Image Getting Stretched when trying to Resize It keeping the aspect Ratio

Question

Im using the following code to resize an image preserving the aspect ratio

 public Bitmap resizeImage(System.Drawing.Image imgToResize, SizeF size)
        {
            int sourceWidth = imgToResize.Width;
            int sourceHeight = imgToResize.Height;

            float nPercent = 0;
            float nPercentW = 0;
            float nPercentH = 0;

            nPercentW = ((float)size.Width / (float)sourceWidth);
            nPercentH = ((float)size.Height / (float)sourceHeight);

            if (nPercentH < nPercentW)
                nPercent = nPercentH;
            else
                nPercent = nPercentW;

            int destWidth = (int)(sourceWidth * nPercent);
            int destHeight = (int)(sourceHeight * nPercent);

            Bitmap b = new Bitmap(destWidth, destHeight);
            Graphics g = Graphics.FromImage((System.Drawing.Image)b);

            // Used to Prevent White Line Border 

           // g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;

            g.DrawImage(imgToResize, 0, 0, destWidth, destHeight);
            g.Dispose();

            return b;
        }

But images with large width gets compressed and the contents seem packed up into a small space.What im trying to achieve is this : Resize the Large Size/Large Resolution image because processing this will take huge time,So when the image width or height exceeds say 1000 i want to resize the image to a Smaller size eg:1000 Width or Height which ever is larger,so that i can save computation time.But it seems the above code is forcibly trying to fit the image into the 1000X1000 Box when i do

if (y.Width > 1000 || y.Height > 1000)
{

y = new Bitmap( resizeImage(y, new Size(1000, 1000)));

}

Answer 1

Try this, its a bit neater

public static Bitmap ResizeImage(Bitmap source, Size size)
{
   var scale = Math.Min(size.Width / (double)source.Width, size.Height / (double)source.Height);   
   var bmp = new Bitmap((int)(source.Width * scale), (int)(source.Height * scale));

   using (var graph = Graphics.FromImage(bmp))
   {
      graph.InterpolationMode = InterpolationMode.High;
      graph.CompositingQuality = CompositingQuality.HighQuality;
      graph.SmoothingMode = SmoothingMode.AntiAlias;
      graph.DrawImage(source, 0, 0, bmp.Width, bmp.Height);
   }
   return bmp;
}