TIFF: save uncompressed by default, like Photoshop (fixes #4484) (#4491)

crates/codecs/src/options.rs

@@ -100,12 +100,13 @@ pub enum PngCompression {
     Best,
 }
 
-/// TIFF strip compression.
+/// TIFF strip compression. The default is none, as in Photoshop: uncompressed strips are the
+/// only kind every TIFF reader opens (Deflate and the predictor are not baseline TIFF, #4484).
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
 pub enum TiffCompression {
+    #[default]
     None,
     Lzw,
-    #[default]
     Deflate,
     PackBits,
 }
@@ -190,7 +191,7 @@ impl Default for EncodeOptions {
             png_interlaced: false,
             webp_lossless: true,
             webp_quality: 80,
-            tiff_compression: TiffCompression::Deflate,
+            tiff_compression: TiffCompression::None,
             tiff_bigtiff: false,
             exr_compression: ExrCompression::Zip16,
             dpx_bits: None,

crates/codecs/tests/tiff_regressions.rs

@@ -150,3 +150,27 @@ fn ccitt_group4_tiff_decodes() {
     assert_ne!(d[0], d[8], "{d:?}");
     assert_eq!(d[0], 255, "white row of a WhiteIsZero image");
 }
+
+/// #4484: a TIFF saved with the default options must open in software that only reads
+/// baseline TIFF (embroidery and plotter tools, older readers). Like Photoshop's default, that
+/// means uncompressed strips with no predictor, classic offsets and unassociated alpha.
+#[test]
+fn default_tiff_is_baseline() {
+    use photocraft_codecs::{ChannelLayout, EncodeOptions, Format, SampleType, encode};
+    use std::io::Cursor;
+    use tiff::tags::Tag;
+
+    for layout in [ChannelLayout::Rgb, ChannelLayout::Rgba] {
+        let img = common::synth(33, 21, layout, SampleType::U8, 7, 0.4);
+        let bytes = encode(&img, Format::Tiff, &EncodeOptions::default()).expect("encode");
+        assert!(bytes.starts_with(b"II*\0") || bytes.starts_with(b"MM\0*"), "{layout:?}: not a classic TIFF");
+        let mut dec = tiff::decoder::Decoder::new(Cursor::new(&bytes[..])).expect("open");
+        assert_eq!(dec.get_tag_u32(Tag::Compression).ok(), Some(1), "{layout:?}: Compression");
+        assert_eq!(dec.find_tag(Tag::Predictor).ok().flatten().and_then(|v| v.into_u16().ok()).unwrap_or(1), 1, "{layout:?}: Predictor");
+        assert!(dec.find_tag(Tag::TileWidth).ok().flatten().is_none(), "{layout:?}: tiled");
+        assert_eq!(dec.get_tag_u32(Tag::PlanarConfiguration).ok().unwrap_or(1), 1, "{layout:?}: planar");
+        let extra = dec.find_tag(Tag::ExtraSamples).ok().flatten().and_then(|v| v.into_u16_vec().ok());
+        assert_eq!(extra, if layout == ChannelLayout::Rgba { Some(vec![2]) } else { None }, "{layout:?}: ExtraSamples");
+        assert_eq!(decode(&bytes).expect("decode").data(), img.data(), "{layout:?}: round trip");
+    }
+}