Support ZSTD compression method for reading (#256)

src/decoder/image.rs

@@ -378,7 +378,11 @@ impl Image {
             CompressionMethod::None => Box::new(reader),
             CompressionMethod::LZW => {
                 Box::new(LZWReader::new(reader, usize::try_from(compressed_length)?))
-            }
+            },
+            #[cfg(feature = "zstd")]
+            CompressionMethod::ZSTD => {
+                Box::new(zstd::Decoder::new(reader)?)
+            },
             CompressionMethod::PackBits => Box::new(PackBitsReader::new(reader, compressed_length)),
             CompressionMethod::Deflate | CompressionMethod::OldDeflate => {
                 Box::new(DeflateReader::new(reader))

src/tags.rs

@@ -184,6 +184,9 @@ pub enum CompressionMethod(u16) unknown("A custom compression method") {
     Deflate = 8,
     OldDeflate = 0x80B2,
     PackBits = 0x8005,
+
+    // Self-assigned by libtiff
+    ZSTD = 0xC350,
 }
 }