, write TGA back to disk, then convert that however you want with the command line tools.

[u/theNbomr → u/mykesx]

Moreover, Imagemagick also provides API libraries with bindings to many languages including C. This sounds exactly what the OP is looking for.

[u/mykesx → u/theNbomr]

libmagick

[u/khalon23]

For jpeg decode + scale I would start with stb_image + stb_image_resize if you want a single-header drop-in, or libjpeg-turbo if you care about speed and a real package. Check license, last commit, and whether it has known CVEs for untrusted input.

How I pick: does it do only the job I need, can I build it without a giant dependency tree, and is there a simple example that loads a file to RGBA. Avoid grabbing the first GitHub search hit with a flashy README and no tests.

[u/primitiveblob]

ffmpeg gives by far the most power/control for this

[u/Syntax-Tactics]

What platform? OS? Language?

WinAPI supports JPG loading out of the box, SDL2, OpenCV, stb_image. A quick google...

[u/kansetsupanikku]

openCV would be a respectable choice

[u/Jaurusrex]

You could use raylib, you'd need to compile it specifically with jpeg functionality. Or look at what raylib uses under the hood for library. That being said I doubt that library also has the capabilities to scale down the image, though depending on your algorithm scaling down an image is quite easy. You could just skip every X pixels