feat(exif): stamp RC_<ts> filenames + EXIF on capture and export

src/utils/exportEngine.ts

@@ -9,6 +9,8 @@ import { TONE_SKSL, getToneUniforms, toneIsActive, toneUniformArray } from './to
 import { CINEMA_SKSL, getCinemaUniforms, cinemaIsActive } from './cinemaShader';
 import { drawFrameOnCanvas, polaroidLayout, POLAROID_CARD, POLAROID_WIN_W, wallframeLayout, WALLFRAME_W, WALLFRAME_H, WALLFRAME_LAND_W, WALLFRAME_LAND_H } from './frameUtils';
 import { patchJpegDpi } from './jpegDpi';
+import { writeJpegExif } from './exifWrite';
+import { nextPhotoPath, readPhotoBytes } from './photoMeta';
 import { applyPhotoRotation } from './skiaImage';
 
 export interface ExportResult {
@@ -76,6 +78,13 @@ export interface ExportOptions {
   // see exactly the orientation the preview showed.
   photoRotation?: 0 | 90 | 180 | 270;
   photoStraighten?: number;
+  // This export came from a photo loaded out of the library (not a live
+  // capture): the file is named RC_<ts>_exported.jpg and the loaded photo's
+  // own EXIF lives on in the output.
+  exported?: boolean;
+  // Shutter instant of a live capture (ms). Absent = keep the loaded photo's
+  // own DateTimeOriginal.
+  capturedAt?: number | null;
 }
 
 // Lightroom-style "Screen" output sharpen: subtle unsharp mask. A 3x3
@@ -111,12 +120,6 @@ function screenSharpenImage(image: SkImage, amount = 0.5): SkImage {
   return sharpened;
 }
 
-// Unique filename per export. A fixed path made every export share one URI, and
-// RN's <Image> cache (keyed by URI) then kept showing the previous photo in the
-// thumbnail after a new capture overwrote the file. A fresh URI per export busts
-// that cache.
-const nextExportFile = () => `${FileSystem.cacheDirectory}camrecipe_pro_export_${Date.now()}.jpg`;
-
 export async function processAndExportPhoto(
   sourceUri: string,
   recipe: Recipe,
@@ -706,10 +709,27 @@ export async function processAndExportPhoto(
       bytes = patchJpegDpi(bytes, options.dpi);
     }
 
+    // 9c. EXIF. Skia's re-encode dropped the loaded photo's metadata block, so
+    // rebuild it here: the source photo donates every tag this app does not
+    // own (camera, lens, exposure) and the fields it is responsible for are
+    // stamped on top — software + version, capture date, GPS, pixel size.
+    bytes = writeJpegExif(
+      bytes,
+      {
+        dateTime: options?.capturedAt ? new Date(options.capturedAt) : null,
+        gps: useGeotag && gpsInfo ? { latitude: gpsInfo.latitude, longitude: gpsInfo.longitude } : null,
+        width: resultImage.width(),
+        height: resultImage.height(),
+        dpi: options?.dpi ?? null,
+      },
+      await readPhotoBytes(sourceUri)
+    );
+
     // 10. Write binary bytes to a unique temporary local file. The unique name
     // is load-bearing: a fixed URI would be served from RN's <Image> cache and
-    // the thumbnail/preview would keep showing the previous export.
-    const exportFile = nextExportFile();
+    // the thumbnail/preview would keep showing the previous export (and the
+    // gallery shows this basename).
+    const exportFile = nextPhotoPath(options?.exported === true);
     try {
       new File(exportFile).write(bytes);
     } catch (e) {