Fix image contentType when transcoding

ts/util/handleImageAttachment.ts

@@ -0,0 +1,61 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import path from 'path';
+import { MIMEType, IMAGE_JPEG } from '../types/MIME';
+import {
+  InMemoryAttachmentDraftType,
+  canBeTranscoded,
+} from '../types/Attachment';
+import { imageToBlurHash } from './imageToBlurHash';
+import { scaleImageToLevel } from './scaleImageToLevel';
+
+export async function handleImageAttachment(
+  file: File
+): Promise<InMemoryAttachmentDraftType> {
+  const blurHash = await imageToBlurHash(file);
+
+  const { contentType, file: resizedBlob, fileName } = await autoScale({
+    contentType: file.type as MIMEType,
+    fileName: file.name,
+    file,
+  });
+  const data = await window.Signal.Types.VisualAttachment.blobToArrayBuffer(
+    resizedBlob
+  );
+  return {
+    fileName: fileName || file.name,
+    contentType,
+    data,
+    size: data.byteLength,
+    blurHash,
+  };
+}
+
+export async function autoScale({
+  contentType,
+  file,
+  fileName,
+}: {
+  contentType: MIMEType;
+  file: File | Blob;
+  fileName: string;
+}): Promise<{
+  contentType: MIMEType;
+  file: Blob;
+  fileName: string;
+}> {
+  if (!canBeTranscoded({ contentType })) {
+    return { contentType, file, fileName };
+  }
+
+  const blob = await scaleImageToLevel(file, true);
+
+  const { name } = path.parse(fileName);
+
+  return {
+    contentType: IMAGE_JPEG,
+    file: blob,
+    fileName: `${name}.jpeg`,
+  };
+}