@SilverWarrior
Yes, I do have an array of TPoints for the straight lines (Later I need rounded "rubber-band line"), so
when the user is happy I draw the lines on the backgound TImage (which is stretched to fit the form).
All looks good on the screen. Save to file.
Problem with the saved bitmap file - it is "original" size, not the larger displayed size - so the drawn lines are in the wrong place! I guess I will have to avoid stretching and obtain an image that is the exact size of the form!
Regarding Paintbox canvas, I also wondered if the PaintBox canvas is actually "transparent" like it appears. If it IS, then some sort of operation (maybe bitblt??) that would combine ANY drawing with background. This would be better for freehand/shapes other than straight lines! I guess otherwise a "pixel by pixel"