Résumé
Quick Response (QR) code is the most popular graphical code in the world today. These codes are used for storage of information, but they have a limited storage capacity. In this paper, we present a two level QR (2LQR) code, which stores information on two levels. The first (public) level is accessible to everyone and can be read by any classical QR code reader. The second (supplementary) level is readable only by a selected group of users, which have a specific reader application. This code increases storage capacity of standard QR code. We use specific textured patterns for construction of a second level. We also suggest a blind pattern recognition method, which is based on maximization of correlation values.