Printing system and method

Abstract

A image is printed from a source of drawing instructions. The image is reducible to pixels arranged in a plurality of ranked image lines. The system employs a storage device having compressed and uncompressed regions. Each region has a designated capacity and each is arranged to store pixels of one more of the plurality of image lines. A drawing processor is coupled to the storage device and can be coupled to the source of drawing instructions for responding thereto. This drawing processor can store new pixels in the storage device for successively selected ones of the image lines. The drawing processor has a conditional device, a decompression device and an insertion device. The conditional device can compressively encode and move from the uncompressed region to the compressed region, a remote one of the image lines, if: a) the selected one of the image lines is in the compressed region, and b) the uncompressed region has reached its designated capacity. The decompression device can expansively decode the selected one of the image lines, if located in the compressed region. The insertion device can insert one or more new pixels according to the drawing instructions into the selected one of the image lines by storing the selected one in the uncompressed region. The printing system also has a printing engine coupled to the storage device for printing the plurality of image lines in rank order, decompressing compressed ones of the image lines from the compressed region before printing.

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.]. .Iadd.selected .Iaddend.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 storage means is volatile and has a total capacity insufficient to hold all of said image lines uncompressed, the densest one of said encoding densities having the capability of reducing the resolution of the two dimensional image and storing it at a density that enables storage in said storage means of all of said image lines, without regard to the number and arrangement of pixels in said image lines, so that nonvolatile memory is unneeded for storing said image lines. 
     
     
       13. A printing system according to claim 8 wherein said decompression means is operable to sense the compression code and in response thereto expansively decode said selected one of said image lines with respect to said chosen one of said encoding densities. 
     
     
       14. A printing system according to claim 13 wherein said conditional means is operable if said compressed region has reached its designated capacity to compressively re-encode at least some of the image lines in said compressed region at a denser one of said densities. 
     
     
       15. A printing system according to claim 13 further comprising a non-volatile memory coupled to said drawing means, said conditional means being operable to move at least some of the image lines in said compressed region to said non-volatile memory, if said compressed region has reached its designated capacity and the image lines in said compressed region are encoded at the densest permissible one of said densities. 
     
     
       16. A printing system according to claim 13 further comprising a non-volatile memory coupled to said drawing means, said conditional means being operable to move at least some of the image lines in said compressed region to said non-volatile memory, if said compressed region has reached its designated capacity. 
     
     
       17. A printing system according to claim 16 wherein said decompression means is operable to expansively decode said selected one of said image lines, if located in said non-volatile memory. 
     
     
       18. A printing system according to claim 2 wherein said drawing means is operable to change the ratio of the capacities of said compressed and said uncompressed regions by redesignating portions of one in favor of the other in response to the availability of storage space in one or more of the regions of said storage means. 
     
     
       19. A printing system according to claim 2 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, said drawing means being operable to change the ratio of the capacities of said compressed and said uncompressed regions by redesignating portions of one in favor of the other in response to the choosing of the chosen one of said encoding densities. 
     
     
       20. A printing system according to claim 2 wherein said drawing means is operable to change the ratio of the capacities of said compressed and said uncompressed regions by redesignating portions of one in favor of the other in response to the size of page to be printed by said printing means. 
     
     
       21. A printing system according to claim 1 wherein said source of drawing instructions comprises a computer assembly having a processor and a computer memory spaced and packaged separately from said storage means, said drawing means and said printing means. 
     
     
       22. A printing system according to claim 21 further comprising: a printer casing containing said storage means, said drawing means and said printing means.   
     
     
       23. A printing system according to claim 6 wherein said source of drawing instructions comprises a computer assembly having a processor and a computer memory spaced and packaged separately from said storage means, said drawing means and said printing means. 
     
     
       24. A printing system according to claim 1 wherein said source of drawing instructions includes a computer assembly having a processor and a computer memory spaced and packaged separately from said printing means, said printing system further comprising: a frame attached to said computer assembly for supporting said drawing means and said storage means.   
     
