Assume you want to read an image file in a common file format from the hard drive, change the color of one pixel, and display the resulting image to the screen, in C++.

Which (open-source) libraries would you recommend to accomplish the above with the least amount of code?

Alternatively, which libraries would do the above in the most elegant way possible?

A bit of background: I have been reading a lot of computer graphics literature recently, and there are lots of relatively easy, pixel-based algorithms which I'd like to implement. However, while the algorithm itself would usually be straightforward to implement, the necessary amount of frame-work to manipulate an image on a per-pixel basis and display the result stopped me from doing it.