1. Create an instance of the AspJpeg object.
   
2. Open the source image from disk or memory using the Open or OpenBinary methods, respectively.
   
3. Set the desired width and height of the thumbnail via the Width and Height properties. To preserve aspect ratio, the original dimensions can be retrieved via the OriginalWidth and OriginalHeight properties.
4. Save the resultant thumbnail to disk, memory, or an HTTP stream by calling Save, Binary, or SendBinary, respectively.

The following code sample opens a disk image and creates a thumbnail with the width hard-coded to a particular value (100 pixels in this sample) while preserving the original aspect ratio:

<% ' Create instance of AspJpeg Set Jpeg = Server.CreateObject("Persits.Jpeg") ' Open source image Jpeg.Open "c:\path\myimage.jpg" ' New width L = 100 ' Resize, preserve aspect ratio Jpeg.Width = L Jpeg.Height = Jpeg.OriginalHeight * L / Jpeg.OriginalWidth ' create thumbnail and save it to disk Jpeg.Save "c:\path\thumbnail.jpg" %>

In the sample above, we calculate the new height as a product of the original height and a scaling factor which, in turn, is computed as a ratio of the new width to the original width.

If we were to inscribe the thumbnail into a given rectangle, i.e. set the longest dimension to a particular value, the following code could be used:

.. If jpeg.OriginalWidth > jpeg.OriginalHeight Then    jpeg.Width = L    jpeg.Height = jpeg.OriginalHeight * L / jpeg.OriginalWidth Else    jpeg.Height = L    jpeg.Width = jpeg.OriginalWidth * L / jpeg.OriginalHeight End If ...

Starting with AspJpeg 1.4, the task of preserving aspect ratio is simplified via the property PreserveAspectRatio. If set to True, it creates a link between the Width and Height properties, so that a change in one dimension automatically causes a proportional change in the other. Using the PreserveAspectRatio property, the code sample above can be simplified as follows:

The SendBinary method must be called from a separate script file which should contain no HTML tags whatsoever. This script should be invoked via the SRC attribute of an <IMG> tag.

The code sample 02_manythumbs.asp contains several <IMG> tags invoking the script 02_sendbinary.asp and passing file path and size parameters to it, as follows:

<IMG SRC="02_sendbinary.asp?path=<% = Path %>&width=300">

Below are the ASP/VB Script and ASP.NET/C# versions of the 02_sendbinary.asp script. Notice that the width of the thumbnail is passed via the query string variable Width, and the height is set to be proportional to the specified width.

Once again, a script calling Jpeg.SendBinary must not contain any HTML tags, or the data stream it generates will be corrupted.

Under .NET, you must use the directive <%@ Page aspCompat="True" %> for the SendBinary method to work properly.

VB Script:

<% Response.Expires = 0 ' create instance of AspJpeg Set Jpeg = Server.CreateObject("Persits.Jpeg") ' Open source file Jpeg.Open( Request("path") ) ' Set new height and width Jpeg.Width = Request("Width") Jpeg.Height = Jpeg.OriginalHeight * Jpeg.Width / Jpeg.OriginalWidth ' Perform resizing and ' send resultant image to client browser Jpeg.SendBinary %>

C#:

<%@ Import Namespace="System.Web" %> <%@ Import Namespace="System.Reflection" %> <%@ Import Namespace="ASPJPEGLib" %> <%@ Page aspCompat="True" %> <script runat="server" LANGUAGE="C#"> void Page_Load(Object Source, EventArgs E) { // this script may not contain any HTML tags, not even comments ASPJPEGLib.IASPJpeg objJpeg; objJpeg = new ASPJPEGLib.ASPJpeg(); // Open source image objJpeg.Open( Request["path"] ); // Set new width objJpeg.Width = int.Parse(Request["width"]); // Preserve aspect ratio objJpeg.Height = objJpeg.OriginalHeight * objJpeg.Width / objJpeg.OriginalWidth; // Send thumbnail data to client browser objJpeg.SendBinary(Missing.Value); } </script>

Click the links below to run this code sample:

The OpenBinary method is demonstrated by the code samples 02_display.asp and 02_fromdatabase.asp. The file 02_display.asp simply invokes another ASP script, 02_fromdatabase.asp, multiple times with various parameters. The file 02_fromdatabase.asp uses the method OpenBinary rather than Open and passes an ADO recordset value containing a source image as an argument.

