Fast compression of periodic halftoned bitonal images

A method for compressing spacially periodic digital images by encoding target vertical edges located τ±n pixels from reference vertical eddies in an image, the method comprising:

• dividing an image contained in horizontal raster sequence image data into horizontal runs of pixels containing digital information indicative of bilevel image color;
• encoding the runs by:
• selecting a value for τ, where τ comprises a periodic distance between run edges and where the run edges are not spacially contiguous;
• and
• encoding a target edge of a run located τ±n pixels from a designated run edge of a reference run.

A method for compressing spacially periodic digital bilevel images by encoding target vertical edges in an image with respect to a reference vertical edge located at a specified distance, the method comprising:

• dividing an image contained in raster sequential data into horizontal runs of data containing digital information indicative of a bilevel image color;
• encoding the runs by:
• selecting a value for τ, where τ comprises a periodic distance between run edges and where the run edges are not spacially continuous;
• and
• encoding a target run edge of a run located τ±n pixels from a designated references edge, where τ≦the length of a horizontal line and τ is contained within the line.

A signal-bearing medium tangibly embodying a program of machine-readable instructions executable by a digital processing apparatus to perform a method for compressing bilevel images by encoding vertical edges with respect to non-contiguous other vertical edges, wherein the edges are contained within causal image data, the method comprising:

• dividing a spacially periodic digital bilevel image into a grid of pixels containing digital information indicative of image color, the image including vertical edges comprising adjacent pixel color changes;
• and
• encoding the vertical edges with respect to non-contiguous non-contiguous vertical edges located at a specified distance within the causal image data, the encoding using the specified distance, causal data, and non-contiguous edge correlations to compress the grid of pixels;
• and
• employing a back-up encoding scheme to encode the vertical edges if the non-contiguous vertical edge correlation is insufficient.

A signal-bearing medium tangibly embodying a program of machine-readable instructions executable by a digital processing apparatus to perform a method for compressing spacially periodic digital bilevel images by encoding vertical edges in an image with respect to non-contiguous other vertical edges located at a specified distance the method comprising:

• dividing an image contained in raster sequential data into horizontal runs of pixels containing digital information indicative of bilevel image color;
• encoding the runs by:
• selecting a value for τ, where τ comprises a periodic distance between run edges and where the run edges are not spacially contiguous;
• and
• encoding a target edge of a run located τ±n pixels from a designated run edge of a reference run, where τ≦the length of a horizontal line and contained within the line.

A signal-bearing medium tangibly embodying a program of machine-readable instructions executable by a digital processing apparatus to perform a method for compressing spacially periodic digital bilevel images by vertically encoding target edges in an image with respect to a reference edge located at a specified distance, the method comprising:

• dividing an image contained in raster sequential data into horizontal run lines of data containing digital information indicative of a bilevel image color;
• encoding the runs by:
• selecting a value for τ, where τ comprises a periodic distance between run edges and where the run edges are not spacially contiguous;
• and
• encoding a target run edge of a run located τ±n pixels from a designated reference edge, where τ≦the length of a horizontal line and τ is contained within the line.

An apparatus for compressing spacially periodic digital images by encoding run edges in an image with respect to non-contiguous other run edges located at a specified distance, the apparatus comprising:

• a processor to divide an image comprising vertical edges;
• an encoder capable of encoding the image for compressing the image by:
• dividing a spacially periodic digital bilevel image into a grid of pixels containing digital information indicative of image color, the image including vertical edges comprising adjacent pixel color changes;
• encoding the vertical edges with respect to non-contiguous other vertical edges located at a specified distance within the causal image data, the encoding using, the specified distance, causal data, and non-contiguous edge correlations to compress the grid of pixels;
• and
• employing a back-up encoding scheme to encode the vertical edges if the non-contiguous vertical edge correlation is insufficient.

An apparatus for compressing spacially periodic digital images by encoding target vertical edges located τ±n pixels from reference vertical edges in an image, the apparatus comprising:

• a processor to divide an image comprising vertical edges;
• an encoder to encode the image by:
• dividing the image contained in horizontal raster sequence image data into horizontal runs of pixels containing digital information indicative of bilevel image color;
• encoding the runs by:
• selecting a value for τ, where τ comprises a periodic distance between run edges and where the run edges are not spacially contiguous;
• and
• encoding a target edge of a run located τ±n pixels from a designated run edge of a reference run.