I really don't know if this is a bug, or it's me who doesn't understand it.

Take a TForm, with a Timage and a TButton.

This is the code of the TButton OnClick event:

`procedure TForm1.Button1Click(Sender: TObject);`

var

Vertex : array[0..3] of TPoint;

begin

with Image1.Picture.Bitmap do

begin

Width := ClientWidth;

Height := ClientHeight;

with Canvas do

begin

Brush.Style := bsSolid;

// red square

Vertex[0].X := 0; Vertex[0].Y := 0;

Vertex[1].X := 20; Vertex[1].Y := 0;

Vertex[2].X := 20; Vertex[2].Y := 20;

Vertex[3].X := 0; Vertex[3].Y := 20;

Brush.Color := clRed;

Polygon(Vertex);

// green square

Vertex[0].X := 20; Vertex[0].Y := 20;

Vertex[1].X := 40; Vertex[1].Y := 20;

Vertex[2].X := 40; Vertex[2].Y := 40;

Vertex[3].X := 20; Vertex[3].Y := 40;

Brush.Color := clGreen;

Polygon(Vertex);

end;

end;

end;

Obviously when user click on the button, two squares are drawn, a red one on the top-left and a green one on the bottom-right of the Timage object.

In fact, in case (A) Timage has Left:=0; Top:=0; Width:=40; Height:=40; I get something like that:

**RRBBX**

RRBBX

BBGGX

BBGGX

XXXXX

Legend:

**R**=RED COLOR

**G**=GREEN COLOR

**B**=BLACK COLOR (canvas background)

**X**=form background (background)

But in case (B) Timage has Left:=10; Top:=10; Width:=40; Height:=40; I get something like that:

**XXXXX**

XRRBX

XRRBX

XBBGX

XXXXX

which IS NOT WHAT I EXPECTED :shock:

I had expected something like that:

**XXXXX**

XRRBB

XRRBB

XBBGG

XBBGG

Am I wrong to expect that or what?

Thanks in advance to who will provide me with an explanation! :wink: