LR-EXP-DNGOPT: DNG export compression (lossless / ZIP / none)

ExportOptions.dng_compression (`dngCompression`: lossless (default) | deflate | uncompressed),
in the export dialog when the format is DNG. Corpus-gated test: all three decode, uncompressed
is the biggest.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/export.rs

@@ -445,6 +445,8 @@ pub struct ExportOptions {
     pub conflict: Conflict,
     /// TIFF compression.
     pub tiff_compression: TiffCompression,
+    /// DNG export: how the raw data is stored.
+    pub dng_compression: DngCompression,
     pub metadata: MetadataPolicy,
     /// Strip GPS / location even when the policy would include it.
     pub remove_location: bool,
@@ -472,6 +474,7 @@ impl Default for ExportOptions {
             subfolder: String::new(),
             conflict: Conflict::Unique,
             tiff_compression: TiffCompression::Deflate,
+            dng_compression: DngCompression::Lossless,
             metadata: MetadataPolicy::All,
             remove_location: false,
             watermark: None,
@@ -513,6 +516,7 @@ impl ExportOptions {
                 Some("zip" | "deflate") => TiffCompression::Deflate,
                 _ => d.tiff_compression,
             },
+            dng_compression: enm(p, "dngCompression").unwrap_or(d.dng_compression),
             metadata: enm(p, "metadata").unwrap_or(d.metadata),
             remove_location: p.get("removeLocation").and_then(Value::as_bool).unwrap_or(d.remove_location),
             watermark: match p.get("watermark") {
@@ -944,7 +948,7 @@ enum Work {
         path: String,
         read: Option<crate::merge::ByteReader>,
         packet: String,
-        dng: bool,
+        dng: Option<DngCompression>,
         label: String,
         size: (usize, usize),
     },
@@ -972,7 +976,7 @@ pub fn prepare_export(
             path: path.clone(),
             read: session.media.file_bytes.clone(),
             packet: crate::sidecar::sidecar_packet(p, &session.catalog),
-            dng: o.format == ExportFormat::Dng,
+            dng: (o.format == ExportFormat::Dng).then_some(o.dng_compression),
             label: p.file_name.clone(),
             size: (p.width as usize, p.height as usize),
         }
@@ -995,15 +999,20 @@ impl PreparedExport {
                     Some(r) => r(&path)?,
                     None => std::fs::read(&path).map_err(|e| format!("{path}: {e}"))?,
                 };
-                if !dng {
+                let Some(dng) = dng else {
                     return Ok(Exported { file_name, bytes, width: size.0, height: size.1, sidecars: vec![("xmp", packet.into_bytes())] });
-                }
+                };
                 if lightcraft_raw::probe(&bytes).is_none() {
                     return Err(format!("{label}: DNG export needs a raw photo"));
                 }
                 let raw = lightcraft_raw::decode(&bytes).map_err(|e| format!("{label}: {e}"))?;
                 drop(bytes);
-                let dng = lightcraft_raw::write_dng(&raw, &lightcraft_raw::DngWriteOptions { xmp: Some(packet), ..Default::default() })
+                let compression = match dng {
+                    DngCompression::Lossless => lightcraft_raw::DngCompression::Lj92 { tile: 256 },
+                    DngCompression::Deflate => lightcraft_raw::DngCompression::Deflate { tile: 256, half: false },
+                    DngCompression::Uncompressed => lightcraft_raw::DngCompression::Uncompressed,
+                };
+                let dng = lightcraft_raw::write_dng(&raw, &lightcraft_raw::DngWriteOptions { xmp: Some(packet), compression, ..Default::default() })
                     .map_err(|e| e.to_string())?;
                 Ok(Exported { file_name, bytes: dng, width: raw.width, height: raw.height, sidecars: Vec::new() })
             }
@@ -1011,6 +1020,18 @@ impl PreparedExport {
     }
 }
 
+/// How an exported DNG stores its raw data.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub enum DngCompression {
+    /// Lossless JPEG (the usual DNG compression).
+    #[default]
+    Lossless,
+    /// Deflate (zip) tiles with prediction.
+    Deflate,
+    Uncompressed,
+}
+
 /// The destination of a batch: a folder (with `ExportOptions::subfolder` and the conflict policy
 /// applied), or one exact file path (single photo; overwritten).
 #[derive(Clone, Debug, Default)]

crates/engine/src/tests_xmp.rs

@@ -415,3 +415,33 @@ fn gps_typed_in_is_saved_to_xmp() {
     s.execute("photo.setMeta", &json!({"gps": null})).unwrap();
     assert!(s.catalog.photo(id).unwrap().meta.gps.is_none());
 }
+
+/// DNG export compression: lossless, zip and none all decode; none is the biggest.
+#[test]
+fn dng_export_compression_choices() {
+    let corpus = std::env::var_os("LIGHTCRAFT_CORPUS")
+        .map(PathBuf::from)
+        .unwrap_or_else(|| Path::new(env!("CARGO_MANIFEST_DIR")).join("../../corpus"))
+        .join("raw/nef-nikon-d5100-uncompressed.nef");
+    if !corpus.exists() {
+        eprintln!("skip: {} absent", corpus.display());
+        return;
+    }
+    let mut s = Session::new().with_fs();
+    s.execute("library.import", &json!({"paths": [corpus.to_string_lossy()]})).unwrap();
+    let id = s.active().unwrap();
+    let mut sizes = Vec::new();
+    for c in ["lossless", "deflate", "uncompressed"] {
+        let o = crate::export::ExportOptions::from_json(&json!({"format": "dng", "dngCompression": c}));
+        let mut out = Vec::new();
+        let mut write = |_: &str, b: &[u8]| {
+            out = b.to_vec();
+            Ok(())
+        };
+        crate::export::export_batch(&mut s, &[id], &o, &crate::export::Destination { dir: "x".into(), exact: None }, &mut write, &|_| false).unwrap();
+        let raw = lightcraft_raw::decode(&out).unwrap_or_else(|e| panic!("{c}: {e}"));
+        assert!(raw.width > 1000, "{c}");
+        sizes.push((c, out.len()));
+    }
+    assert!(sizes[2].1 > sizes[0].1 && sizes[2].1 > sizes[1].1, "uncompressed is the biggest: {sizes:?}");
+}