     
       25. A printing system according to claim 24 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. 
     
     
       26. A printing system according to claim 25 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. 
     
     
       27. A printing method employing a storage means having a compressed region and an uncompressed region for printing from a source of drawing instructions a two dimensional image reducible to pixels arranged in a plurality of ranked image lines, comprising the steps of: storing new pixels in said storage means for successively selected ones of said image lines by:   (a) 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 capacity;   (b) expansively decoding said selected one of said image lines, if located in said compressed region; and   (c) 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 said plurality of image lines in rank order, decompressing compressed ones of said image lines from said compressed region before printing.   
     
     
       28. A printing method according to claim 27 wherein the step of storing new pixels comprises the steps of: successively decomposing one or more of the instructions from said source of drawing instructions into a list of simpler directions, while numerically limiting the instructions to keep said list within a designated size; and   saving said list in said storage means.   
     
     
       29. A printing method according to claim 28 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, the step of storing new pixels comprises the steps of: scanning the bands and restricting selection of said image lines to those allocated to a current one of said bands; and   cyclically executing 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.   
     
     
       30. A printing method according to claim 29 comprising the steps of: overwriting the list of directions by decomposing and storing in said storage means unused ones of the instructions from said source of drawing instructions;   rescanning the bands and restricting selection of said image lines to those allocated to a current one of said bands; and   again cyclically executing 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.   
     
     
       31. A printing method according to claim 30 comprising the steps of: compressively encoding said image lines at a chosen one of a plurality of encoding densities; and   storing said image lines in said compressed region with a compression code signifying said chosen one of said encoding densities.   
     
     
       32. A printing method according to claim 31 comprising the step of: sensing the compression code and in response thereto expansively decoding said selected one of said image lines with respect to said chosen one of said encoding densities.   
     
     
       33. A printing method according to claim 32 comprising the step of: compressively re-encoding at least some of the image lines in said compressed region at a denser one of said densities, if said compressed region has reached its capacity.   
     
     
       34. A printing method according to claim 31 comprising the step of: determining at least one of the characteristics of the image, said chosen one of said densities being selected in dependence upon said one of the characteristics of said image.   
     
     
       35. A printing method according to claim 31 wherein the step of storing said selected one of said image lines after decompression in said .[.compressed.]. .Iadd.uncompressed .Iaddend.region is performed by storing said selected one with an uncompressed code signifying a lack of compression, the step of printing being performed by storing said image lines in said storage means without a code signifying a lack of compression. 
     
     
       36. A printing method according to claim 31 wherein said storage means is volatile and has a total capacity insufficient to hold all of said image lines uncompressed, the densest one of said encoding densities having the capability of reducing the resolution of the two dimensional image and storing it at a density that enables storage in said storage means of all of said image lines, without regard to the number and arrangement of pixels in said image lines, so that nonvolatile memory is unneeded for storing said image lines. 
     
     
       37. A printing method according to claim 27 wherein the step of compressively encoding and moving is performed by encoding and moving 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, so that lines are moved in groups. 
     
     
       38. A printing method according to claim 37 wherein the step of expansively decoding is performed by decoding and moving 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, so that lines are moved in groups. 
     
     
       39. A printing method according to claim 27 further comprising the step of changing the ratio of the capacities of said compressed and said uncompressed regions by redesignating portions of one in favor of the other in response to the availability of storage space in one or more of the regions of said storage means.   
     
     
       40. A printing method according to claim 27 further comprising the steps of: compressively encoding said image lines at a chosen one of a plurality of encoding densities; and   moving said image lines to said compressed region with a compression code signifying said chosen one of said encoding densities; and   changing the ratio of the capacities of said compressed and said uncompressed regions by redesignating portions of one in favor of the other in response to the choosing of the chosen one of said encoding densities.   
     
     
       41. A printing method according to claim 27 further comprising the step of: changing the ratio of the capacities of said compressed and said uncompressed regions by redesignating portions of one in favor of the other in dependence upon the size of page to be printed. .Iadd.   
     
