Hidden Barcode in Sub-Images with Invisible Locating Marker

The prevalence of the Internet of Things has led to the widespread adoption of 2D barcodes as a means of offline-to-online communication. Whereas, 2D barcodes are not ideal for publicity materials due to their space-consuming nature. Recent works have proposed 2D image barcodes that contain invisible codes or hyperlinks to transmit hidden information from offline to online. However, these methods undermine the purpose of the codes being invisible due to the the requirement of markers to locate them. The conference version of this work presented a novel imperceptible information embedding framework for display or print-camera scenarios, which includes not only hiding and recovery but also locating and correcting. With the assistance of learned invisible markers, hidden codes can be rendered truly imperceptible. A highly effective multi-stage training scheme is proposed to achieve high visual fidelity and retrieval resiliency, wherein information is concealed in a sub-region rather than the entire image. However, our conference version does not address the optimal sub-region for hiding, which is crucial when dealing with local region concealment problems. In this article extension, we consider human perceptual characteristics and introduce an optimal hiding region recommendation algorithm that comprehensively incorporates Just Noticeable Difference and visual saliency factors into consideration. Extensive experiments demonstrate superior visual quality and robustness compared to state-of-the-art methods. With the assistance of our proposed hiding region recommendation algorithm, concealed information becomes even less visible than the results of our conference version without compromising robustness.