Grafix

by Tim McGuinness

The graphics capabilities of the ATARI computers are very powerful, but seem mysterious to many ATARI owners. I am going to show you some tricks that can be used to do some professional graphics work, and from BASIC no less!

Some new, and older, software products get amazing results, especially when used together. I have developed a few routines to fit these together in your programs. For fuller discussion of the ATARI's graphics, refer to De Re Atari, or other publications of that kind.

Among the better graphics programs available are: Micropainter by DataSoft, Graphics Master by DataSoft, Graphics Composer by Versa Computing, Graphics Generator by DataSoft, and The Next Step by Sierra/On Line. Also, included in my toolbox is a product called Versawriter by Versa Computing. These are not the only graphics products on the market. It is just that these are the only ones I possess.

Versawriter, to the best of my knowledge, is the only graphics digitizer tablet available for the ATARI. An articulated arm mounted in a plastic tablet transmits the position of its locating head to the computer. The digitizer connects to ATARI Port 4. Included with the Versawriter are programs which allow you to trace a drawing from almost any original and convert it to a display in Graphics Mode 8 on the screen. Other included utilities are: Graphics 7 drawing, a text writer for Gr. 7 or 8, and calibration (which is critical!). The product, though, is somewhat out of the normal consumer price range at $300.00.

The Next Step has two functions. One is a color pallette to examine various color combinations, and the other is a character editor for a set of 128 characters. There are some serious display bugs in this program, but it does work well. There is some question about continued availability of this product, so get it while you can. The palette program seems of little real use, but the character editor has some features that make it worth having. You can load and save character sets to and from files on the disk, but the program also writes BASIC code for you, which can be included in your program using the command ENTER. Also, as you edit a given character the program displays the ATASCII value associated with that character. The program sells for about $35.00.

Graphics Generator is one program that every serious Atari programmer should have. This is a character-set editor with special features. It allows the user to edit or define up to five different character sets at a time, and to create character matrices. A character matrix is a group of characters which can be used to construct a complex object on the screen. Graphics Generator creates up to 26 matrices of up to 32 characters each, and allows them to be edited or merged. DataSoft deserves congratulations for this product, which sells for about $40.00.

Graphics Composer contains some very useful additions to the Versawriter program package. Besides the same Gr. 7 and Gr. 8 drawing utilities, it has a geometric-shapedrawing utility for circles, squares, rectangles, polygons, triangles, arcs, and moire patterns. Also included is an excellent Player editor, allowing the editing of two side-byside players, with an enlarged viewing area for simplified editing. It includes the ability to load or save Player data directly to disk. This alone makes it worth having. The product sells for about $40.00.

Graphics Master, also by DataSoft, is a Gr. 8 drawing product. It has three modes: Edit, Draw, and Text. Edit mode manipulates images using an Edit window, adjustable to a variety of sizes. The window can "grab" images on the screen and then enlarge, reduce, skew, or rotate them. Draw mode allows line drawings with various geometric shapes. Text mode allows the placement of text anywhere on the screen in the standard text, or from special sets loaded from disk. This product also permits two screens to be created at one time, and even overlaid upon each other. This is an excellent product, and sells for about $40.00.

Micropainter is basically a drawing product, allowing creation of screen images in the four-color Antic E Mode (Gr. 7.5). This has the vertical pixel size of Gr. 8; but the horizontal width of Gr. 7, with four real colors. You can select between a full screen to create your image, or a magnified view of a small portion of the screen. You can draw in any one of the four colors, or you can combine them in horizontal, vertical, or checkerboard patterns. Th program includes a high-speed fill function, to make the task of coloring much easier. One real problem is that the documentation was designed for children. Micropainter sells for about $40.00.

Techniques

These basic tools can be used to simplify your graphics creation jobs. Lets start with character sets, and the editors. moved etc As most of you know, the ATARI has its normal character ' set located in Read-Only-Memory. But, with just a POKE or two j you can direct your machine to some other charac ter set located in the user RAM space. If you want to create and load this set yourself, you can, or you can have the computer do most of the work.

To edit or create a given character, I prefer the Graphics Generator. Simply follow the easy product instructions. Once you have created the perfect character set, save it to disk. Then use The Next Step to translate it to BASIC code for you.

You still need to do something useful with this new set in your program. Many well-known products use this tech nique ("Eastern Front" by Chris Crawford, for example). Character matrices are much the same. Use Graphics Gen erator to create a matrix, that is, define the characters and their relationship to one another. Then edit them one by one. or as a complete matrix, save them to disk, and load them into The Next Step. This time you will have to keep track of each character your matrix used.

Alternatively, you can follow the demo provided with Graphics Generator to load the matrix into your program directly from disk.

Creation of screen images is more time consuming, but not much more difficult than the creation of character sets. I find it hard to draw free-hand images using a joystick. It is much easier to draw on paper first and use the Versawriter to trace the drawing into the system. Trace the drawing by using one foreground color, and follow the pattern of your drawing. Don't try to make it perfect yet. Save the drawing to disk. If geometric shapes are to be part of the image, then add them with Graphics Composer and save this screen to disk. Change file names each time a new screen is saved to disk. This will record the changed file, and leave an unmodified backup. It would be a good idea to use a number in the file extension; like 1, 2, 3, etc.

Use the Graphics Master next to convert (shift) the Versa products screen image file to the DataSoft format used by Graphics Master and Micropainter. At this point you can add text to your screen, or manipulate the design using Graphics Master. However, it is generally best to refine the screen first using Micropainter. After finishing with Graphics Master, save the screen image to disk, using a new extender.

Now Micropainter is used, and your screen file is loaded. The process of conversion from a Gr. 8 (Antic F) Mode used with the Versa products to an Antic E screen used by Micropainter, randomly assigns the foreground pixels to one of the three foreground color registers. Therefore, it is now necessary to convert your previously-traced drawing to a single foreground color. This is done by re-drawing those Pixels (dots) that you want to change.

Now refine the screen image to your liking, and add the appropriate colors. If you wish, you can save this screen and go back to Graphics Master to add text. Your final screen image is saved to disk, and can then be used as a title page, as a complex background over which Players can be moved, etc. To use these screen or display files, vou will need two utility routines. One of these is a screen-file loader, and the other is an Antic E converter. These are provided in Listings 1, 2, and 3. Listing 1 is the BASIC code to load the screen file using the Assembly program contained in Listing 2. Listing 3 is a routine to convert the loaded screen file's display list to Antic E mode. After conversion, simply adi..c, the color registers for the correct colors (Registers 0, 1, 2, and 3).

This may sound like a lot of work, but it really is not. Most screens can be completed in an hour or less, with far better results than if you used a single product, drawing free-hand by joystick, or even used the Versawriter alone. think you will be very pleased with this approach.

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