A new color space that maps image pixel values in a mosaiced sampling pattern (such as that generated by a Bayer color filter array) into four color channels that correspond to rectangular sampling patterns. Because these new channels correspond to a rectangular sampling grid, they are much more amenable to processing steps such as compression. In one embodiment, the transformation from the original mosaic-patterned pixels into the new four-channel color space can be made reversible in integer arithmetic. That allows for the implementation of efficient lossless image compression systems for mosaiced (e.g., raw, or raw Charged Couple Device (CCD)) images.