For sure not a lot of people is using “save as .h” capability in TheGimp. But this is a really easy to use solution when you want to embed some icons or image into a C/C++ source code. I used this functionality with Arduino to display graphical elements and I was convinced of it.
I also reused this format to transfer an image over Bluetooth as this format have the advantage to encode RGB values into printable characters. The format is not too much expensive as 3x8bits RGB values are encoded with 4 chars.
This post gives detail on this encoding and a procedure example to encode your bitmap into this format. The decoding procedure is given by TheGimp in the .h file itself.