I created a test document in Scribus showing ISBN barcodes produced in Bookland, Scribus, and Inkscape and reduced in size. I reduced the height on the Inkscape sample from 30 to 20 in Inkscape itself. The resulting bar code had very heavy bars compared to the other samples.

http://wexfordpress.net/bar.pdf

I don't know if these heavy bars will scan or not. Could someone please do their own comparisions and test to see if the Inkscape barcode is acceptable?

Inkkscape 48.1.