     
       42.  A method for producing image-defining data, comprising the steps of: storing in a memory a plurality of drawing instructions;   executing a first drawing instruction of said plurality of drawing instructions to generate data;   compressing said data;   storing said compressed data in said memory;   executing a second drawing instruction of said plurality of drawing instructions, said second drawing instruction creating a need to modify said compressed data;   decompressing said compressed data in response to said need to modify said compressed data; and   modifying said decompressed data in accordance with said second drawing instruction to produce modified data..Iaddend..Iadd.43. The method of claim 42, wherein said data comprise a set of data..Iaddend..Iadd.44. The method of claim 43, wherein said set of data comprises an image line of data..Iaddend..Iadd.45. The method of claim 43, wherein said set of data comprises at least a portion of a band of data including a plurality of image lines of data..Iaddend..Iadd.46. The method of claim 42, wherein said data comprise pixel data..Iaddend..Iadd.47. The method of claim 42, wherein said modification step adds data to said decompressed data..Iaddend..Iadd.48. The method of claim 42, further comprising the   
     
     
        step of printing an image based on said modified data..Iaddend..Iadd.49. The method of claim 42, wherein said compressing step comprises: compressing at least a portion of a set of data at a first compression density;   determining when said memory is insufficient to contain said compressed data;   further compressing said compressed portion of said set of data using a second compression density, said second compression density being denser than said first compression density..Iaddend..Iadd.50. The method of claim 49, wherein said first compression density is selected based on a sensed parameter..Iaddend..Iadd.51. The method of claim 50, wherein said sensed parameter is selected from the group consisting of identification of a printer, characteristics of a printer, examination of drawing instructions, interrogation of a printer, available memory, and combinations thereof..Iaddend..Iadd.52. The method of claim 42, wherein said compressing step comprises using a data compression technique enabling storage in said memory of substantially all of said image defining data..Iaddend..Iadd.53. The method of claim 52, wherein said data compression technique compresses data to a density which results in a loss of data..Iaddend..Iadd.54. The method of claim 53, wherein said data   
     
     
        compression technique is a discrete cosine transform..Iaddend..Iadd.55. The method of claim 52, wherein said data compression technique compresses data to a density which results in a reduction of resolution..Iaddend..Iadd.56. The method of claim 42, further comprising the step of recompressing said modified data..Iaddend..Iadd.57. The method of claim 52, further comprising the step of further compressing said compressed data so that said data may be stored in said memory at a density which enables storage of substantially all of said image defining data..Iaddend..Iadd.58. The method of claim 42, further comprising the step of printing an image based on a mixture of compressed and uncompressed data, said compressed data being decompressed prior to being printed..Iaddend..Iadd.59. A method for producing image-defining data in accordance with drawing instructions, said data capable of being used to generate an image, said method comprising the steps of: compressing said data;   decompressing said compressed data in response to a need to modify at least a portion of said data; and   modifying at least a portion of said data to provide modified data, said modification step occurring prior to generating any image based on said data..Iaddend..Iadd.60. The method of claim 59, wherein said compressing step comprises using a data compression technique enabling storage in a memory of substantially all of said image defining data..Iaddend..Iadd.61. The method of claim 60, wherein said data compression technique compresses said data to a density which results in a loss of data..Iaddend..Iadd.62. The method of claim 61, wherein said data compression technique is a discrete cosine transform..Iaddend..Iadd.63. The method of claim 62, wherein said data compression technique compresses data to a density which results in a reduction of resolution..Iaddend..Iadd.64. The method of claim 59, where said data comprises a band of data..Iaddend..Iadd.65. The method of claim 64, wherein said band of data comprises a plurality of image lines of data..Iaddend..Iadd.66. The method of claim 59, wherein said data comprise pixel data..Iaddend..Iadd.67. The method of claim 64, wherein said modification step adds data to said decompressed band of data..Iaddend..Iadd.68. The method of claim 64, further comprising the step of printing an image based on said modified band of data..Iaddend..Iadd.69. A method for producing image-defining data in accordance with drawing instructions, said data capable of being used to generate an image, said method comprising the steps of:   compressing at least a portion of said data; and   modifying at least a portion of said compressed data in accordance with a drawing instruction requiring said modification, said modifying step occurring prior to generating any image based on said   
     
     
        data..Iaddend..Iadd. 0.  The method of claim 69, wherein said compressing step comprises using a data compression technique enabling storage of substantially all of said image defining data in a memory..Iaddend..Iadd.71. The method of claim 70, wherein said data compression technique compresses data to a density which results in a loss of data..Iaddend..Iadd.72. The method of claim 70, wherein said data compression technique compresses data to a density which results in a reduction of resolution..Iaddend..Iadd.73. The method of claim 69, wherein said modifying step comprises: decompressing at least a portion of compressed data requiring modification; and   modifying at least a portion of said decompressed data..Iaddend..Iadd.74. The method of claim 73, further comprising the step of generating an image   
     
