stb_image_write 

Current version : see file source versions in each .h file.
Source: https://github.com/nothings/stb

Patch file:
- Download original/new source code from github.
- Inspect current .patch file to understand local modifications.
- Merge existing code with new code to incorporate patches.
- Generate new patch:
     diff -ruN <path to original/new source> stb_image.h > stb_image.patch
