Starting October 12th, 2023 GitHub is enforcing mandatory two-factor authentication on my account.
I'm not going to comply and move all my activity to GitLab instead.
Any future updates / releases will be available at: https://gitlab.com/gitendo/bmp2cgb
Thanks and see you there!

Complete solution for converting graphics and real time palette adjustments for Game Boy Color. Heavily inspired by original utility created by Ars of Fatality in 1999. It's tiny, fast, command line driven and doesn't require any dependencies, so you can compile it without any problems on Windows or *nix systems.

-c    disable character optimization
-x    disable horizontal flip optimization
-y    disable vertical flip optimization
-z    disable horizontal & vertical flip optimization
-o    disable palette optimization

-e#   expand map width to 32 blocks using character (0-255)
-m#   map padding - starting character (1-511)
-p#   palette padding - starting slot (1-7)
-r    rebase character map to $8800-$97FF ($8000-$8FFF is default)

-d    extended debug information without data output
-s#   sprites output (transparent color RGB hex value ie. 4682b4)
-t    RGBTuner ROM image output

You can read the manual if you need more detailed explanation or don't know how to use it.

Currently only BITMAPINFOHEADER is supported. This one is most common and widely used so it shouldn't really matter. However if you end up with Unsupported bitmap type, BITMAPINFOHEADER not found! you might want to check settings of your graphics software ie. for Gimp you need to enable Do not write color space information in Compatibility Options while exporting image to BMP.

• fixed bug related to trimmed palettes in 4bpp/8bpp bitmaps

• add support for BITMAPV4HEADER and BITMAPV5HEADER
• get rid of all level 2 warnings

Hopefully none. Let me know if you find any.