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| Keyword | Abbreviation | Token (hex) | Version(s) | Classification |
| RLUM | R{Shift+L} | CE | 3.5 | Function |
| DCLOSE | DC{Shift+L} | CE | 4.x | Command and Statement |
| varies | varies | CE ?? | 7.0 | 2-byte Functions |
RLUM ( colorSource )
| Parameters | Type | Legal Value(s) | Note(s) |
| colorSource | Integer | 0. background (bitmap & text)
1. bitmap foreground
2. bitmap multi-color 1
3. bitmap multi-color 2
4. border | |
| Returns | Type | Value(s) | Note(s) |
| chipLuminance | Integer | 0 ~ 7 | |
Returns the chipLuminance assigned to a graphic screen element.
The RLUM function is a partial complement to COLOR. It returns the chipLuminance
that has been assigned to a colorSource. The other (primary) partial complement to COLOR is RCLR.
See COLOR for a list of colors and their assigned luminance values.
The text color can be changed by printing special "control codes" with CHR$ (or some reverse-font characters
in text strings). However, RLUM does not work with text colors, only bitmap colors
and the screen background/border. You have to PEEK a secret variable,
"Text Attribute" to get the luminance of the text.
In an act of incompatibility, BASIC v7.0 does not support RLUM of v3.5... the token $CE (or 206 decimal)
is used as the first byte for new 2-byte extended functions. Any version 3.5 program using RLUM
will cause SYNTAX ERROR in v7.0. Although I won't argue with the decision to use $CE for an extension
(all tokens except $FE were in use, but $FE is used for extended commands/statements, not functions),
it is not necessary to generate SYNTAX ERROR. A code of $CE $28 could have been used
in version 7.0 to maintain compatibility... well limited compatibility!
The reason they choose to sacrifice RLUM (I'm betting) is because neither video chip
in the target machine (C128) has 8 levels of luminance per color.
If colorSource is omitted or is not a valid expression, SYNTAX ERROR occurs.
If colorSource is a string, TYPE MISMATCH ERROR occurs; you can use VAL
to make a string numeric. Otherwise the colorSource is converted with INT.
If the result is not a LegalValue (see table above) then ILLEGAL QUANTITY ERROR occurs.
Examples (from Plus/4, default values):
PRINT RLUM("0")
?TYPE MISMATCH ERROR
READY.
PRINT RLUM(0) : REM bitmap/text background
7 maximum (for white)
READY.
PRINT RLUM(1) : REM bitmap foreground
1 very low (black)
READY.
PRINT RLUM(2) : REM bitmap multi-color 1
3 medium (blue)
READY.
PRINT RLUM(3) : REM bitmap multi-color 2
5 a bit high (for pink)
READY.
PRINT RLUM(4) : REM 40-column border
6 very high (light purple)
READY.
PRINT RLUM(5)
?ILLEGAL QUANTITY ERROR
READY.
|
RCLR, RDOT, RGR,
RSPCOLOR, RSPRITE
CHR$, COLOR, GRAPHIC,
SPRCOLOR, SPRITE
SCNCLR
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