code: func (remote *RemoteDebugger) CaptureScreenshot(format string, quality int, fromSurface bool) ([]byte, error) {
  	if format == "" {
  		format = "png"
  	}
  
  	res, err := remote.SendRequest("Page.captureScreenshot", Params{
  		"format":      format,
  		"quality":     quality,
  		"fromSurface": fromSurface,
  	})
  
  	if err != nil {
  		return nil, err
  	}
  
  	if res == nil {
  		return nil, ErrorNoResponse
  	}
  
  	return base64.StdEncoding.DecodeString(res["data"].(string))
  }
docs: // CaptureScreenshot takes a screenshot, uses "png" as default format.