Four color gradient
Four color gradient
The RGB macro selects a red, green, blue (RGB) color based on the arguments supplied and the color capabilities of the output device. The intensity for each argument is in the range 0 through 255. If all three intensities are zero, the result is black. If all three intensities are 255, the result is white.
Following procedure create gradient at startup.
procedure TForm1.FormCreate(Sender: TObject);
Var
C, R, H, W, L : Integer;
Step : Real;
begin
{ Get form size }
H:=Image1.Height;
W:=Image1.Width;
{ Set fill size }
L:=W Div 3;
{ Set fill step size }
Step:=255/L;
C:=0;
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;
{ Fill area by drawing lines }
Image1.Canvas.MoveTo(R,0);
Image1.Canvas.LineTo(R,H);
End;
end;
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