Rewritable data embedding in JPEG XT image using coefficient count across layers

A JPEG XT format-compliant data embedding method is put forward by exploiting the natural relationship of coefficient count in the base and residual layers. Specifically, the number of coefficients for each MCU in the base layer is often larger than that of the respective MCU in the residual layer. This happens when the quality factor of the base layer is ≥ 75 and the quality factor of the residual layer is lower than that of the base layer. The proposed method then swaps the MCUs within these two layers to embed data. In case when a MCU is indistinguishable, a marker is injected to explicitly mark this bad MCU. When only AC coefficients are swapped, the output image quality can be maintained with some expansion of bit stream size. On the other hand, when both DC and AC coefficients are swapped, the proposed method is able to generate a fully distorted output image, hence masking the perceptual semantic of the image. Experiments are carried out to evaluate the performance of the proposed data embedding method.