项目面板的 WPF RenderTargetBitmap 但省略某些元素

Question

我正在使用 RenderTargetBitmap.Render(panel) 来拍摄项目面板的快照。

但是我想省略某些元素（例如 OmitWhileRenderingToBitmap 属性设置为 false 的自定义项目）。

有没有一些简单的方法可以做到这一点，即从项目面板中删除项目，拍摄快照，然后将它们添加回来？

编辑：本质上，这是我的自定义列表框类中的关键位。拆下过滤器位，一切都按预期工作。

    protected void UpdatePanelBitmapSource()
    {
        if (this._itemsPanel != null) //_itemsPanel here is the canvas within the ListBox. Not rendering the ListBox for a reason.
        {
            Matrix m = PresentationSource.FromVisual(this._itemsPanel).CompositionTarget.TransformToDevice;

            var existingFilter = this.Items.Filter;

            // Add filter
            this.Items.Filter = item =>
            {
                var mgvListBoxItem = this.ItemContainerGenerator.ContainerFromItem(item) as MGVListBoxItem;

                if (mgvListBoxItem != null)
                    return !mgvListBoxItem.IsEditable;
                else
                    return false;
            };

            var panelBitmap = new RenderTargetBitmap(
                (int)Math.Floor(this._itemsPanel.ActualWidth),
                (int)Math.Floor(this._itemsPanel.ActualHeight),
                m.M11 * 96.0,
                m.M22 * 96.0,
                PixelFormats.Default);
            panelBitmap.Render(this._itemsPanel);

            // Remove filter
            this.Items.Filter = existingFilter;

            this.PanelBitmapSource = panelBitmap;
        }
    }

Answer 1

只需应用一个过滤器：

// Add filter
yourItemsControl.Items.Filter = o =>
    {
        YourType item = (YourType)o;
        return !item.OmitWhileRenderingToBitmap;
    };


// Render to bitmap
// ...

// Remove filter
yourItemsControl.Items.Filter = null;

Answer 2

最后我做了这样的事情

        protected void OnUpdatePanelBitmapSource()
    {
        if (this._itemsPanel != null)
        {
            Matrix m = PresentationSource.FromVisual(this._itemsPanel).CompositionTarget.TransformToDevice;

            var hiddenItems = new List<MGVListBoxItem>();

            foreach(var item in this.Items)
            {
                var mgvListBoxItem = this.ItemContainerGenerator.ContainerFromItem(item) as MGVListBoxItem;
                if (mgvListBoxItem != null && mgvListBoxItem.IsEditable && mgvListBoxItem.IsVisible)
                {
                    mgvListBoxItem.Visibility = Visibility.Hidden;
                    hiddenItems.Add(mgvListBoxItem);
                }
            }

            var panelBitmap = new RenderTargetBitmap(
                (int)Math.Floor(this._itemsPanel.ActualWidth),
                (int)Math.Floor(this._itemsPanel.ActualHeight),
                m.M11 * 96.0,
                m.M22 * 96.0,
                PixelFormats.Default);

            panelBitmap.Render(this._itemsPanel);

            foreach (var mgvListBoxItem in hiddenItems)
            {
                mgvListBoxItem.Visibility = Visibility.Visible;
            }

            this.PanelBitmapSource = panelBitmap;
        }
    }