fix: decode standard images saved with a RAW extension

src-tauri/src/formats.rs

@@ -89,6 +89,16 @@ pub fn is_raw_file<P: AsRef<Path>>(path: P) -> bool {
         .any(|(raw_ext, _)| raw_ext.eq_ignore_ascii_case(ext))
 }
 
+/// Returns true when the bytes start with the signature of a standard (non-RAW) image
+/// format. Used to catch files whose RAW extension does not match their contents, e.g.
+/// JPEGs that cloud photo exports save under the original `.ARW`/`.RW2` filename.
+pub fn has_non_raw_image_signature(bytes: &[u8]) -> bool {
+    const JPEG: &[u8] = &[0xFF, 0xD8, 0xFF];
+    const PNG: &[u8] = &[0x89, b'P', b'N', b'G', 0x0D, 0x0A, 0x1A, 0x0A];
+
+    bytes.starts_with(JPEG) || bytes.starts_with(PNG)
+}
+
 pub fn is_supported_image_file<P: AsRef<Path>>(path: P) -> bool {
     let path = path.as_ref();
 
@@ -116,3 +126,24 @@ pub fn is_supported_image_file<P: AsRef<Path>>(path: P) -> bool {
         .iter()
         .any(|non_raw_ext| non_raw_ext.eq_ignore_ascii_case(ext))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn detects_standard_image_signatures() {
+        assert!(has_non_raw_image_signature(&[0xFF, 0xD8, 0xFF, 0xE0, 0x00]));
+        assert!(has_non_raw_image_signature(&[
+            0x89, b'P', b'N', b'G', 0x0D, 0x0A, 0x1A, 0x0A
+        ]));
+    }
+
+    #[test]
+    fn ignores_raw_signatures() {
+        // Little-endian TIFF header used by ARW, NEF, DNG, ...
+        assert!(!has_non_raw_image_signature(&[0x49, 0x49, 0x2A, 0x00]));
+        assert!(!has_non_raw_image_signature(b"FUJIFILMCCD-RAW"));
+        assert!(!has_non_raw_image_signature(&[]));
+    }
+}

src-tauri/src/image_loader.rs

@@ -3,7 +3,7 @@ use crate::app_settings::{AppSettings, load_settings};
 use crate::app_state::{AppState, LoadedImage};
 use crate::exif_processing;
 use crate::file_management::{parse_virtual_path, read_file_mapped};
-use crate::formats::is_raw_file;
+use crate::formats::{has_non_raw_image_signature, is_raw_file};
 use crate::image_processing::ImageMetadata;
 use crate::image_processing::{
     apply_orientation, apply_srgb_to_linear, remove_raw_artifacts_and_enhance,
@@ -104,10 +104,16 @@ pub fn load_base_image_from_bytes(
         bytes,
     );
 
-    if is_raw_file(path_for_ext_check)
-        && !use_fast_raw_dev
-        && settings.use_apple_raw9.unwrap_or(false)
-    {
+    let mut decode_as_raw = is_raw_file(path_for_ext_check);
+    if decode_as_raw && has_non_raw_image_signature(bytes) {
+        log::info!(
+            "'{}' has a RAW extension but contains a standard image, decoding it as such",
+            path_for_ext_check
+        );
+        decode_as_raw = false;
+    }
+
+    if decode_as_raw && !use_fast_raw_dev && settings.use_apple_raw9.unwrap_or(false) {
         if let Some((tracker, generation)) = &cancel_token
             && tracker.load(Ordering::SeqCst) != *generation
         {
@@ -128,7 +134,7 @@ pub fn load_base_image_from_bytes(
         }
     }
 
-    if is_raw_file(path_for_ext_check) {
+    if decode_as_raw {
         match panic::catch_unwind(move || {
             crate::raw_processing::develop_raw_image(
                 bytes,