//If the user can change the background color of a component,
//make sure that the caption/text is displayed in a contrasting color.
unit Unit1;
interface
uses
Windows, SysUtils, Graphics, Controls, Forms, StdCtrls, Buttons, ComCtrls,
Classes;
type
TForm1 = class(TForm)
Edit1: TEdit;
BitBtn1: TBitBtn;
procedure BitBtn1Click(Sender: TObject);
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
function ContrastColor(clBackground: TColor): TColor;
begin
with TRGBQuad(clBackground) do
if (rgbRed * 0.3) + (rgbGreen * 0.59) + (rgbBlue * 0.11) > 127.5 then
Result:= clBlack
else Result:= clWhite;
end;
//To test:
procedure TForm1.BitBtn1Click(Sender: TObject);
begin
Edit1.Color:= Random(255) shl 16 + Random(255) shl 8 + Random(255);
Edit1.Font.Color:= ContrastColor(Edit1.Color);
end;
end.