Author: Tomas Rutkauskas

I have a TEdit control and there are two color properties I wish to set: 
TEdit.Color and TEdit.Font.Color. I did something like

TEdit.Color := clBlack
TEdit.Font.Color := TEdit.Color xor $7FFFFFFF;

but TEdit.Font.Color doesn't show as contrast of TEdit.Color. Can anybody advise on 
that. I wish to make the TEdit.Color and TEdit.Font.Color always contrast to each 
other. My application allows the user to change the TEdit.color at runtime.

Answer:

Try this one:

1   function InverseColor(color: TColor): TColor;
2   var
3     rgb_: TColorRef;
4   
5     function Inv(b: Byte): Byte;
6     begin
7       if b > 128 then
8         result := 0
9       else
10        result := 255;
11    end;
12  
13  begin
14    rgb_ := ColorToRgb(color);
15    rgb_ := RGB(Inv(GetRValue(rgb_)), Inv(GetGValue(rgb_)), Inv(GetBValue(rgb_)));
16    Result := rgb_;
17  end;