It is not an easy task to convert the doc files to images using barebone programming. You might use some component for that matter. You may try Aspose.Words for Java. Aspose.Words for Java provides feature of converting doc files to images. This is a simple Jar having an easy to learn and implement API. Please see if this might help in your scenario.
Developer Evangelist @ Aspose. I love to explore and learn new technologies and help other developers along the way.