In one embodiment, an image decoding system for a YCbCr formatted signal includes a color space converter capable of representing an RGB image signal with one or two negative image signal components. The image decoding system further includes a degamma correction unit and an image signal formatter. An offset of the image black level from zero corresponding to the image signal offset produced by the color space converter is employed to perform degamma correction. In a further embodiment, gain, offset, and sign are removed from the image signal produced by the color space converter prior to degamma correction. The image signal formatter may utilize a one-dimensional and a three-dimensional lookup table to produce an image signal that may include secondary and white image components. The system advantageously accommodates decoding xvYCC-encoded image data in conventional as well as new hardware display system architectures.