The script 02_fromdatabase.asp/aspx is shown below:

VB Script:

<% ' Using ADO, open database with an image blob strConnect = "DRIVER={Microsoft Access Driver (*.mdb)};DBQ=" & Server.MapPath("../db/aspjpeg.mdb") Set rs = Server.CreateObject("adodb.recordset") SQL = "select image_blob from images2 where id = " & Request("id") rs.Open SQL, strConnect, 1, 3 Set Jpeg = Server.CreateObject("Persits.Jpeg") ' Open image directly from recordset Jpeg.OpenBinary rs("image_blob").Value ' Resize jpeg.Width = Request("Width") ' Set new height, preserve original aspect ratio jpeg.Height = jpeg.OriginalHeight * jpeg.Width / jpeg.OriginalWidth Jpeg.SendBinary rs.Close %>

C#:

<%@ Import Namespace="System.Web" %> <%@ Import Namespace="ASPJPEGLib" %> <%@ Import Namespace="System.Data" %> <%@ Import Namespace="System.Data.OleDb" %> <%@ Import Namespace="System.Reflection" %> <%@ Page aspCompat="True" %> <script runat="server" LANGUAGE="C#"> void Page_Load(Object Source, EventArgs E) { ASPJPEGLib.IASPJpeg objJpeg; objJpeg = new ASPJPEGLib.ASPJpeg(); // Connect to database String strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Server.MapPath("../db/aspjpeg.mdb"); OleDbConnection myConnection = new OleDbConnection(strConn); myConnection.Open(); OleDbCommand myCommand = new OleDbCommand("select image_blob from images2 where id = " + Request["id"], myConnection); OleDbDataReader myReader = myCommand.ExecuteReader(); myReader.Read(); // Open source image objJpeg.OpenBinary( myReader["image_blob"] ); // Resize objJpeg.Width = int.Parse(Request["Width"]); // Set new height, preserve aspect ratio objJpeg.Height = objJpeg.OriginalHeight * objJpeg.Width / objJpeg.OriginalWidth; // Create thumbnail and send it directly to client browser // aspCompat=True is required. objJpeg.SendBinary( Missing.Value ); myReader.Close(); myConnection.Close(); } </script>

Click the links below to run this code sample:

<% ... Set rs = Server.CreateObject("adodb.recordset") rs.Open "images", strConnect, 1, 3 rs.AddNew rs("image_blob").Value = Jpeg.Binary rs.Update ... %>

The XMLHTTP object enables you to specify a URL to download the image from, and perform the download to a memory array, which can then be passed directly to AspJpeg's OpenBinary method. This frees your application from the necessity to create a temporary file on the server's hard drive:

VB Script:

<% Set objHTTP = Server.CreateObject("MSXML2.ServerXMLHTTP") objHTTP.Open "GET", "http://www.aspjpeg.com/images/ps_logo.gif" objHTTP.Send Set Jpeg = Server.CreateObject("Persits.Jpeg") Jpeg.OpenBinary(objHTTP.responseBody) ... %>

In .NET, the code is somewhat more complicated as there is no object to perform a binary download straight to memory:

C#:

<%@ Import Namespace="System.IO" %> <%@ Import Namespace="System.Net" %> <%@ Import Namespace="ASPJPEGLib" %> <script runat="server" LANGUAGE="C#"> void Page_Load(Object Source, EventArgs E) {   String Url = "http://www.aspjpeg.com/images/ps_logo.gif";   WebRequest request = WebRequest.Create(Url);   WebResponse response = request.GetResponse();   Stream responseStream = response.GetResponseStream();   int nLen = (int)response.ContentLength;   byte[] ImageBytes = new byte[nLen];   int n = 0;   int nBuffer = 4096;   while( n < nLen )   {     int nBytesRead = responseStream.Read(ImageBytes, n,       (nLen - n < nBuffer) ? nLen - n : nBuffer);     n += nBytesRead;   }   IASPJpeg objJpeg = new ASPJpeg();   objJpeg.OpenBinary( ImageBytes );   ... } </script>