Struct LosslessDecoder

pub(crate) struct LosslessDecoder<R> {
    bit_reader: BitReader<R>,
    transforms: [Option<TransformType>; 4],
    transform_order: Vec<u8>,
    width: u16,
    height: u16,
}

Fields

bit_reader: BitReader<R>

transforms: [Option<TransformType>; 4]

transform_order: Vec<u8>

width: u16

height: u16

Implementations

impl<R: BufRead> LosslessDecoder<R>

pub(crate) const fn new(r: R) -> Self

Create a new decoder

pub(crate) fn decode_frame( &mut self, width: u32, height: u32, implicit_dimensions: bool, buf: &mut [u8], ) -> Result<(), DecodingError>

Decodes a frame.

In an alpha chunk the width and height are not included in the header, so they should be provided by setting the implicit_dimensions argument. Otherwise that argument should be None and the frame dimensions will be determined by reading the VP8L header.

fn decode_image_stream( &mut self, xsize: u16, ysize: u16, is_argb_img: bool, data: &mut [u8], ) -> Result<(), DecodingError>

Reads Image data from the bitstream

Can be in any of the 5 roles described in the Specification. ARGB Image role has different behaviour to the other 4. xsize and ysize describe the size of the blocks where each block has its own entropy code

fn read_transforms(&mut self) -> Result<u16, DecodingError>

Reads transforms and their data from the bitstream

fn adjust_color_map(color_map: &mut [u8])

Adjusts the color map since it’s subtraction coded

fn read_huffman_codes( &mut self, read_meta: bool, xsize: u16, ysize: u16, color_cache: Option<ColorCache>, ) -> Result<HuffmanInfo, DecodingError>

Reads huffman codes associated with an image

fn read_huffman_code( &mut self, alphabet_size: u16, ) -> Result<HuffmanTree, DecodingError>

Decodes and returns a single huffman tree

fn read_huffman_code_lengths( &mut self, code_length_code_lengths: Vec<u16>, num_symbols: u16, ) -> Result<Vec<u16>, DecodingError>

Reads huffman code lengths

fn decode_image_data( &mut self, width: u16, height: u16, huffman_info: HuffmanInfo, data: &mut [u8], ) -> Result<(), DecodingError>

Decodes the image data using the huffman trees and either of the 3 methods of decoding

fn read_color_cache(&mut self) -> Result<Option<u8>, DecodingError>

Reads color cache data from the bitstream

fn get_copy_distance( bit_reader: &mut BitReader<R>, prefix_code: u16, ) -> Result<usize, DecodingError>

Gets the copy distance from the prefix code and bitstream

fn plane_code_to_distance(xsize: u16, plane_code: usize) -> usize

Gets distance to pixel

Trait Implementations

impl<R: Debug> Debug for LosslessDecoder<R>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.