DTP Masks

by Terry Nottle


When working with a DTP package, interesting effects can be achieved by using a mask overlaid on a picture so that the image is only visible through the transparent areas of the mask. This enables you to simulate non-rectangular frames, as well as many other useful graphic effects. A set of masks is supplied on this disc to get you started.

Double-clicking on the !Masks icon in a directory viewer, or running this item from the RISC User menu, opens a directory viewer containing a Draw file called Masks. This contains a series of shapes, each of which may be extracted from the file and saved separately as a mask for use with DTP.

To try one out, load a picture sprite into Draw, and open the mask library (by double-clicking on its icon, or by dragging the file into Draw). Make sure that the Select tool is activated in the mask library window and click over the mask to be used (a red dashed bounding rectangle should just about be visible).

From the Draw menu, use the Save option, and by moving right, the Selection option, and drag the Draw icon from the Save box into the Draw window containing the picture. Provided the selected mask is positioned over the picture the effect of the mask should be clear.

You can, of course, resize the mask within Draw, but if you do this other than by quite a small amount you will see the potential disadvantage of pixel-based images. When sprites are magnified, what were smooth images become much more jagged. You will find you get the best results by creating a mask as close as possible to the final size you will need. The same consideration applies to the use of Impression or Ovation, but as before picture and mask can be positioned independently. And in Impression Publisher you would also be able to create an irregular frame which would reasonably follow the outer contours of the mask. In other DTP packages the same result can usually be achieved, but by much more tedious manual efforts.

To use the masks with a DTP package, first create two graphics frames which can eventually be positioned one (the mask) over the other (the picture), making sure that the background 'colour' of the mask frame is set to transparent. Drag the picture into its frame, and the mask into the mask frame, and slide one over the other, again resizing and rescaling as required.

Once you begin to get the hang of the process then all sorts of possibilities open up. In the examples supplied, the mask has no visible border, and the area outside of the mask is white (thus usually invisible). Both of these could be changed, with a suitable border being created in Draw, say, and an outer colour being applied in Paint. The possibilities are enormous.

Further information, including details on how to create your own masks, is given in Into the Arc in this month's RISC User magazine.

 Copyright RISC User 1994