Graphics Workshop

by Allan Knopp

 

Issue 20

Mar/Apr 86

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In ANTIC magazine, June 1985 there was a program written by Lyn Buchanan demonstrating the technique of pixel averaging. I was intrigued by the possibilities of the technique and therefore set about writing a drawing program for the GTIA modes which could incorporate pixel averaging and the resulting program was the Graphics Workshop presented here.

The program incorporates many of the facilities you would expect from a drawing program and includes a few extras. As well as the pixel averaging technique which gives results similar to digitised pictures, there is a colour rotate feature to give animated effects (anything the ST can do!..). The rest of the facilities and all commands are explained.

GRAPHICS WORKSHOP COMMANDS

The appropriate keypresses are indicated. In many cases the reversal of an instruction is to press the same key with CONTROL.

A AIRBRUSH CTRL A to end.

B BOX Position cursor to one corner, press Fire button to plot point, move cursor to diagonally opposite corner and press START.

C COLOUR Will change the background colour in modes 9 and 11. Use the joystick. Forward will decrease by 16 thus keeping the same luminence but changing the colour. Left will decrease by 1, right will increase by 1. Press START to return to the drawing.

D DRAWTO Plot one end of line, move the cursor to the other end and press START to draw a line between the two.

E ERASE Clears the graphics screen. Answer y to the prompt to clear the screen.

F FILL Plot top left, move to bottom left and press START. This is the standard XIO FILL over the background from left to right until it hits a pixel which is lit.

G GRAPHICS Select modes 9, 10 or 11 without clearing the screen. The colour selection bar looks a little odd in graphics 10 but just use the top 8 blocks (colours 1 to 8) plus the background (colour 0), ignore the rest.

K COLOUR CHANGE In graphics 10, colours 0 to 8 are available. Select which colour you wish to alter and use the joystick to change. Press SELECT for another colour, START to return to the drawing.

L LOAD From disk or cassette.

M MOVE CURSOR SLOWLY For detailed work. CTRL M to end.

N NO BAR This will remove the colour bar from the right hand side of the screen. CTRL N will replace it.

O CIRCLE Plot the centre bottom of the circle, move the cursor vertically to the centre and press START. You will not be able to plot a circle which extends off the screen, you will get an error message and be asked to try again.

P PIXEL AVERAGING This is the routine which appeared in ANTIC, June 1985. It is really only intended to be used in Graphics 9 although some interesting effects can be obtained in 10 and 11. It has the effect of softening hard edges and smoothing contours. Once the routine is started, it cannot be stopped until it has finished, except by pressing RESET and losing the picture. Once the screen has been completely converted, it is possible to retouch it and add text.

R ROTATE COLOURS This can be used only in graphics 10. It enables you to rotate colours through the colour registers to give some animation to your picture. It is possible to rotate through any of the nine registers, including the background. The registers must however be consecutive.

S SAVE To disk or cassette.

T TEXT Print text to the screen, one character at a time. Position the cursor and select the colour before pressing T. To cancel press CTRL T and RETURN.

W WIDE BRUSH CTRL W to end.

UP ARROW MOVE CURSOR SELECTOR UP

DOWN ARROW MOVE CURSOR SELECTOR DOWN

1 -9 JUMP CURSOR Will position cursor instantly at the relevant point on the screen.

That's it. I would be pleased to see any pictures you have drawn with the Graphics Workshop. Please send them in to the Editor and he will send them on. All disks or cassettes will be returned.

DISK SUBSCRIBERS. Your disk for this issue will contain several picture files for use with the Graphics Workshop including those demonstrating the pixel averaging technique. Full details of use will be on the disk.

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