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Resize

takes a byte[], and ints for width/height. returns a byte[] for the new image. keeps a static copy of previously provided sizes to reduce GC activity.

Source

private static readonly IList<Tuple<Rectangle, Image>> BitmapSizes = new List<Tuple<Rectangle, Image>>();
     //adapted from http://www.webcosmoforums.com/asp/321-create-high-quality-thumbnail-resize-image-dynamically-asp-net-c-code.html
//TODO: figure out how expensive this method is
//TODO: see if there's a way to make the IDisposable objects static
//TODO: make sure caching is set up properly to reduce usage
public static byte[] Resize(this byte[] source, int width, int height) {
   try {
      using (var image = Image.FromStream(new MemoryStream(source), true, true)) {
         var srcWidth = image.PhysicalDimension.Width;
         var srcHeight = image.PhysicalDimension.Height;
         if (srcWidth == width && srcHeight == height)
            return source;
         var scaleW = (double)width / srcWidth;
         var scaleH = (double)height / srcHeight;
         if (scaleW < scaleH) {
            width = (int)Math.Round((scaleW * srcWidth));
            height = (int)Math.Round((scaleW * srcHeight));
         } else {
            width = (int)Math.Round((scaleH * srcWidth));
            height = (int)Math.Round((scaleH * srcHeight));
         }
         var bmpTouple = BitmapSizes.FirstOrDefault(t => t.Item1.Height == height && t.Item1.Width == width);
         if (bmpTouple == null) {
            bmpTouple = new Tuple<Rectangle, Image>(
               new Rectangle(0, 0, width, height),
               new Bitmap(width, height));
            BitmapSizes.Add(bmpTouple);
         }
         var rect = bmpTouple.Item1;
         var bmp = bmpTouple.Item2;
         using (Graphics gr = Graphics.FromImage(bmp)) {
            gr.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            gr.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
            gr.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
            gr.DrawImage(image, rect);
            using (var outStream = new MemoryStream()) {
               bmp.Save(outStream, ImageFormat.Jpeg);
               return outStream.ToArray();
            }
         }
      }
   } catch (Exception ex) {
      throw;
   }
   return null;
}

Example

public byte[] ImageResult(byte[] imageData, int width, int height) {
   return imageData.Resize(width, height);
}

Author: esp

Submitted on: 17 apr 2011

Language: C#

Type: System.Image

Views: 3433