Merge PR #1410

# Conflicts:
#	docs/whats-new.md

crates/engine/src/camera_preview.rs

@@ -345,6 +345,7 @@ fn proxies(raw: &RawImage, bytes: &[u8], transform: &CameraTransform, size: usiz
     let decoded = crate::files::decode_raw_preview(
         bytes,
         lightcraft_codecs::DecodeOptions { max_size: Some((edge, edge)), max_pixels: FIT_PREVIEW_MAX_PIXELS },
+        None,
     )?;
     let mut reference = decoded.to_working();
     let (a, crop) = (raw.active_area, raw.crop.clipped(raw.active_area.width, raw.active_area.height));

crates/engine/src/files.rs

@@ -622,11 +622,16 @@ fn preview_orientation(raw_bytes: &[u8], jpeg_orientation: u16) -> Orientation {
     lightcraft_meta::extract(raw_bytes).orientation.unwrap_or(Orientation::Normal)
 }
 
-/// What stands in for a raw file we can't decode: its largest embedded JPEG, else, for a TIFF-based
-/// raw, the file's own first image when the TIFF reader can show it (a reduced RGB copy: the only
-/// preview some containers carry). Returns image bytes for [`lightcraft_codecs::decode`].
-fn stand_in_image(bytes: &[u8]) -> Option<std::borrow::Cow<'_, [u8]>> {
-    if let Some(jpeg) = lightcraft_raw::embedded_preview(bytes) {
+/// What stands in for a raw file we can't decode: its largest embedded JPEG (with `covering`, the smallest one that is
+/// at least that big, [`lightcraft_raw::embedded_preview_covering`]), else, for a TIFF-based raw, the file's own first
+/// image when the TIFF reader can show it (a reduced RGB copy: the only preview some containers carry). Returns image
+/// bytes for [`lightcraft_codecs::decode`].
+fn stand_in_image(bytes: &[u8], covering: Option<usize>) -> Option<std::borrow::Cow<'_, [u8]>> {
+    let jpeg = match covering {
+        Some(edge) => lightcraft_raw::embedded_preview_covering(bytes, u32::try_from(edge).unwrap_or(u32::MAX)),
+        None => lightcraft_raw::embedded_preview(bytes),
+    };
+    if let Some(jpeg) = jpeg {
         return Some(std::borrow::Cow::Owned(jpeg));
     }
     let undecodable = lightcraft_raw::probe(bytes).is_some_and(|f| !f.is_supported());
@@ -634,9 +639,14 @@ fn stand_in_image(bytes: &[u8]) -> Option<std::borrow::Cow<'_, [u8]>> {
         .then_some(std::borrow::Cow::Borrowed(bytes))
 }
 
-/// Shared colour interpretation for quick previews, unsupported RAW fallback and camera-look fitting.
-pub(crate) fn decode_raw_preview(bytes: &[u8], opts: lightcraft_codecs::DecodeOptions) -> Option<lightcraft_codecs::Decoded> {
-    let jpeg = stand_in_image(bytes)?;
+/// Shared colour interpretation for quick previews, unsupported RAW fallback and camera-look fitting (`covering`: see
+/// [`stand_in_image`]).
+pub(crate) fn decode_raw_preview(
+    bytes: &[u8],
+    opts: lightcraft_codecs::DecodeOptions,
+    covering: Option<usize>,
+) -> Option<lightcraft_codecs::Decoded> {
+    let jpeg = stand_in_image(bytes, covering)?;
     // the colour space is a property of the JPEG; a TIFF stand-in is read by the TIFF reader
     let is_jpeg = matches!(jpeg, std::borrow::Cow::Owned(_));
     match lightcraft_raw::embedded_preview_color_space(bytes).filter(|_| is_jpeg) {
@@ -653,7 +663,7 @@ pub(crate) fn decode_raw_preview(bytes: &[u8], opts: lightcraft_codecs::DecodeOp
 
 /// Oriented size of the embedded preview of a raw file.
 fn embedded_preview_size(bytes: &[u8]) -> Option<(u32, u32)> {
-    let jpeg = stand_in_image(bytes)?;
+    let jpeg = stand_in_image(bytes, None)?;
     // headers only, as for other images (issue #367): decoding a full-size preview just for its
     // size took about a second per file in an import; a decode remains the fallback
     let (mut w, mut h, orientation) = match lightcraft_codecs::read_header(&jpeg) {
@@ -671,16 +681,18 @@ fn embedded_preview_size(bytes: &[u8]) -> Option<(u32, u32)> {
 
 /// The embedded preview of a raw file as a working-space image no larger than `max_edge`, oriented.
 pub fn load_embedded_preview(bytes: &[u8], max_edge: usize) -> Option<(Rgb32f, SourceInfo)> {
-    let d = decode_raw_preview(bytes, fit_box(max_edge))?;
+    // always the largest JPEG: a source's geometry must not depend on its size level (previews match exports)
+    let d = decode_raw_preview(bytes, fit_box(max_edge), None)?;
     let img = d.to_working();
     let img = if img.width.max(img.height) > max_edge { fit(&img, max_edge, max_edge, Filter::Mitchell) } else { img };
     Some((img.oriented(preview_orientation(bytes, d.orientation)), SourceInfo::default()))
 }
 
 /// The embedded preview of a raw file for display (sRGB, oriented, no larger than `max_edge`): the
-/// loupe and grid show it until the raw itself has been developed ([`crate::media::QuickJob`]).
+/// loupe and grid show it until the raw itself has been developed ([`crate::media::QuickJob`]). The smallest
+/// embedded JPEG that covers `max_edge` is decoded, not the largest.
 pub fn embedded_preview_srgb(bytes: &[u8], max_edge: usize) -> Option<lightcraft_raster::Rgba8> {
-    let mut d = decode_raw_preview(bytes, fit_box(max_edge))?;
+    let mut d = decode_raw_preview(bytes, fit_box(max_edge), Some(max_edge))?;
     if d.image.width.max(d.image.height) > max_edge {
         d.image = fit(&d.image, max_edge, max_edge, Filter::Box);
         d.alpha = None;
@@ -708,7 +720,9 @@ pub fn fs_preview_loader() -> PreviewLoader {
         let len = std::fs::metadata(path).map(|m| usize::try_from(m.len()).unwrap_or(usize::MAX)).unwrap_or(0);
         let gate = crate::memory::work_gate();
         let _permit = if crate::memory::is_background() { gate.acquire(len.saturating_mul(2)) } else { gate.acquire_urgent(len.saturating_mul(2)) };
-        if let Some(image) = preview_window(path).ok().flatten().and_then(|(header, window, _)| quick_image_srgb(&header, &window, max_edge)) {
+        if let Some(image) =
+            preview_window(path, max_edge).ok().flatten().and_then(|(header, window, _)| quick_image_srgb(&header, &window, max_edge))
+        {
             return Some(image);
         }
         embedded_preview_srgb(&std::fs::read(path).ok()?, max_edge)
@@ -743,7 +757,9 @@ impl PreviewRead {
 
