We have tested our method on a wide variety of images. Figure 5 shows eight results generated by our method and a complete gallery of halftone QR codes could be found in the supplementary material.
The default QR code setting of symbol version 5 and error correction level H ∗ is used for generating all the results.
Our algorithm is computationally efficient and takes less than a second to generate a result using unoptimized codes on a PC with 3.4GHz CPU and 8 GB system memory.
The performance of our algorithm is dependent on the size of QR code and the number of data modules involved in the optimization. The halftone nature makes our results gain visual quality superior to existing visual QR codes as viewed from a distance; and our representation model that shows stable image quality under the variation of QR codes also enables an effortless extension to combine QR codes with video clips to generate animated halftone QR codes. Although a simple frame-by-frame synthesis is employed without taking into account the temporal coherence between consecutive halftone images, the generated results are quite satisfactory in terms of visual quality and readability during the video playback (see supplementary video).