This is documentation for the snes-bitplanes crate.

The Super NES includes stores its graphics in bitplanes, a packed format in which the bits representing a specific pixel are spread across multiple bytes in the same bit position.

For example, 2-bit-per-pixel data stored as bitplanes might have the byte representation:

00101110 //  0, bitplane 1
01100101 //  1, bitplane 2
11101001 //  2, bitplane 1
10010101 //  3, bitplane 2
// ...
00010101 // 14, bitplane 1
00101110 // 15, bitplane 2

The Super NES is little-endian, so the leftmost bits represent the earliest decoded bytes. Also note that the second bitplane is the more significant bit in the output.

In total, 2bpp data will inflate to 4 times its original size (because Bitplanes iterators yield bytes themselves, even though the values are generally smaller).

Usage

let bitplanes_data = vec![0u8; 128]; // Extremely boring data
let decoded: Vec<Tile> = Bitplanes::new(&bitplanes_data).collect();
for pixel_row in decoded[0].chunks(8) {
    // the Tile struct wraps a 64-byte array, and has a similar API
}

Currently only 4-bits-per-pixel (16 color) bitplanes are decodable with this crate.

Thanks

This crate would not be possible without the research of others, notably

• FDwR (Frank Dwayne) /snesgfx.txt 1998
• Qwertie (David Piepgrass) /snesdoc.html 1998