update at 2025-09-25 22:35:01

2025-09-25 22:35:01 +08:00
parent a60cdd593c
commit c9ce811ce9
11 changed files with 1192 additions and 21 deletions
--- a/src/exif-orientation.ts
+++ b/src/exif-orientation.ts
@@ -0,0 +1,117 @@
+/*
+ * Lightweight EXIF orientation reader + conditional JPEG -> PNG converter.
+ * We only care about orientation values 3,6,8 (rotations). Others return as-is.
+ */
+
+export async function readOrientation(blob: Blob): Promise<number | null> {
+  try {
+    console.log(`[readOrientation] Blob type: ${blob.type}, size: ${blob.size}`);
+    if (blob.type !== 'image/jpeg' && blob.type !== 'image/jpg') {
+      console.log(`[readOrientation] Not a JPEG, blob type: ${blob.type}`);
+      return null;
+    }
+    const buf = await blob.arrayBuffer();
+    const view = new DataView(buf);
+    console.log(`[readOrientation] ArrayBuffer length: ${buf.byteLength}`);
+    // JPEG starts with 0xFFD8
+    if (view.getUint16(0) !== 0xFFD8) {
+      console.log(`[readOrientation] Not a valid JPEG, header: ${view.getUint16(0).toString(16)}`);
+      return null;
+    }
+    console.log(`[readOrientation] Valid JPEG detected`);
+    let offset = 2;
+    const length = view.byteLength;
+    while (offset < length) {
+      if (view.getUint8(offset) !== 0xFF) break;
+      const marker = view.getUint8(offset + 1);
+      console.log(`[readOrientation] Processing marker: 0xFF${marker.toString(16).padStart(2, '0')} at offset ${offset}`);
+      if (marker === 0xE1) { // APP1 EXIF
+        const size = view.getUint16(offset + 2, false);
+        const exifHeader = offset + 4;
+        console.log(`[readOrientation] Found APP1 segment, size: ${size}`);
+        if (view.getUint32(exifHeader, false) === 0x45786966) { // 'Exif'
+          console.log(`[readOrientation] Found EXIF header`);
+          const tiff = exifHeader + 6;
+          const endian = view.getUint16(tiff, false);
+          const little = endian === 0x4949; // 'II'
+          console.log(`[readOrientation] Endian: ${little ? 'little' : 'big'} (${endian.toString(16)})`);
+          const getU16 = (p:number) => view.getUint16(p, little);
+          const getU32 = (p:number) => view.getUint32(p, little);
+          if (getU16(tiff + 2) !== 0x002A) {
+            console.log(`[readOrientation] Invalid TIFF magic: ${getU16(tiff + 2).toString(16)}`);
+            return null;
+          }
+          const ifdOffset = getU32(tiff + 4);
+          let dir = tiff + ifdOffset;
+          const entries = getU16(dir); 
+          console.log(`[readOrientation] IFD has ${entries} entries`);
+          dir += 2;
+          for (let i=0;i<entries;i++) {
+            const entry = dir + i*12;
+            const tag = getU16(entry);
+            if (tag === 0x0112) { // Orientation
+              const orientationValue = getU16(entry + 8);
+              console.log(`[readOrientation] Found Orientation tag: ${orientationValue}`);
+              return orientationValue;
+            }
+          }
+          console.log(`[readOrientation] No Orientation tag found, returning 1`);
+          return 1; // treat as normal
+        }
+        offset += 2 + size;
+      } else if (marker === 0xDA) { // SOS
+        console.log(`[readOrientation] Reached SOS marker, stopping`);
+        break;
+      } else {
+        const size = view.getUint16(offset + 2, false);
+        offset += 2 + size;
+      }
+    }
+  } catch (e) {
+    console.error(`[readOrientation] Error reading orientation:`, e);
+  }
+  console.log(`[readOrientation] No orientation found, returning null`);
+  return null;
+}
+
+/**
+ * Converts JPEG to PNG without rotation, regardless of orientation.
+ * Returns a PNG blob + suggested filename.
+ */
+export async function convertJpegIfNeeded(blob: Blob, filename: string): Promise<{blob: Blob; filename: string; changed: boolean; orientation: number | null}> {
+    console.log(`[exif-orientation] Processing ${filename}, blob type: ${blob.type}, size: ${blob.size}`);
+    const ori = await readOrientation(blob);
+    console.log(`[exif-orientation] Detected orientation for ${filename}: ${ori}`);
+    return new Promise((resolve) => {
+        const url = URL.createObjectURL(blob);
+        const img = new Image();
+        img.onload = () => {
+            const w = img.naturalWidth;
+            const h = img.naturalHeight;
+            const canvas = document.createElement('canvas');
+            const ctx = canvas.getContext('2d');
+            if (!ctx) {
+                URL.revokeObjectURL(url);
+                resolve({ blob, filename, changed: false, orientation: ori });
+                return;
+            }
+            canvas.width = w;
+            canvas.height = h;
+            ctx.drawImage(img, 0, 0);
+            canvas.toBlob(b => {
+                URL.revokeObjectURL(url);
+                if (!b) {
+                    resolve({ blob, filename, changed: false, orientation: ori });
+                    return;
+                }
+                const pngName = filename.replace(/\.(jpe?g)$/i, '') + '_converted.png';
+                resolve({ blob: b, filename: pngName, changed: true, orientation: ori });
+            }, 'image/png');
+        };
+        img.onerror = () => {
+            URL.revokeObjectURL(url);
+            resolve({ blob, filename, changed: false, orientation: ori });
+        };
+        img.src = url;
+    });
+}