Add TIFF compression and corresponding tests

src/encoder/compression/mod.rs

@@ -0,0 +1,58 @@
+use std::io::prelude::*;
+
+use crate::{
+    encoder::{ColorType, DirectoryEncoder, TiffKind, TiffValue},
+    error::TiffResult,
+    tags::CompressionMethod,
+};
+
+mod deflate;
+mod lzw;
+mod uncompressed;
+
+pub use self::deflate::{Deflate, DeflateLevel};
+pub use self::lzw::Lzw;
+pub use self::uncompressed::Uncompressed;
+
+/// An algorithm used for compression with associated optional buffers and/or configurations.
+pub trait Compression: Default {
+    /// The corresponding tag to the algorithm.
+    const COMPRESSION_METHOD: CompressionMethod;
+
+    /// Write the data of a specific color type to the given encoder and return the offset and byte count, respectively.
+    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;
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::encoder::{colortype::Gray8, compression::Compression, TiffEncoder};
+    use std::io::Cursor;
+
+    pub const TEST_DATA: &'static [u8] =
+        b"This is a string for checking various compression algorithms.";
+
+    pub fn compress<C: Compression>(data: &[u8], compressor: C) -> Vec<u8> {
+        let mut buffer = Vec::new();
+
+        // Compress the data
+        {
+            let mut encoder = TiffEncoder::new(Cursor::new(&mut buffer)).unwrap();
+            let encoder = encoder
+                .new_image_with_compression::<Gray8, _>(data.len() as u32, 1, compressor)
+                .unwrap();
+            encoder.write_data(&data).unwrap();
+        }
+
+        // Remove the meta data written by the encoder
+        buffer.drain(..8);
+        buffer.drain(buffer.len() - 178..);
+
+        buffer
+    }
+}