crates/ui-egui/src/panels/dialogs.rs

@@ -559,6 +559,10 @@ pub fn show(app: &mut LightcraftApp, ctx: &egui::Context) {
                         use lightcraft_engine::export::TiffCompression as Z;
                         choices(ui, "Compression", "exportTiffCompression", &[(Z::None, "None"), (Z::Lzw, "LZW"), (Z::Deflate, "ZIP")], &mut opts.tiff_compression);
                     }
+                    if opts.format == F::Dng {
+                        use lightcraft_engine::export::DngCompression as Z;
+                        choices(ui, "Compression", "exportDngCompression", &[(Z::Lossless, "Lossless"), (Z::Deflate, "ZIP"), (Z::Uncompressed, "None")], &mut opts.dng_compression);
+                    }
                     field(ui, "File name", |ui| {
                         ui.add(egui::TextEdit::singleline(&mut opts.naming).hint_text("{name}-{seq}  ·  {date}").desired_width(f32::INFINITY))
                     });

docs/parity.md

@@ -39,7 +39,7 @@ and prints the summary; `cargo xtask parity --write` refreshes the summary table
 | P. Enhance (ENH) | 0 | 0 | 2 | 0 | — | — |
 | Q. HDR (HDR) | 0 | 0 | 5 | 0 | — | — |
 | R. Video (VID) | 0 | 0 | 5 | 1 | — | 0/2 (0%) |
-| S. Export (EXP) | 15 | 0 | 3 | 0 | 7/7 (100%) | 7/7 (100%) |
+| S. Export (EXP) | 15 | 1 | 2 | 0 | 7/7 (100%) | 7/7 (100%) |
 | T. Share (SHARE) | 0 | 0 | 0 | 4 | — | — |
 | U. Map & location (MAP) | 0 | 1 | 1 | 0 | — | 0/1 (0%) |
 | V. Preferences (PREF) | 5 | 0 | 3 | 3 | 1/1 (100%) | 4/4 (100%) |
@@ -48,9 +48,9 @@ and prints the summary; `cargo xtask parity --write` refreshes the summary table
 | Y. Menus | 79 | 2 | 4 | 8 | 46/47 (98%) | 22/23 (96%) |
 | Z. Keyboard shortcuts (desktop) | 74 | 3 | 3 | 1 | 49/52 (94%) | 22/23 (96%) |
 | Lightroom Classic extras | 22 | 10 | 47 | 9 | — | 18/21 (86%) |
-| **Total** | 370 | 25 | 105 | 37 | 193/198 (97%) | 132/144 (92%) |
+| **Total** | 370 | 26 | 104 | 37 | 193/198 (97%) | 132/144 (92%) |
 
-Weighted completion (✅ = 1, 🟡 = ½, 🚫 left out): **76.5%** of 500 in-scope rows — P0 98.7% of 198 · P1 94.4% of 144 · P2 32.3% of 158.
+Weighted completion (✅ = 1, 🟡 = ½, 🚫 left out): **76.6%** of 500 in-scope rows — P0 98.7% of 198 · P1 94.4% of 144 · P2 32.6% of 158.
 <!-- /parity:summary -->
 
 ## Top gaps
@@ -420,7 +420,7 @@ under the UI command that wraps it (a no-op error); the UI command now wins.
 | LR-EXP-NAMING | File naming | P1 | ✅ | `cmd:app.export` (`naming`: `{name}`, `{seq}`, `{date}`; `startNumber`) | free-form template rather than a list of named schemes |
 | LR-EXP-LOCATION | Destination folder | P0 | ✅ | `cmd:app.export` (`dir`, `subfolder`, `conflict`: unique / overwrite / skip), `crates/ui-egui/src/panels/dialogs.rs` (Choose… folder picker) | folder picker on the desktop; existing files get `-2`, `-3`… by default |
 | LR-EXP-PREVIOUS | Export with previous settings | P0 | ✅ | `cmd:app.exportPrevious`, `cmd:dialog.export` | last options persist in prefs.json; dialog prefilled; no named export presets yet |
-| LR-EXP-DNGOPT | DNG options | P2 | ⬜ | | |
+| LR-EXP-DNGOPT | DNG options | P2 | 🟡 | `cmd:app.export` (`dngCompression`), `crates/engine/src/export.rs` | compression: lossless JPEG (default), ZIP or none; no embedded JPEG preview size, no lossy DNG output |
 | LR-EXP-ORIGINAL | Original + XMP | P1 | ✅ | `cmd:app.export` (`format: original`) | file copied byte for byte, sidecar named after the output |
 | LR-EXP-PHOTOS | Export to the system photo library | P2 | ⬜ | | |
 | LR-EXP-PSD | Round trip to an external editor | P2 | ✅ | `cmd:photo.editExternal`, `cmd:photo.editInExternal`, `crates/engine/src/cmd/convert.rs` | a 16-bit TIFF `-Edit` copy with the edits (Adobe RGB / ProPhoto / P3 / sRGB) next to the original, added stacked on top of it and opened in the editor set in Settings ▸ General (or the system default) |