In this paper, we present an automatic algorithm to create a new type of visual QR code, called halftone QR code, that combines halftone images with QR codes (see Figure 1 and Figure 2(d)).
To eliminate the aforementioned problems, the key insight is a representation model that minimally binds to original modules and is flexible to adapt to target halftone images.
In our approach, we subdivide each module into 3 × 3 sub-modules and bind the module’s
color to the center sub-module, which leaves the remaining eight sub-modules free to independently change their appearance. We use this flexibility to characterize the appearance of modules using a set of binary patterns. In addition, we evaluate the pattern reliability of
each binary pattern that represents a probability of retaining module’s readability when it is replaced by the pattern. Specifically, we estimate the probability by learning from a database of synthetic QR codes that is automatically generated using binary patterns and a barcode reader is employed to statistically evaluate pattern’s reliability. Finally, to generate halftone QR codes, we introduce a novel optimization method to compute and assign a binary pattern to each module by balancing two competing terms, reliability and regularization, corresponding to preferring the assignment of high reliability patterns and regularizing the appearance of modules towards target halftone images, respectively. (Please refer to the project page to create your own halftone QR codes for non-commercial use.)