     
        based on said modified decompressed data..Iaddend..Iadd.75.  The method of claim 74, wherein said generating step comprises printing an image based on said modified decompressed data..Iaddend..Iadd.76. The method of claim 69, wherein said data comprise a set of data..Iaddend..Iadd.77. The method of claim 76, wherein said set of data comprises an image line of data..Iaddend..Iadd.78. The method of claim 69 or 73, wherein said set of data comprises a band of data including a plurality of image lines of data..Iaddend..Iadd.79. The method of claim 69, wherein said modifying step comprises adding data to said decompressed data..Iaddend..Iadd.80. The method of claim 69, wherein said modifying step comprises: decompressing at least the portion of compressed data requiring modification; and   modifying at least a portion of said decompressed data..Iaddend..Iadd.81. The method of claim 80, further comprising the step of generating an image based on said modified decompressed data..Iaddend..Iadd.82. The method of claim 69, further comprising the step of generating an image based on said   
     
     
        modified compressed data..Iaddend..Iadd.83.  The method of claim 69, further comprising the step of generating an image based on uncompressed data and said compressed modified data..Iaddend..Iadd.84. A method for producing image-defining data in accordance with drawing instructions, said method comprising the steps of: successively storing, in a memory having a finite capacity, data generated in accordance with successive drawing instructions, said memory having an uncompressed region and a compressed region, the relative sizes of said compressed region and said uncompressed region varying in response to the memory requirements of said data;   determining whether said data can be stored in said uncompressed region without exceeding said uncompressed region's capacity;   responsive to a determination that said data will exceed said capacity of said uncompressed region, compressing said data;   increasing the amount of memory devoted to said compressed region;   storing said compressed data in said compressed region;   decompressing said compressed data and storing said decompressed data in said memory in response to a second drawing instruction; and   modifying said decompressed data in accordance with said second drawing instruction to produce modified data..Iaddend..Iadd.85. The method of claim 84, further comprising the step of recompressing said modified   
     
     
        data..Iaddend..Iadd.86.  The method of claim 85, further comprising the step of printing an image based at least in part on said recompressed data..Iaddend..Iadd.87. A method for producing a set of image-defining data in response to drawing instructions, said method comprising the steps of: storing a first set of data produced in accordance with a first drawing instruction in a memory having a data storage capacity, said memory also storing, in a compressed form, one or more other sets of data that were produced in accordance with other, previous drawing instructions;   compressing said first set of data in said memory in response to (i) a need to modify, in accordance with a subsequent drawing instruction, a selected one of said compressed other sets of data stored in said memory, and (ii) a determination that said memory has reached a predetermined limit of its designated data storage capacity;   decompressing at least a portion of said selected one of said other sets of data to produce a second set of data; and   modifying at least a portion of said second set of data in accordance with said subsequent drawing instruction..Iaddend..Iadd.88. The method of claim 87, wherein said compressing step comprises:   compressing at least a portion of a set of data at a first compression density;   determining when said memory is insufficient to contain said compressed data;   further compressing said compressed portion of said set of data using a second compression density, said second compression density being denser than said first compression density..Iaddend..Iadd.89. The method of claim 88, wherein said first compression density is selected based on a sensed parameter..Iaddend..Iadd.90. The method of claim 89, wherein said sensed parameter is selected from the group consisting of identification of a printer, characteristics of a printer, examination of drawing instructions, interrogation of a printer, available memory, and combinations thereof..Iaddend..Iadd.91. The method of claim 87, wherein said compressing step comprises further compressing said data so that it may be stored in said memory at a density which enables storage of substantially all of said image defining data..Iaddend..Iadd.92. The method of claim 91, wherein said data compression technique compresses data to a density which results in a reduction of image clarity..Iaddend..Iadd.93. A method for creating image-defining data in accordance with drawing instructions, said data existing as stored sets of data in a memory and capable of being modified by subsequent ones of said drawing instructions, said method comprising the steps of:   determining whether a set of data, desired to be modified in accordance with a drawing instruction, is stored in said memory in an uncompressed or a compressed form;   producing a modified set of data by: (1) if said data are determined to be uncompressed, modifying at least a portion of said set of data in accordance with said drawing instruction, and   (2) if said data are determined to be compressed, decompressing at least a portion of said compressed data to which said drawing instruction relates and modifying at least a portion of said decompressed set of data; wherein:     said decompressing and modifying step occurs before any image is generated   
     
