On Sat, 23 Sep 2017, James Richters wrote:
I have several Similar arrays as follows for translating various color schemes
into RGB565, I currently have 5 arrays but may add more.
ACI256: Array[0..255] of VGARGBRec = (
(R:$00; G:$00; B:$00; RGB:$0000), //[ 0]
(R:$FF; G:$00; B:$00; RGB:$F800), //[ 1]
(R:$FF; G:$FF; B:$00; RGB:$FFE0), //[ 2]
(R:$00; G:$FF; B:$00; RGB:$07E0), //[ 3]
(R:$00; G:$FF; B:$FF; RGB:$07FF), //[ 4]
..
(R:$FF; G:$FF; B:$FF; RGB:$FFFF)); //[255]
VGA256: Array[0..255] of VGARGBRec = (
(R:$00; G:$00; B:$00; RGB:$0000), //[000]
(R:$00; G:$00; B:$AA; RGB:$0015), //[001]
(R:$00; G:$AA; B:$00; RGB:$0540), //[002]
(R:$00; G:$AA; B:$AA; RGB:$0555), //[003]
(R:$AA; G:$00; B:$00; RGB:$A800), //[004]
..
(R:$00; G:$00; B:$00; RGB:$0000)); //[255]
I have some simple functions that use these arrays for example this one to find
the closest value to specified Red, Green, and Blue values:
Function Find_VGA(r ,g ,b : Word) : Byte;
Var
Dist,closest:Double;
i,bestchoice:Byte;
Begin
Closest:=200000;
For i:= 0 to 255 do
Begin
Dist := ((R-VGA256[i].R))*((R-VGA256[i].R)) +
((G-VGA256[i].G)*(G-VGA256[i].G)) + ((B-VGA256[i].B)*(B-VGA256[i].B));
If Dist<Closest Then
Begin
Closest:=Dist;
BestChoice:=i;
End;
End;
Find_VGA:=BestChoice;
End;
Instead of having a bunch of separate functions,
I would like to know if there is a way I can specify which constant to use
directly so the one function could use any of the arrays.
Something like
function Find_Color(Array_to_use:var ;r ,g ,b : Word) : Byte;
then use Array_to_use[i] instead of VGA256[i] in my formula...
so calling Find_Color(VGA256,$00,$FF,$FC) would use the VGA256 array and
calling Find_Color(ACI256,$00,$FF,$FC) would use the ACI256 array.. etc..
Is this kind of thing even possible? Or do I just need separate functions?
This is certainly possible.
First, define
Type
TVGA256Array = Array[0..255] of VGARGBRec;
PVGA256Array = ^TVGA256Array;
And redeclare your arrays as:
ACI256: TVGA256Array = (
// etc
VGA256: TVGA256Array = (
// etc
Then define
function Find_Color(anArray :PVGA256Array; r ,g ,b : Word) : Byte;
Var
Dist,closest:Double;
i,bestchoice:Byte;
begin
Closest:=200000;
For i:= 0 to 255 do
Begin
Dist := ((R-AnArray^[i].R))*((R-AnArray^[i].R))
+ ((G-AnArray^[i].G)*(G-Anarray^[i].G))
+ ((B-AnArray^[i].B)*(B-AnArray^[i].B));
If Dist<Closest Then
Begin
Closest:=Dist;
BestChoice:=i;
End;
End;
Find_VGA:=BestChoice;
end;
Call as
Find_Color(@VGA256,$00,$FF,$FC)
etc.
Alternatively, you can avoid the pointer if you declare the function as
function Find_Color(constref anArray :TVGA256Array; r ,g ,b : Word) : Byte;
you can then get rid of the dereferencing:
Dist := ((R-AnArray[i].R))*((R-AnArray[i].R))
+ ((G-AnArray[i].G)*(G-Anarray[i].G))
+ ((B-AnArray[i].B)*(B-AnArray[i].B));
The loop can still be optimized, but that is another topic.
Michael.
_______________________________________________
fpc-pascal maillist - fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