 /// The file's header and its embedded preview, read without the rest of the file: `(header bytes,
 /// preview bytes, what was read)`. `None` when the header points at no preview this build can find,
-/// which is the caller's cue to read the file whole.
+/// which is the caller's cue to read the file whole. `max_edge` is the size the preview is for: where a file keeps
+/// several JPEGs (the plan route), the window is the one [`embedded_preview_srgb`] decodes for that size, the smallest
+/// that covers it ([`lightcraft_raw::embedded_preview_covering`]).
 ///
 /// Why it exists: a 56 MB Fuji RAF keeps its JPEG in the first 5.6 MB (measured: `DSCF9492.RAF`),
 /// so reading the file whole to extract it costs ten times the bytes — and on a network share ten
@@ -751,7 +767,7 @@ impl PreviewRead {
 /// still needs the whole container, so the header comes back with the window; for a preview taken
 /// out of a container that carries no preview colour space of its own (Nikon's maker note) the
 /// whole-file fallback stays in charge.
-pub fn preview_window(path: &str) -> Result<Option<(Vec<u8>, Vec<u8>, PreviewRead)>, String> {
+pub fn preview_window(path: &str, max_edge: usize) -> Result<Option<(Vec<u8>, Vec<u8>, PreviewRead)>, String> {
     use std::io::{Read, Seek, SeekFrom};
 
     let mut file = std::fs::File::open(path).map_err(|e| format!("{path}: {e}"))?;
@@ -773,7 +789,7 @@ pub fn preview_window(path: &str) -> Result<Option<(Vec<u8>, Vec<u8>, PreviewRea
         // preview tag sits past the prefix, the containers whose preview only a scan finds: ask the
         // sparse planner which ranges `embedded_preview` reads before handing the caller the
         // whole-file fallback.
-        return planned_preview(&mut file, path, total);
+        return planned_preview(&mut file, path, total, max_edge);
     };
     // A preview at the file's end may have been padded past it: clamp rather than fail.
     let end = range.offset.saturating_add(range.window_len).min(total);
@@ -838,7 +854,7 @@ const PLAN_PREFIX: u64 = 64 * 1024;
 /// below). The planner's contract is the one its corpus test asserts over real files (what it loaded
 /// gives what the whole file gives), so a window that still fails to decode ends in the same
 /// whole-file fallback in [`fs_preview_loader`], never in a wrong picture.
-fn planned_preview(file: &mut std::fs::File, path: &str, total: u64) -> Result<Option<(Vec<u8>, Vec<u8>, PreviewRead)>, String> {
+fn planned_preview(file: &mut std::fs::File, path: &str, total: u64, max_edge: usize) -> Result<Option<(Vec<u8>, Vec<u8>, PreviewRead)>, String> {
     use std::io::{Read, Seek, SeekFrom};
 
     if total > MAX_PREVIEW_PLAN_BYTES {
@@ -867,7 +883,9 @@ fn planned_preview(file: &mut std::fs::File, path: &str, total: u64) -> Result<O
                 }
             }
             lightcraft_raw::sparse::HeaderPlan::Ready => {
-                let Some(window) = lightcraft_raw::embedded_preview(&buf) else { return Ok(None) };
+                // the plan loads every preview's strips, so the JPEG picked for `max_edge` is the whole file's pick
+                let edge = u32::try_from(max_edge).unwrap_or(u32::MAX);
+                let Some(window) = lightcraft_raw::embedded_preview_covering(&buf, edge) else { return Ok(None) };
                 // The quick path hands the JPEG to the decoder alone, so what the *container* says
                 // about the preview has to be something the bytes it is handed can show. Two container
                 // facts change the pixels and are not in the JPEG: the preview's colour space (which
@@ -1125,7 +1143,7 @@ mod tests {
         let path = path.to_string_lossy().into_owned();
         let max_edge = 512;
 
-        let (header, window, read) = preview_window(&path).expect("the file reads").expect("it has a preview");
+        let (header, window, read) = preview_window(&path, max_edge).expect("the file reads").expect("it has a preview");
         assert_eq!(header.len(), lightcraft_raw::PREVIEW_PREFIX, "the header prefix is bounded");
         assert!(read.header_path, "the header path is what answered");
         assert!(!read.planned, "a RAF pointer in the header needs no planner");
@@ -1142,8 +1160,8 @@ mod tests {
         // A file with no locatable preview declines (the caller then reads it whole), a missing file errors.
         let plain = dir.join("plain.jpg");
         std::fs::write(&plain, &jpeg).unwrap();
-        assert!(preview_window(&plain.to_string_lossy()).expect("a plain file reads").is_none());
-        assert!(preview_window(&dir.join("nope.raf").to_string_lossy()).is_err());
+        assert!(preview_window(&plain.to_string_lossy(), max_edge).expect("a plain file reads").is_none());
+        assert!(preview_window(&dir.join("nope.raf").to_string_lossy(), max_edge).is_err());
         let _ = std::fs::remove_dir_all(&dir);
     }
 
