我最初构建了面向.NET 2.0的项目,并使用System.Drawing类来执行load / resize / save.相关代码包括：

original = Image.FromFile(inputFile); //NOTE: Reused for each of the 3 target sizes
Bitmap resized = new Bitmap(size,size);
//Draw the image to a new image of the intended size
Graphics g = Graphics.FromImage(resized);
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
g.Clear(Color.White);
g.DrawImage(original,center - width / 2f,center - height / 2f,width,height);
g.Dispose();
//Save the new image to the output path
resized.Save(outputFile,ImageFormat.Jpeg);

我想将此项目移植到.NET 3.5,所以尝试使用System.Windows.Media类来执行相同的功能.我得到它的工作,但表现是可怕的;每张图片的处理时间约为50倍.绝大多数时间都是加载图像.相关代码包括：

BitmapImage original = new BitmapImage(); //Again,reused for each of the 3 target sizes
original.BeginInit();
original.StreamSource = new MemoryStream(imageData); //imageData is a byte[] of the data loaded from a FileStream
original.CreateOptions = BitmapCreateOptions.None;
original.CacheOption = BitmapCacheOption.Default;
original.EndInit(); //Here's where the vast majority of the time is spent
original.Freeze();

// Target Rect for the resize operation
Rect rect = new Rect(center - width / 2d,center - height / 2d,height);

// Create a DrawingVisual/Context to render with
DrawingVisual drawingVisual = new DrawingVisual();
using (DrawingContext drawingContext = drawingVisual.RenderOpen())
{
    drawingContext.DrawImage(original,rect);
}

// Use RenderTargetBitmap to resize the original image
RenderTargetBitmap resizedImage = new RenderTargetBitmap(
    size,size,// Resized dimensions
    96,96,// Default DPI values
    PixelFormats.Default);              // Default pixel format
resizedImage.Render(drawingVisual);

// Encode the image using the original format and save the modified image
SaveImageData(resizedImage,outputFile);

我在这里做错了什么,要花太多时间？我已经尝试使用BitmapImage上的构造函数,该构造函数使用了URI,那里也是一样的性能问题.任何人以前都做过这样的事情,知道是否有更多的表现方式来做到这一点？还是我还需要使用System.Drawing？谢谢！