     
        based on said set of data..Iaddend..Iadd.94.  A method for producing image-defining data in accordance with drawing instructions, said data organized as a plurality of raster lines stored in a plurality of bands of raster lines in a memory and capable of being used to generate an image based on said raster lines, said method comprising the steps of: compressing a band of raster lines;   decompressing said compressed band of raster lines in response to a drawing instruction requiring modification of at least a portion of said band of raster lines; and   modifying at least a portion of said decompressed band of raster lines to provide a modified band of raster lines, said modification step occurring prior to generating any image based on said raster lines..Iaddend..Iadd.95. The method of claim 94, wherein said modification step adds raster lines to said decompressed bands of raster   
     
     
        lines..Iaddend..Iadd.96.  The method of claim 94, further comprising the step of printing an image based on said modified bands of raster lines..Iaddend..Iadd.97. The method of claim 94, further comprising the step of printing an image based on compressed and uncompressed raster lines..Iaddend..Iadd.98. The method of claim 94, wherein said compressing step comprises: compressing at least a portion of a set of raster lines at a first compression density;   determining when said memory is insufficient to contain said compressed raster lines;   further compressing said compressed portion of said set of raster lines using a second compression density, said second compression density being denser than said first compression density..Iaddend..Iadd.99. The method of claim 98, wherein said first compression density is selected based on a sensed parameter, said sensed parameter being selected from the group consisting of identification of a printer, characteristics of a printer, examination of drawing instructions, interrogation of a printer, available memory, and combinations thereof..Iaddend..Iadd.100. The method of claim 94, wherein said compressing step comprises using a data compression technique enabling storage in said memory of substantially all of said raster lines..Iaddend..Iadd.101. The method of claim 100, wherein said data compression technique compresses data to a density which results in a loss of said raster line data accuracy..Iaddend..Iadd.102. The method of claim 101, wherein said data compression technique is a discrete cosine transform..Iaddend..Iadd.103. The method of claim 94, wherein said data compression technique compresses said raster line data to a density which results in a reduction of image resolution..Iaddend..Iadd.104. The method of claim 42, 60, 70, 84, 87, or 94 further comprising the steps of:   successively decomposing drawing instructions into a display list having a simpler set of commands;   storing said display list in said memory, said memory having a finite capacity;   determining when said display list reaches a predetermined amount of said finite capacity;   responsive to a determination that said display list has reached said predetermined amount of said finite capacity, modifying or creating said data in accordance with at least one command in said display list..Iaddend..Iadd.105. The method of claim 104, wherein said data comprise a plurality of bands of data..Iaddend..Iadd.106. The method of claim 105, wherein modifying or creating said plurality of bands of data further comprises:   determining whether a display list command affects a successive band of said plurality of bands of data;   responsive to a determination that a display list command affects a band of data, modifying said band of data in accordance with said display list   
     
     
        element..Iaddend..Iadd.107.  The method of claim 104, further comprising the steps of: determining whether executing a display list command and purging said command would increase the amount of memory available; and   responsive to a determination that executing and purging said command would increase the amount of memory available, purging said command after said modifying step, thereby freeing said memory for additional display list commands..Iaddend..Iadd.108. Apparatus for producing image-defining data, comprising:   means for storing a plurality of drawing instructions;   means for executing a first drawing instruction of said plurality of drawing instructions to generate data;   means for compressing said data;   means for storing said compressed data;   means for executing a second drawing instruction of said plurality of drawing instructions, said second drawing instruction creating a need to modify said compressed data;   means for decompressing said compressed data in response to said need to modify said compressed data; and   means for modifying said decompressed data in accordance with said second drawing instruction to produce modified data..Iaddend..Iadd.109. The apparatus of claim 108, wherein said data comprise a set of data..Iaddend..Iadd.110. The apparatus of claim 109, wherein said set of   
     
