wpf 将绘图图像转换为位图图像

Convert DrawingImage to BitmapImage

提问by Hossein Narimani Rad

I want to draw large number of shapes (lines, ellipses and ...) and then save them as bitmap or png. I made the drawings and the question is: how can I convert a DrawingImageto BitmapImagein C#? the code is something like this:

我想绘制大量形状（线条、椭圆和...），然后将它们保存为位图或 png。我制作了图纸，问题是：如何在 C#中将 DrawingImage转换为BitmapImage？代码是这样的：

DrawingGroup drawingGroup = new DrawingGroup();
using(DrawingContext context = drawingGroup.Open())
{
    //make some drawing 
}
DrawingImage drawingImage = new DrawingImage(drawingGroup)

// your suggestion? DrawingImage - > BitmapImage

回答by Clemens

You may put the ImageDrawing into an Image control and render that into a RenderTargetBitmap, which is a BitmapSource and can therefore be serialized by a BitmapEncoder(PngBitmapEncoder in this example).

您可以将 ImageDrawing 放入一个 Image 控件并将其渲染到一个RenderTargetBitmap 中，它是一个 BitmapSource，因此可以由BitmapEncoder（在本例中为 PngBitmapEncoder）序列化。

public void SaveDrawingToFile(Drawing drawing, string fileName, double scale)
{
    var drawingImage = new Image { Source = new DrawingImage(drawing) };
    var width = drawing.Bounds.Width * scale;
    var height = drawing.Bounds.Height * scale;
    drawingImage.Arrange(new Rect(0, 0, width, height));

    var bitmap = new RenderTargetBitmap((int)width, (int)height, 96, 96, PixelFormats.Pbgra32);
    bitmap.Render(drawingImage);

    var encoder = new PngBitmapEncoder();
    encoder.Frames.Add(BitmapFrame.Create(bitmap));

    using (var stream = new FileStream(fileName, FileMode.Create))
    {
        encoder.Save(stream);
    }
}

Note that you don't actually need a BitmapImage for encoding, because BitmapSource (or any derived class like RenderTargetBitmap) will be accepted as argument to BitmapFrame.Create.

请注意，您实际上不需要 BitmapImage 进行编码，因为 BitmapSource（或任何派生类，如 RenderTargetBitmap）将被接受为BitmapFrame.Create 的参数。

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A slightly different solution would involve a DrawingVisualinstead of a DrawingImage:

稍微不同的解决方案将涉及DrawingVisual代替DrawingImage：

public void SaveDrawingToFile(Drawing drawing, string fileName, double scale)
{
    var drawingVisual = new DrawingVisual();

    using (var drawingContext = drawingVisual.RenderOpen())
    {
        drawingContext.PushTransform(new ScaleTransform(scale, scale));
        drawingContext.PushTransform(new TranslateTransform(-drawing.Bounds.X, -drawing.Bounds.Y));
        drawingContext.DrawDrawing(drawing);
    }

    var width = drawing.Bounds.Width * scale;
    var height = drawing.Bounds.Height * scale;
    var bitmap = new RenderTargetBitmap((int)width, (int)height, 96, 96, PixelFormats.Pbgra32);
    bitmap.Render(drawingVisual);

    var encoder = new PngBitmapEncoder();
    encoder.Frames.Add(BitmapFrame.Create(bitmap));

    using (var stream = new FileStream(fileName, FileMode.Create))
    {
        encoder.Save(stream);
    }
}

回答by Pratap Singh Mehra

I found it pretty easy this way:

我发现这样很容易：

public static BitmapSource ToBitmapSource(DrawingImage source)
{
    DrawingVisual drawingVisual = new DrawingVisual();
    DrawingContext drawingContext = drawingVisual.RenderOpen();
    drawingContext.DrawImage(source, new Rect(new Point(0, 0), new Size(source.Width, source.Height)));
    drawingContext.Close();

    RenderTargetBitmap bmp = new RenderTargetBitmap((int)source.Width, (int)source.Height, 96, 96, PixelFormats.Pbgra32);
    bmp.Render(drawingVisual);
    return bmp;
}

You may use it to get System.Drawing.Bitmap

您可以使用它来获取 System.Drawing.Bitmap

using (MemoryStream ms = new MemoryStream())
{
    PngBitmapEncoder encoder = new PngBitmapEncoder();
    encoder.Frames.Add(BitmapFrame.Create(ToBitmapSource(drawingImage)));
    encoder.Save(ms);

    using (System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(ms))
    {
        bmpOut = new System.Drawing.Bitmap(bmp);
    }
}