视频播放列表更新，增加分享海报生成

gcanvas/env/tool.js

@@ -0,0 +1,24 @@
+
+export function ArrayBufferToBase64 (buffer) {
+    var binary = '';
+    var bytes = new Uint8ClampedArray(buffer);
+    for (var len = bytes.byteLength, i = 0; i < len; i++) {
+        binary += String.fromCharCode(bytes[i]);
+    }
+    return btoa(binary);
+}
+	
+export function Base64ToUint8ClampedArray(base64String) {
+	const padding = '='.repeat((4 - base64String.length % 4) % 4);
+	const base64 = (base64String + padding)
+		.replace(/\-/g, '+')
+		.replace(/_/g, '/');
+
+	const rawData = atob(base64);
+	const outputArray = new Uint8ClampedArray(rawData.length);
+
+	for (let i = 0; i < rawData.length; ++i) {
+		outputArray[i] = rawData.charCodeAt(i);
+	}
+	return outputArray;
+}