Hi,
How can I vectorize small piece of cardboard? Should I scan it first? And then?
Thanks

Hello there,
Depends on what you want to do. Do you want to create a fully vector texture?

I just need to vectorize cardboard precise outline.

Hi there,
I often needed to make templates from paper test pieces I'd already cut, and I found it easiest to scan the paper piece and then trace the outline by hand in Inkscape. Just scan your paper or cardboard prototype and save it as a jpg, png, or whatever your scanner prefers, then open that image in Inkscape and trace along the edge of it using the pen tool. Save the completed tracing as an svg file, then delete the png, or other image that you traced, and save as svg again.

Unless you can scan to exact size, Scanning will very likely give you an image thats much bigger than the original piece, so be careful to check the measurements on your Inkscape drawing and in the print preview window before printing or cutting.

The great thing about making templates in Inkscape is that you can scale them up, or down, and all the relative proportions will remain unchanged.
It makes resizing paper and wood-cut craft project patterns very easy. Scan all the pieces of your project in one image if you can, so that everything will come out at the same relative size.

I have made my cardboard outlines with drawing pen so far. Yes you are right about scanned image- it is bigger than the original, but how can I change the size in inkscape to get exact size like original piece of cardboard? Thanks

You can set the dimensions of the objects at the top menu when in object mode -F1-.
When inputting the measures of the exact cardboard size in like mm, be avare that inkscape runs in 90 dpi.
Here is a good topic on the resolution:
http://www.inkscapeforum.com/viewtopic.php?f=5&t=14450&hilit=dpi