Delphi Простая градиентная заливка на WinApi

function GradientFill(DC: HDC; Vertex: Pointer; //PMyTriVertex
  dwNumVertex: ULONG; pMesh: Pointer;
  dwNumMesh, dwMode: ULONG): BOOL; stdcall; external 'Msimg32.dll';

type
  MyCOLOR16 = Word;
  PMyTriVertex = ^TMyTriVertex;
  TMyTriVertex = packed record
    x: Longint;
    y: Longint;
    Red: MyCOLOR16;
    Green: MyCOLOR16;
    Blue: MyCOLOR16;
    Alpha: MyCOLOR16;
  end;

// совместимо с Delphi 7 - XE
 
function GradientFill(DC: HDC; Vertex: Pointer; //PMyTriVertex
  dwNumVertex: ULONG; pMesh: Pointer;
  dwNumMesh, dwMode: ULONG): BOOL; stdcall; external 'Msimg32.dll';
 
procedure Gradient2D(h: HWND; x1,y1:integer; color1: TColor; x2,y2:integer; color2:TColor; Vertical: boolean = false);
type
  MyCOLOR16 = Word;
  PMyTriVertex = ^TMyTriVertex;
  TMyTriVertex = packed record
    x: Longint;
    y: Longint;
    Red: MyCOLOR16;
    Green: MyCOLOR16;
    Blue: MyCOLOR16;
    Alpha: MyCOLOR16;
  end;
var
  t:array[0..1] of TMyTriVertex;
  tt: PMyTriVertex;
  g:TGradientRect;
  mode: Cardinal;
begin
  t[0].x:=x1;
  t[0].y:=y1;
  t[0].Red:=round((GetRValue(color1)/255)*65535);
  t[0].Green:=round((GetGValue(color1)/255)*65535);
  t[0].Blue:=round((GetBValue(color1)/255)*65535);
  t[0].Alpha:=0;
  t[1].x:=x2;
  t[1].y:=y2;
  t[1].Red:=round((GetRValue(color2)/255)*65535);
  t[1].Green:=round((GetGValue(color2)/255)*65535);
  t[1].Blue:=round((GetBValue(color2)/255)*65535);
  t[1].Alpha:=0;
  g.UpperLeft:=0;
  g.LowerRight:=1;
  tt:=@t[0];
  if Vertical then mode := GRADIENT_FILL_RECT_V else mode := GRADIENT_FILL_RECT_H;
  GradientFill(h,tt,2,@g,1,mode);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  // Цвета расчитаны через APE Цветик
  Gradient2D(Canvas.Handle,0,0,14772545,100,100,16711935,false);
  Gradient2D(Canvas.Handle,100,0,14772545,200,100,16711935,true);
end;