1use crate::{encoder::compression::*, tags::CompressionMethod};
2use std::io::Write;
3use weezl::encode::Encoder as LZWEncoder;
4
5/// The LZW algorithm used to compress image data in TIFF files.
6#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
7pub struct Lzw;
8
9impl Compression for Lzw {
10 const COMPRESSION_METHOD: CompressionMethod = CompressionMethod::LZW;
11
12 fn get_algorithm(&self) -> Compressor {
13 Compressor::Lzw(*self)
14 }
15}
16
17impl CompressionAlgorithm for Lzw {
18 fn write_to<W: Write>(&mut self, writer: &mut W, bytes: &[u8]) -> Result<u64, io::Error> {
19 let mut encoder: Encoder = LZWEncoder::with_tiff_size_switch(order:weezl::BitOrder::Msb, size:8);
20 let result: StreamResult = encoder.into_stream(writer).encode_all(read:bytes);
21 let byte_count: u64 = result.bytes_written as u64;
22 result.status.map(|_| byte_count)
23 }
24}
25
26#[cfg(test)]
27mod tests {
28 use super::*;
29 use crate::encoder::compression::tests::TEST_DATA;
30 use std::io::Cursor;
31
32 #[test]
33 fn test_lzw() {
34 const EXPECTED_COMPRESSED_DATA: [u8; 63] = [
35 0x80, 0x15, 0x0D, 0x06, 0x93, 0x98, 0x82, 0x08, 0x20, 0x30, 0x88, 0x0E, 0x67, 0x43,
36 0x91, 0xA4, 0xDC, 0x67, 0x10, 0x19, 0x8D, 0xE7, 0x21, 0x01, 0x8C, 0xD0, 0x65, 0x31,
37 0x9A, 0xE1, 0xD1, 0x03, 0xB1, 0x86, 0x1A, 0x6F, 0x3A, 0xC1, 0x4C, 0x66, 0xF3, 0x69,
38 0xC0, 0xE4, 0x65, 0x39, 0x9C, 0xCD, 0x26, 0xF3, 0x74, 0x20, 0xD8, 0x67, 0x89, 0x9A,
39 0x4E, 0x86, 0x83, 0x69, 0xCC, 0x5D, 0x01,
40 ];
41
42 let mut compressed_data = Vec::<u8>::new();
43 let mut writer = Cursor::new(&mut compressed_data);
44 Lzw.write_to(&mut writer, TEST_DATA).unwrap();
45 assert_eq!(EXPECTED_COMPRESSED_DATA, compressed_data.as_slice());
46 }
47}
48