Re: Hires Graphics trouble

[mjmahon@aol.com (Michael J. Mahon)]

Simon Williams wrote:

>> >   10 HGR2
>> >   20 PRINT CHR$(4);"BLOAD MY.PICTURE,A$4000"
>> >   30 GET GARBAGE$
>
>> 
>> 	Alternatively he could change line 30 and have it call HGR and poke (I 
>> think) $C052 to get full screen mode.
>
>Not sure if I misinterpreted that. I converted the hex to decimal and
>called and poked as indicated but got nothing (literally, it just
>froze... I thought that only happened to Windows.).

Don't CALL it, just PEEK it.  (POKE will work, but hits the switch
twice, so it's best to get out of the habit.)

The PEEK for full-screen graphics is only useful if you're loading
the graphic into hi-res page 1, and using HGR first to set it up.

If you use HGR2, the default is full-screen, so no PEEK is needed.

>> >   10 HGR2
>> >   20 PRINT CHR$(4);"BLOAD MY.PICTURE,A$4000"
>> >   30 GET GARBAGE$
>
>This one just gives me a screen full of garbage... 

Then something's wrong, because this program is correct,
assuming that 80-column mode is inactive.

LIST it and check it again.

>After a bit (read: a lot) of fiddling I got to this:
>
>	10 PRINT CHR$ (4) "PR#3"
>	20 PRINT CHR$ (4) "BLOAD MY.PICTURE"
>	30 HGR2
>	40 GET GARBAGE$
>
>...and this seems to works quite well, though even I can see it looks
>wrong. I thought it might be a hardware problem that's causing the
>weirdness, but unless the same thing is wrong with my //c and //e,
>that's not it.  I tried a different 80 column card in the //e, but no
>difference.

1. Don't switch to 80-column mode with PR#3--that turns on some of
the Double hi-res stuff, and you don't want that.

2. Since you omitted the BLOAD address, the picture loads at its
default address, which, if it is visible at all, must be $4000.

3. HGR2 after you BLOAD will clear the screen.  This must be
done _before_ loading the picture.

As I said, the 3-line program beginning with 10 HGR2 is correct.
None of the others will give you a persistent, full-screen display.

BTW, if the same thing happens on two computers, it is not a
hardware problem.  ;-)


-michael

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