first commit

src/pdf/pdfThumbnailService.ts

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+import * as pdfjsLib from 'pdfjs-dist';
+import pdfjsWorker from 'pdfjs-dist/build/pdf.worker?worker&url';
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+(pdfjsLib as any).GlobalWorkerOptions.workerSrc = pdfjsWorker;
+
+type RotationsMap = Record<number, number>;
+
+export async function generateThumbnails(
+  arrayBuffer: ArrayBuffer,
+  maxHeight = 150
+): Promise<string[]> {
+  return generateThumbnailsInternal(arrayBuffer, {}, maxHeight);
+}
+
+export async function generateThumbnailsWithRotations(
+  arrayBuffer: ArrayBuffer,
+  rotations: RotationsMap,
+  maxHeight = 150
+): Promise<string[]> {
+  return generateThumbnailsInternal(arrayBuffer, rotations, maxHeight);
+}
+
+async function generateThumbnailsInternal(
+  arrayBuffer: ArrayBuffer,
+  rotations: RotationsMap,
+  maxHeight: number
+): Promise<string[]> {
+  const loadingTask = pdfjsLib.getDocument({ data: arrayBuffer });
+  const pdf = await loadingTask.promise;
+
+  const thumbs: string[] = [];
+
+  for (let pageNum = 1; pageNum <= pdf.numPages; pageNum++) {
+    const page = await pdf.getPage(pageNum);
+    const viewport = page.getViewport({ scale: 1 });
+    const scale = maxHeight / viewport.height;
+    const scaledViewport = page.getViewport({ scale });
+
+    const baseCanvas = document.createElement('canvas');
+    const baseCtx = baseCanvas.getContext('2d');
+    if (!baseCtx) {
+      thumbs.push('');
+      continue;
+    }
+
+    baseCanvas.width = scaledViewport.width;
+    baseCanvas.height = scaledViewport.height;
+
+    const renderTask = page.render({
+      canvasContext: baseCtx,
+      viewport: scaledViewport,
+    });
+    await renderTask.promise;
+
+    const originalIndex = pageNum - 1;
+    const rotationDegRaw = rotations[originalIndex] ?? 0;
+    const rotationDeg = ((rotationDegRaw % 360) + 360) % 360;
+
+    if (rotationDeg === 0) {
+      thumbs.push(baseCanvas.toDataURL('image/png'));
+      continue;
+    }
+
+    const rotatedCanvas = document.createElement('canvas');
+    const rotatedCtx = rotatedCanvas.getContext('2d');
+    if (!rotatedCtx) {
+      thumbs.push(baseCanvas.toDataURL('image/png'));
+      continue;
+    }
+
+    const rad = (rotationDeg * Math.PI) / 180;
+
+    if (rotationDeg === 90 || rotationDeg === 270) {
+      rotatedCanvas.width = baseCanvas.height;
+      rotatedCanvas.height = baseCanvas.width;
+    } else {
+      rotatedCanvas.width = baseCanvas.width;
+      rotatedCanvas.height = baseCanvas.height;
+    }
+
+    rotatedCtx.save();
+
+    switch (rotationDeg) {
+      case 90:
+        rotatedCtx.translate(rotatedCanvas.width, 0);
+        rotatedCtx.rotate(rad);
+        break;
+      case 180:
+        rotatedCtx.translate(rotatedCanvas.width, rotatedCanvas.height);
+        rotatedCtx.rotate(rad);
+        break;
+      case 270:
+        rotatedCtx.translate(0, rotatedCanvas.height);
+        rotatedCtx.rotate(rad);
+        break;
+      default:
+        break;
+    }
+
+    rotatedCtx.drawImage(baseCanvas, 0, 0);
+    rotatedCtx.restore();
+
+    thumbs.push(rotatedCanvas.toDataURL('image/png'));
+  }
+
+  return thumbs;
+}