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:
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
- FDwR (Frank Dwayne) /snesgfx.txt 1998
- Qwertie (David Piepgrass) /snesdoc.html 1998
Structs
Bitplanes |
An iterator over 4-bits-per-pixel bitplanes. |
Tile |
|