feat(frame): give ROTATE quarter turns plus a fine straighten

src/utils/exportEngine.ts

@@ -9,7 +9,7 @@ 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 { rotateSkImage90 } from './skiaImage';
+import { applyPhotoRotation } from './skiaImage';
 
 export interface ExportResult {
   uri: string;
@@ -70,10 +70,12 @@ export interface ExportOptions {
   // visible through the opening, so the file matches the preview. Null /
   // undefined = centered 1x (the historical full-image draw).
   frameWindowZoom?: { s: number; u: number; v: number } | null;
-  // Library FRAME-tab rotation (90 = clockwise). Applied to the decoded source
-  // before the ratio crop, so the frame layout and cover maths see exactly the
-  // orientation the preview showed.
-  photoRotation?: 0 | 90;
+  // Library FRAME-tab rotation: the quarter turn in degrees clockwise
+  // (0/90/180/270) and the fine STRAIGHTEN offset in degrees, applied to the
+  // decoded source before the ratio crop, so the frame layout and cover maths
+  // see exactly the orientation the preview showed.
+  photoRotation?: 0 | 90 | 180 | 270;
+  photoStraighten?: number;
 }
 
 // Lightroom-style "Screen" output sharpen: subtle unsharp mask. A 3x3
@@ -139,7 +141,8 @@ export async function processAndExportPhoto(
     let skImage = skImage0;
     // FRAME-tab rotation first: the pixel-dimension swap then propagates
     // through the ratio crop, frame layout and cover maths unchanged.
-    if (options?.photoRotation === 90) skImage = rotateSkImage90(skImage) ?? skImage;
+    skImage =
+      applyPhotoRotation(skImage, options?.photoRotation, options?.photoStraighten) ?? skImage;
     let width = skImage.width();
     let height = skImage.height();
     // 1b. Aspect-ratio crop (composition): center-largest upright crop of the
@@ -445,7 +448,10 @@ export async function processAndExportPhoto(
       // Card proportions follow the UN-rotated source, so rotating the print
       // inside the frame never resizes the frame (same rule as the viewfinder).
       const frameAspect =
-        ratioWH ?? (options?.photoRotation === 90 ? height / width : width / height);
+        ratioWH ??
+        (options?.photoRotation === 90 || options?.photoRotation === 270
+          ? height / width
+          : width / height);
       const outH = Math.round(
         width * (POLAROID_CARD.sideMargin + POLAROID_CARD.bottomDeck) +
           (width * POLAROID_WIN_W) / frameAspect

src/utils/skiaImage.ts

@@ -25,3 +25,44 @@ export function rotateSkImage90(image: SkImage | null): SkImage | null {
   canvas.drawImage(image, 0, 0);
   return surface.makeImageSnapshot() ?? image;
 }
+
+// Fine rotation about the centre (the FRAME tab's STRAIGHTEN), keeping the
+// original pixel dimensions: the content is scaled up just enough that the
+// rotated rectangle still covers the frame, so no empty corner shows. The
+// scale is the axis-aligned wrap of the counter-rotated frame — slightly
+// conservative, which crops a hair more rather than leaking a corner.
+// ponytail: one offscreen surface per call, same trade as rotateSkImage90.
+export function rotateSkImageBy(image: SkImage | null, degrees: number): SkImage | null {
+  if (!image) return null;
+  const w = image.width();
+  const h = image.height();
+  if (!(w > 0 && h > 0)) return null;
+  if (!degrees) return image;
+  const rad = (degrees * Math.PI) / 180;
+  const cos = Math.abs(Math.cos(rad));
+  const sin = Math.abs(Math.sin(rad));
+  const k = Math.max((w * cos + h * sin) / w, (w * sin + h * cos) / h);
+  const surface = Skia.Surface.Make(w, h);
+  if (!surface) return image; // keep the unrotated photo on allocation failure
+  const canvas = surface.getCanvas();
+  canvas.clear(Skia.Color('transparent'));
+  canvas.translate(w / 2, h / 2);
+  canvas.rotate(degrees, 0, 0);
+  canvas.scale(k, k);
+  canvas.drawImage(image, -w / 2, -h / 2);
+  return surface.makeImageSnapshot() ?? image;
+}
+
+// The whole FRAME-tab photo orientation in one call: the quarter turn first
+// (rotateSkImage90 swaps the pixel dimensions, which then propagates through
+// every consumer unchanged), then the fine STRAIGHTEN on top of it.
+export function applyPhotoRotation(
+  image: SkImage | null,
+  quarter = 0,
+  straighten = 0
+): SkImage | null {
+  let out = image;
+  for (let i = 0; i < Math.round(quarter / 90) % 4; i++) out = rotateSkImage90(out);
+  if (straighten) out = rotateSkImageBy(out, straighten);
+  return out;
+}