Tim Mackey's Weblog

public static ImageCodecInfo GetEncoderInfo(String mimeType)
{
	int j;
	ImageCodecInfo[] encoders;
	encoders = ImageCodecInfo.GetImageEncoders();
	for(j = 0; j < encoders.Length; ++j)
		if(encoders[j].MimeType == mimeType)
			return encoders[j];
	return null;
}

public static Bitmap resizeImage(Bitmap originalImage, int max)
{
	// never increase the size of an image from this method because it loses resolution
	if(originalImage.Height <= max && originalImage.Width <= max)
		return originalImage;

	int height, width;
	if(originalImage.Width > originalImage.Height)
	{
		width = max;
		height = (int)(max/((double)originalImage.Width / (double)originalImage.Height));
	}
	else
	{				
		height = max;
		width = (int)(max/((double)originalImage.Height / (double)originalImage.Width));
	}

	Bitmap thumb = new Bitmap(originalImage as Image, width, height);
	Graphics resizer = Graphics.FromImage(thumb);
	resizer.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
	resizer.DrawImage(originalImage, 0, 0, width, height);
	resizer.Dispose();
	return thumb;
}

public static bool ThumbnailCallback()
{
	return false;
}

this lovely code highlighted in red solved problems i was having with resizing JPEGs using .net.   without the code in red, some images would appear very grainy when reduced in size.  i got this tip from http://forums.asp.net/p/532033/532033.aspx.