feat: add loading image from fetching URL (#482)

Author: EscapedGibbon

src/load/__tests__/fetchURL.test.ts

@@ -0,0 +1,24 @@
+import { encodeDataURL } from '../../save/encodeDataURL.js';
+import { fetchURL } from '../fetchURL.js';
+
+describe('testing fetchURL', () => {
+  test('decodes image from data URL', async () => {
+    const image = await fetchURL(
+      'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAAAAACoBHk5AAAAFklEQVR4XmNggID///+DSCCEskHM/wCAnQr2TY5mOAAAAABJRU5ErkJggg==',
+    );
+    expect(image.bitDepth).toBe(8);
+    expect(image.getRawImage().data).toEqual(
+      new Uint8Array([
+        0, 0, 0, 0, 0, 0, 255, 255, 255, 0, 0, 255, 0, 255, 0, 0, 255, 255, 255,
+        0, 255, 0, 255, 0, 255,
+      ]),
+    );
+  });
+  test('encoded URL must be equal to decoded one', async () => {
+    const dataURL =
+      'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAAAAACoBHk5AAAAFklEQVR4XmNggID///+DSCCEskHM/wCAnQr2TY5mOAAAAABJRU5ErkJggg==';
+    const image = await fetchURL(dataURL);
+    const result = encodeDataURL(image);
+    expect(result).toEqual(dataURL);
+  });
+});

src/load/fetchURL.ts

@@ -0,0 +1,13 @@
+import { decode } from './decode.js';
+
+/**
+ * Fetches image URL and decodes it.
+ * @param dataUrl - Image URL.
+ * @returns decoded image data.
+ */
+export async function fetchURL(dataUrl: string) {
+  const response = await fetch(dataUrl);
+  const arrayBuffer = await response.arrayBuffer();
+  const image = decode(new DataView(arrayBuffer));
+  return image;
+}

src/load/index.ts

@@ -6,3 +6,4 @@ export * from './load.types.js';
 export * from './read.js';
 export * from './readCanvas.js';
 export * from './readImg.js';
+export * from './fetchURL.js';