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Context Dependent DPCM Image Compression

Efficient compression of image data requires the understanding of the noise characteristics of sensors as well as the redundancy expected in imagery. Herein, the techniques of Differential Pulse Code Modulation' (DPCM) are reviewed and modified for information preserving data compression. The modifications include: o Mappings from intensity to a user selected equal noise variance space, o Context dependent one and two dimensional predictors, o Rationale for non-linear DPCM encoding based upon an image quality model, o Context dependent variable length encoding of 2x2 data blocks, o Feed back control for constant output rate systems. Images have been processed at compression rates between 1.3 and 2.8 bits per pixel. The need for larger block sizes, 2D context dependent predictors, and the hope for sub-bits-per-pixel compression which maintains spacial resolution (information preserving) are discussed also.