add screenshot

src/controls/screenshot.js

@@ -0,0 +1,38 @@
+import { append, tooltip, secondToTime } from '../utils';
+import icons from '../icons';
+
+export default class Screenshot {
+  constructor(option) {
+    this.option = option;
+  }
+
+  apply(art) {
+    this.art = art;
+    const { events: { proxy }, i18n, notice } = this.art;
+    this.$screenshot = append(this.option.$control, icons.screenshot);
+    tooltip(this.$screenshot, i18n.get('Screenshot'));
+    proxy(this.$screenshot, 'click', () => {
+      try {
+        this.captureFrame();
+      } catch (error) {
+        notice.show(error);
+      }
+    });
+  }
+
+  captureFrame() {
+    const { $video } = this.art.refs;
+    const canvas = document.createElement('canvas');
+    canvas.width = $video.videoWidth;
+    canvas.height = $video.videoHeight;
+    canvas.getContext('2d').drawImage($video, 0, 0);
+    const dataUri = canvas.toDataURL('image/png');
+    const elink = document.createElement('a');
+    elink.style.display = 'none';
+    elink.href = dataUri;
+    elink.download = `${secondToTime($video.currentTime)}.png`;
+    document.body.appendChild(elink);
+    elink.click();
+    document.body.removeChild(elink);
+  }
+}