Display Image-Barcodes Using Blue/Red Channel Embedding

Barcodes and watermarks offer different trade-offs for carrying data through a displayed image. Barcodes offer robust detection and decoding with high data capacity but are visually obtrusive. Watermarks are imperceptible but their detection and decoding is less robust, and they offer lower data capacity. Image-barcodes straddle this trade-off by attempting to reduce perceptual obtrusiveness compared with conventional barcodes, while minimally compromising data robustness. We propose an image-barcode for display applications that is simple, yet novel. The proposed method encodes the data into a monochrome barcode and embeds it into a suitably chosen region in the blue/red channel of a displayed image. The reduced sensitivity of the human visual system to changes in these channels (particularly the blue channel) reduces the perceptual impact of the image barcode compared with conventional black and white barcodes. The data can, however, still be robustly recovered from a typical color image capture of the displayed image-barcode by decoding only the channels with the embedding. We assess visual distortion and robustness of data recovery for the proposed method and experimentally compare against a baseline black and white barcode for two barcode modes representative of potential usage scenarios. Visual distortion for the proposed method is significantly better. Under typical settings, the proposed method introduces a mean SCIELAB-CIEDE2000 distortion of ∆E = 0.39 for the blue channel embedding and ∆E = 0.35 for the red channel embedding, compared with ∆E = 0.59 for the baseline method. For data recovery, the blue and red channel embeddings using the proposed method match the 100% decoding success rate and synchronization success rate for the baseline method, although, the pre-errorcorrection observed mean bit error rate of 0.047% (0.08%) for the blue (red) channel embedding is marginally worse than the performance of the baseline method. Introduction Machine readable image-based data interfaces [1], such as barcodes and watermarks, have widespread applications due to their ability to connect the analog physical world and digital cyber world [2–9]. Barcodes encode the data in the form of image patterns and offer high data capacity and robust decoding performance, although at the cost of obtrusive visual appearance. Watermarks hide the data in a pre-existing image maintaining the aesthetics and primary functionality of the image. Although the watermarks are visually imperceptible, they offer lower data capacity and less robust detection and decoding. Image-barcodes [10–13] represent yet another class of image-based data interfaces that reside in space of trade-offs between barcodes and watermarks; the aesthetics are improved compared with barcodes with little compromise in the robustness of data communication. Traditionally image-based data interfaces have been used in print. With increasing prevalence of high resolution displays and ubiquitous availability of mobile devices with high resolution cameras and adequate computational power, image-based data interfaces are also becoming increasingly common in displays. Specific examples include connectivity for advertised content, immediate information access (for instance at transit points), enabling point-of-sale interactions [14,15], and encoding boarding pass information displayed on smartphones to automate boarding (Aztec codes are common for this application). For several of these applications, visual appearance is minimally important, whereas for others, such as for personalized advertisements embedded within existing video and image content, it is desirable to minimize the perceptual impact. Several alternative image-based data interfaces have been employed for personalized advertisements. Figure 1 shows a frame from a 45 second commercial on a television show by a fashion retailer [16] which debuted the use of conventional black and white barcodes in television ads. In [17], a novel video barcode technology named Vcode, with high data capacity and real time decoding ability, connects a retailer with a customer by permitting users to download the content to their mobile devices. PiCode and ViCode [11, 18] are aesthetically designed Figure 1: Conventional (black and white) 2D barcode embedded in a video advertisement [16] picture-embedding barcodes which maintain a trade-off between visual quality of the image and decoding robustness with higher preference for perceptual aesthetics of the image. Color imagebarcodes such as ColorCode [19] and Pictorial Image Code [12] have also been proposed for display advertising. Additionally, digital watermarks have been used create multiple hot-spots [20] in advertisement images/videos with each hot-spot connecting the consumer to different products of interests. In these applications, the obtrusiveness of barcodes is often undesirable, whereas watermarks are often not adequately robust. Additionally watermarks face a challenge in adoption because viewers of the content do not realize that additional functionality is available through watermarks unless some additional visual indication is inserted, deIS&T International Symposium on Electronic Imaging 2018 Media Watermarking, Security, and Forensics 2018 159-1 https://doi.org/10.2352/ISSN.2470-1173.2018. 07.MWSF-159 © 2018, Society for Imaging Science and Technology