fix(media): strip data URI prefix from base64 media strings

packages/node/src/base64.ts

@@ -55,6 +55,8 @@ export const downloadImageFromURLAsBase64 = async (url: string): Promise<string>
 
 const isBuffer = (file: string | Buffer): file is Buffer => file instanceof Buffer;
 
+const base64DataUriPrefix = /^data:[^,]*;base64,/;
+
 const fileToBase64 = (file: string | Buffer): Promise<string> =>
   isFilePromise(file).then((isFile) =>
     isFile
@@ -76,10 +78,12 @@ const fileToBase64 = (file: string | Buffer): Promise<string> =>
 /**
  * Converts media into a base64 string so that it can be sent to Weaviate.
  *
- * @param {Media} media The media as a base64 string, a file path, a URL, a `Uint8Array` (including `Buffer`), or a `Blob`. A base64 string is returned as is.
+ * @param {Media} media The media as a base64 string, a base64 data URI, a file path, a URL, a `Uint8Array` (including `Buffer`), or a `Blob`. A base64 string is returned as is and a data URI has its `data:<mime>;base64,` prefix removed.
  * @returns {Promise<string>} The base64 string.
  */
 export const toBase64FromMedia = async (media: Media): Promise<string> => {
+  if (typeof media === 'string' && base64DataUriPrefix.test(media))
+    return media.replace(base64DataUriPrefix, '');
   if (media instanceof Blob) return Buffer.from(await media.arrayBuffer()).toString('base64');
   if (media instanceof Uint8Array)
     return Buffer.from(media.buffer, media.byteOffset, media.byteLength).toString('base64');

packages/test/node/base64/unit.test.ts

@@ -0,0 +1,19 @@
+import { toBase64FromMedia } from '@weaviate/node';
+import { describe, expect, it } from 'vitest';
+
+describe('Unit testing of toBase64FromMedia in the node client', () => {
+  const short = Buffer.from('image bytes').toString('base64');
+  const long = Buffer.alloc(6000, 7).toString('base64');
+
+  it.each([
+    ['a short png data URI', `data:image/png;base64,${short}`, short],
+    ['a long jpeg data URI', `data:image/jpeg;base64,${long}`, long],
+    ['a data URI with media type parameters', `data:image/png;name=img.png;base64,${short}`, short],
+  ])('should strip the prefix from %s', async (_, media, expected) => {
+    expect(await toBase64FromMedia(media)).toEqual(expected);
+  });
+
+  it('should return a base64 string as is', async () => {
+    expect(await toBase64FromMedia(long)).toEqual(long);
+  });
+});

packages/test/web/base64.test.ts

@@ -0,0 +1,17 @@
+import { describe, expect, it } from 'vitest';
+import { toBase64FromMedia } from '../../web/src/base64.js';
+
+describe('Unit testing of toBase64FromMedia in the web client', () => {
+  const b64 = Buffer.from('image bytes').toString('base64');
+
+  it.each([
+    ['a png data URI', `data:image/png;base64,${b64}`],
+    ['a data URI with media type parameters', `data:image/png;name=img.png;base64,${b64}`],
+  ])('should strip the prefix from %s', async (_, media) => {
+    expect(await toBase64FromMedia(media)).toEqual(b64);
+  });
+
+  it('should return a base64 string as is', async () => {
+    expect(await toBase64FromMedia(b64)).toEqual(b64);
+  });
+});

packages/web/src/base64.ts

@@ -25,6 +25,8 @@ const blobToBase64 = (blob: Blob): Promise<string> =>
     reader.readAsDataURL(blob);
   });
 
+const base64DataUriPrefix = /^data:[^,]*;base64,/;
+
 export const downloadImageFromURLAsBase64 = async (url: string): Promise<string> => {
   if (!isUrl(url)) {
     throw new Error('Invalid URL');
@@ -43,13 +45,17 @@ export const downloadImageFromURLAsBase64 = async (url: string): Promise<string>
  * Converts media input into a base64 string.
  * Accepts:
  * - A base64 string (returns it unchanged)
+ * - A base64 data URI (returns it without the `data:<mime>;base64,` prefix)
  * - A URL (fetches the image and converts to base64)
  * - A `Blob` or `File` (uses FileReader)
  * - A `Uint8Array` (copied into a `Blob`, which rejects `SharedArrayBuffer`-backed views)
  */
 export const toBase64FromMedia = (media: Media): Promise<string> => {
   if (typeof media === 'string') {
-    if (media.startsWith('data:') || /^[A-Za-z0-9+/=]+$/.test(media)) {
+    if (base64DataUriPrefix.test(media)) {
+      // Base64 data URI, strip the data:mime/type;base64, prefix
+      return Promise.resolve(media.replace(base64DataUriPrefix, ''));
+    } else if (media.startsWith('data:') || /^[A-Za-z0-9+/=]+$/.test(media)) {
       // Already base64 string
       return Promise.resolve(media);
     } else if (isUrl(media)) {