Sending thumbnail image to browser

Question

Hi,
I have web-application that lets users see a customized page. This page contains images that are stored in a table. Some of the images are thumbnails, and some are full size images.
So far I can send the full size images to the browser using the OrdHttpJspResponseHandler:
OrdImage media = (OrdImage)result.getCustomDatum(1, OrdImage.getFactory());
handler.setPageContext(pageContext);
handler.sendImage(media);
Is it possible to dynamically create a thumbnail image and send it to the browser instead of the full size image? I have seen code that uses the OrdImage.process() or OrdImage.processCopy() functions. Both these functions are used to update the image in a table. Is it possible to do the same but leave the original image unchanged? I don't need to store the thumbnail images in the database table. I am thinking of something like this:
OrdImage media = (OrdImage)result.getCustomDatum(1, OrdImage.getFactory());
handler.setPageContext(pageContext);
- - >>> process image here ????
handler.sendImage(media);

Answer 1

First of all...let me state that in most cases THIS IS A VERY BAD IDEA. Image processing is very CPU intensive. Most thumbnails take only a fraction of the original image space, so it is BEST TO PREPROCESS THUMBNAILS in most cases.
For example, let us say we have an image that is 1000X1000, no compression. It is
1,000,000 bytes. A LARGE thumbnail that is 1/4 the size would be 250X250 or 62,500 bytes.
1,000,000 - Original (uncompressed)
62,500 - thumbnail (uncompressed).
As you can see, the thumbnail takes less than 1/10 the original image. After Compression will probably make it about 1/10.
So the question is, do you want to make your on-line users wait? Or do you want to pre-process the image so your application is quicker?
The processing will affect, not only the user waiting for the processing the image, but others as well who are waiting for CPU time.
OK that being said, if you don't see the error of you ways, or if scaling is done so infrequently that it does not matter, or you have some other VERY SPECIAL CASE, here is the rope you can hang yourself on.
It takes a URL of the form:
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Types;
import java.sql.PreparedStatement;
import javax.servlet.ServletException;
import javax.servlet.ServletConfig;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.naming.NamingException;
import oracle.jdbc.OracleResultSet;
import oracle.jdbc.OracleCallableStatement;
import oracle.jdbc.pool.OracleConnectionPoolDataSource;
import oracle.jdbc.pool.OraclePooledConnection;
import oracle.jdbc.driver.OracleConnection;
import oracle.ord.im.OrdImage;
import oracle.ord.im.OrdHttpResponseHandler;
import oracle.ord.im.OrdMultipartWrapper;
public class deliveryServletScale extends HttpServlet
OracleConnection conn = null;
String servletURL = null;
* Servlet initialization method.
public void init( ServletConfig config ) throws ServletException
super.init(config);
* Get a pooled database connection
private void getPooledConnection() throws SQLException, NamingException
javax.naming.InitialContext ic = new javax.naming.InitialContext();
OracleConnectionPoolDataSource ds = (OracleConnectionPoolDataSource)
ic.lookup("jdbc/pool/OracleMediaPoolDS");
OraclePooledConnection pc = (OraclePooledConnection)
ds.getPooledConnection();
conn = (OracleConnection)pc.getConnection();
// conn.setAutoCommit(false); // just query. No need for this
* Process an HTTP GET request used to deliver an image column
public void doGet( HttpServletRequest request,
HttpServletResponse response )
throws ServletException, IOException
String id = request.getParameter( "id" );
String procCmd = request.getParameter( "p" );
try
if (conn == null) getPooledConnection();
OracleCallableStatement cstmt = (OracleCallableStatement)
conn.prepareCall (
"declare " +
" imgobj ordimage; " +
" thmbobj ordimage := ordimage.init(); " +
"begin \n" +
" select image into imgobj from photos " +
" where id = ? ; \n" +
" DBMS_LOB.CreateTemporary(thmbobj.source.localdata, TRUE); " +
" imgobj.processCopy('" + procCmd + "', thmbobj);" +
" ? := thmbobj; " +
" dbms_lob.Freetemporary(thmbobj.source.localdata); " +
"end;");
cstmt.setString( 1, id );
cstmt.registerOutParameter(2, Types.STRUCT, "ORDIMAGE");
cstmt.execute();
OrdImage thumb =
(OrdImage)cstmt.getORAData(2, OrdImage.getORADataFactory());
cstmt.close();
// Create an OrdHttpResponseHandler object, then use it to retrieve
// the image from the database and deliver it to the browser.
OrdHttpResponseHandler handler =
new OrdHttpResponseHandler( request, response );
handler.sendImage( thumb );
catch (Exception se)
conn = null; // We may need a new connection
throw new ServletException(se);
}