void OnProcessButtonClicked(object sender, EventArgs e)
{
(sender as Button).IsEnabled = false;
switch (picker.SelectedIndex)
{
case 0:
pixmap = image.ToGreyscale();
break;
case 1:
pixmap = image.OtsuThreshold();
break;
case 2:
pixmap = image.ToSepia();
break;
}
canvasView.InvalidateSurface();
(sender as Button).IsEnabled = true;
}