Add TIFF compression and corresponding tests

src/encoder/compression/lzw.rs

@@ -0,0 +1,79 @@
+use std::{
+    convert::TryInto,
+    io::{Seek, Write},
+};
+
+use weezl::encode::Encoder as LZWEncoder;
+
+use crate::{
+    encoder::{
+        colortype::ColorType, compression::Compression, DirectoryEncoder, TiffKind, TiffValue,
+    },
+    tags::CompressionMethod,
+    TiffResult,
+};
+
+/// The LZW algorithm used to compress image data in TIFF files.
+#[derive(Debug, Clone)]
+pub struct Lzw {
+    buffer: Vec<u8>,
+}
+
+impl Default for Lzw {
+    fn default() -> Self {
+        // Lets be greedy and allocate more bytes in advance. We will likely encode longer image strips.
+        const DEFAULT_BUFFER_SIZE: usize = 256;
+        Self {
+            buffer: Vec::with_capacity(DEFAULT_BUFFER_SIZE),
+        }
+    }
+}
+
+impl Compression for Lzw {
+    const COMPRESSION_METHOD: CompressionMethod = CompressionMethod::LZW;
+
+    fn write_to<'a, T: ColorType, K: TiffKind, W: 'a + Write + Seek>(
+        &mut self,
+        encoder: &mut DirectoryEncoder<'a, W, K>,
+        value: &[T::Inner],
+    ) -> TiffResult<(K::OffsetType, K::OffsetType)>
+    where
+        [T::Inner]: TiffValue,
+    {
+        let bytes = value.data();
+        let compressed_byte_count = {
+            let mut encoder = LZWEncoder::with_tiff_size_switch(weezl::BitOrder::Msb, 8);
+            let result = encoder.into_vec(&mut self.buffer).encode_all(&bytes);
+            result.status.map(|_| result.consumed_out)
+        }?
+        .try_into()?;
+
+        let offset = encoder
+            .write_data(self.buffer.as_slice())
+            .and_then(K::convert_offset)?;
+
+        // Clear the buffer for the next compression.
+        self.buffer.clear();
+
+        Ok((offset, compressed_byte_count))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::encoder::compression::tests::{compress, TEST_DATA};
+
+    #[test]
+    fn test_lzw() {
+        const EXPECTED_COMPRESSED_DATA: [u8; 63] = [
+            0x80, 0x15, 0x0D, 0x06, 0x93, 0x98, 0x82, 0x08, 0x20, 0x30, 0x88, 0x0E, 0x67, 0x43,
+            0x91, 0xA4, 0xDC, 0x67, 0x10, 0x19, 0x8D, 0xE7, 0x21, 0x01, 0x8C, 0xD0, 0x65, 0x31,
+            0x9A, 0xE1, 0xD1, 0x03, 0xB1, 0x86, 0x1A, 0x6F, 0x3A, 0xC1, 0x4C, 0x66, 0xF3, 0x69,
+            0xC0, 0xE4, 0x65, 0x39, 0x9C, 0xCD, 0x26, 0xF3, 0x74, 0x20, 0xD8, 0x67, 0x89, 0x9A,
+            0x4E, 0x86, 0x83, 0x69, 0xCC, 0x5D, 0x01,
+        ];
+
+        let compressed_data = compress(TEST_DATA, super::Lzw::default());
+        assert_eq!(compressed_data, EXPECTED_COMPRESSED_DATA);
+    }
+}