Blind quantization ratio estimation for JPEG images using digital watermarking

Most image acquisition and editing tools use the JPEG standard for image compression. In this paper, a simple quantization ratio estimation scheme based on digital watermarking is proposed. An 8×8 pixel block is selected from the original image and inserted in the whole image using digital watermarking. If the receiver does not know the quantization ratio (quality factor) with which image is compressed, it can apply a set of all possible quantization ratios to the received compressed image. The inserted watermark can be extracted correctly only with the same quantization ratio which was used to compress the image. Hence image can be decompressed (reconstructed) without the prior knowledge of quantization ratio.