@@ -1163,6 +1181,12 @@ mod tests {
     /// `tail` bytes. The writer puts each IFD's table after its own chunk, so a `strip` bigger than
     /// the plan's bounded header puts IFD0 (and any orientation tag in it) out of that header's reach.
     fn tiff_with_preview_strip(strip: &[u8], tail: usize, what: Fixture) -> Vec<u8> {
+        tiff_with_preview_strips(strip, &[], tail, what)
+    }
+
+    /// [`tiff_with_preview_strip`] that also keeps the `smaller` JPEGs in sub-IFDs of IFD0, as an ARW keeps its
+    /// 1616 px preview beside the full-size one.
+    fn tiff_with_preview_strips(strip: &[u8], smaller: &[&[u8]], tail: usize, what: Fixture) -> Vec<u8> {
         use lightcraft_tiff::{IfdBuilder, ImageData, TiffWriter, Value, tags as t};
         let mut preview = IfdBuilder::new();
         if what.dng {
@@ -1189,6 +1213,15 @@ mod tests {
         preview.set(t::IMAGE_WIDTH, Value::Long(vec![48]));
         preview.set(t::IMAGE_LENGTH, Value::Long(vec![32]));
         preview.set_image(ImageData::Strips { rows_per_strip: 32, strips: vec![strip.to_vec()] });
+        for jpeg in smaller {
+            let mut sub = IfdBuilder::new();
+            sub.set(t::COMPRESSION, Value::Short(vec![7]));
+            sub.set(t::PHOTOMETRIC, Value::Short(vec![t::photometric::RGB]));
+            sub.set(t::IMAGE_WIDTH, Value::Long(vec![48]));
+            sub.set(t::IMAGE_LENGTH, Value::Long(vec![32]));
+            sub.set_image(ImageData::Strips { rows_per_strip: 32, strips: vec![jpeg.to_vec()] });
+            preview.add_sub_ifd(sub);
+        }
         let mut raw = IfdBuilder::new();
         raw.set(t::COMPRESSION, Value::Short(vec![1]));
         raw.set(t::PHOTOMETRIC, Value::Short(vec![t::photometric::CFA]));
@@ -1216,7 +1249,7 @@ mod tests {
         let path = path.to_string_lossy().into_owned();
         let max_edge = 512;
 
-        let (header, window, read) = preview_window(&path).expect("the file reads").expect("the plan locates its preview");
+        let (header, window, read) = preview_window(&path, max_edge).expect("the file reads").expect("the plan locates its preview");
         assert_eq!(header.len(), PLAN_PREFIX as usize, "the plan's header is bounded");
         assert!(read.planned, "the planner is what answered");
         assert!(read.header_path, "and it is still a bounded read");
@@ -1234,7 +1267,39 @@ mod tests {
         // caller's whole-file read is what answers (no guessing at what a file might hold).
         let not_a_raw = tiff_with_preview_strip(&jpeg, 400_000, Fixture::default());
         std::fs::write(&path, &not_a_raw).unwrap();
-        assert!(preview_window(&path).expect("the file reads").is_none(), "an unknown container falls back");
+        assert!(preview_window(&path, max_edge).expect("the file reads").is_none(), "an unknown container falls back");
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+
+    /// A raw that keeps several JPEGs is shown, on the plan route as on the whole-file path, from the smallest one that
+    /// covers the box (`embedded_preview_covering`). The plan route used to hand on the largest whatever the size: an
+    /// A7R VI ARW's 9984 × 6656 JPEG for a 512 px thumbnail instead of its 1616 × 1080 one.
+    #[test]
+    fn preview_loading_plans_the_smallest_covering_jpeg() {
+        let jpeg = |w: u32, h: u32| {
+            let rgb: Vec<u8> = (0..w * h * 3).map(|i| (i * 31 % 247) as u8).collect();
+            encode_jpeg(&EncodeImage::new(w, h, 3, Samples::U8(&rgb)), 90, ChromaSubsampling::S420, &EncodeMeta::default()).unwrap()
+        };
+        let (big, small) = (jpeg(96, 64), jpeg(48, 32));
+        assert!(big.len() > small.len(), "the full-size JPEG is the largest");
+        let file = tiff_with_preview_strips(&big, &[&small], 400_000, Fixture { dng: true, ..Default::default() });
+        let dir = crate::tests_xmp::temp_dir("preview-plan-covering");
+        let path = dir.join("two-previews.dng");
+        std::fs::write(&path, &file).unwrap();
+        let path = path.to_string_lossy().into_owned();
+
+        for (edge, want, which) in [(48, &small, "small"), (49, &big, "full-size"), (usize::MAX, &big, "full-size")] {
+            let (header, window, read) = preview_window(&path, edge).expect("the file reads").expect("the plan locates its preview");
+            assert!(read.planned, "the planner is what answered");
+            assert!(&window == want, "a {edge} px box takes the {which} JPEG");
+            let quick = quick_image_srgb(&header, &window, edge).expect("the window holds a decodable preview");
+            let whole = embedded_preview_srgb(&file, edge).expect("the whole file decodes too");
+            assert_eq!(
+                (quick.width, quick.height, quick.data),
+                (whole.width, whole.height, whole.data),
+                "{edge} px: the plan and the whole file agree"
+            );
+        }
         let _ = std::fs::remove_dir_all(&dir);
     }
 
@@ -1262,7 +1327,7 @@ mod tests {
         assert_eq!(lightcraft_meta::extract(&file).orientation, Some(Orientation::from_exif(6)), "the fixture states an orientation");
         assert!(lightcraft_meta::extract(&file[..PLAN_PREFIX as usize]).orientation.is_none(), "which the bounded header cannot see");
         assert!(lightcraft_meta::extract(&jpeg).orientation.is_none(), "and the preview JPEG carries none of its own");
-        assert!(preview_window(&path).expect("the file reads").is_none(), "the whole-file path keeps it");
+        assert!(preview_window(&path, usize::MAX).expect("the file reads").is_none(), "the whole-file path keeps it");
         let _ = std::fs::remove_dir_all(&dir);
     }
 
@@ -1285,12 +1350,12 @@ mod tests {
         let adobe = tiff_with_preview_strip(&jpeg, 400_000, Fixture { sony: true, color_space: Some(0xFFFF), ..Default::default() });
         assert_eq!(lightcraft_raw::embedded_preview_color_space(&adobe), Some(PreviewColorSpace::AdobeRgb), "the fixture declares Adobe RGB");
         std::fs::write(&path, &adobe).unwrap();
-        assert!(preview_window(&path).expect("the file reads").is_none(), "the whole-file path applies the space");
+        assert!(preview_window(&path, usize::MAX).expect("the file reads").is_none(), "the whole-file path applies the space");
 
         let srgb = tiff_with_preview_strip(&jpeg, 400_000, Fixture { sony: true, color_space: Some(1), ..Default::default() });
         assert_eq!(lightcraft_raw::embedded_preview_color_space(&srgb), Some(PreviewColorSpace::Srgb), "the fixture declares sRGB");
         std::fs::write(&path, &srgb).unwrap();
-        let (_, window, read) = preview_window(&path).expect("the file reads").expect("sRGB is what the JPEG-only decode assumes");
+        let (_, window, read) = preview_window(&path, usize::MAX).expect("the file reads").expect("sRGB is what the JPEG-only decode assumes");
         assert!(read.planned, "the plan still answers");
         assert!(window.starts_with(&[0xff, 0xd8]), "and hands on the JPEG");
     }