     
        data comprises an image line of data..Iaddend..Iadd.111.  The apparatus of claim 109, wherein said set of data comprises at least a portion of a band of data including a plurality of image lines of data..Iaddend..Iadd.112. The apparatus of claim 108, wherein said data comprise pixel data..Iaddend..Iadd.113. The apparatus of claim 108, wherein said means for modifying data adds data to said decompressed data..Iaddend..Iadd.114. The apparatus of claim 108, further comprising means for printing an image based on said modified data..Iaddend..Iadd.115. The apparatus of claim 108, wherein said compressing means comprises: means for compressing at least a portion of a set of data at a first compression density;   means for determining when said memory is insufficient to contain said compressed data;   means for further compressing said compressed portion of said set of data using a second compression density, said second compression density being denser than said first compression density..Iaddend..Iadd.116. The apparatus of claim 115, wherein said first compression density is selected based on a sensed parameter..Iaddend..Iadd.117. The apparatus of claim 116, wherein said sensed parameter is selected from the group consisting of identification of a printer, characteristics of a printer, examination of drawing instructions, interrogation of a printer, available memory, and combinations thereof..Iaddend..Iadd.118. The apparatus of claim 108, wherein said compressing means comprises means for using a data compression technique enabling storage in said memory of substantially all of said image defining data..Iaddend..Iadd.119. The apparatus of claim 118, wherein said data compression technique compresses data to a density which results in a loss of data..Iaddend..Iadd.120. The apparatus of claim 119, wherein said data compression technique is a discrete cosine transform..Iaddend..Iadd.121. The apparatus of claim 118, wherein said data compression technique compresses data to a density which results in a reduction of resolution..Iaddend..Iadd.122. The apparatus of claim 108, further comprising means for recompressing said modified data..Iaddend..Iadd.123. The apparatus of claim 118, further comprising means for further compressing said compressed data so that said data may be stored in said memory at a density which enables storage of substantially all of said image defining data..Iaddend..Iadd.124. The apparatus of claim 108, further comprising means for printing an image based on a mixture of compressed and uncompressed data..Iaddend..Iadd.125. Apparatus for producing image-defining data in accordance with drawing instructions, said data capable of being used to generate an image, said apparatus comprising:   means for compressing said data;   means for decompressing said compressed data in response to a need to modify at least a particle of said data; and   means for modifying at least a portion of said data to provide modified data, said modification occurring prior to generating any image based on   
     
     
        said data..Iaddend..Iadd.126.  The apparatus of claim 125, further comprising memory means, wherein said compressing means comprises using a data compression technique enabling storage in said memory means of substantially all of said image defining data..Iaddend..Iadd.127. The apparatus of claim 126, wherein said data compression technique compresses said data to a density which results in a loss of data..Iaddend..Iadd.128. The apparatus of claim 127, wherein said data compression technique is a discrete cosine transform..Iaddend..Iadd.129. The apparatus of claim 128, wherein said data compression technique compresses data to a density which results in a reduction of resolution..Iaddend..Iadd.130. The apparatus of claim 125, where said data comprises a band of data..Iaddend..Iadd.131. The apparatus of claim 130, wherein said band of data comprises a 
     
     
        plurality of image lines of data..Iaddend..Iadd.132.  The apparatus of claim 125, wherein said data comprise pixel data..Iaddend..Iadd.133. The apparatus of claim 130, wherein said modification means adds data to said decompressed band of data..Iaddend..Iadd.134. The apparatus of claim 130, further comprising means for printing an image based on said modified band of data..Iaddend..Iadd.135. Apparatus for producing image-defining data in accordance with drawing instructions, said data capable of being used to generate an image, said apparatus comprising: means for compressing at least a portion of said data; and   means for modifying at least a portion of said compressed data in accordance with a drawing instruction requiring said modification, said modifying occurring prior to generating any image based on said data..Iaddend..Iadd.136. The apparatus of claim 135, wherein said compressing means comprises a data compression technique for enabling storage of substantially all of said image defining data in a memory..Iaddend..Iadd.137. The apparatus of claim 136, wherein said data compression technique compresses data to a density which results in a loss   
     
