创建图像的缩略图并将其存储在缓存中

4 回答

• 4

  这是我不久前写的一种可能对你有帮助的方法 .

  byte[] IImageResizer.CreateThumbnailBytes(byte[] originalImage)
      {
          Image thumbnail = null;
  
          Image tempImage = Image.FromStream(new MemoryStream(originalImage));
  
          int desiredWidth = 160;
  
          int newPixelWidth = tempImage.Width;
          int newPixelHeight = tempImage.Height;
  
          if (newPixelWidth > desiredWidth)
          {
              float resizePercent = ((float)desiredWidth / (float)tempImage.Width);
  
              newPixelWidth = (int)(tempImage.Width * resizePercent) + 1;
              newPixelHeight = (int)(tempImage.Height * resizePercent) + 1;
          }
  
          Bitmap bitmap = new Bitmap(newPixelWidth, newPixelHeight);
  
          using (Graphics graphics = Graphics.FromImage((Image)bitmap))
          {
              graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
              graphics.DrawImage(tempImage, 0, 0, newPixelWidth, newPixelHeight);
          }
  
          thumbnail = (Image)bitmap;
  
          MemoryStream ms = new MemoryStream();
          thumbnail.Save(ms, ImageFormat.Jpeg);
  
          return ms.ToArray();
      }
  

  我传入原始图像二进制文件，并将图像大小调整为大约160px左右 .

  希望能帮助到你！

  回复于 2024-04-29T03:13:55+08:00
• 2

  您可以使用 InterpolationMode.HighQualityBicubic 创建合适的拇指位图

  Bitmap bitmap = ...
     Bitmap thumbBitmap = new System.Drawing.Bitmap(thumbWidth, thumbHeight);
     using (Graphics g = Graphics.FromImage(thumbBitmap))
     {
        g.InterpolationMode = InterpolationMode.HighQualityBicubic;
        g.DrawImage(bitmap, 0, 0, thumbWidth, thumbHeight);
     }
  

  如果您在后台线程中创建拇指，只需将它们保存到内存流中，然后您可以在请求时懒惰地使用它来创建 BitmapImage ：

  _ms = new MemoryStream();
     thumbBitmap.Save(_ms, ImageFormat.Png);
     _ms.Position = 0;
     ImageLoaded = true;
  
  
      //thumb image property of this class, use in binding  
      public BitmapImage ThumbImage
      {
          get
          {
              if (_thumbImage == null && ImageLoaded)
              {
                  BitmapImage bi = new BitmapImage();
                  bi.BeginInit();
                  bi.StreamSource = _ms;
                  bi.EndInit();
                  _thumbImage = bi;
              }
              return _thumbImage;
          }
      }
  

  回复于 2024-04-29T03:13:55+08:00
• 0

  在检查MSDN后，我没有看到任何直接的方法来做到这一点，但也许你可以只是每隔这么多像素采样图像并将数据写入新图像，然后清理完整尺寸的图像 .

  回复于 2024-04-29T03:13:55+08:00
• 2

  问题在于，当存在大量图像时，由于图像的大小，RAM使用天空火箭 .

  来自的C＃示例：http://msdn.microsoft.com/en-us/library/ms748873.aspx

  // Create source
  BitmapImage myBitmapImage = new BitmapImage();
  
  // BitmapImage.UriSource must be in a BeginInit/EndInit block
  myBitmapImage.BeginInit();
  myBitmapImage.UriSource = new Uri(@"C:\Water Lilies.jpg");
  
  // To save significant application memory, set the DecodePixelWidth or  
  // DecodePixelHeight of the BitmapImage value of the image source to the desired 
  // height or width of the rendered image. If you don't do this, the application will 
  // cache the image as though it were rendered as its normal size rather then just 
  // the size that is displayed.
  // Note: In order to preserve aspect ratio, set DecodePixelWidth
  // or DecodePixelHeight but not both.
  myBitmapImage.DecodePixelWidth = 200;
  myBitmapImage.EndInit();
  //
  //when you are ready to render the BitmapImage, do:
  imageThumb.Source = myBitmapImage;
  

  请注意DecodePixelWidth和DecodePixelHeight属性，以便以所需的缩小像素大小缓存图像 . 使用两者来拉伸图像以适合缩略图大小 .

  回复于 2024-04-29T03:13:55+08:00