protected void OnManipulationDelta(object sender, ManipulationDeltaRoutedEventArgs e)
{
if (e.OriginalSource != _mainpage)
return;
var compositeTransform = (CompositeTransform)_mainpage.MainCanvas.RenderTransform;
var tmpTranslate = new TranslateTransform
{
X = compositeTransform.CenterX,
Y = compositeTransform.CenterY
};
var center = compositeTransform.Inverse.TransformPoint(e.Position);
var localPoint = tmpTranslate.Inverse.TransformPoint(center);
//Now scale the point in local space
localPoint.X *= compositeTransform.ScaleX;
localPoint.Y *= compositeTransform.ScaleY;
//Transform local space into world space again
var worldPoint = tmpTranslate.TransformPoint(localPoint);
//Take the actual scaling...
var distance = new Point(
worldPoint.X - center.X,
worldPoint.Y - center.Y);
//...and balance the jump of the changed scaling origin by changing the translation
compositeTransform.TranslateX += distance.X;
compositeTransform.TranslateY += distance.Y;
//Also set the scaling values themselves, especially set the new scale center...
compositeTransform.ScaleX *= e.Delta.Scale;
compositeTransform.ScaleY *= e.Delta.Scale;
compositeTransform.CenterX = center.X;
compositeTransform.CenterY = center.Y;
//And consider a translational shift
compositeTransform.TranslateX += e.Delta.Translation.X;
compositeTransform.TranslateY += e.Delta.Translation.Y;
_mainpage.MainCanvas.RenderTransform = compositeTransform;
Settings.ZoomLevel = compositeTransform.ScaleX;
}
