How to create gradient colour schemes #139

var
  MyColor: TColor;
begin
  R1 := 255;
  G1 := 0;
  B1 := 0;
  R2 := 0;
  G2 := 0;
  B2 := 0;
  Percent := 0.5;
  MyNewColor := GetGradientColor2(R1, G1, B1, R2, G2, B2, Percent);

function ColorFromRGB(Red, Green, Blue: Integer): Integer;
  {Returns the color made up of the red, green, and blue components.
  Red, Green, and Blue can be from 0 to 255.}
begin
  {Convert Red, Green, and Blue values to color.}
  Result := Red + Green * 256 + Blue * 65536;
end;

function GetPigmentBetween(P1, P2, Percent: Double): Integer;
  {Returns a number that is Percent of the way between P1 and P2}
begin
  {Find the number between P1 and P2}
  Result := Round(((P2 - P1) * Percent) + P1);
  {Make sure we are within bounds for color.}
  if Result > 255 then
    Result := 255;
  if Result < 0 then
    Result := 0;
end;

function GetGradientColor2(R1, G1, B1, R2, G2, B2, Percent: Double): Integer;
  {Gets a color that is inbetween the colors defined by (R1,G1,B1)
  and (R2,G2,B2) Percent ranges from 0 to 1.0 (i.e. 0.5 = 50%)
  If percent = 0 then the color of (R1,G1,B1) is returned
  If Percent = 1 then the color of (R2,G2,B2) is returned
  if Percent is somewhere inbetween, then an inbetween color is returned.}
var
  NewRed, NewGreen, NewBlue: Integer;
begin
  {Validate input data in case it is off by a few thousanths.}
  if Percent > 1 then
    Percent := 1;
  if Percent < 0 then
    Percent := 0;
  {Calculate Red, green, and blue components for the new color.}
  NewRed := GetPigmentBetween(R1, R2, Percent);
  NewGreen := GetPigmentBetween(G1, G2, Percent);
  NewBlue := GetPigmentBetween(B1, B2, Percent);
  {Convert RGB to color}
  Result := ColorFromRGB(NewRed, NewGreen, NewBlue);
end;

function GetGradientColor3(R1, G1, B1, R2, G2, B2, R3, G3, B3,
  Percent: Double): Integer;
  {Gets a color that is inbetween the color spread defined (R1,G1,B1),
  (R2,G2,B2) and (R3,G3,B3). This is similar to GetGradientColor2,
  except that it allows you to specify 3 colors instead of 2.}
begin
  {Use GetGradient2 to do most the work}
  if Percent < 0.5 then
    Result := GetGradientColor2(
      R1, G1, B1, R2, G2, B2, Percent * 2
    )
  else
    Result := GetGradientColor2(
      R2, G2, B2, R3, G3, B3, (Percent - 0.5) * 2
    );
end;