No ads, can read inverted codes and can generate barcodes.

Uses the ZXing ("Zebra Crossing") barcode scanning library. Supported barcode formats are: AZTEC, CODABAR, CODE 39, CODE 93, CODE 128, DATA MATRIX, DX FILM EDGE, EAN 8, EAN 13, ITF, MAXICODE (partial), PDF417, QR CODE, Micro QR Code, rMQR Code, RSS 14, RSS EXPANDED, UPC A, UPC E, UPC EAN EXTENSION

This is open source:

https://github.com/markusfisch/BinaryEye