Delphi Changing Dynamic Value of the GrayScale Weight - image

Question

I know Delphi for almost a month,
I have found a function code that change the color of the gray-scale by changing the color weights, I would like to ask, is there a faster way than this code for changing color or weighting the color?
function tform1.changecolorweighting(coloredbmp:tbitmap):tbitmap;
Var
X, Y: Integer;
P : TColor;
r,g,b: byte;
RP,GP,BP:single;
changegray:tbitmap;
changecolor:tbitmap;
begin
x:=RedWeight.value+GreenWeight.value+BlueWeight.value;
RP:=RedWeight.value/x;
GP:=Greenweight.value/x;
BP:=BlueWeight.value/x;
changegray := tbitmap.Create;
changegray.Width := coloredbmp.Width;
changegray.Height := coloredbmp.Height;
changecolor.Assign(coloredbmp);
For X := 0 to changecolor.Width do
begin
For y := 0 to changecolor.Height do
begin
P := changecolor.Canvas.Pixels[X, Y];
r := (P and $00000FF);
g := (P and $00FF00) shr 8;
b := (P and $FF0000) shr 16;
changegray.Canvas.Pixels[X, Y] := round(r * RP + g * GP + b*BP) * $010101;
end;
end;
result := changegray;
end;
if there is someone of you has a faster way of changing the color weights, please correct the code that I have found in the internet, or if you have something to offer faster than that code, please help.
The code above, it takes 1 second before the gray-scale applied with the color weighting.
thank you

Answer 1

This is the answer that I'm looking for, it's from Embarcadero:
https://community.embarcadero.com/blogs/entry/converting-to-grayscale-with-tbitmapscanline-property-39051
procedure ToGray(aBitmap: Graphics.TBitmap; redweightvalue,greenweightvalue,blueweightvalue:integer);
var w, h: integer; CurrRow, OffSet: integer;
x: byte; pRed, pGreen, pBlue: PByte;
function RGBToGray(R, G, B: byte): byte;
var x:integer;
RP,GP,BP:single;
begin
x:=redweightvalue+greenweightvalue+blueweightvalue;
RP:=redweightvalue/x;
GP:=greenweightvalue/x;
BP:=blueweightvalue/x;
//Result := round(0.2989*R + 0.5870*G + 0.1141*B); // coeffs from Matlab
Result := round(rp*R + gp*G + bp*B);
end;
begin
if aBitmap.PixelFormat <> pf24bit then exit;
CurrRow := Integer(aBitmap.ScanLine[0]);
OffSet := Integer(aBitmap.ScanLine[1]) - CurrRow;
for h := 0 to aBitmap.Height - 1 do
begin
for w := 0 to aBitmap.Width - 1 do
begin
pBlue := pByte(CurrRow + w*3);
pGreen := pByte(CurrRow + w*3 + 1);
pRed := pByte(CurrRow + w*3 + 2);
x := RGBToGray(pRed^, pGreen^, pBlue^);
pBlue^ := x;
pGreen^ := x;
pRed^ := x;
end;
inc(CurrRow, OffSet);
end;
end;