Playing With Video Part 4 by John Kowalski (Sock Master)
** Breaking the 64 color barrier - displaying 1000 simultaneous colors **

*NOTE: This program does not work with the CoCo3 emulator*

Last time I showed a program that could load 256 color 320x200 BMP (bitmap)
graphics files and convert them into a 'custom' CoCo graphics mode that could
display 343 or 1000 colors on the screen.  I was supposed to take the CoCo's
graphics one step higher this time around, but unfortunately, I was kind of
busy with work so I'll try to get that ready in time for the next issue of
CFDM.

I did add a new option to the HICOLOR program from last issue.  It now lets
you save any image as an executable program.  Yep, a program!  Once an image
is saved, all you have to do is LOADM and EXEC the file to see it on the
screen!  I think it's pretty neat.  Unfortunately, the graphics are still not
compressed, so the files are rather large...  31 granules per picture, or
about 68K.  You can still fit two images on one side of a disk, or if you're
lucky, 8 images on a double sided 3.5 inch disk.  Since it's so easy to load
the pictures, it's a snap to make a slideshow with them.  You could also put
4 pictures in RAMdisk if you have 512K to make a faster loading slideshow.

Here's the bad news.  It's VERY slow to save a picture.  Because I used a
fancy technique to allow MMU bank switching 'mid-load', files can be larger
than 64K.  But to do this, I have to write my own save routine (rather than
use RSDOS's SAVEM command) ...and...well, the save routine is written
entirely in basic.  In 1Mhz mode, it take about 18 minutes to save a picture
disk disk.  If your DOS can handle double speed operation, I recommend you
put a POKE65497,0 in line 1000 of HICOLOR.BAS and that should speed up saves
by about a factor of three.   The good news is that you only have to save a
file once, and loading them back into memory is very fast.

I already put two 'preconverted' and 'presaved' files on the disk.  They
should be TOWN.BIN and SHIP.BIN   Try LOADMing and EXECing them to see them.

I didn't put any BMP files on the disk, but you can take last issues' BMP
files and convert them to loadmable BIN files (which will let you see them
much faster than previously) or you can transfer any 320x200, 256 color BMP
file from a PC to the CoCo and try viewing or converting them.  Most graphics
files you find aren't 320x200, but you can use a paint program to resize them
and/or reduce the colors to 256.

Next time, I'll try to tackle the 4096 color graphics mode.