47 lines
1.7 KiB
Rust
47 lines
1.7 KiB
Rust
use crate::encoder::compression::*;
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use weezl::encode::Encoder as LZWEncoder;
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/// The LZW algorithm used to compress image data in TIFF files.
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#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
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pub struct Lzw;
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impl Compression for Lzw {
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const COMPRESSION_METHOD: CompressionMethod = CompressionMethod::LZW;
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fn get_algorithm(&self) -> Compressor {
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Compressor::Lzw(*self)
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}
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}
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impl CompressionAlgorithm for Lzw {
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fn write_to<W: Write>(&mut self, writer: &mut W, bytes: &[u8]) -> Result<u64, io::Error> {
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let mut encoder = LZWEncoder::with_tiff_size_switch(weezl::BitOrder::Msb, 8);
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let result = encoder.into_stream(writer).encode_all(bytes);
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let byte_count = result.bytes_written as u64;
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result.status.map(|_| byte_count)
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use crate::encoder::compression::tests::TEST_DATA;
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use std::io::Cursor;
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#[test]
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fn test_lzw() {
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const EXPECTED_COMPRESSED_DATA: [u8; 63] = [
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0x80, 0x15, 0x0D, 0x06, 0x93, 0x98, 0x82, 0x08, 0x20, 0x30, 0x88, 0x0E, 0x67, 0x43,
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0x91, 0xA4, 0xDC, 0x67, 0x10, 0x19, 0x8D, 0xE7, 0x21, 0x01, 0x8C, 0xD0, 0x65, 0x31,
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0x9A, 0xE1, 0xD1, 0x03, 0xB1, 0x86, 0x1A, 0x6F, 0x3A, 0xC1, 0x4C, 0x66, 0xF3, 0x69,
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0xC0, 0xE4, 0x65, 0x39, 0x9C, 0xCD, 0x26, 0xF3, 0x74, 0x20, 0xD8, 0x67, 0x89, 0x9A,
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0x4E, 0x86, 0x83, 0x69, 0xCC, 0x5D, 0x01,
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];
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let mut compressed_data = Vec::<u8>::new();
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let mut writer = Cursor::new(&mut compressed_data);
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Lzw.write_to(&mut writer, TEST_DATA).unwrap();
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assert_eq!(EXPECTED_COMPRESSED_DATA, compressed_data.as_slice());
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}
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}
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