crates/engine/tests/preview_read.rs

@@ -20,8 +20,9 @@ fn a_preview_reads_only_the_header_and_the_preview() {
     assert!(file_len > 0, "empty file");
 
     let started = Instant::now();
-    let window =
-        lightcraft_engine::files::preview_window(&path).expect("the file reads").expect("it carries an embedded preview the header can point at");
+    let window = lightcraft_engine::files::preview_window(&path, usize::MAX)
+        .expect("the file reads")
+        .expect("it carries an embedded preview the header can point at");
     let elapsed = started.elapsed();
     let (_, preview, read) = window;
 

crates/raw/src/lib.rs

@@ -56,7 +56,7 @@ pub use lightcraft_meta::Metadata;
 pub use lightcraft_raster::Rgb32f;
 pub use opcodes::{Opcode, OpcodeLists};
 pub use preview::{
-    PREVIEW_PREFIX, PreviewColorSpace, PreviewRange, bounded_preview, embedded_preview, embedded_preview_color_space,
+    PREVIEW_PREFIX, PreviewColorSpace, PreviewRange, bounded_preview, embedded_preview, embedded_preview_color_space, embedded_preview_covering,
     embedded_preview_dynamic_range_optimized, embedded_preview_from_range,
 };
 pub use semantic::{SemanticMask, semantic_masks};

crates/raw/src/preview.rs

@@ -65,31 +65,43 @@ pub fn embedded_preview_dynamic_range_optimized(bytes: &[u8]) -> Option<bool> {
     crate::vendor::arw::dynamic_range_optimizer(&mn)
 }
 
-/// Whether `b` looks like a displayable (DCT) JPEG: SOI, and the first SOF marker is not lossless.
-fn is_dct_jpeg(b: &[u8]) -> bool {
-    if b.len() < 4 || b[0] != 0xff || b[1] != 0xd8 {
-        return false;
+/// The first frame (SOF) marker of a JPEG and its position, from the marker segments before the first scan.
+fn first_frame(b: &[u8]) -> Option<(u8, usize)> {
+    if b.len() < 4 || !b.starts_with(&[0xff, 0xd8]) {
+        return None;
     }
-    let mut i = 2;
-    while i + 4 <= b.len() {
-        if b[i] != 0xff {
-            return false;
+    let mut i = 2usize;
+    while i.checked_add(4)? <= b.len() {
+        if *b.get(i)? != 0xff {
+            return None;
         }
-        let m = b[i + 1];
+        let m = *b.get(i + 1)?;
         if m == 0xff {
             i += 1;
             continue;
         }
         match m {
-            0xc0..=0xc2 => return true,
-            0xc3 | 0xc5..=0xc7 | 0xcb | 0xcd..=0xcf => return false,
-            0xda | 0xd9 => return false,
+            0xc0..=0xc3 | 0xc5..=0xc7 | 0xcb | 0xcd..=0xcf => return Some((m, i)),
+            0xda | 0xd9 => return None,
             _ => {}
         }
-        let len = u16::from_be_bytes([b[i + 2], b[i + 3]]) as usize;
-        i += 2 + len;
+        let len = usize::from(u16::from_be_bytes([*b.get(i + 2)?, *b.get(i + 3)?]));
+        i = i.checked_add(2 + len)?;
     }
-    false
+    None
+}
+
+/// Whether `b` looks like a displayable (DCT) JPEG: SOI, and the first SOF marker is not lossless.
+fn is_dct_jpeg(b: &[u8]) -> bool {
+    first_frame(b).is_some_and(|(m, _)| matches!(m, 0xc0..=0xc2))
+}
+
+/// Width, height and component count of a displayable (DCT) JPEG, from its frame header.
+fn jpeg_frame(b: &[u8]) -> Option<(u32, u32, u8)> {
+    let (_, i) = first_frame(b).filter(|(m, _)| matches!(m, 0xc0..=0xc2))?;
+    let at = |k: usize| b.get(i.checked_add(k)?).copied();
+    let be16 = |k: usize| Some(u32::from(u16::from_be_bytes([at(k)?, at(k + 1)?])));
+    Some((be16(7)?, be16(5)?, at(9)?))
 }
 
 /// Whether `b` is a JPEG XL file: a bare codestream or the ISO-BMFF container's signature box.
@@ -139,6 +151,33 @@ fn candidates<'a>(data: &'a [u8], ifd: &Ifd, base: u64, out: &mut Vec<&'a [u8]>)
 /// The largest embedded preview, if any: a JPEG, or (DNG 1.7) a JPEG XL file — both decode with
 /// `lightcraft_codecs::decode`.
 pub fn embedded_preview(bytes: &[u8]) -> Option<Vec<u8>> {
+    preview_covering(bytes, None)
+}
+
+/// The smallest embedded JPEG whose long edge is at least `min_edge` and that looks like a copy of the largest preview
+/// (its aspect ratio within 1 %, so not a letterboxed or cropped thumbnail, and as many colour components, so not a
+/// grey mask or depth map), else [`embedded_preview`]. Only TIFF-based raws keep several: an A7R VI's 1616 × 1080
+/// preview is 0.3 MB beside its 9984 × 6656 one (5.6 MB), so a stand-in up to 1616 px decodes about a twentieth of the data.
+pub fn embedded_preview_covering(bytes: &[u8], min_edge: u32) -> Option<Vec<u8>> {
+    preview_covering(bytes, Some(min_edge))
+}
+
+/// Of the DCT JPEGs in `found`, the one with the shortest long edge of at least `min_edge` with `largest`'s aspect
+/// ratio (within 1 %) and component count.
+fn smallest_covering<'a>(found: &[&'a [u8]], largest: &[u8], min_edge: u32) -> Option<&'a [u8]> {
+    let (bw, bh, bc) = jpeg_frame(largest)?;
+    let like = |(w, h, c): (u32, u32, u8)| {
+        let (a, b) = (u64::from(w) * u64::from(bh), u64::from(h) * u64::from(bw));
+        w > 0 && h > 0 && c == bc && a.abs_diff(b) * 100 <= a
+    };
+    found
+        .iter()
+        .filter_map(|&s| jpeg_frame(s).filter(|&f| like(f) && f.0.max(f.1) >= min_edge).map(|(w, h, _)| (s, w.max(h))))
+        .min_by_key(|&(_, long)| long)
+        .map(|(s, _)| s)
+}
+
+fn preview_covering(bytes: &[u8], min_edge: Option<u32>) -> Option<Vec<u8>> {
     if bytes.starts_with(b"FUJIFILMCCD-RAW") {
         let j = crate::vendor::raf::header(bytes).ok()?.jpeg?;
         return is_dct_jpeg(j).then(|| trim_eoi(j).to_vec());
@@ -173,10 +212,11 @@ pub fn embedded_preview(bytes: &[u8]) -> Option<Vec<u8>> {
     if let Some(p) = crate::vendor::orf::preview(bytes) {
         found.push(p);
     }
-    let best = found
-        .into_iter()
-        .filter(|s| is_dct_jpeg(s) || is_jxl(s))
-        .max_by_key(|s| s.len())
+    let largest = found.iter().copied().filter(|s| is_dct_jpeg(s) || is_jxl(s)).max_by_key(|s| s.len());
+    let best = min_edge
+        .zip(largest)
+        .and_then(|(min, big)| smallest_covering(&found, big, min))
+        .or(largest)
         .map(|s| if is_jxl(s) { s.to_vec() } else { trim_eoi(s).to_vec() });
     // a TIFF raw we can't decode whose preview no tag points to (Leaf MOS, Epson ERF)
     best.or_else(|| format.filter(|f| !f.is_supported()).and_then(|_| scan_for_jpeg(bytes)))
@@ -543,6 +583,61 @@ mod tests {
         }
     }
 
