Whenever I can come up with a reason to, I try to write interesting shaders and postprocessing effects. These are some of my favorite results.

Kuwahara Filter:

Symmetrical Discrete Cosine Transform

Noise-based Distortion and Transitions

Engine: Unity/OpenGL

Languages: Cg (variant of HLSL)/C++

Spreadsheet program similar to Google Sheets. I wrote a spreadsheet front-end in C# with a formula parser as well as a dependency graph to update dependent cells. Afterwards I worked on a TCP/IP based multi-threaded server in C++ utilizing the boost library.

Team Size: 4

Languages: C#/C++

Wrote a custom image codec for ffmpeg in C. The objective was to achieve a compression of 1/3 the original size. My partner and I came up with a strategy of storing alternating color channels for each pixel (red, green, blue, etc), then averaging neighboring pixels to get an approximation of the image's original color.

Team Size: 2

Language: C