Commodore 64 (Retro) image converter...

This might be a fun one that you can use your dithering algorithms for. A program that converts images into the commodore 64 (c64) standard bitmap (hi-res) mode. Hi-res mode is a 40x25 grid of 8x8 pixel squares (320x200 total) with the limitation that each 8x8 square can only use two of the c64's 16 colors. Here's a link on the mode as well as a few examples of artwork that work within this limitation:

[Video Explaining Standard Bitmap Mode](https://www.youtube.com/watch?v=Tfh0ytz8S0k&t=108s)
[Standard Bitmap Mode on C64-Wiki](https://www.c64-wiki.com/wiki/Standard_Bitmap_Mode)

[Example Image 1](https://www.nightfallcrew.com/wp-content/uploads/2013/01/hermires125.png)
[Example Image 2](https://www.nightfallcrew.com/wp-content/uploads/2013/01/HermIRES.png?ef6e10)
[Example Image 3](http://multipaint.kameli.net/images/modesel.png)

[The C64 color pallet](https://www.c64-wiki.com/wiki/Color)

Extra credit:

1. Implement multi-color mode (explained in the video after standard bitmap mode). Pixels are twice as wide, but you can have 4 colors per cell.
2. Implement something to convert an image to [2-color PETSCII](https://en.wikipedia.org/wiki/PETSCII)