+    /// A JPEG like [`fake_jpeg`] whose frame header says `w` x `h` with `nc` components.
+    fn sized_jpeg(w: u16, h: u16, nc: u8, n: usize) -> Vec<u8> {
+        let mut j = vec![0xff, 0xd8, 0xff, 0xc0, 0x00, 8 + 3 * nc, 8];
+        j.extend_from_slice(&h.to_be_bytes());
+        j.extend_from_slice(&w.to_be_bytes());
+        j.push(nc);
+        for c in 0..nc {
+            j.extend_from_slice(&[c + 1, 0x11, 0]);
+        }
+        j.extend(std::iter::repeat_n(0x55u8, n));
+        j.extend_from_slice(&[0xff, 0xd9]);
+        j
+    }
+
+    /// A TIFF raw holding `jpegs` as JPEG-compressed strips: the first in IFD0, the others in sub-IFDs.
+    fn tiff_with_jpegs(jpegs: &[&[u8]]) -> Vec<u8> {
+        let ifd = |j: &[u8]| {
+            let mut ifd = IfdBuilder::new();
+            ifd.set(t::COMPRESSION, Value::Short(vec![6]));
+            ifd.set(t::IMAGE_WIDTH, Value::Long(vec![1]));
+            ifd.set(t::IMAGE_LENGTH, Value::Long(vec![1]));
+            ifd.set_image(ImageData::Strips { rows_per_strip: 1, strips: vec![j.to_vec()] });
+            ifd
+        };
+        let mut ifd0 = ifd(jpegs[0]);
+        for j in &jpegs[1..] {
+            ifd0.add_sub_ifd(ifd(j));
+        }
+        TiffWriter::default().write(&[ifd0]).unwrap()
+    }
+
+    /// A stand-in decodes the smallest JPEG that covers its box and shows the same picture as the largest: not a
+    /// thumbnail of another shape (a letterboxed one) or a grey mask, and the largest when no smaller one is big enough.
+    #[test]
+    fn a_stand_in_takes_the_smallest_covering_jpeg_of_the_same_shape() {
+        let (big, small, boxed) = (sized_jpeg(9984, 6656, 3, 500), sized_jpeg(1616, 1080, 3, 50), sized_jpeg(160, 120, 3, 10));
+        // a ProRAW DNG keeps grey semantic masks of the picture's shape as JPEGs too
+        let mask = sized_jpeg(768, 512, 1, 20);
+        let file = tiff_with_jpegs(&[&small, &big, &boxed, &mask]);
+        assert_eq!(embedded_preview(&file).unwrap(), big, "unchanged: the largest");
+        assert_eq!(embedded_preview_covering(&file, 1600).unwrap(), small, "1616 px covers a 1600 px box");
+        assert_eq!(embedded_preview_covering(&file, 1616).unwrap(), small);
+        assert_eq!(embedded_preview_covering(&file, 1617).unwrap(), big, "too small: the largest");
+        assert_eq!(embedded_preview_covering(&file, u32::MAX).unwrap(), big);
+        assert_eq!(embedded_preview_covering(&file, 100).unwrap(), small, "the 4:3 thumbnail and the grey mask are not this picture");
+        // a small copy of the same shape (within 1 %) is taken
+        let thumb = sized_jpeg(160, 107, 3, 10);
+        let file = tiff_with_jpegs(&[&small, &big, &thumb]);
+        assert_eq!(embedded_preview_covering(&file, 100).unwrap(), thumb);
+        assert_eq!(embedded_preview_covering(&tiff_with_jpegs(&[&big]), 100).unwrap(), big, "one preview: that one");
+        for n in (0..file.len()).step_by(7) {
+            let _ = embedded_preview_covering(&file[..n], 100);
+        }
+    }
+
     /// CR3 with a full-size JPEG track: that JPEG wins over the smaller `PRVW` box.
     #[test]
     fn cr3_prefers_the_full_size_jpeg_track() {

