Png图片的透明部分穿透测试

       private void Window_MouseMove(object sender, MouseEventArgs e)
{
           NavBtnList.Clear();
                Point mouseP = e.GetPosition(this);
                VisualTreeHelper.HitTest(this, new HitTestFilterCallback(HitFilter),
                    new HitTestResultCallback(HitResult), new PointHitTestParameters(mouseP));

                if (NavBtnList.Count > 0)
                {
                    for (int k = 0; k < NavBtnList.Count; k++)
                    {
                        IconBtn element = NavBtnList[k] as IconBtn;

                        DrawingVisual drawingVisual = new DrawingVisual();
                        using (DrawingContext context = drawingVisual.RenderOpen())
                        {
                            VisualBrush brush = new VisualBrush(element) { Stretch = Stretch.None };
                            context.DrawRectangle(brush, null,
                                new Rect(0, 0, element.ActualWidth, element.ActualHeight));
                            context.Close();
                        }

                        //dpi可以自己设定
                        // 获取dpi方法：PresentationSource.FromVisual(this).CompositionTarget.TransformToDevice
                        RenderTargetBitmap bitmap = new RenderTargetBitmap((int)element.ActualWidth,
                            (int)element.ActualHeight, 96, 96, PixelFormats.Pbgra32);
                        bitmap.Render(drawingVisual);

                        Point p = this.TranslatePoint(mouseP, element); //全局坐标转为局部坐标point

                        //获取鼠标下像素颜色值
                        var c = getImagePointColor((bitmap as BitmapSource), (int)p.X, (int)p.Y);
                        if (c != Convert16ToColor("#00000000"))
                        {
                            if (element.IsEnabled)
                            {
                            }
                            break;

                        }
                        bitmap.Clear();
                    }
}

        //鼠标按下获得所有IconBtnFrame 存储在NavBtnList里
        List<IconBtn> NavBtnList = new List<IconBtn>();

        public HitTestFilterBehavior HitFilter(DependencyObject dObject)
        {
            if (dObject is IconBtn)
            {
                NavBtnList.Add(dObject as IconBtn);
            }
            return HitTestFilterBehavior.Continue;
        }

        public HitTestResultBehavior HitResult(HitTestResult result)
        {
            return HitTestResultBehavior.Continue;
        }