Increasing image compression rate using steganography

•Two new image compression algorithms based on DCT-JPEG and DWT-JPEG, called Stego-JPEG (DCT) and Stego-JPEG (DWT), are investigated.•The key idea is to compress a block of an image using lossy JPEG, and then hide the resulting bits into subsequent blocks.•Increasing compression ratio is improved with high quality for both Stego-JPEG (DCT) and Stego-JPEG (DWT).•For color images, Stego-JPEG (DCT) and Stego-JPEG (DWT) have more compression ratio than grayscale also decrease of PSNR is better than grayscale. The goal of image compression is to remove the redundancies for minimizing the number of bits required to represent an image while steganography works by embedding the secret data in redundancies of the image in invisibility manner. Our focus in this paper is the improvement of image compression through steganography. Even if the purposes of digital steganography and data compression are by definition contradictory, we use these techniques jointly to compress an image. Hence, two schemes exploring this idea are suggested. The first scheme combines a steganographic algorithm with the baseline DCT-based JPEG, while the second one uses this steganographic algorithm with the DWT-based JPEG. In this study data compression is performed twice. First, we take advantage of energy compaction using JPEG to reduce redundant data. Second, we embed some bit blocks within its subsequent blocks of the same image with steganography. The embedded bits not only increase file size of the compressed image, but also decrease the file size further more. Experimental results show for this promising technique to have wide potential in image coding.