Incorporating Memory Constraints in the design of Color Error Diffusion Halftoning Systems

摘要

We analyze color error diffusion with memory constraints. Color error diffusion requires the storage of error terms in an error buffer. We explore memory reduction by representing the error buffer in the YIQ space and allocating a finite number of bits to each channel. The error buffer is represented in a packed-bit format. This constrains the error buffer to a desired bit-width. However such a constraint degrades performance. The degradation is observed as an increase in perceived color quantization noise. We derive an optimal solution for the error filter coefficients which minimize the visual effect of the memory constraint. Our formulation allows the filter coefficients to be matrix-valued allowing cross-channel diffusion of color errors. The optimal filter depends on the color characteristics of the device, viewing distance and the specific bit allocations used for the error buffer and the the rendering frame buffer.