GradientFill found in 'msimg32.dll'

GradientFill found in 'msimg32.dll'
This Delphi source code shows how the GradientFill function can be used to add smooth shading to a triangle or rectangle. For a triangle call the GradientFill function with the three triangle endpoints. GDI will linearly interpolate and fill the triangle.

To add smooth shading to a rectangle, call GradientFill with the upper-left and lower-right coordinates of the rectangle. There are two shading modes used when drawing a rectangle. In horizontal mode, the rectangle is shaded from left-to-right. In vertical mode, the rectangle is shaded from top-to-bottom. First, you need the GradientFill function declaration (Windows.pas contains wrong dectaration of GradientFill function):

type
  TRIVERTEX = packed record
    X, Y : DWORD;
    Red, Green, Blue, Alpha : Word;
  end;

function GradientFill(DC : hDC; pVertex : Pointer; dwNumVertex : DWORD;
  pMesh : Pointer; dwNumMesh, dwMode: DWORD) : DWord; stdcall;
  external 'msimg32.dll';

The following example shows a horizontal rectangle call.

procedure TForm1.Button1Click(Sender: TObject); var vert : array[0..1] of TRIVERTEX; gRect : GRADIENT_RECT; begin vert [0] .x := 0; vert [0] .y := 0; vert [0] .Red := $0000; vert [0] .Green := $0000; vert [0] .Blue := $0000; vert [0] .Alpha := $0000; vert [1] .x := 100; vert [1] .y := 32; vert [1] .Red := $0000; vert [1] .Green := $0000; vert [1] .Blue := $ff00; vert [1] .Alpha := $0000; gRect.UpperLeft := 0; gRect.LowerRight := 1; GradientFill(Form1.Canvas.Handle, @vert,2,@gRect,1,GRADIENT_FILL_RECT_H); end;