tiff/encoder/compression/
lzw.rs

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

tiff/encoder/compression/
lzw.rs