docs/parity-checklist.md

@@ -82,7 +82,7 @@ differences and missing bindings are in [ui-parity.md](ui-parity.md#shortcuts).
 | LR-IMP-SIDECAR-SPLIT | Separate XMP sidecar variants | P2 | ⬜ | `cmd:library.xmpPreferences` | sidecar naming option exists (stem/full), no split sidecars |
 | LR-IMP-FORMATS | Supported formats | P0 | 🟡 | `crates/codecs/src/lib.rs`, `crates/raw/src/lib.rs`, `crates/raw/src/jxl.rs` | JPEG, PNG, TIFF (1- to 64-bit integer, 16- to 64-bit float, incl. bilevel and CCITT fax), WebP, JXL, PSD, GIF, BMP (lossy wide-gamut JXL decodes to the right colours: jxl-oxide desaturated XYB rendered to P3/Rec. 2020, worked around in `crates/codecs/src/jxl.rs`); DNG (incl. lossy / Smart Preview DNG and DNG 1.7 JPEG XL tiles/strips: lossless ones decode bit-exactly on synthetic CFA and LinearRaw files, lossy ones are restored to the declared linear primaries without clipping or gamut mapping, checked on one real file with 108 lossy tiles, and any tile that fails to decode makes the file preview-only; DNG 1.7 row/column-interleaved rasters (`RowInterleaveFactor` / `ColumnInterleaveFactor`) are undone before the mosaic is read, so a file from Adobe's converter with a 2×2 interleave no longer decodes as four scaled-down copies in the wrong colours; a dimension the factor does not divide decodes with short trailing fields; verified on 4 real ILCE-6400 JPEG XL DNGs rendering bit-identical to their non-interleaved twins, factors above 2 rest on the plain reading of the tag; a single-chunk JPEG XL preview IFD is offered as the embedded preview; a DNG whose samples pile up at one value well below its stated `WhiteLevel`, as a camera app's 12-bit Bayer DNG that states 4095 and clips at 3567, has those samples raised to the white level on decode, so highlight reconstruction sees the clipped areas instead of white balance tinting them magenta, issue #548, `crates/raw/src/saturation.rs`), CR2 (colour-filter layout from the file's `CR2CFAPattern` tag, issue #85), ARW (pre-2017 bodies: white balance and black level from the encrypted `SR2SubIFD`, issue #148, its `WB_RGGBLevels` being the white balance the camera applied, issue #535; the DSLR-A900's packed 12-bit strip, two pixels per three bytes, read only when the strip is exactly 1.5 bytes per pixel, with its camera-JPEG window centred, checked on one CC0 file (A850 unmeasured); downsized Sony lossless YCbCr 4:2:0 / 4:2:2 tiles decoded to linear RGB, verified on private ILCE-7M4 3:2 & 4:3 examples including 16-bit full-resolution export; Sony DSC-R1 .SR2 decodes, its big-endian 16-bit words read in the order that fits the sample range, checked on the CC0 3221 sample; its crop and white balance live in the SR2SubIFD and are not read yet; ARW6 Compressed / Compressed (HQ) of the ILCE-7RM6 (`crates/raw/src/vendor/arw6.rs`, `crates/raw/src/llvc.rs`; 12-bit codes exact against a black-box oracle on 8 CC0 files, FF over the full frame, APS-C in the interior (LibRaw's own edge rows differ); output through our own companding curve, measured from CC0 lossless / ARW6 pairs; geometry checked against the camera JPEG, `docs/arw6-compression.md`; the ILCE-7M5 writes the same codec, unverified)), NEF (uncompressed, lossless and lossy compressed 12/14-bit, `crates/raw/src/vendor/nefc.rs`), RAF (uncompressed, lossless/lossy compressed Bayer and X-Trans; `crates/raw/src/vendor/rafc.rs`, full sensor verification on 13 bodies, `docs/raf-compression.md`), RW2 / Leica RWL / Panasonic RAW in every raw format (compressed 4 and 6, the prefix-coded strips of format 8 from the GH6 on, packed 2/5/7, the 16-bit words of the 2005–2007 bodies; black levels, in-camera aspect crops and mapped-out defect pixels; 178 CC0 files from 118 bodies checked, `crates/raw/src/vendor/rw2.rs`), PEF, ORF (uncompressed; colour-filter layout from the file's Exif `CFAPattern`; 12.8 bit/px 16-byte blocks of ten 12-bit samples + a zero pad byte, E-300 / E-330 / E-500 verified on CC0 files, E-M5 Mark II / PEN-F high-res files decode smooth but CFA and black unverified), Kodak DCS520C TIFF (a two-component 12-bit lossless JPEG strip, the two components the even and odd columns; the file's `GrayResponseCurve` table linearises the companded samples to 12 bits, black measured per CFA position, white balance from the `KodakIFD`; `RawFormat::KodakDcs`, `crates/raw/src/vendor/kodak.rs`, checked on the one CC0 sample against its IFD0 thumbnail), Hasselblad 3FR and FFF (a TIFF without a DNG version tag that describes its CFA IFD, levels, crop and white balance with DNG's tags; `RawFormat::CfaTiff`, read by `dng::decode_as`, RGGB when the file states no `CFAPattern`): uncompressed (X1D, X1D II, X2D, CFV 100C) and Hasselblad's lossless JPEG with scan selection value 8 (every FFF; H3D, H4D and CFV-50c 3FR), `ljpeg::decode_hasselblad`, its rule measured on 14 CC0 files with the ljpeg-explorer tool, Samsung SRW without compression (NX5, NX10, NX11 and the NX20-generation bodies NX20, NX200, NX210, NX1000 and NX1100 as 12-bit packed samples in either bit order, EX1 and WB2000 as 16-bit words; layout, camera-JPEG framing, levels and white balance from the maker note, `crates/raw/src/vendor/srw.rs`; median ΔE vs the camera JPEG 2.2–7.6 on 11 of the 12 files from 10 bodies checked, 10.7 (5.7 registered)Line truncated
 | LR-IMP-CAMERA-COVERAGE | Camera coverage, verified per model | P0 | 🟡 | `crates/raw/tests/corpus.rs`, `xtask/src/main.rs` | a supported container is not the same as every camera that writes it decoding correctly: ~55 CC0 corpus files plus 6 exact-sensor CR3 cases and 4 pinned EOS R5 Mark II files (plus ~60 NEFs checked by hand and 178 Panasonic / Leica RW2, RWL and RAW files from 118 bodies, checked against each file's own JPEG) against the >1,000 models Lightroom lists; per-model differences still surface (e.g. the CR2 colour-filter layout differed by model until it was read from the file's own tag, issue #85, checked on 35 CR2 bodies; CR2 black levels were read from border columns light already reaches, left of `SensorInfo`'s border, so CR2s rendered dark with crushed shadows (EOS 6D: 2591 instead of 2047), now measured from the masked columns only, checked on 8 corpus bodies; pre-2017 Sony ARWs opened green until their scrambled white balance / black level were read, issue #148, checked on 16 ARWs from 15 Sony bodies; their white balance now comes from the encrypted `SR2SubIFD`'s `WB_RGGBLevels`, the gains the camera applied, which 14 bodies (DSLR-A450 … A700, NEX-3/5/C3, SLT-A33/A35/A55, ILCE-6001, UMC-R10C) had no other source for and which the maker-note estimate read before missed by up to 100 % on preset shots, issue #535, checked against ExifTool on 100 decoded ARWs from 87 Sony bodies; the encrypted SR2 black level is now read from its directory entry (the DSLR-A450/A500/A550/A700 read 354–975 instead of 512), checked on 126 ARWs from 97 Sony bodies, and downsized lossless M/S ARWs use their measured black level 1024 instead of 512, checked on 12 files from 4 bodies, issue #535, and on a fifth, the ILCE-7CM2 (issue #697: 0.5.0 rendered its lossless M file with that 512 pedestal, the darkest half of a dusk scene +11 L* and blue, the lamplight white; its darkest 0.1 % per channel sits at 1017/1020/1024, and with 1024 the render is within +3 L* of the camera JPEG; the body's compressed and uncompressed "M-size" files are Bayer at 4736×3132 with black 512, two public ones in the corpus); pre-2017 Sony bodies shot in the camera's 16:9 mode (ILCE-7SM2, DSLR-A580) now get the 16:9 crop of their camera JPEG instead of the whole 3:2 frame with padding columns, issue #535; Canon PowerShot and EOS M CR2s whose `ColorData` is stored as bytes opened green until the bytes were read as 16-bit words, 25 files from 