Printing system and method - Patent Review 5150454

Claims

We claim:

1. A printing system for printing from a source of drawing instructions a two dimensional image reducible to pixels arranged in a plurality of ranked image lines, comprising:

a storage means having a compressed region and an uncompressed region, each having a designated capacity and each being arranged to store pixels of one or more of said plurality of image lines;

drawing means coupled to said storage means and adapted to be coupled to said source of drawing instructions for responding thereto, said drawing means being operable to store new pixels in said storage means for successively selected ones of said image lines, said drawing means including:

(a) conditional means for compressively encoding and moving from said uncompressed region to said compressed region a remote one of said image lines, if (i) the selected one of said image lines is in said compressed region and (ii) said uncompressed region has reached its designated capacity;

(b) decompression means for expansively decoding said selected one of said image lines, if located in said compressed region; and

(c) insertion means for inserting one or more new pixels according to said drawing instructions into said selected one of said image lines by storing said selected one in said uncompressed region; and

printing means coupled to said storage means for printing said plurality of image lines in rank order, decompressing compressed ones of said image lines from said compressed region before printing.

2. A printing system according to claim 1 wherein said drawing means is operable to store in the storage means pixels associated with a full page worth of the instructions, said printing means being operable to await the storage in said storage means of said full page worth of said pixels before printing the image lines of said page.

3. A printing system according to claim 2 wherein said decompression means is operable to compressively encode and move from said uncompressed region to said compressed region said remote one of said image lines together with a plurality of other ones of said image lines proximate said remote one, so that lines are moved in groups.

4. A printing system according to claim 3 wherein said decompression means is operable to expansively decode and move from said compressed region to said uncompressed region said selected one of said image lines together with a plurality of other ones of said image lines proximate said remote one, so that lines are moved in groups.

5. A printing system according to claim 2 wherein said drawing means is operable to successively decompose one or more of the instructions from said source of drawing instructions into a list of simpler directions and store said list in said storage means, said drawing means being operable to numerically limit the instructions to keep said list within a designated size.

6. A printing system according to claim 5 wherein said two dimensional image comprises a plurality of contiguous bands and each of the image lines is allocated to a corresponding one of said bands, said drawing means being operable to scan the bands and restrict selection of said image lines to those allocated to a current one of said bands, said drawing means being operable to cyclically execute the directions of said list with a scope limited to storing pixels in the storage means for the image lines contained within the current one of said bands.

7. A printing system according to claim 6 wherein said drawing means is operable to overwrite the list of directions by decomposing and storing in said storage means unused ones of the instructions from said source of drawing instructions, said drawing means being operable to rescan the bands and restrict selection of said image lines to those allocated to a current one of said bands, said drawing means being operable to again cyclically execute the latest ones of the directions with a scope limited to storing pixels in the storage means for the image lines contained within the current one of said bands.

8. A printing system according to claim 7 wherein said conditional means is operable to compressively encode said image lines at a chosen one of a plurality of encoding densities and is operable to move said image lines to said compressed region with a compression code signifying said chosen one of said encoding densities.

9. A printing system according to claim 8 comprising:

means for determining at least one of the characteristics of the image, said drawing means being operable to select said chosen one of said densities in response to said one of the characteristics of said image.

10. A printing system according to claim 8 wherein said storage means has a printing region, said printing means being operable to expansively decode said image lines in rank order and store them in said printing region.

11. A printing system according to claim 8 wherein said decompression means is operable to store said selected one of said image lines after decompression in said uncompressed region with an uncompressed code signifying a lack of compression, said printing means being operable to store said image lines in said printing region without a code signifying a lack of compression.

12. A printing system according to claim 8 wherein said st