Abstract
This paper presents a watermarking method in the spatial domain with HVS-imperceptibility for High Dynamic Range (HDR) images. The proposed method combines the content readability afforded by invisible watermarking with the visual ownership identification afforded by visible watermarking. The HVS-imperceptibility is guaranteed thanks to a Luma Variation Tolerance (LVT) curve, which is associated with the transfer function (TF) used for HDR encoding and provides the information needed to embed an imperceptible watermark in the spatial domain. The LVT curve is based on the inaccuracies between the non-linear digital representation of the linear luminance acquired by an HDR sensor and the brightness perceived by the Human Visual System (HVS) from the linear luminance displayed on an HDR screen. The embedded watermarks remain imperceptible to the HVS as long as the TF is not altered or the normal calibration and colorimetry conditions of the HDR screen remain unchanged. Extensive qualitative and quantitative evaluations on several HDR images encoded by two widely-used TFs confirm the strong HVS-imperceptibility capabilities of the method, as well as the robustness of the embedded watermarks to tone mapping, lossy compression, and common signal processing operations.
Highlights
High Dynamic Range (HDR) images are characterized by a wide range of visible luminance values that can accurately represent the radiance of the scene, ranging from direct sunlight to faint starlight
From the UVW technique, which embeds copyright information in the spatial domain of Standard Dynamic Range (SDR) regions with low visibility, the HDRIW method embeds imperceptible watermarks in the spatial domain by exploiting the inaccuracies among the non-linear digital representation of the linear luminance acquired by an HDR sensor, the linear luminance radiated by an HDR screen by means of a transfer function (TF), and the brightness perceived by the Human Visual System (HVS) from the displayed luminance
In this paper, we proposed the HDR-IW method to protect HDR images by embedding binary watermarks in the spatial domain that are imperceptible to the HVS
Summary
HDR images are characterized by a wide range of visible luminance values that can accurately represent the radiance of the scene, ranging from direct sunlight to faint starlight. Visible watermarking allows to visually assert the media’s ownership without the need for such keys or extra information This is usually achieved by performing the embedding process in the spatial domain; e.g., by altering pixel values. From the UVW technique, which embeds copyright information in the spatial domain of SDR regions with low visibility, the HDRIW method embeds imperceptible watermarks in the spatial domain by exploiting the inaccuracies among the non-linear digital representation of the linear luminance acquired by an HDR sensor, the linear luminance radiated by an HDR screen by means of a TF, and the brightness perceived by the HVS from the displayed luminance The latter is achieved by using the information provided by a Luma Variation Tolerance (LVT) curve [4].
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