Merge PR #1666

# Conflicts:
#	docs/whats-new.md

crates/raw/src/dngwrite.rs

@@ -112,15 +112,24 @@ pub fn write_dng(raw: &RawImage, opts: &DngWriteOptions) -> Result<Vec<u8>> {
     ifd.set(t::PHOTOMETRIC, Value::Short(vec![if raw.cfa.is_some() { photometric::CFA } else { photometric::LINEAR_RAW }]));
     ifd.set(t::DNG_VERSION, Value::Byte(vec![1, 4, 0, 0]));
     ifd.set(t::DNG_BACKWARD_VERSION, Value::Byte(vec![1, 3, 0, 0]));
-    let make = raw.metadata.make.clone().unwrap_or_default();
-    let model = raw.metadata.model.clone().unwrap_or_default();
+    let make = raw.metadata.make.as_deref().unwrap_or_default();
+    let model = raw.metadata.model.as_deref().unwrap_or_default();
     if !make.is_empty() {
-        ifd.set(t::MAKE, Value::Ascii(make.clone()));
+        ifd.set(t::MAKE, Value::Ascii(make.to_owned()));
     }
     if !model.is_empty() {
-        ifd.set(t::MODEL, Value::Ascii(model.clone()));
+        ifd.set(t::MODEL, Value::Ascii(model.to_owned()));
     }
-    let unique = format!("{make} {model}").trim().to_string();
+    let model_includes_make = !make.is_empty()
+        && model.get(..make.len()).is_some_and(|prefix| prefix.eq_ignore_ascii_case(make))
+        && model.get(make.len()..).is_some_and(|suffix| suffix.chars().next().is_none_or(|c| !c.is_alphanumeric() && c != '_'));
+    let unique = if model_includes_make || make.is_empty() {
+        model.to_owned()
+    } else if model.is_empty() {
+        make.to_owned()
+    } else {
+        format!("{make} {model}")
+    };
     ifd.set(t::UNIQUE_CAMERA_MODEL, Value::Ascii(if unique.is_empty() { "LightCraft".into() } else { unique }));
     ifd.set(t::ORIENTATION, Value::Short(vec![raw.orientation.to_exif()]));
     ifd.set(t::SOFTWARE, Value::Ascii(SOFTWARE.into()));

crates/raw/tests/dng.rs

@@ -90,6 +90,45 @@ fn assert_same(a: &RawImage, b: &RawImage) {
     assert_eq!(b.metadata.rating, Some(3));
 }
 
+#[test]
+fn writer_camera_identity_tags_roundtrip() {
+    let cases = [
+        (Some("Canon"), Some("Canon EOS R6"), "Canon EOS R6"),
+        (Some("CANON"), Some("cAnOn EOS R6"), "cAnOn EOS R6"),
+        (Some("Canon"), Some("Canon"), "Canon"),
+        (Some("Canon"), Some("Canon-EOS R6"), "Canon-EOS R6"),
+        (Some("Canon"), Some("Canon_EOS R6"), "Canon Canon_EOS R6"),
+        (Some("Canon"), Some("Canonic R6"), "Canon Canonic R6"),
+        (Some("Canon"), Some("Canon2 R6"), "Canon Canon2 R6"),
+        (Some("Canon"), Some("Canoné R6"), "Canon Canoné R6"),
+        (Some("Canon"), Some("EOS R6"), "Canon EOS R6"),
+        (Some("Eastman Kodak"), Some("eAsTmAn kOdAk DCS Pro"), "eAsTmAn kOdAk DCS Pro"),
+        (Some("Eastman Kodak"), Some("Eastman Kodakish DCS Pro"), "Eastman Kodak Eastman Kodakish DCS Pro"),
+        (Some("Eastman Kodak"), Some("Eastman DCS Pro"), "Eastman Kodak Eastman DCS Pro"),
+        (Some(""), Some("EOS R6"), "EOS R6"),
+        (Some("Canon"), Some(""), "Canon"),
+        (Some(""), Some(""), "LightCraft"),
+        (None, Some("EOS R6"), "EOS R6"),
+        (Some("Canon"), None, "Canon"),
+        (None, None, "LightCraft"),
+    ];
+    for (make, model, unique) in cases {
+        let mut raw = synthetic(16, 16, Some(Cfa::bayer("RGGB").unwrap()), 1);
+        raw.metadata.make = make.map(str::to_owned);
+        raw.metadata.model = model.map(str::to_owned);
+        for order in [ByteOrder::Little, ByteOrder::Big] {
+            let bytes = write_dng(&raw, &DngWriteOptions { compression: DngCompression::Uncompressed, order, xmp: None }).unwrap();
+            let tiff = lightcraft_tiff::Tiff::parse(&bytes).unwrap();
+            let ifd = &tiff.ifds[0];
+            assert_eq!(ifd.value(t::UNIQUE_CAMERA_MODEL), Some(&Value::Ascii(unique.into())), "{make:?} / {model:?}, {order:?}");
+            for (tag, original) in [(t::MAKE, make), (t::MODEL, model)] {
+                let expected = original.filter(|s| !s.is_empty()).map(|s| Value::Ascii(s.into()));
+                assert_eq!(ifd.value(tag), expected.as_ref(), "tag {tag}, {make:?} / {model:?}, {order:?}");
+            }
+        }
+    }
+}
+
 #[test]
 fn writer_roundtrip_all_layouts() {
     for (w, h) in [(64, 48), (70, 45), (33, 17)] {

docs/whats-new.md

@@ -85,6 +85,11 @@
 - A demo photo whose stored size was damaged (a width of 4294967295) is rendered at its own size instead of
   one that overflows.
 
+### DNG camera identity
+- DNG export and Convert to DNG no longer duplicate the camera make when the model already
+  contains it: `Canon EOS R6` stays `Canon EOS R6`, rather than `Canon Canon EOS R6` (the camera
+  identity subissue in #840). The separate Make and Model tags keep their original values.
+  This does not change colour matrices, camera calibration or RAW noise rendering.
 ### Slider drags on large raws
 - Dragging a slider no longer re-renders the edited photo's filmstrip thumbnail on every frame; it follows once you
   let go. On a 64 MP raw the first of those renders decoded the whole file again, which held up the loupe's