size of image in 640*480

Hi everybody.
I created some images in PNG format.
When I use it after "graphics 640, 480" (and without any "setscale" call), these images appears with scale twice than expected.
If I use it after "graphics 800, 600" then the size is what I expected when I created the image.
I don't understand why...
An explanation ?

OK, forget for the post....
I just realize that it's normal.
"Real" size of 20 pixels is bigger in a 640*480 format than in a 800*600 format.
I must be stupid....
;-)

Yes you'll need to write a little function for resolution independence. I work at 1024x768 and scale up/down from there, but it's very easy to do.

800 is not exactly twice 640 though ;]

Yeah, Blitz2D is supposed to be an imitation of the pixel perfect old school bliting style, not a real 2D as 3D thing.

I like it this way... When I tried doing 2D as 3D stuff with Blitz3D, getting it pixel perfect was difficult.