()()()()››                MAGNIFY›    Brought to you by OL' HACKERS.  The› program "MAGNIFY.COM" will be found on› OHAUG  Jan/Feb 1996  newsletter  disk.› The programmer is unkown.›› WHAT DOES IT DO?››     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.›› BACKGROUND!››     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.›› PROBLEMS FACED.››     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.›› WHAT I DID!››     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.›› COMBINING TWO METHODS.››     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!›› BRINGING IN ASSEMBLY!››     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.›› COMPROMISES MADE!››     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.›› GRAPHICS 8 PICTURE.››     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.›› DIFFERENT CONTROL COMMANDS:››     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 GO TO DIRECTORY MENU:››     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.›› ENJOY!››     I hope you find MAGNIFY  a  useful› program.   I  certainly do, and I also› learned  a  lot  about  the  fantastic› graphics   capabilities    of    Atari› computers  while  writing  it.    Have› fun!›                *****›