Tileset and backgroundscaling

Say I want Juni to walk on the background (like the mountian in a picture of a mountain or similar.)

As the editor scale tilesets and background differently (the tilesets gets smaller than the .png file), I find I have to "counterscale" tilesets (of cutouts from the background) I want to match the background.

So does anyone have a number for how much bigger a cutout tileset need to be to match the background? I think it would take me a while to find out by trying and failing ...

Plus, how do you do it? Do you got a clever solution? (Exept for making a mountain tileset and putting it over a sky background. Doesn't really apply to what I'm wondering about )

(extra question: the world window in the editor seems to be 598x238pxl, and the game window seems to be 599x240pxl, as opposed to the picture file. (600x240pxl) Why is this? Just curious.)

As the editor scale tilesets and background differently (the tilesets gets smaller than the .png file)

I'm sorry, I don't get what you mean by that. The editor doesn't scale images at all, neither backgrounds nor tilesets.

(extra question: the world window in the editor seems to be 598x238pxl, and the game window seems to be 599x240pxl, as opposed to the picture file. (600x240pxl) Why is this? Just curious.)

I'm pretty sure it's the window borders that are eating up part of the screen; it's also a little different between OSes (XP to Vista/7).

I'm sorry, I don't get what you mean by that. The editor doesn't scale images at all, neither backgrounds nor tilesets.

Oh, ops, I just discovered something. You are right, and my picture editing program scales inserted pictures as a preset. Well, that was stupid.