XMM images typically contain quite a lot of pixels which are outside the field of view of the instrument. These contain zero values and therefore result in a lot of black ink being used in hard copy output. It may be desirable to the user to print or display these out-of-FOV pixels as white, or even to manipulate the image size so as to maximise the relative size of those parts within the FOV. To do this, an exposure map can be loaded as a mask, or the mask can be deduced from the input images themselves. The parameter that enables this functionality is withmask. If this is set true, the user can specify the colour of the unmasked bits at the edges of the image via the parameter greylevel. If parameter maskstyle=`user', the name of a mask set is expected to be supplied via maskset; if maskstyle=`self', the task attempts to use the input images for this purpose. The final relevant parameter, expandtomask, controls whether the full image is displayed or whether it is expanded until the masked central section just touches the borders of the display.