APERTUS C/C++ CHALLENGE

My solution for the T872 qualification challenge.

The Challenge

Write a C/CPP program for loading a RAW12 image (portrait-gainx2-offset2047-20ms-02.raw12) into the memory - separate the 4 channels (in memory - 8 bits). Output the intensity values of the first 5x5 pixels (square tile) R, G, G, B channels.
Save the channels (separately) as valid image files (8 bits per pixel) named appropriately without use of any external libraries (e.g. openJPG/lodePNG). (Hint: PPM file format).
Debayer the CFA (color filter array) data (in memory using nearest neighbour / bilinear) - output the image as a valid image file (8-bit, without use of any external library).

Additional task(for T763)-

Save the debayered RGB image as a BMP file (without use of any external libraries) - expected that you create the BMP file from scratch. As an alternative, you can save the image as a single frame in an AVI file without use of external libraries (bonus points).

Use cmake for building the C/CPP program.
Abide by the C/CPP coding guidelines (https://gist.github.com/lefticus/10191322) and project structuring (create appropriate directories, header files, c/cpp files to modularize the code in meaningful ways).
If you can load part of your program as a dynamic library (.so file)
If you use a nonlinear curve for the 12 to 8 bit conversion, without ignoring the bottom 4 bits (lots of different solutions possible) and explain your choice (why did you choose that curve).

The output ppm files are stored in the build directory by the name -