Select cover image from images in metadata.

README.md

@@ -219,13 +219,30 @@ orderTags(nativeTags: ITag[]): [tagId: string]: any[]
 ```
 
 #### ratingToStars function
+
+   Can be used to convert the normalized rating value to the 0..5 stars, where 0 an undefined rating, 1 the star the lowest rating and 5 the highest rating.
+
+   ```ts
+   ratingToStars(rating: number): number
+   ```
+#### selectCover function
 
-Can be used to convert the normalized rating value to the 0..5 stars, where 0 an undefined rating, 1 the star the lowest rating and 5 the highest rating.
+Select cover image based on image type field, otherwise the first picture in file.
 
 ```ts
-ratingToStars(rating: number): number
+export function selectCover(pictures?: IPicture[]): IPicture | null
 ```
 
+```js
+import * as mm from 'music-metadata';
+
+(async () => {
+  const {common} = await mm.parseFile(filePath);
+  const cover = mm.selectCover(common.picture); // pick the cover image
+}
+)();
+ ```
+
 ### Options
 *   `duration`: default: `false`, if set to `true`, it will parse the whole media file if required to determine the duration.
 *   `observer: (update: MetadataEvent) => void;`: Will be called after each change to `common` (generic) tag, or `format` properties.

lib/core.ts

@@ -2,7 +2,7 @@ import * as Stream from 'stream';
 import * as strtok3 from 'strtok3/lib/core';
 
 import {ParserFactory} from './ParserFactory';
-import { IAudioMetadata, INativeTagDict, IOptions, IPrivateOptions, IRandomReader, ITag } from './type';
+import { IAudioMetadata, INativeTagDict, IOptions, IPicture, IPrivateOptions, IRandomReader, ITag } from './type';
 import { RandomBufferReader } from './common/RandomBufferReader';
 import { APEv2Parser } from './apev2/APEv2Parser';
 import { hasID3v1Header } from './id3v1/ID3v1Parser';
@@ -70,6 +70,19 @@ export function ratingToStars(rating: number): number {
   return rating === undefined ? 0 : 1 + Math.round(rating * 4);
 }
 
+/**
+ * Select most likely cover image.
+ * @param pictures Usually metadata.common.picture
+ * @return Cover image, if any, otherwise null
+ */
+export function selectCover(pictures?: IPicture[]): IPicture | null {
+  return pictures ? pictures.reduce((acc, cur) => {
+    if (cur.name && cur.name.toLowerCase() in ['front', 'cover', 'cover (front)'])
+      return cur;
+    return acc;
+  }) : null;
+}
+
 export async function scanAppendingHeaders(randomReader: IRandomReader, options: IPrivateOptions = {}) {
 
   let apeOffset = randomReader.fileSize;

lib/index.ts

@@ -11,7 +11,7 @@ export { IAudioMetadata, IOptions, ITag, INativeTagDict, ICommonTagsResult, IFor
 
 const debug = _debug("music-metadata:parser");
 
-export { parseFromTokenizer, parseBuffer, IFileInfo } from './core';
+export { parseFromTokenizer, parseBuffer, IFileInfo, selectCover } from './core';
 
 /**
  * Parse audio from Node Stream.Readable

test/test-common.ts

@@ -92,6 +92,40 @@ describe('Convert rating', () => {
 
 });
 
+describe('function selectCover()', () => {
+
+  const samplePath = path.join(__dirname, 'samples');
+
+  const multiCoverFiles = [
+    'MusicBrainz - Beth Hart - Sinner\'s Prayer [id3v2.3].V2.mp3',
+    'MusicBrainz - Beth Hart - Sinner\'s Prayer [id3v2.3].wav',
+    'MusicBrainz - Beth Hart - Sinner\'s Prayer [id3v2.4].V2.mp3',
+    'MusicBrainz - Beth Hart - Sinner\'s Prayer [id3v2.4].aiff',
+    'MusicBrainz - Beth Hart - Sinner\'s Prayer.ape',
+    'MusicBrainz - Beth Hart - Sinner\'s Prayer.flac',
+    'MusicBrainz - Beth Hart - Sinner\'s Prayer.m4a',
+    'MusicBrainz - Beth Hart - Sinner\'s Prayer.ogg',
+    'id3v2.4.mp3',
+    'issue-266.flac',
+    'monkeysaudio.ape'
+  ];
+
+  it('Should pick the front cover', async () => {
+    for (const multiCoverFile of multiCoverFiles) {
+      const filePath = path.join(samplePath, multiCoverFile);
+      const {common} = await mm.parseFile(filePath);
+      assert.isTrue(common.picture.length > 1);
+      const cover = mm.selectCover(common.picture);
+      if (cover.type) {
+        assert.equal(cover.type, 'Cover (front)', 'cover.type');
+      } else {
+        assert.equal(cover.data, common.picture[0].data, 'First picture if no type is defined');
+      }
+    }
+  });
+
+});
+
 describe('MimeType', () => {
 
   it('should be able to decode basic MIME-types', () => {