     
        of data..Iaddend..Iadd.138.  The apparatus of claim 136, wherein said data compression technique compresses data to a density which results in a reduction of resolution..Iaddend..Iadd.139. The apparatus of claim 135, wherein said modifying means comprises: means for decompressing at least a portion of compressed data requiring modification; and   means for modifying at least a portion of said decompressed data..Iaddend..Iadd.140. The apparatus of claim 139, further comprising means for generating an image based on said modified decompressed data..Iaddend..Iadd.141. The apparatus of claim 140, wherein said generating means comprises printing means for printing an image based on said modified decompressed data..Iaddend..Iadd.142. The apparatus of claim 135, wherein said data comprise a set of data..Iaddend..Iadd.143. The apparatus of claim 142, wherein said set of data comprises an image line of data..Iaddend..Iadd.144. The apparatus of claim 135 or 139, wherein said set of data comprises a band of data including a plurality of image lines of data..Iaddend..Iadd.145. The apparatus of claim 135, wherein said modifying means comprises adding data to said decompressed data..Iaddend..Iadd.146. The apparatus of claim 145, wherein said modifying means comprises:   means for decompressing at least the portion of compressed data requiring modification; and   means for modifying at least a portion of said decompressed   
     
     
        data..Iaddend..Iadd.147.  The apparatus of claim 146, further comprising means for generating an image based on said modified decompressed data..Iaddend..Iadd.148. The apparatus of claim 135, further comprising means for generating an image based on said modified compressed data..Iaddend..Iadd.149. The apparatus of claim 135, further comprising means for generating an image based on uncompressed data and said compressed modified data..Iaddend..Iadd.150. Apparatus for producing image-defining data in accordance with drawing instructions comprising: memory means having a finite capacity;   means for successively storing in said memory data generated in accordance with successive drawing instructions, said memory means having an uncompressed region and a compressed region, the relative sizes of said compressed region and said uncompressed region varying in response to the memory requirements of said data;   means for determining whether said data can be stored in said uncompressed region without exceeding said uncompressed region's capacity;   means responsive to a determination that said data will exceed said capacity of said uncompressed region for compressing said data;   means for increasing the amount of memory devoted to said compressed region;   means for decompressing said compressed data and storing said decompressed data in said memory in response to a second drawing instruction; and   means for modifying said decompressed data in accordance with said second   
     
     
        drawing instruction to produce modified data..Iaddend..Iadd.151.  The apparatus of claim 150, further comprising means for recompressing said modified data..Iaddend..Iadd.152. The apparatus of claim 151, further comprising means for printing an image based at least in part on said recompressed data..Iaddend..Iadd.153. Apparatus for producing a set of image-defining data in response to drawing instructions comprising: memory having a data storage capacity;   means for storing a first set of data produced in accordance with a first drawing instruction in said memory, said memory also storing, in a compressed form, one or more other sets of data that were produced in accordance with other, previous drawing instructions;   means for compressing said first set of data in said memory in response to (i) a need to modify, in accordance with a subsequent drawing instruction, a selected one of said compressed other sets of data stored in said memory, and (ii) a determination that said memory has reached a predetermined limit of its designated data storage capacity;   means for decompressing at least a portion of said selected one of said other sets of data to produce a second set of data; and   means for modifying at least a portion of said second set of data in   
     
     
        accordance with said subsequent drawing instruction..Iaddend..Iadd.154. The apparatus of claim 153, wherein said compressing means comprises: means for compressing at least a portion of a set of data at a first compression density;   means for determining when said memory is insufficient to contain said compressed data;   means for further compressing said compressed portion of said set of data using a second compression density, said second compression density being denser than said first compression density..Iaddend..Iadd.155. The apparatus of claim 154, wherein said first compression density is selected based on a sensed parameter..Iaddend..Iadd.156. The apparatus of claim 155, wherein said sensed parameter is selected from the group consisting of identification of a printer, characteristics of a printer, examination of drawing instructions, interrogation of a printer, available memory, and combinations thereof..Iaddend..Iadd.157. The apparatus of claim 153, wherein said compressing means comprises means for further compressing said data so that said data may be stored in said memory at a density which enables storage of substantially all of said image defining   
     
