Uint8Array migration

ts/test-electron/util/canvasToBytes_test.ts

@@ -0,0 +1,40 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+import { IMAGE_JPEG, IMAGE_PNG } from '../../types/MIME';
+import { sniffImageMimeType } from '../../util/sniffImageMimeType';
+
+import { canvasToBytes } from '../../util/canvasToBytes';
+
+describe('canvasToBytes', () => {
+  let canvas: HTMLCanvasElement;
+  beforeEach(() => {
+    canvas = document.createElement('canvas');
+    canvas.width = 100;
+    canvas.height = 200;
+
+    const context = canvas.getContext('2d');
+    if (!context) {
+      throw new Error('Test setup error: cannot get canvas rendering context');
+    }
+    context.fillStyle = '#ff9900';
+    context.fillRect(10, 10, 20, 20);
+  });
+
+  it('converts a canvas to an Uint8Array, JPEG by default', async () => {
+    const result = await canvasToBytes(canvas);
+
+    assert.strictEqual(sniffImageMimeType(result), IMAGE_JPEG);
+
+    // These are just smoke tests.
+    assert.instanceOf(result, Uint8Array);
+    assert.isAtLeast(result.byteLength, 50);
+  });
+
+  it('can convert a canvas to a PNG Uint8Array', async () => {
+    const result = await canvasToBytes(canvas, IMAGE_PNG);
+
+    assert.strictEqual(sniffImageMimeType(result), IMAGE_PNG);
+  });
+});