chrome/browser/resources/feedback/js/take_screenshot.js

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 /**
   6  * Function to take the screenshot of the current screen.
   7  * @param {function(HTMLCanvasElement)} callback Callback for returning the
   8  *                                      canvas with the screenshot on it.
   9  */
  10 function takeScreenshot(callback) {
  11   var screenshotStream = null;
  12   var video = document.createElement('video');
  13
  14   video.addEventListener('canplay', function(e) {
  15     if (screenshotStream) {
  16       var canvas = document.createElement('canvas');
  17       canvas.setAttribute('width', video.videoWidth);
  18       canvas.setAttribute('height', video.videoHeight);
  19       canvas.getContext('2d').drawImage(
  20           video, 0, 0, video.videoWidth, video.videoHeight);
  21
  22       video.pause();
  23       video.src = '';
  24
  25       screenshotStream.stop();
  26       screenshotStream = null;
  27
  28       callback(canvas);
  29     }
  30   }, false);
  31
  32   navigator.webkitGetUserMedia(
  33     {
  34       video: {
  35         mandatory: {
  36           chromeMediaSource: 'screen',
  37           maxWidth: 4096,
  38           maxHeight: 2560
  39         }
  40       }
  41     },
  42     function(stream) {
  43       if (stream) {
  44         screenshotStream = stream;
  45         video.src = window.URL.createObjectURL(screenshotStream);
  46         video.play();
  47       }
  48     },
  49     function(err) {
  50       console.error('takeScreenshot failed: ' +
  51           err.name + '; ' + err.message + '; ' + err.constraintName);
  52     }
  53   );
  54 }