LOW TO HIGH CONVERTER by Richard Karsmakers and Sven Krppel

Originally  published in ST NEWS Volume 1 Issue  4,  launched  on 
September 7th 1986.

In  Level  16,  a 16-bit dedicated computer magazine  (which  I've 
heard  has  ceased  to exist),  of March  1986,  I  saw  a  useful 
conversion routine to convert Neochrome low resolution pictures to 
32000  bytes High resolution screen data.  It was very  nice,  but 
awfully slow (converting a picture took about half an hour). Also, 
the  user had to create a Degas picture from those 32000 bytes  by 
himself.
Since  I  thought this program was much,  much  too  slow  (mainly 
because it used the wrong Basic language) and not complete enough, 
I decided that a better version of the program had to be  written, 
using  File Selector Boxes,  Alert Boxes,  etc.  And it had to  be 
faster,  too.  So we decided to use GfA Basic,  and rewrote Sven's 
basic routine into a more complete, faster concept. The program is 
added  on  the disk on which you've found this  bulletin,  and  is 
called "CONVERT.BAS". It is the first program to be delivered with 
ST NEWS, the first in a - hopefully - long row. At the moment that 
this article was written,  a good friend of ours was working on  a 
deluxe  C  version of the program.  We don't know yet if  we  will 
publish  it in ST NEWS,  but we will try to obtain it  very  hard. 
Converting might then turn out to be a question of seconds  rather 
then  minutes  (now,  it still takes 6 minutes  to  complete  one 
conversion).

We  regret  that we cannot give you any details about  the  actual 
conversion routine;  that's because we didn't get the picture from 
Sven  -  if  you  know what I  mean.  It's  just  Sven's  routine, 
converted to GfA Basic. All the POKE commands from ST Basic (which 
are  16-bit POKEs) had to be converted to DPOKE in GfA (because  a 
normal POKE in GfA is 8-bit,  whereas DPOKE is 16 and LPOKE is  32 
bit),  and the IF-THEN routines had to be adapted (with  GfA,  all 
arguments have to be on different lines!).  At first,  that caused 
quite a lot of trouble, but we managed (as you can see).
A note to the ALERT command may also be written down here:  as you 
may  remember,  in  Volume 1 Issue 2 of ST  NEWS,  Delta  Software 
Productions  wrote a review of GfA Basic,  in which he  forgot  to 
explain the first variable ('n', remember?) of the command:

           ALERT n,"TEXT|IN|BOX",d,"TEXT|FOR|BUTTONS",b

Well, this 'n' can have four values, ranging from 0 to 3:

           0        Normal Alert Box
           1        Watch out! Alert Box
           2        What's happening? Alert Box
           3        Stop right there! Alert Box

In  the converter,  we used number 1 and number 3.  It  also  took 
quite  a while to find out how we could POKE on  16745024!  In  ST 
Basic, it was normally possible to POKE there, but in GfA you need 
to enter the supervisor mode. Therefore, SPOKE was introduced. Was 
I  glad I had a list of GfA commands at hand (which you will  find 
elsewhere in ST NEWS as well, with the GfA Basic Tips & Tricks)!
If you have discovered any nasty bugs in our converter,  or if you 
think   something  should  be   altered/debugged/improved/adapted, 
please contact us at our correspondence address.






Since  we hope to publish some more GfA Basic  programs,  we  also 
hope that you will help us.  Start writing nice utilities in  this 
versatile  language and send them to us,  wo we can use them in  a 
next issue of ST NEWS. At the moment, we are writing a Disk sorter 
ourselves,  which  will  enable you to create files  of  all  your 
programs on all your disks.  But it might take a while before it's 
finished! Ofcourse, you may also send 100% basic games.


