Patent EP0585522A1 successfully refreshed from Google Patents.
EP0585522A1
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EP
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Page printer having automatic font compression
Assignee: HP Inc
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Filing: 1993-04-21
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Granted: —
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Expires: 2013-04-21
Abstract
Abstract A page printer (10) includes random access memory (RAM) (20) whose capacity is insufficient to store certain page configurations; a processor (12); and a control memory (24) that holds at least one data compression procedure. The page printer (10) performs a font compression method that comprises the steps of: issuing a memory low/out signal (54) when insufficient RAM is available to store portions of an input data stream; if raster graphics images are present in portions of the input data stream, attempting to compress those images to remove the memory low/out signal (58); if no raster graphics images are present in the input data stream, compressing font characters by use of a data compression procedure (62); and if the attempted compression of the raster graphics images is unsuccessful in removing the memory low/out signal, compressing font characters by use of a data compression procedure (62). The page printer also may be controlled to automatically data compress a large size font whose size exceeds a second threshold (which may be related to available printer RAM), under circumstances where a memory low/out signal is not present.
Inventors
- 👤 Gary Zimmerman
- 👤 Russ Campbell
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 20:06
CPC Classifications
G; G06; G06F; G06F3/00; G06F3/12; G06F3/1297; G06K; G06K15/00; G06K2215/00; G06K2215/0002; G06K2215/002; G06K2215/0028; G06K2215/0031; G06K2215/0062; G06K2215/0071
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
176 words
In a peripheral unit (10) that converts an input data stream to a page arranged output and has random access memory (20) that is insufficient to store certain page configurations, said peripheral unit (10) including a processor (12) and a control memory (22) including at least one data compression procedure, said peripheral unit (10) adapted to compress character fonts, said peripheral unit (10) performing a method comprising the steps of: a) issuing a memory low/out signal (54) when insufficient random access memory is available to store portions of said input data stream; b) if graphics images are present (58) in portions of said input data stream, attempting to compress said graphics images to remove said memory low/out signal; c) if said attempted compression recited in step (b) is unsuccessful in removing said memory low/out signal (60), compressing font characters by use of a said data compression procedure (62); and d) if no graphics images are present in said portion of said input data stream, compressing font characters, by use of a said data compression procedure (62).
Claim 2
Dependent Claim
22 words
The method as recited in claim 1, wherein steps, (c) and (d) are applied to character fonts stored in said peripheral unit.
Claim 3
Dependent Claim
27 words
The method as recited in claim 1 wherein, in step (b), a lossless data compression method is employed in said attempt to compress said raster graphics image.
Claim 4
Dependent Claim
41 words
The method as recited in claim 3 comprising the further step of: e) compressing a font character received in said input data stream, irrespective of a said memory out/low signal, if said font character exceeds a first size threshold (132, 134).
Claim 5
Dependent Claim
46 words
The method as recited in claim 5 wherein each font character is accompanied by data that enables a size of a character to be determined, said data being compared against said first size threshold to determine if said font character exceeds said first size threshold (132).
Claim 6
Dependent Claim
131 words
In a peripheral unit (10) that converts an input data stream to a page arranged output and has random access memory (20) that is insufficient to store certain page configurations, said peripheral unit (10) including a processor (12) and a control memory (22) including at least one data compression procedure, said peripheral unit (10) performing a method for compressing fonts received via said input data stream, said method comprising the steps of: a) dividing a font character bit map into a number of sequential bands (32, 34, 36), each said band having a determined number of raster scan rows; b) data compressing each said band of said font character bit map so as to substitute for said bit map, a code (42, 44) that indicates bit arrangements within each said band.
Claim 7
Dependent Claim
47 words
The method as recited in claim 6, wherein a first data compression method employed in step (b) provides commands which indicate vertical redundancies existing between succeeding rows of a band of raster data and further provides commands indicative of horizontal data redundancies occurring in a said row.
Claim 8
Dependent Claim
132 words
The method as recited in claim 7, wherein said data compression method employed in step (b) comprises the further steps of: performing run-length encoding (252) for data segments in an initial row of a said band of raster scan rows and outputting, for each run of a data segment in a said raster scan row, a run length command indicating a run count and an identification of the run data segment; for data segments in a subsequent row of said band, comparing (256) whether said data segments are the same as or different from data segments in an immediately previous raster scan row in said band; and issuing commands which identify for said subsequent raster scan row, which of said data segments exhibits a "same" condition and further indicates "different" data segments.
Claim 9
Dependent Claim
66 words
The method as recited in claim 7 comprising the further step of: determining (112) if said first data compression method compressed said font character and if not and if said font character size is less than a predetermined threshold, employing (120) a second data compression method on said font character that identifies runs of like bits in each band raster bit map of said font character.
Claim 10
Dependent Claim
48 words
The method as recited in claim 9 wherein a count of like bits is represented by an n-bit data segment, with a first field of n/2 bits representative of a one bit run count and a second field of n/2 bits representative of a 0 bit run count.
Claim 11
Dependent Claim
47 words
The method as recited in claim 10 wherein a count of bits of one kind that exceeds the ability of n/2 bits to represent, is evidenced by succeeding n-bit data segments, each with the field representative of a number of second kind bits set equal to zero.
Claim 12
Dependent Claim
86 words
The method as recited in claim 6 wherein a said page configuration is divided into a plurality of strips (200, 202, 204), portions of a font character present in at least a pair of contiguous strips (200, 202), the method comprising the further steps of: c) determining (222) which band comprising a font character intersects a boundary between said contiguous strips and is present in a strip being processed; and d) decompressing (226) a said compressed character by commencing with the band that intersects said boundary.
Claim 13
Dependent Claim
60 words
The method as recited in claim 12 wherein step (d) comprises the further steps of: converting (226) said band into a plurality of raster scan rows; and selecting (228) for said strip being processed a portion of said band that commences with a raster scan row that is the same as a first raster row of said strip being processed.
Claim 14
Dependent Claim
69 words
In a peripheral unit (10) that converts an input data flow to a page arranged output, said data flow including data describing an image, said data flow further containing font data, the method comprising the step of: automatically applying (132, 134) a lossless compression technique to said font data if a font represented by said font data is at least equal in size to a predetermined first threshold value.
Claim 15
Dependent Claim
48 words
The method of claim 14 wherein, if said font size is not equal to said predetermined level, applying a lossless compression procedure (188) to said font data only in the event random access memory is insufficient in capacity to store information derived from said input data flow (178).
Claim 16
Dependent Claim
40 words
The method of claim 15 wherein said lossless compression procedure is applied to font data only in the event said font data exceeds a second threshold value (184) in size, said second threshold value less than said first threshold value.
Claim 17
Dependent Claim
38 words
The method of claim 16, comprising the further step of: automatically revising a said threshold value in accordance with available memory so that compression/decompression time is not expended if sufficient memory is available to store uncompressed font data.
References Cited (Backward Citations)
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