US 2003/0112468 A1 · Reduced-buffer error diffusion

Abstract

An error diffusion method is provided where a plurality of n error values derived from processing one or more previous scanlines of input pixel values are sub-sampled without the n error values being stored in a buffer to derive m error values (m<n). In one example, a reduction factor R is used according to m=n/R. In another example, a two-dimensional reduction operation is performed. The m error values, rather than the original n error values, are used as input for subsequent error diffusion operations. This allows for storage of m error values rather than n error values and, thus, error buffer requirements are reduced. Image quality has been found to be comparable to conventional error diffusion operations when the reduction factor used is maintained within reasonable limits. The sub-sampling operation can be accomplished according to any suitable method. As described herein, either an averaging operation or a summation operation (with appropriate weight adjustments in the error diffusion operations) can be used to derive the m error values from the n original error values.

Claims20

Dependent claims

A method of processing a digital image that is defined in terms of a plurality of scanlines each comprising n input pixel values, said method comprising:

performing an error diffusion operation on a first scanline of n input pixel values;
deriving a first plurality of error values from said error diffusion operation performed on said first scanline of n input pixel values;
deriving m error values from said first plurality of error values, wherein m<said first plurality of error values;
storing said m error values in an error buffer;
and,
performing an error diffusion operation on a second scanline of n input pixel values to modify said input pixel values of said second scanline using said m error values stored in said error buffer.

3 more elements

Dependencies are inferred from the claim text.

Reduced-buffer error diffusion

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Reduced-buffer error diffusion

Life of this patent

Abstract

Claims20