Why can't I draw on my image's canvas?

Question

I'm using Delphi XE8.

I'm loading a background image to my Image:

var
  Png: TPngImage;
begin
  Png := TPngImage.Create;
  try
    Png.LoadFromResourceName(HInstance, 'background');
    Image1.Picture.Graphic := Png;
  finally
    Png.Free;
  end;

This works alright, but when I try to draw on the image's canvas (I tried LineTo) I get this error:

Can only modify an image if it contains a bitmap

How can I draw on an image which I have loaded a picture into?

Answer 1

The answer can be found in the error message that you quoted:

Can only modify an image if it contains a bitmap.

So, create a bitmap object, assign the PNG image to that bitmap, and then assign that bitmap to the TImage control's Picture.