25 bodies checked; private Z 8 crop verified; the Nikon D4, which records no CropArea, gets its image area and white level measured on 148 NEFs against the camera JPEG (optical-black stripes and magenta clipped highlights gone); the D7100, whose data holds picture beyond the camera's frame, develops at Lightroom's frame (the camera JPEG's size) in full frame and 1.3x crop, so Lightroom crops line up (#1248).; CR2 white levels came from masked rows holding samples at 16383, so on the EOS 50D, 60D, 450D (Rebel XSi), 500D (Rebel T1i), 550D (Rebel T2i), 1200D (Rebel T5) and 100D (Rebel SL1) clipped highlights sat at 81–98% of the range and were not treated as clipped, now taken from the active area only, issue #1272). Compressed RAF sensor arrays verified on 13 Fujifilm bodies (`docs/raf-compression.md`). ILCE-7RM6 ARW6 12-bit codes verified on 8 CC0 files (FF and APS-C, both compression modes). Sony ILCE-7CR (61 MP): lossless compressed L and M and compressed ARW2 samples of one scene in the corpus (black level, default crop, as-shot gains, lossless vs compressed mosaic agreement, fitted camera look), and all nine public codings (also uncompressed, small and APS-C crop) decode and fit. Grow the CC0 corpus per model and test each sample decodes with plausible colour. Nikon CropArea and untagged-preview colour-space regression tests; the Nikon D4, which records no CropArea, gets its image area and white level measured on 148 NEFs against the camera JPEG (optical-black stripes and magenta clipped highlights gone). Pentax PEFs without area tags (KP, KF, K-3 Mark III, K-70, K-1, K-1 Mark II, K-S1, K-S2, 645Z) no longer keep their masked border: black, empty and saturated lines are trimmed against the maker-note BlackPoint, issue #1271, measured on 38 CC0 PEFs from 30 bodies.; Canon PowerShot and EOS M CR2s whose `ColorData` is stored as bytes opened green until the bytes were read as 16-bit words, 25 files from 25 bodies checked). Compressed RAF sensor arrays verified on 13 Fujifilm bodies (`docs/raf-compression.md`). ILCE-7RM6 ARW6 12-bit codes verified on 8 CC0 files (FF and APS-C, both compression modes). Sony ILCE-7CR (61 MP): lossless compressed L and M and compressed ARW2 samples of one scene in the corpus (black level, default crop, as-shot gains, lossless vs compressed mosaic agreement, fitted camera look), and all nine public codings (also uncompressed, small and APS-C crop) decode and fit. Grow the CC0 corpus per model and test each sample decodes with plausible colour. Nikon CropArea andLine truncated
-| LR-IMP-PREVIEW-READ | Preview reads the header, not the raw | P0 | ✅ | `crates/raw/src/preview.rs` (`bounded_preview`, `embedded_preview_from_range`), `crates/engine/src/files.rs` (`preview_window`), `docs/raw-preview-reads.md`, `crates/engine/src/files.rs` (`preview_window`, `planned_preview`), `crates/raw/src/sparse.rs` (`preview_plan`) | a grid thumbnail and a loupe preview of an unedited raw show the camera's embedded JPEG, which sits near the start of the file (a 24 MP Fuji RAF keeps its 5.6 MB JPEG in a 56 MB file), so the preview loader reads the header and that JPEG instead of the whole file: 56.5 MB → 5.9 MB and ~10 s → 0.96 s measured on one real RAF over a GVFS/SMB Wi-Fi share (byte-identical preview pixels; `LIGHTCRAFT_PROFILE=1` reports the bytes); the RAF pointer is read from its fixed header fields, a CR3's boxes and a TIFF raw whose preview tag sits past the prefix are read through `lightcraft_raw::sparse::preview_plan`, which names the ranges `embedded_preview` reads and nothing else; a cached render as stand-in, an edited photo and a raw without an embedded JPEG still render; the formats it cannot describe (CRW/MRW/X3F are found by scanning, NEF/ORF/PEF probe from samples) keep the whole-file path, and a lying pointer, a short read or a file that changes underneath us falls back to it rather than losing the preview. An unedited raw's **grid thumbnail is that camera JPEG itself**, so no sensor decode is scheduled behind it (`Session::embedded_thumb_is_final`, `grid::skips_the_real_render`): drawing a 512 px thumbnail used to decode the whole raw — 45 s a photo at 1.2 MB/s, 8.3 GB for a 149-raw folder — and the queue it built delayed the render the user was waiting for |
+| LR-IMP-PREVIEW-READ | Preview reads the header, not the raw | P0 | ✅ | `crates/raw/src/preview.rs` (`bounded_preview`, `embedded_preview_from_range`, `embedded_preview_covering`), `crates/engine/src/files.rs` (`preview_window`), `docs/raw-preview-reads.md`, `crates/engine/src/files.rs` (`preview_window`, `planned_preview`), `crates/raw/src/sparse.rs` (`preview_plan`) | a grid thumbnail and a loupe preview of an unedited raw show the camera's embedded JPEG, which sits near the start of the file (a 24 MP Fuji RAF keeps its 5.6 MB JPEG in a 56 MB file), so the preview loader reads the header and that JPEG instead of the whole file: 56.5 MB → 5.9 MB and ~10 s → 0.96 s measured on one real RAF over a GVFS/SMB Wi-Fi share (byte-identical preview pixels; `LIGHTCRAFT_PROFILE=1` reports the bytes); the RAF pointer is read from its fixed header fields, a CR3's boxes and a TIFF raw whose preview tag sits past the prefix are read through `lightcraft_raw::sparse::preview_plan`, which names the ranges `embedded_preview` reads and nothing else; a cached render as stand-in, an edited photo and a raw without an embedded JPEG still render; the formats it cannot describe (CRW/MRW/X3F are found by scanning, NEF/ORF/PEF probe from samples) keep the whole-file path, and a lying pointer, a short read or a file that changes underneath us falls back to it rather than losing the preview. An unedited raw's **grid thumbnail is that camera JPEG itself**, so no sensor decode is scheduled behind it (`Session::embedded_thumb_is_final`, `grid::skips_the_real_render`): drawing a 512 px thumbnail used to decode the whole raw — 45 s a photo at 1.2 MB/s, 8.3 GB for a 149-raw folder — and the queue it built delayed the render the user was waiting for. Stand-ins and grid thumbnails decode the smallest embedded JPEG that covers the requested size and is a copy of the largest (aspect ratio within 1 %, same component count), not always the largest, on the whole-file and the plan route alike: an A7R VI's 1616 × 1080 JPEG (0.3 MB) instead of its 9984 × 6656 one (5.6 MB), and mid-sized NEF / RW2 JPEGs |
 | LR-IMP-CULL-AT-IMPORT | Culling analysis at import | P2 | 🟡 | `cmd:photo.analyze` | run Assisted Culling on the imported photos (they're selected after an import); not automatic |
 | LR-IMP-MOVE | Move on import [Classic] | P1 | ✅ | `cmd:library.import` (`mode` move), `crates/engine/src/import_move.rs`, `crates/engine/src/tests_import_move.rs`, `crates/ui-egui/src/import.rs` | Transfer ▸ Move with Copy's destination, folders (day / month / one folder / custom template), rename template and example destination; XMP sidecars (both namings) move along; each source is removed only after its destination is written (hard link on the same volume, else copied, synced and compared byte for byte) and its catalog record is saved; failed, duplicate, unchecked files keep their sources, taken names get -1, -2…, never overwritten; files already in the destination/library are added in place; sources that can't be removed (read-only card) are kept and reported (`kept`). Undo removes the photos from the library but leaves the moved files at the destination. No Copy as DNG while moving |
 | LR-IMP-DNG-CONVERT | Convert to DNG on import [Classic] | P2 | ✅ | `cmd:library.import` (`dng`), `crates/ui-egui/src/import.rs` | copy imports: Raw files ▸ Copy as DNG (lossless; the card is untouched); the raw copy is removed only once its DNG is verified and on disk (issue #106) |

