Crate snes_bitplanes [−] [src]

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:

ⓘThis example is not tested
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 initial decoded values are 00, 10, 11, 00, 01, 11, 01, 10.

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. More color depths will be added later.

Thanks

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

Structs

Bitplanes

An iterator over 4-bits-per-pixel bitplanes.
Tile

Tile is a tuple struct wrapping an 8x8 byte array: conceptually a tile of SNES graphics.