This one has four-color circular gradient.

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Following procedure create gradient at startup. Main technique of this procedure is fill pixels that have black color. Because within the form black exists only in text area.

procedure TForm1.FormCreate(Sender: TObject);
Var
    Y, C, R, H, W, L : Integer;
    Step : Real;
begin
    { Get form size }
    H:=Image1.Height;
    W:=Image1.Width;

    { Fill area with form color }
    Image1.Canvas.Pen.Color:=Form1.Color;
    Image1.Canvas.Brush.Color:=Form1.Color;
    Image1.Canvas.Rectangle(0,0,W,H);

    { Insert text }
    Image1.Canvas.Font.Name:='Arial Black';
    Image1.Canvas.Font.Size:=35;
    Image1.Canvas.Font.Style:=[fsBold];
    Image1.Canvas.TextOut(5,20,'digitalcoding.com');

    { Set fill size }
    L:=W Div 3;

    { Set fill step size }
    Step:=255/L;

    For R:=0 To W Do
    Begin
        { Select color for gradient starting from RED
        to YELLOW }

        { Change fill color }
        If R<=L Then
        Begin
            C:=Round(R*Step);
            { Red -> Green }
            Image1.Canvas.Pen.Color:=RGB(255-C,C,0);
        End
        Else If R<=2*L Then
        Begin
            C:=Round((R-L)*Step);
            { Green -> Blue }
            Image1.Canvas.Pen.Color:=RGB(0,255-C,C)
        End
        Else If R<=3*L Then
        Begin
            C:=Round((R-2*L)*Step);
            { Blue -> Yellow }
            Image1.Canvas.Pen.Color:=RGB(C,C,255-C);
        End;

        For Y:=0 to H Do
        { Fill only text area using text color}
        If Image1.Canvas.Pixels[R,Y]=clBlack Then
            Image1.Canvas.Pixels[R,Y]:=Image1.Canvas.Pen.Color;
    End;
end;

 

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