How to create watermark background in crystal report

It may not be the most elegant solution to the problem but you can use a textbox, and fill it with underscores. It will give the illusion of a line and since it will show above the image.

Note: It may not look that good in the report preview (it sometimes shows as separated dashes), but when you actually run it, export it to pdf or print it, it looks fine.

There's a developer-provided workaround here, using textboxes: http://scn.sap.com/thread/1916479

1. Insert a text object and enter nothing.
2. Change the size (the height matches the line width) and background (background color matches the line color).
3. Right click on the text object and select Move | To Front. And then the "line" will be on top of the picture.

Unforunately, using Crystal Reports 2008, this would only allow me to shrink the textbox to a certain height (0.042 inches), which was still too big for a 1-pixel line.