如何从WPF窗口创建缩略图并将其转换为字节[],以便我可以坚持下去？

Question

我想从我的wpf窗口创建缩略图,并希望将其保存到数据库中并稍后显示.有什么好的解决方案吗？

我已经开始使用RenderTargetBitmap,但我找不到任何简单的方法将它变成字节.

RenderTargetBitmap bmp = new RenderTargetBitmap(180, 180, 96, 96, PixelFormats.Pbgra32);
bmp.Render(myWpfWindow);

使用user32.dll和Graphics.CopyFromScreen()对我来说并不好,因为它在这里是因为我想从用户控件做一个截图.

谢谢

Answer 1

Steven Robbins撰写了一篇关于捕获控件截图的精彩博文,其中包含以下扩展方法:

public static class Screenshot
{
    /// <summary>
    /// Gets a JPG "screenshot" of the current UIElement
    /// </summary>
    /// <param name="source">UIElement to screenshot</param>
    /// <param name="scale">Scale to render the screenshot</param>
    /// <param name="quality">JPG Quality</param>
    /// <returns>Byte array of JPG data</returns>
    public static byte[] GetJpgImage(this UIElement source, double scale, int quality)
    {
        double actualHeight = source.RenderSize.Height;
        double actualWidth = source.RenderSize.Width;

        double renderHeight = actualHeight * scale;
        double renderWidth = actualWidth * scale;

        RenderTargetBitmap renderTarget = new RenderTargetBitmap((int) renderWidth, (int) renderHeight, 96, 96, PixelFormats.Pbgra32);
        VisualBrush sourceBrush = new VisualBrush(source);

        DrawingVisual drawingVisual = new DrawingVisual();
        DrawingContext drawingContext = drawingVisual.RenderOpen();

        using (drawingContext)
        {
            drawingContext.PushTransform(new ScaleTransform(scale, scale));
            drawingContext.DrawRectangle(sourceBrush, null, new Rect(new Point(0, 0), new Point(actualWidth, actualHeight)));
        }
        renderTarget.Render(drawingVisual);

        JpegBitmapEncoder jpgEncoder = new JpegBitmapEncoder();
        jpgEncoder.QualityLevel = quality;
        jpgEncoder.Frames.Add(BitmapFrame.Create(renderTarget));

        Byte[] _imageArray;

        using (MemoryStream outputStream = new MemoryStream())
        {
            jpgEncoder.Save(outputStream);
            _imageArray = outputStream.ToArray();
        }

        return _imageArray;
    }
}

此方法采用控件和比例因子并返回字节数组.所以这似乎非常适合您的要求.

查看帖子以获得进一步阅读和一个非常整洁的示例项目.