Three graphical tools are disclosed providing functionalities that can readily cooperate with each other in research, or teaching environments, to provide powerful visual analysis tools, A grid tool is provided which allows a user-defined grid of a selected style to be laid over an image at any location, and which provides a grid reference co-ordinate display. An on-screen ruler tool is disclosed that may be added to an image to provide a clear indication of scale. Also, a calliper tool may be used to read off dimensions of the image that are not discernible from the on-screen ruler. All of these functionalities can therefore be used to greatly enhance the visual impact and effectiveness of a presentation, as well as increasing the amount of useful data that can be extracted from an image.