Function to_sprite_pointer 

pub const fn to_sprite_pointer(address: u16) -> u8

Calculate sprite pointer from pattern address

To make a given sprite show the pattern that’s stored in RAM at address (which must be divisible with 64), set the contents of the corresponding sprite pointer address to address divided by 64. For instance, if the sprite pattern begins at address 704, the pointer value will be 704 / 64 = 11.

Examples

const SPRITE_ADDRESS: u16 = 0x2000;
const SPRITE_PTR: u8 = to_sprite_pointer(SPRITE_ADDRESS);

When called as const, assertions are done at compile time:

const INVALID_SPRITE_ADDRESS: u16 = 0x2001; // compile time error

Image conversion

Image files can be converted using ImageMagick:

convert image.png -alpha off -resize 24x21! -monochrome sprite.png

and then converted into a byte array using Python:

import numpy as np
from PIL import Image
image = Image.open('sprite.png')
bits = (~np.asarray(image).reshape(int(24*21/8), 8))
for bits_in_byte in bits.astype(int):
    print(int(''.join('01'[i] for i in bits_in_byte), 2), end=',')