colour
single
Colours on the OL can be either a solid colour or a stipple - a mixture
of
two colours
to
some predefined
pattern'.
Colour specification on the OL can be up
to
three items; •
a colour, a contrast colour and a stipple pattern.
colour:
= composite_colour
The
single argument specifies the three parts
of
the colour specification. The main colour
is
contained
in
the bottom three bits
of
the colour
byte.
The next three bits contain the
exclusive or
(XOR)
of
the main colour and the contrast
colour.
The top two bits indicate
the stipple pattern.
_______________
stipple
---------contrast
XOR
main
(mix)
iCOlour
bit
7 6 5
4 3 2
o
By specifying only the bottom three bits
(i.e.
the required colour) no stipple
will
be
requested and a single solid colour
will
be used for display.
double colour:= background, contrast •
The colour
is
a stipple
of
the two specified colours. The default checkerboard stipple
is
assumed (stipple
3).
triple colour: = background, contrast, stipple
Background and contrast colours and stipple are each defined separately.
colours The codes for colour selection depend on the screen mode
in
use:
code
bit pattern composition colour
8 colour 4 colour
a
000
black black
1
a a 1
blue blue black
2
a 1 a
red red
red
3
011
red
+ blue magenta
red
4
100
green green green
5 1 a 1 green
+
blue cyan green
6 1 1 a
green
+
red
yellow
white
•
7 1 1 1
green
+
red
+
blue white white
Colour
Composition and Codes
stipples Stipples mix a backgound and a contrast colour
In
a fine stpple pattern. Stipples can
be used on the OL
In
the same manner
as
ordinary solid colours although stipples may
not be reproduced correctly on
an
ordinary domestic television. There
are
four stipple
patterns:
Stipple
a Stipple 1
Stipple 2
Stipple 3
12
Stipple 3
is
the default.
example
i.
PAPER
255 : ct.s
ii.
PAPER
2,4:
CLS
iii.
PAPER
0,2,0
:
CLS
•
warning Stipples may not reproduce correctly on a domestic television
set
which
IS
fed via the
UHF
socket.
12/84
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