Select Particular Portion from JMapFrame in geotools using java

[Leo Nolan]

Hello guys I am building an app in java for GIS in which I am facing a problem while reading a particular section of Jmap contentpane.
in code shown below I have generated a rectangle and converted it into world coordinates to read the particular section of the jmapframe and then convert it to image and print it..
I have rectangle values handy.
libraries used are geotools api 8.0

r= new Rectangle(StPos.x, StPos.y, FiPos.x, FiPos.y);
                System.out.println("Rectangle:"+r);
                AffineTransform screenToWorld = Main.mapFrame.getMapPane().getScreenToWorldTransform();
                Rectangle2D worldRect = screenToWorld.createTransformedShape(r).getBounds2D();
                ReferencedEnvelope bbox = new ReferencedEnvelope(worldRect,Main.mapFrame.getMapContent().getCoordinateReferenceSystem());
                MapContent map = Main.mapFrame.getMapContent();
                CreateImage c = new CreateImage(map, bbox);
                BufferedImage fore = c.getimage();
                CreateImage c2 = new CreateImage();
                BufferedImage back = c2.display_frame();
                print.OverlayImage o = new OverlayImage(fore, back);

what I want is to display the selected rectangular area.
please help me out, m totally exhausted on this.