docs/raw-preview-reads.md

@@ -111,17 +111,36 @@ Measured on the real folder: idle for a minute, the app read 12 previews (**26.9
 **zero** raws for thumbnails, against 638 MB of whole-file reads for the same 12 photos before. The
 render queue stayed empty.
 
+## The smallest JPEG that covers the box
+
+Many TIFF-based raws keep more than one embedded JPEG. A Sony A7R VI ARW holds a 1616 × 1080 one
+(0.3 MB) beside the 9984 × 6656 one (5.6 MB), and Nikon NEF and Panasonic RW2 files have mid-sized
+copies too. The loupe stand-in and the grid thumbnail (`embedded_preview_srgb`) decode the smallest
+JPEG whose long edge is at least the size asked for (`lightcraft_raw::embedded_preview_covering`).
+They take the largest one when no other JPEG is big enough. The plan route picks the same way
+(`preview_window` takes the size asked for), so a raw read through the plan gets the JPEG the whole
+file would give. A smaller JPEG only counts as a copy of the picture when its aspect ratio is within
+1 % of the largest one's and it has the same number of colour components. That rules out letterboxed
+thumbnails of another shape and the grey masks an iPhone ProRAW DNG keeps at the picture's shape.
+Sources for editing (an unsupported raw's JPEG, `load_embedded_preview`) and the camera-look fit still
+use the largest JPEG, so their geometry and colour do not depend on the size level.
+
 ## Tests
 
 - `crates/raw/src/preview.rs`: the header-only range matches `embedded_preview` byte for byte; a
   clamped prefix, a padded extent, a late pointer, a lying pointer and a non-JPEG window are all
-  covered.
+  covered. `a_stand_in_takes_the_smallest_covering_jpeg_of_the_same_shape` covers the picker: a
+  smaller JPEG that covers the box is taken, the largest when none does, and a thumbnail of another
+  shape or a grey mask never is.
 - `crates/engine/src/files.rs`: on a synthetic RAF with a 200 KB tail, the quick path and the
   whole-file path produce identical pixels, and the read stays under half the file. On a synthetic
   TIFF/DNG whose preview only its tags locate — the plan path — the same identity holds and the CFA
   strip is not read; the same structure without the tag that makes it a raw declines instead of
   guessing, and the caller keeps reading it whole. So do a file whose own orientation or Adobe RGB
   colour space only the whole-file path can show, while one that states sRGB stays on the fast path.
+  A synthetic DNG with a full-size and a half-size JPEG gets, on the plan path, the half-size one for
+  a box it covers and the full-size one otherwise, with the same pixels as the whole-file path
+  (`preview_loading_plans_the_smallest_covering_jpeg`).
 - `crates/raw/tests/sparse_corpus.rs`: `preview_plan` is asked for **every** corpus file, not only
   the ones whose header plan is `Ready`, and the preview it yields must equal the whole file's with
   the skipped bytes `0` and `0xFF`. The test prints what each format reads.

docs/whats-new.md

@@ -22,6 +22,11 @@
 - With Dehaze on, panning a photo zoomed to 1:1 or moving a slider while zoomed no longer samples the whole
   original again to find the haze colour. On a 64 MP raw (Sony A7R VI) that took ~0.2 s of CPU per pan and per
   slider step; a slider step now takes ~5 ms on the GPU.
+### Thumbnails of raw files appear sooner
+- Grid thumbnails and the first picture in the loupe of an unedited raw now come from the smallest JPEG the camera
+  stored that is big enough, not always from the largest one. On a Sony A7R VI file a 512 px thumbnail decodes
+  0.3 MB of JPEG instead of 5.6 MB and is ready several times sooner; Nikon and Panasonic raws with a mid-sized
+  JPEG get faster too.
 ## 2026-10-12
 
 ### Canon CR2 highlights