For a widely used library like FreeType, a test framework to check font rasterization is a must have. Having a test framework to test the output of the library avoids many possible errors in early-stage. The project is based on enabling the programmers visualize what exactly is changing and helping them decode why is it changing.
Output Glyph --> Test_Framework --> Debugging- -> Quality Code
The working of the Test_Framework
1.Generating glyph images (using libpng) for both "base" and the "test"(developer) version of the FreeType library. This is done by linking both version's DLL to the code.
2.Comparing the images pixel by pixel and making a sprite sheet for each of the glyph. Each image in the sprite sheet corresponds to an effect after comparison.
3.An web interface is generated which lists all the glyphs that are rendered incorrectly in the 'test' version. Selecting a particular image will animate the glyph. (Using the concept of CSS Sprite Sheet Animation) (Various animation effects used as per the needs of the developer.)
All the code is written in ANSI C.