將繪圖圖像轉換為位圖圖像

Question

我想繪制大量形狀（線條、橢圓和...），然后將它們保存為位圖或 png。 我制作了圖紙，問題是：如何在 C#中將 DrawingImage轉換為BitmapImage ？ 代碼是這樣的：

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

// your suggestion? DrawingImage - > BitmapImage

Answer 1

您可以將 ImageDrawing 放入一個 Image 控件並將其渲染到一個RenderTargetBitmap 中，它是一個 BitmapSource，因此可以由BitmapEncoder （在本例中為 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);
    }
}

請注意，您實際上不需要 BitmapImage 進行編碼，因為 BitmapSource（或任何派生類，如 RenderTargetBitmap）將被接受為BitmapFrame.Create 的參數。

---

稍微不同的解決方案將涉及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);
    }
}

Answer 2

我發現這樣很容易：

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;
}

您可以使用它來獲取 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);
    }
}