Delphi print a custom area of a form - delphi

Question

I have a form which I need to print but only a certain section of it and then enlarge it (increase the scale). So far I have the following code:
procedure TForm1.PrintButtonClick(Sender: TObject);
var
printDialog : TPrintDialog;
begin
printDialog := TPrintDialog.Create(Form1);
if printDialog.Execute then
begin
Printer.Orientation := poLandscape; //Better fit than portrait
Form1.PrintScale:=poPrintToFit;
Form1.Print;
end;
end;
However, this prints the whole form. I've googled around and found a few different things that might help but I'm not sure how to use them:
GetFormImage - Is there a way of selecting a specific area with this or does it just take the whole form?
Using a rectangle with given coordinates e.g rectangle1:= rect(Left, Top, Right, Bottom); but then how do I print scale the rectangle to a larger size and print it? As well, seen as though Delphi only gives Left and Top properties, is Right just another name for the furthest left value you want to go to?
UPDATE:
I have tried to create a custom bitmap and then stretch it but I'm not using the strechdraw correctly. It doesn't actually stretch when printed:
procedure TForm1.PrintButtonClick(Sender: TObject);
var
printDialog: TPrintDialog;
Rectangle, stretched: TRect;
Bitmap: TBitmap;
begin
Bitmap := TBitmap.Create;
try
Rectangle := Rect(0, 90, 1450, 780);
stretched := Rect(0, 0, 5000, 3000); //what numbers do i put in here for streching it?
Bitmap.SetSize(Form1.Width, Form1.Height);
Bitmap.Canvas.CopyRect(Rectangle, Form1.Canvas, Rectangle);
Bitmap.Canvas.StretchDraw(stretched, Bitmap); //not sure how to use this
finally
printDialog := TPrintDialog.Create(Form1);
if printDialog.Execute then
begin
with printer do
begin
BeginDoc;
Canvas.Draw(0, 90, Bitmap);
EndDoc;
end;
end;
Bitmap.Free;
end;
end;
Is the try and finally necessary?
When I printed without the stretchdraw it was really small but when I printed with the stretchdraw, a lot of the image was missing so I must be using it wrong

Answer 1

Get rid of your stretched variable and the Bitmap.Canvas.StretchDraw (you can also get rid of the TPrintDialog if you'd like).
// Capture your bitmap content here, and then use this code to scale and print.
Printer.Orientation := poLandscape;
Printer.BeginDoc;
Printer.Canvas.StretchDraw(Rect(0, 0, Printer.PageWidth, Printer.PageHeight), Bitmap);
Printer.EndDoc;