Storage of digital camera images

We describe a simple technique to improve the quality of images that are compressed for storage on a digital camera. We assume that the camera is designed to store a fixed number of images, and that lossy rate controlled compression is used to ensure that each image fits in the space allocated to it. Whenever the user takes fewer than the maximum allowed number of images a portion of the disk is empty, which is wasteful. Ideally we would like to make full use of the storage space, and not leave any empty. We show that when an image is JPEG compressed it is possible to produce a secondary compressed version for marginal additional computation. At the decoder the secondary version allows decoding of the image with much greater fidelity than is possible using the primary alone. Thus if the user takes half or fewer of the maximum allowed number of images, each will be reconstructed with far greater fidelity, and some images will always have enhanced quality provided that the disk does not fill