Creating thumbnail images

Suppose you have a Web Form where uploading of files is enabled, using the HtmlInputFile HTML control, and a user is uploading an image. If you accept only images of a specified size, you might need to shrink the uploaded image / create a thumnail.
Here's how to create thumbnail images in ASP.NET Delphi web applications.
 

procedure GenerateThumbNail(const FileName : string; const ImageStream : Stream; const tWidth, tHeight : Double) ;
var
   g : System.Drawing.Image;
   thumbSize : Size;
   imgOutput : Bitmap;
   imgStream : MemoryStream;
begin
//This function creates the Thumbnail image and returns the
//image created in Byte() format

   g := System.Drawing.Image.FromStream(ImageStream) ;
   thumbSize := NewThumbSize(g.Width, g.Height, tWidth, tHeight) ;

   imgOutput := Bitmap.Create(g, thumbSize.Width, thumbSize.Height) ;
   imgStream := MemoryStream.Create;
   imgOutput.Save(imgStream, g.RawFormat) ;
   imgOutput.Save(Path.Combine('c:LocationOnServer',FileName)) ;
   g.Dispose;
   imgOutput.Dispose;
end;

function NewThumbSize(const currentwidth, currentheight, newWidth, newHeight : Double) : Size;
var
   tempMultiplier : Double;
   NewSize : Size;
begin
   if currentheight > currentwidth Then
    tempMultiplier := newHeight / currentheight
   else
    tempMultiplier := newWidth / currentwidth;

   NewSize := Size.Create(Convert.ToInt32(currentwidth * tempMultiplier), Convert.ToInt32(currentheight * tempMultiplier)) ;
   Result := NewSize;
end;

//Usage:
GenerateThumbNail('ThumbnameOnServer', ImageFile.PostedFile.InputStream, thumbWidth, thumbHeight) ;

//Where
//ImageFile : System.Web.UI.HtmlControls.HtmlInputFile;