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Data hiding technique is using a cover medium to conceal secret data and delivering it to receiver over public computer networks for secret data delivery. A color image is a good cover medium because a color image consists of more redundant space than a gray scale image or halftone image, that means, a color image can be used to carry more secret data. Block truncation coding (BTC) is a lossy compression technique that can significantly reduce the size of digital images with acceptable visual quality. Traditional color BTC compression method uses three bitmaps to compress a color image for saving the storage cost. Chang et al. proposed a data hiding method to conceal secret data into BTC compression code. Chang et al. use a genetic algorithm (GA) to generate a common bit-map to improve the compression rate then uses the common bit-map to increase embedding capacity in a color image. However, Chang et al.'s method is time consuming for generating a common bit-map. In this paper, a novel data hiding method is presented to save the computation cost for common bit-map generation and improve the visual quality of stego images. From the experimental results, the proposed method not only successfully conceals secret data into compression code but also saves the computation cost of common bit-map generation.