In this paper, a novel color image steganography scheme using gray invariant in AMBTC compression domain is proposed. Unlike the conventional schemes, the proposed scheme embeds the secret data into a compressed color image while keeping gray pixel values intact. First, the proposed scheme partitions each color component (R, G, B) of a cover image into non-overlapping blocks with the same size and calculates the standard deviation and variance of the sub-block. Next, two least complex blocks having minimum variance out of the three-color blocks are compressed using dynamic AMBTC compression and the secret data is embedded into bit-planes of smooth compressed blocks. To keep the gray pixel values invariant, the pixel values of the most complex color block are adjusted according to the pixel intensity on the reconstructed compressed blocks. Therefore, the proposed scheme can reduce the size of the color image and embed a significant amount of data while keeping gray pixel values intact. The main advantages of the proposed scheme are: (1) reduces the required bandwidth for image transmission due to AMBTC compression, (2) preserves gray values of the original cover image, which helps in many applications such as black and white printing, fingerprint scanning and so on, (3) uses color plane blocks selectively for data hiding which makes the proposed scheme more robust, and (4) uses a dynamic AMBTC compression for least complex color planes, which helps in achieving good PSNR and high embedding capacity.

中文翻译：

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AMBTC压缩域中使用灰度不变量的彩色图像隐写方案

在本文中，提出了一种在 AMBTC 压缩域中使用灰色不变量的新型彩色图像隐写术方案。与传统方案不同，所提出的方案将秘密数据嵌入到压缩的彩色图像中，同时保持灰度像素值不变。首先，所提出的方案将封面图像的每个颜色分量（R、G、B）划分为具有相同大小的非重叠块，并计算子块的标准偏差和方差。接下来，使用动态 AMBTC 压缩对三色块中具有最小方差的两个最不复杂的块进行压缩，并将秘密数据嵌入到平滑压缩块的位平面中。为了保持灰度像素值不变，根据重构压缩块上的像素强度调整最复杂色块的像素值。因此，所提出的方案可以减少彩色图像的大小并嵌入大量数据，同时保持灰度像素值不变。该方案的主要优点是：(1) 由于 AMBTC 压缩减少了图像传输所需的带宽，(2) 保留了原始封面图像的灰度值，这有助于黑白打印、指纹扫描等许多应用依此类推，(3) 选择性地使用颜色平面块进行数据隐藏，这使得所提出的方案更加健壮，以及 (4) 对最不复杂的颜色平面使用动态 AMBTC 压缩，这有助于实现良好的 PSNR 和高嵌入容量。