Decrease the preferred size for PDF417 barcodes

Merged Volker Krause requested to merge work/improve-pdf417-preferred-size into master

Unlike the other two-dimensional codes its smallest output element is not 1x1 but 1x3 pixels, so a scale factor of 2 already gives us enough area for barcode scanners to work with, and avoids PDF417 barcodes becoming unreasonably large by default.

The implementation is a bit hacky unfortunately, as surprisingly the base class has no knowledge about the specific barcode type.

Merge request reports