¢MAGNIFY¢¢¢ MAGNIFY is a program which allows you to take any graphics 8 or graphics 7 1/2 (Micro-Painter format) file and dump it to your Epson (or compatible) printer. There are several extra features in this program which make it different from the many public domain screen dump utilities around.¢¢ I had started out with such a program (KWIKDUMP), and started adding extra features. In the end, it was becoming too slow, since it was written in Atari Basic, and I was unable to add the last few special features, so I decided to write the whole thing in machine language.¢¢ One problem I had with KWIKDUMP was that it simply dumped the screen to the printer with no editing capabilities. Any 1-bits in the picture printed as black and 0-bits printed as white. Depending on the choice of colour registers in the picture, the printed image could end up looking like a negative. To resolve this in my modified version of KWIKDUMP, I created a routine to flip all the bits in the picture.¢¢ Another problem was the printed pictures were too small, taking up less than 1/4 of the page. I wanted them to be closer to a full page in size. My first cut at magnifying the picture was to take each bit and print it as a 2x2 square of bits with the same value. Each 1-bit would become 2 1-bits side by side which were printed twice. This worked fine, but led to rather blocky pictures. It also did not allow for the fact that graphics 7 1/2 pictures have four colours, and it would be nice to try to differentiate between them.¢¢ I decided to try to magnify each pair of bits together, calling it 2-bit horizontal magnification. Each pair of bits beside each other horizontally on the screen (1 pixel in graphics 7 1/2) are treated as one entity to be magnified. A bit pattern consisting of a 1 followed by a 0 (i.e. 10) becomes 1010. This bit pattern would be printed two times, thus supplying the vertical magnification. This helped to distinguish between the 4 colours of the original picture, since a 10 or 01 pattern would look gray instead of black.¢¢ However, this method still had some problems in the vertical direction. I therefore decided to add another routine which would treat each pair of bits in the vertical direction as one entity for magnification, calling it 2-bit vertical magnification. Instead of taking a 1 and 0 vertically and making them 1100, I made them 1010 vertically. This helped to alleviate some of the problems.¢¢ Finally, I created a routine which implemented both 2-bit magnifications, calling it 2-bit horizontal and vertical magnification.¢¢ I was now able to print pictures the way I wanted, using the much modified KWIKDUMP, with a number of machine language subroutines stored as strings doing the magnifying and flipping. However, I could not tell what the picture was going to look like until I printed it in all of the different modes. Why not magnify it on the screen, and scroll around the picture, thus deciding which magnification technique was best!¢¢ Goodbye basic and hello assembly language! MAGNIFY was born. Writing it was a great learning experience. I had to be able to read the disk directory and display it, read the picture file itself, implement smooth scrolling, and dump the picture to the printer, and all in one program! Great stuff.¢¢ In writing this program, I had to make several compromises due to memory restrictions. It will only read Micro-Painter format picture files (i.e. uncompressed), and does no error trapping when reading the file. I can only magnify the middle 32 bytes of the 40 bytes per line of picture. The ANTIC chip does not allow a display line to cross a 4K boundary. When implementing smooth horizontal scrolling, you create a display line which is wider than the screen, and you only show part of it. To make the magnification and scrolling routines as simple as possible, I chose a display line width which divided evenly into 4096 (4K). The best choice was 64, which is 2x32. Besides, I didn't have enough memory to magnify the whole 7680 bytes of a graphics 7 1/2 picture.¢¢USING MAGNIFY¢¢ The MAGNIFY program should be put on a DOS disk as an autorun file (i.e. name it AUTORUN.SYS for DOS 2.0). Boot your computer without any cartridges (hold down OPTION on XL/XE's).¢¢ Once MAGNIFY has loaded and gives you the startup screen, remove the program disk and put in your picture disk and press START. You will now see a list of all the files on the disk which have an extender of .?IC where the ? is any legal character for a filename. This allows for .MIC and .PIC. Each file has a letter beside it. Press the appropriate letter for the picture you want and it will be loaded.¢¢ The picture will initially be displayed in graphics 8. If you are using a television as your display device, artifacting could make your picture look rather interesting. I use a monitor, and in hi-res mode it displays the pictures properly without any artifacting.¢¢ To invert all bits (exchanging black and white), press OPTION.¢¢ To switch back and forth between graphics 8 and 7 1/2, press SELECT.¢¢ Now plug a joystick into port 1 and let's start magnifying. If you press the joystick button you will cycle through the 5 magnification modes, which are:¢¢ (1) none¢ (2) 1-bit horizontal and vertical¢ (3) 2-bit horizontal and 1-bit vertical¢ (4) 1-bit horizontal and 2-bit vertical¢ (5) 2-bit horizontal and vertical.¢¢ In any of the four magnified modes you can scroll around the picture, checking out how different areas look. Once you have decided which magnification technique should work best on your printer, press START. The full picture will be printed in the same magnification mode as is currently on the display.¢¢ To return to the directory menu, press the ESC key. If you want to change picture disks, simply press ESC again, change disks and press START.¢¢ I hope you find MAGNIFY a useful program. I certainly do, and I also learned a lot about the graphics capabilities of Atari computers while writing it. Have fun!¢
