desktopCapturer: Screenshot of desktop (not video) is slightly out of focus (little blurry)


With the example of this page ( I take screenshots of the desktop (not videos). Everthing ist allright - but the image of the screenshot is is slightly out of focus (little blurry).

I’ve also build with NW.js ( a tool to take screenshots - but also with NW.js the image has the unwanted effect: The screenshot is is slightly out of focus (little blurry). It seems, NW.js uses the Navigator.getUserMedia() too. Therfor I think the reason of the unwanted effect is in Navigator.getUserMedia().

In the example the access to getUserMedia is as follows:

 audio: false,
 video: {
  mandatory: {
   chromeMediaSource: 'desktop',
   chromeMediaSourceId: sources[i].id,
   minWidth: 1280,
   maxWidth: 1280,
   minHeight: 720,
   maxHeight: 720
}, handleStream, handleError)

I could imagine that there is an option to take screenshot without “blur” …

How can I take screenshot without blur?


After rebooting everthing is ok without modification - strange … I will keep an eye on it.


The problem still exists: After first start of my app (Windows 7) I take a screenshot - everthing is ok. Then only I resize the window of my app and take a screenshot again: The image is a little bit blurry. The same issue occurs with NW.js too. Does anyone confirm the issue? Does anyone know a workaround - e. g. redraw the window before capturing?


I found my error:

After capturing I crop the screenshot with the graphic functions of canvas. Now I realized, that the values in my “cropper” sometimes contains numbers with comma. But they have to be integer - problem solved.

PS: The function “win.capturePage” ( makes screenshots much easier than “desktopCapturer” (

PS2: “win.capturePage” has manipulation functions ( e.g. crop - but canvas has more functions …