Groups > comp.sys.acorn.programmer > #5363

Re: Simple programming query

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From	Richard Ashbery <basura@invalid.addr.uk>
Newsgroups	comp.sys.acorn.programmer
Subject	Re: Simple programming query
Date	Fri, 12 Jan 2018 21:24:00 +0000 (GMT)
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In article <c7a1799e-efd3-4b58-9bac-8c3aa34b8327@googlegroups.com>,
   <xltardy@gmail.com> wrote:
> Le jeudi 11 janvier 2018 18:24:40 UTC+1, j...@mdfs.net a écrit :
> > xltardy wrote:
> > > > In BBC BASIC, what is (are) the command(s) to output a filled
> > > > rectangle with a colour in 256 colour mode 13.
> > 

[snip]

> > 
> > GCOL 0,%00abcdef TINT %gh000000 for plot foreground colour and
> > GCOL 0,%10abcdef TINT %gh000000 for plot background colour

> Thanks.
> I will try to use that tonight.
> I should have said my machine is a BBCA3000 with RISC OS 3.11.
> (old VIDC with its not freely selectable 256 colour screen modes).

My understanding of the VIDC system colour system is that you only
have a total of 64 colours but their shade can be altered with the
TINT keyword. This gives 256 possible colour variations (64 different
colours multiplied by 4 shades). Although the TINT keyword can handle
256 variations it only has 4 distinct levels.....
(0-64,64-128,128-192,192-255). So a TINT range of 0-63 for example only
gives a single effective TINT level (no additional brightness). You can
see this action with a simple example...

MODE 13
PRINT "Press any key to new display tint value"
FOR x = 0 TO 128
GCOL 0,3 TINT x
RECTANGLE FILL 200,200,100
g = GET
PRINT TAB(0,30)"Tint value = ";x
NEXT

TINT transitions are at 63(64-1) and 127(128-1).

jgh@mdfs.net examples show the binary equivalent - this is useful
because it shows the bits that need setting for GCOL - bit 7 sets
foreground/background colour (0 for foreground, 1 for background).

The TINT statement requires bits 6 and 7 to be set to 00 (0-64),01
(64-128),10 (128-192) and 11 (192-255).

Richard

Thread

Simple programming query xltardy@gmail.com - 2018-01-11 03:05 -0800
  Re: Simple programming query Alan Adams <alan@adamshome.org.uk> - 2018-01-11 12:11 +0000
    Re: Simple programming query xltardy@gmail.com - 2018-01-11 06:01 -0800
    Re: Simple programming query jgh@mdfs.net - 2018-01-11 09:24 -0800
      Re: Simple programming query xltardy@gmail.com - 2018-01-11 10:15 -0800
        Re: Simple programming query Richard Ashbery <basura@invalid.addr.uk> - 2018-01-12 21:24 +0000
          Re: Simple programming query Rick Murray <Rick@bogus.email.address> - 2018-01-13 11:16 +0100
            Re: Simple programming query xltardy@gmail.com - 2018-03-01 23:09 -0800
              Re: Simple programming query Rick Murray <Rick@bogus.email.address> - 2018-03-02 22:45 +0100
                Re: Simple programming query xltardy@gmail.com - 2018-04-07 00:38 -0700
                Re: Simple programming query David Feugey <dfeugey@riscos.fr> - 2018-04-07 13:50 +0200
                Re: Simple programming query xltardy@gmail.com - 2018-04-09 11:40 -0700
                Re: Simple programming query David Feugey <dfeugey@riscos.fr> - 2018-04-10 08:31 +0200
                Re: Simple programming query druck <news@druck.org.uk> - 2018-04-09 21:05 +0100

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