Image resizing with GDI+

Question

I\'m really trying to nail out a little more performance out of this tidbit of code. It\'s not a heavly used bit of code but is used every time a new image is uploaded, and 4 ti

Answer 1

For completeness, here is the solution to the second part of the question which was never answered. When processing a low resolution image the image was being cut off. The solution now, seems obvious. The problem lies in this bit of code from above:

using (Bitmap newImage = new Bitmap(newSize.Width, newSize.Height, 
                                                    PixelFormat.Format32bppRgb))

The problem being that I'm selecting the PixelFormat, not letting it be the format of the original image. The correct code is here:

public static byte[] ResizeImageFile(byte[] imageFile, int targetSize)
{
    using (System.Drawing.Image oldImage = System.Drawing.Image.FromStream(new MemoryStream(imageFile)))
    {
        Size newSize = CalculateDimensions(oldImage.Size, targetSize);

    using (Bitmap newImage = new Bitmap(newSize.Width, newSize.Height,  
                                                        oldImage.PixelFormat))
    {
        newImage.SetResolution(oldImage.HorizontalResolution, 
                                                   oldImage.VerticalResolution);
        using (Graphics canvas = Graphics.FromImage(newImage))
        {
            canvas.SmoothingMode = SmoothingMode.AntiAlias;
            canvas.InterpolationMode = InterpolationMode.HighQualityBicubic;
            canvas.PixelOffsetMode = PixelOffsetMode.HighQuality;
            canvas.DrawImage(oldImage, new Rectangle(new Point(0, 0), newSize));
            MemoryStream m = new MemoryStream();
            newImage.Save(m, ImageFormat.Jpeg);
            return m.GetBuffer();
        }
    }

   }
}