尝试调整尺寸时图像被拉伸以保持宽高比

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;
}