Implement DEFLATE compression level control properly, with a semver break

benches/encode.rs

@@ -4,7 +4,7 @@ extern crate tiff;
 use criterion::{black_box, Criterion, Throughput};
 use std::io::Cursor;
 use tiff::encoder::colortype::RGB32Float;
-use tiff::encoder::{Compression, DeflateLevel, Predictor, TiffEncoder};
+use tiff::encoder::{Compression, Predictor, TiffEncoder};
 
 const WIDTH: u32 = 500;
 const HEIGHT: u32 = 500;
@@ -14,7 +14,7 @@ fn encode_image_f32_float_predictor_deflate(data: &[f32]) {
     TiffEncoder::new(&mut buf)
         .unwrap()
         .with_predictor(Predictor::FloatingPoint)
-        .with_compression(Compression::Deflate(DeflateLevel::Fast))
+        .with_compression(Compression::Deflate(1))
         .write_image::<RGB32Float>(WIDTH, HEIGHT, black_box(data))
         .unwrap();
 }

src/encoder/compression/deflate.rs

@@ -7,24 +7,15 @@ pub struct Deflate {
     level: FlateCompression,
 }
 
-/// The level of compression used by the Deflate algorithm.
-/// It allows trading compression ratio for compression speed.
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
-#[non_exhaustive]
-#[derive(Default)]
-pub enum DeflateLevel {
-    /// The fastest possible compression mode.
-    Fast = 1,
-    /// The conserative choice between speed and ratio.
-    #[default]
-    Balanced = 6,
-    /// The best compression available with Deflate.
-    Best = 9,
-}
-
 impl Deflate {
     /// Create a new deflate compressor with a specific level of compression.
-    pub fn with_level(level: DeflateLevel) -> Self {
+    ///
+    /// The valid levels are 1 through 9 inclusive. The default level is 6.
+    ///
+    /// - `1` stands for light but fast compression
+    /// - `6` is the recommended balanced default
+    /// - `9` is maximum compression ratio at the cost of slow encoding
+    pub fn with_level(level: u8) -> Self {
         Self {
             level: FlateCompression::new(level as u32),
         }
@@ -33,7 +24,7 @@ impl Deflate {
 
 impl Default for Deflate {
     fn default() -> Self {
-        Self::with_level(DeflateLevel::default())
+        Self::with_level(6)
     }
 }
 

src/encoder/compression/mod.rs

@@ -9,7 +9,7 @@ mod packbits;
 mod uncompressed;
 
 #[cfg(feature = "deflate")]
-pub use self::deflate::{Deflate, DeflateLevel};
+pub use self::deflate::Deflate;
 
 #[cfg(feature = "lzw")]
 pub use self::lzw::Lzw;

src/encoder/mod.rs

@@ -38,8 +38,6 @@ use self::writer::*;
 /// [Predictor::Horizontal] is for integer sample types.
 /// [Predictor::FloatingPoint] is for floating-point sample types (f32, f64).
 pub type Predictor = crate::tags::Predictor;
-#[cfg(feature = "deflate")]
-pub type DeflateLevel = compression::DeflateLevel;
 
 #[derive(Clone, Copy, PartialEq, Default)]
 pub enum Compression {
@@ -48,7 +46,7 @@ pub enum Compression {
     #[cfg(feature = "lzw")]
     Lzw,
     #[cfg(feature = "deflate")]
-    Deflate(DeflateLevel),
+    Deflate(u8),
     Packbits,
 }
 

tests/encode_images_with_compression.rs

@@ -5,7 +5,6 @@ use tiff::{
     decoder::{Decoder, DecodingResult},
     encoder::{
         colortype::{self, ColorType},
-        compression::*,
         Compression, TiffEncoder, TiffValue,
     },
 };
@@ -147,9 +146,9 @@ fn encode_decode_with_lzw() {
 #[test]
 #[cfg(feature = "deflate")]
 fn encode_decode_with_deflate() {
-    encode_decode_with_compression(Compression::Deflate(DeflateLevel::Fast));
+    encode_decode_with_compression(Compression::Deflate(1));
-    encode_decode_with_compression(Compression::Deflate(DeflateLevel::Balanced));
+    encode_decode_with_compression(Compression::Deflate(6));
-    encode_decode_with_compression(Compression::Deflate(DeflateLevel::Best));
+    encode_decode_with_compression(Compression::Deflate(9));
 }
 
 #[test]