     
        data..Iaddend..Iadd.158.  The apparatus of claim 157, wherein said data compression technique compresses data to a density which results in a reduction of image clarity..Iaddend..Iadd.159. Apparatus for creating image-defining data in accordance with drawing instructions, said data existing as stored sets of data in a memory and capable of being modified by subsequent ones of said drawing instructions, said apparatus comprising: means for determining whether a set of data, desired to be modified in accordance with said drawing instruction, is stored in said memory in an uncompressed or a compressed form;   means for producing a modified set of data by: (1) if said data are determined to be uncompressed, modifying at least a portion of said set of data in accordance with said drawing instruction, and   (2) if said data are determined to be compressed, decompressing at least a portion of said compressed data to which said drawing instruction relates and modifying at least a portion of said decompressed set of data; wherein:     said decompressing and modifying occurs before any image is generated based on said set of data..Iaddend..Iadd.160. Apparatus for producing image-defining data in accordance with drawing instructions, said data organized as a plurality of raster lines stored in a plurality of bands of raster lines in a memory and capable of being used to generate an image based on said raster lines, said apparatus comprising:   means for compressing a band of raster lines;   means for decompressing said compressed band of raster lines in response to a drawing instruction requiring modification of at least a portion of said band of raster lines; and   means for modifying at least a portion of said decompressed band of raster lines to provide a modified band of raster lines, said modifying occurring prior to generating any image based on said raster   
     
     
        lines..Iaddend..Iadd.   .  The apparatus of claim 160, wherein said modifying means adds raster lines to said decompressed bands of raster lines..Iaddend..Iadd.162. The apparatus of claim 160, further comprising means for printing an image based on said modified bands of raster lines..Iaddend..Iadd.163. The apparatus of claim 160, further comprising means for printing an image based on compressed and uncompressed raster lines..Iaddend..Iadd.164. The apparatus of claim 160, wherein said compressing means further comprise: means for compressing at least a portion of a set of raster lines at a first compression density;   means for determining when said memory is insufficient to contain said compressed raster lines;   means for further compressing said compressed portion of said set of raster lines using a second compression density, said second compression density being denser than said first compression density..Iaddend..Iadd.165. The apparatus of claim 164, wherein said first compression density is selected based on a sensed parameter, said sensed parameter being selected from the group consisting of identification of a printer, characteristics of a printer, examination of drawing instructions, interrogation of a printer, available memory, and combinations thereof..Iaddend..Iadd.166. The apparatus of claim 160, wherein said compressing means comprises using a data compression technique enabling storage in said memory of substantially all of said raster lines. .Iadd.167. The apparatus of claim 166, wherein said data compression technique compresses data to a density which results in a loss of said raster line data accuracy..Iaddend..Iadd.168. The apparatus of claim 167, wherein said data compression technique is a discrete cosine transform..Iaddend..Iadd.169. The apparatus of claim 160, wherein said data compression technique compresses said raster line data to a density which results in a reduction of image resolution..Iaddend..Iadd.170. The apparatus of claim 118, 126, 136, 150, 153, 159, or 160, further comprising:   memory having a finite capacity;   means for successively decomposing drawing instructions into a display list;   means for storing said display list in said memory;   means for determining when said display list reaches a predetermined amount of said finite capacity;   means for modifying or creating said data in accordance with at least one command in said display list in response to a determination that said display list has reached said predetermined amount of said finite   
     
     
        capacity..Iaddend..Iadd.171.  The apparatus of claim 170, wherein said data comprise a plurality of bands of data..Iaddend..Iadd.172. The apparatus of claim 171, wherein said means for modifying or creating said plurality of bands of data further comprises: means for determining whether a display list command affects a successive band of said plurality of bands of data;   means responsive to a determination that a display list command affects a band of data for modifying said band of data in accordance with said display list element..Iaddend..Iadd.173. The apparatus of claim 170, further comprising:   means for determining whether executing a display list command and purging said command would increase the amount of memory available; and   means responsive to a determination that executing and purging said command would increase the amount of memory available, for purging said command after said modifying said data, thereby freeing said memory for additional display list commands..Iaddend.