Question

我一直在使用Asp.Net hadler中的GDI +实现来调整图像大小。我发现文章Resizing images from the server using WPF/WIC instead of GDI+描述了使用Windows.Media.Imaging调整图像大小更有效（更快，消耗更少的系统资源）。

这种方法还有一个优点，我可以从源图像中读取单个帧，如gif。这是我的代码的一部分：

var photoDecoder = BitmapDecoder.Create(inputStream, BitmapCreateOptions.PreservePixelFormat,
                                                BitmapCacheOption.None);
IEnumerable<BitmapFrame> bitmapFrames = from bitmapFrame in photoDecoder.Frames
                                                select bitmapFrame;

var bitmapFramesList = new List<BitmapFrame>();
bitmapFramesList.AddRange(bitmapFrames);

var firstFrame = bitmapFramesList.First();

int inputWidth = Convert.ToInt32(firstFrame.Width);
int inputHeight = Convert.ToInt32(firstFrame.Height);

var firstFrameSize= new Size(inputWidth, inputHeight);

//if targetSize is bigger than image Size render image as is
bool targetSizeIsBiggerOrEmpty = targetSize.IsEmpty || (targetSize.Width > firstFrameSize.Width && targetSize.Height > firstFrameSize.Height);   
if (targetSizeIsBiggerOrEmpty)
{
   inputStream.Position = ZERO;
   inputStream.CopyTo(catalogImage.Stream);
}
else
{
   //calculate size of target image
   Size imageSize = SizeCalculator.CalculateImageSize(new Size(Convert.ToInt32(firstFrame.Width),Convert.ToInt32(firstFrame.Height)), targetSize);
   if (targetSize.Width == ZERO)
      targetSize.Width = imageSize.Width;
   if (targetSize.Height == ZERO)
      targetSize.Height = imageSize.Height;

   double scaleX = Convert.ToDouble(imageSize.Width) / Convert.ToDouble(firstFrame.Width);
   double scaleY = Convert.ToDouble(imageSize.Height) / Convert.ToDouble(firstFrame.Height);
   double scale = Math.Min(scaleX, scaleY);

   var targetFrames= new Collection<BitmapFrame>();
   foreach (var sourceFrame in bitmapFramesList)
   {                    
      var transform = new ScaleTransform {ScaleX = scale, ScaleY = scale};
      var transformedBitmap = new TransformedBitmap(sourceFrame, transform);
      BitmapFrame bitmapFrame = BitmapFrame.Create(transformedBitmap);
      targetFrames.Add(bitmapFrame);
   }

   //my own method for saving image to response output stream
   SaveCatalogImage(catalogImage, targetFrames);

}

但这是一个小问题。每个帧具有不同的大小，并且我无法根据第一帧大小找到每个帧位置。我还需要在源图像中的目标图像计时。

我可以在源图像中找到这些信息吗？

如何使用Windows.Media.Imaging命名空间调整动画gif的大小

0 个答案: