Facsimile and static presentation processing – Static presentation processing – Character or font
Reexamination Certificate
1998-05-22
2001-06-26
Coles, Edward (Department: 2722)
Facsimile and static presentation processing
Static presentation processing
Character or font
C358S001100, C358S001120, C358S001130, C358S001140, C358S001150, C358S001160, C358S001170
Reexamination Certificate
active
06252671
ABSTRACT:
BACKGROUND
The invention relates to the transmission of fonts to a hardcopy device. More particularly, the invention relates to the transmission of fonts to a hardcopy device using a page description language.
Continual advances in computer technology are making possible cost-effective computers capable of displaying images and text at high resolution. Concurrently, user friendly operating systems with a graphical user interface (GUI) have been developed to take advantage of computer hardware. These operating systems support multiple fonts which allows users to be more proficient and effective at tasks such as desktop publishing.
The multi-font capability on GUI operating systems in turn is driving the demand for high resolution hard copy devices or printers. Typically, a computer sends data to a hard copy device such as a printer in the form of characters or images to be printed. For characters, the printer receives the character data and places ink onto a sheet of paper in accordance with glyphs associated with the characters. Glyphs are objects which specify exact shapes of characters. In this context, a font is a collection of glyphs, all of a similar design.
Early printers had a limited number of fonts and characters in their character generators. The characters were typically laid out in matrix structures known as bitmaps, or rectangular arrays of bits where each bit represents a pixel that may be turned on during the generation of that character onto paper. Originally, the bitmaps were stored in Read Only Memory (ROM) devices. However, as only a fixed number of fonts may be supported by the ROM device, Random Access Memory (RAM) devices were added to allow fonts to be downloaded from the computer to the printer. To provide more flexibility and higher quality output, page description languages were developed whereby a page with graphics, text, and images that may be positioned anywhere on the page, and in any order, is represented using successive commands of the page description language.
One popular page description language is the PostScript® page description language available from Adobe Systems, Inc. of San Jose, California. The PostScript® page description language is described in more detail in a document entitled
PostScript Language Reference Manual,
2d. ed. (1993), available from Adobe Systems, Inc., and hereby incorporated by reference. In PostScript® compatible printers, after receiving the commands, a desired image is rasterized so that a print engine in the printer can generate the page by turning on or off a series of individual dots or pixels across the printed page in a raster scan line.
In certain personal computers which work with a Microsoft Windows 95® operating system available from Microsoft Corporation of Redmond, Washington, applications may specify a host system font such as a TrueType font or a PostScript® font. During printing, the TrueType or PostScript® line layout determination requires accesses to font specific glyphs and thus these glyphs need to be downloaded to the printer. Generally, when an application sends glyph data with the host font to a PostScript® compatible printer, software drivers on the computer may convert host font glyphs into unscalable bitmaps, unhinted outlines, or native TrueType or PostScript® font data into PostScript® formatted data. The driver software may analyze glyph usage within a document, determine glyph dependencies, and send only the glyphs required for the current print job to the printer. However, such an approach may require a significant amount of host memory storage and processor capacity. Moreover, such an approach may greatly increase the amount of data being sent to the printer. As such, the printer may require a substantial amount of memory to handle the data stream generated by the computer. Such memory requirements may also cause the software driver to free previously used memory in the printer in order to allocate space for the additional glyphs. However, in the event that subsequent commands access a released glyph, the released glyph must be resent to the printer. Hence, the computer and the printer's throughputs may be substantially reduced.
SUMMARY OF THE INVENTION
In accordance with the present invention, an apparatus downloads a font available on a computer to an output device which supports a page description language such as PostScript®. The page description language has a page description language download format for supporting complex fonts. The apparatus determines whether a character set associated with the font can be represented as a byte and if so, downloads the font to the output device using a first format. Otherwise, the apparatus determines whether the number of glyphs in the font is below a threshold such as 2
14
(16K) glyphs and if so, downloads the font to the output device using the page description download format. Otherwise, the apparatus breaks the font glyph data into one or more blocks of glyph data, each of which having fewer glyphs than the threshold. Once the glyphs have been broken into small blocks, the apparatus downloads the blocks to the output device using the page description language download format. The output device then stitches the blocks together during a subsequent font reassembly.
In one aspect, the apparatus creates PostScript® CIDFont character maps and CIDFont fonts according to vertical or horizontal line layouts of the font available from the operating system. CIDFont character maps and CIDFont fonts are created which support glyph-index based access and character based access. Further, the apparatus creates glyph-ordered vertical and horizontal fonts, as well as character ordered vertical and horizontal fonts.
In another aspect, the apparatus duplicates composite glyphs referenced in a current block but residing in other blocks into a buffer in the current block. Glyphs in the current block as well as the buffer are combined or “stitched” together. The stitching of non-resident referenced composite glyphs together with glyphs in the current block allows all composite glyphs to be defined, even when they reside outside of the current block.
In yet another aspect, unique identification information is generated for each font so that the printer can cache glyphs across print jobs for faster printing. The identification information is also accessible to a printer driver in the computer so that the driver can readily determine whether a version of a downloaded font matches a version on the computer.
In another aspect, the apparatus compresses glyph data before downloading the font-data. The compression may be performed by encoding the font as ASCII85 encoding.
In another aspect, the method transmits the font available on a computer to the output device supporting a PostScript® page description language by breaking the font glyph data into one or more blocks of glyph data; downloading the blocks to the output device using the PostScript® CIDFont format; and in the output device, stitching the referenced composite glyphs together with glyphs in the current block to define all composite glyphs.
Advantages of the present invention include the following. The present invention supports TrueType fonts on a PostScript® compatible printer in a manner that minimizes memory requirements on the printer. Moreover, only a small print file needs to be sent from the computer to the printer. Additionally, the present invention reduces unnecessary or duplicative transmissions data of glyphs in printing TrueType characters. The amount of unnecessary processing is reduced so that the computer may be more responsive to other application's needs. Similarly, the reduced processing and data storage requirements on the printer maximize the printer's effectiveness in serving a wide range of applications.
REFERENCES:
patent: 4907282 (1990-03-01), Daly et al.
patent: 4931960 (1990-06-01), Morikawa
patent: 5410639 (1995-04-01), Gruel
patent: 5579449 (1996-11-01), Strobel
patent: 5602976 (1997-02-01), Cooper et al.
patent: 5771034 (1998-06-01), Gibson
patent:
Jacobs Matthew A.
Patterson John A.
Peng Xiantu
Adobe Systems Incorporated
Coles Edward
Fish & Richardson P.C.
Lamb Twyler
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