You could try stb_image for reading and stb_image_write for writing. These are very small libraries.
http://nothings.org/
https://github.com/nothings/stb
Link to my question on gamedev I've got to know about this site:
https://gamedev.stackexchange.com/questions/9083/library-to-load-images-into-textures-linux-c-and-opengl