Difference between revisions of "Reading current colours"
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[[OSBYTE_&A0|OSBYTE 160]] reads the VDU variables, and OSBYTE 160,87 to OSBYTE 160,90 read the current text and graphics colours: | [[OSBYTE_&A0|OSBYTE 160]] reads the VDU variables, and OSBYTE 160,87 to OSBYTE 160,90 read the current text and graphics colours: | ||
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==See also== | ==See also== | ||
| − | * [http://mdfs.net/Archive/BBCMicro/2015/10/24/221305.htm | + | * [http://mdfs.net/Archive/BBCMicro/2015/10/24/221305.htm BBC Micro Mailing List] |
| − | [[User:Jgharston|Jgharston]] ([[User talk:Jgharston|talk]]) 17: | + | [[User:Jgharston|Jgharston]] ([[User talk:Jgharston|talk]]) 17:03, 31 October 2015 (UTC) |
Revision as of 18:03, 31 October 2015
OSBYTE 160 reads the VDU variables, and OSBYTE 160,87 to OSBYTE 160,90 read the current text and graphics colours:
| OSBYTE 160,87: | read foreground text colour |
| OSBYTE 160,88: | read background text colour |
| OSBYTE 160,89: | read foreground graphics colour |
| OSBYTE 160,90: | read background graphics colour |
Unfortunately, they don't return the actual logical colour supplied as the parameter to COLOUR or GCOL. They return the bitmap that that colour stores in the screen memory:
| 2 colours: | &00, &FF |
| 4 colours: | &00, &0F, &F0, &FF |
| 16 colours: | &00, &03, &0C, &0F, &30, &33, &3C, &3F, &C0, &C3, &CC, &CF, &F0, &F3, &FC, &FF |
The values returned in 2-colour and 4-colour MODEs can be converted to logical colour numbers quite easily:
colour% =FNosword(160,whatever) maxColour%=FNosword(160,96) colour%=(colour% DIV 8) AND maxColour%
or:
LDX #whatever:JSR osword160:PHA :\ read colour mask LDX #96:JSR osword160:STA temp :\ read max. colour PLA:LSR A:LSR A:LSR A :\ divide colour mask by 8 AND temp :\ AND with max. colour
Converting 16-colour colour masks is more complicated. Also, on the Master the graphics colour is stored elsewhere.
