function HSLtoRGB (H, S, L: double): TColor;
var
M1, M2: double;
function HueToColourValue (Hue: double) : byte;
var
V : double;
begin
if Hue < 0 then
Hue := Hue + 1
else if Hue > 1 then
Hue := Hue - 1;
if 6 * Hue < 1 then
V := M1 + (M2 - M1) * Hue * 6
else if 2 * Hue < 1 then
V := M2
else if 3 * Hue < 2 then
V := M1 + (M2 - M1) * (2/3 - Hue) * 6
else
V := M1;
Result := round (255 * V)
end;
var
R, G, B: byte;
begin
if S = 0 then
begin
R := round (255 * L);
G := R;
B := R
end else begin
if L <= 0.5 then
M2 := L * (1 + S)
else
M2 := L + S - L * S;
M1 := 2 * L - M2;
R := HueToColourValue (H + 1/3);
G := HueToColourValue (H);
B := HueToColourValue (H - 1/3)
end;
Result := RGB(R, G, B)
end;
function HSLRangeToRGB (H, S, L : Integer): TColor;
begin
Result := HSLToRGB (H / (HSLRange-1), S / HSLRange, L / HSLRange)
end;
procedure RGBtoHSL (RGB: TColor; var H, S, L : double);
function Max (a, b : double): double;
begin
if a > b then
Result := a
else
Result := b
end;
function Min (a, b : double): double;
begin
if a < b then
Result := a
else
Result := b
end;
var
R, G, B, D, Cmax, Cmin: double;
begin
R := GetRValue (RGB) / 255;
G := GetGValue (RGB) / 255;
B := GetBValue (RGB) / 255;
Cmax := Max (R, Max (G, B));
Cmin := Min (R, Min (G, B));
L := (Cmax + Cmin) / 2;
if Cmax = Cmin then
begin
H := 0;
S := 0
end else begin
D := Cmax - Cmin;
if L < 0.5 then
S := D / (Cmax + Cmin)
else
S := D / (2 - Cmax - Cmin);
if R = Cmax then
H := (G - B) / D
else if G = Cmax then
H := 2 + (B - R) /D
else
H := 4 + (R - G) / D;
H := H / 6;
if H < 0 then
H := H + 1
end
end;