add directory Linux-0.98
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Linux-0.98/Yggdrasil-0.98.3/usr/lib/ghostscript/doc/language.doc
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Linux-0.98/Yggdrasil-0.98.3/usr/lib/ghostscript/doc/language.doc
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Copyright (C) 1989-1992 Aladdin Enterprises. All rights reserved.
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Distributed by Free Software Foundation, Inc.
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This file is part of Ghostscript.
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Ghostscript is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY. No author or distributor accepts responsibility
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to anyone for the consequences of using it or for whether it serves any
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particular purpose or works at all, unless he says so in writing. Refer
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to the Ghostscript General Public License for full details.
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Everyone is granted permission to copy, modify and redistribute
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Ghostscript, but only under the conditions described in the Ghostscript
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General Public License. A copy of this license is supposed to have been
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given to you along with Ghostscript so you can know your rights and
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responsibilities. It should be in a file named COPYING. Among other
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things, the copyright notice and this notice must be preserved on all
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copies.
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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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This file, language.doc, describes the Ghostscript language.
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For an overview of Ghostscript and a list of the documentation files, see
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README.
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The Ghostscript interpreter, except as noted below, is intended to execute
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properly any source program written in a language defined by reference to
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the December 1990 printing of the PostScript Language Reference Manual
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(Second Edition) published by Addison-Wesley (ISBN 0-201-18127-4). The
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Ghostscript language includes the following elements of the PostScript
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(TM) language:
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- The full PostScript Level 1 language, as also defined in the
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first edition of the PostScript Language Reference Manual, ISBN
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0-201-10174-2, Addison-Wesley, 1985.
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- The CMYK color, file system, version 25.0 language, and
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miscellaneous additions listed in sections A.1.4, A.1.6, A.1.7, and A.1.8
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of the Second Edition respectively.
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- The Display PostScript extensions listed in section A.1.3 of the
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Second Edition, but excluding the operators listed in section A.1.2, and
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also excluding setbbox, xshow, xyshow, and yshow. These extensions are
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only available if the dps feature was selected at the time that
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Ghostscript was compiled and linked.
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- A few other PostScript Level 2 operators, listed below.
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Ghostscript also includes a number of operators defined below that are not
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in the PostScript language.
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Stub facilities
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---------------
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The following operators, while provided in the current release, have only
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a partial or dummy implementation.
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Character and font operators:
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cshow, rootfont, setcachedevice2
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Graphics state operators:
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currentblackgeneration, currentcmykcolor, currentcolorscreen,
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currentcolortransfer, currenthalftonephase, currentundercolorremoval,
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setblackgeneration, setcmykcolor, setcolorscreen,
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setcolortransfer, sethalftonephase, setundercolorremoval,
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currenthalftone, sethalftone,
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setbbox
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Interpreter parameter operators:
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setucacheparams, ucachestatus
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Path construction operators:
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ucache
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Virtual memory operators:
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currentshared, scheck, setshared, setvmthreshold, shareddict,
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SharedFontDirectory, vmreclaim
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Level 2 operators
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-----------------
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The following PostScript Level 2 operators are available in
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Ghostscript. Unless otherwise noted, these are only available if the
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level2 feature was selected at the time that Ghostscript was compiled
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and linked.
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File operators:
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filter (not all filters are implemented, and most of the
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implemented ones are only available if the filter feature was
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selected when Ghostscript was built)
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Graphics state operators:
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currentcolor, currentcolorspace, setcolor, setcolorspace
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(for DeviceGray, DeviceRGB, and DeviceCMYK only)
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currentstrokeadjust, setstrokeadjust (even if level2 is
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not selected)
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In addition, Ghostscript supports the following Level 2 facilities:
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- Use of a string with the status operator (even if level2 is
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not selected);
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- Use of a dictionary with the image and imagemask operators;
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- Use of a string or a file as data source with the image,
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imagemask, and colorimage operators (even if level2 is not selected).
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Ghostscript-specific additions
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==============================
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Miscellaneous
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-------------
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^Z is counted as whitespace.
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run can take either a string or a file as its argument. In the former
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case, it uses findlibfile to open the file (searching directories as
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needed). In the latter case, it just runs the file, closing it at the
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end, and trapping errors just as for the string case.
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Mathematical operators
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----------------------
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<number> arccos <number>
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Computes the arc cosine of a number between -1 and 1.
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<number> arcsin <number>
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Computes the arc sine of a number between -1 and 1.
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Dictionary operators
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--------------------
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<dict> <integer> setmaxlength -
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Changes the capacity of a dictionary, preserving its
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contents. Causes a dictfull error if the requested
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capacity is less than the current number of occupied
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entries.
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String operators
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----------------
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<string|name|other> <patternString> stringmatch <boolean>
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Determines whether the string or name matches the given
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pattern. In the pattern, `*' matches any substring of
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the string, `?' matches any single character, and `\'
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quotes the next character. If the first argument is not
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a string or name, stringmatch returns true if
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patternString is a single *, and false otherwise.
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<state> <fromString> <toString> type1encrypt <newState> <toSubstring>
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Encrypts fromString according to the algorithm for Adobe
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Type 1 fonts, writing the result into toString.
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toString must be at least as long as fromString or a
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rangecheck error occurs. state is the initial state of
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the encryption algorithm (a 16-bit non-negative
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integer); newState is the new state of the algorithm.
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<state> <fromString> <toString> type1decrypt <newState> <toSubstring>
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Decrypts fromString according to the algorithm for Adobe
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Type 1 fonts, writing the result into toString. Other
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specifications are as for type1encrypt.
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Relational operators
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--------------------
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<number|string> <number|string> max <number|string>
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Returns the larger of two numbers or strings.
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<number|string> <number|string> min <number|string>
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Returns the smaller of two numbers or strings.
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File operators
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--------------
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<string> findlibfile <foundstring> <file> true or <string> false
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Opens the file of the given name for reading. If the file
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cannot be opened using the supplied name, searches
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through directories as described in use.doc. If the
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search fails, findlibfile simply pushes false on the
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stack and returns, rather than causing an error.
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<file> <integer> unread -
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Pushes back the last-read character onto the front of the
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file. If the file is only open for writing, or if the
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integer argument is not the same as the last character
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read from the file, causes an ioerror error. May also
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cause an ioerror if the last operation on the file was not
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a reading operation.
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<file> <device> writeppmfile -
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Writes the contents of the device, which must be an image
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device, onto the file, in Portable PixMap (ppm) format.
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Does not close the file.
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Path operators
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--------------
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<x> <y> <width> <height> rectappend -
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<numarray> rectappend -
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<numstring> rectappend -
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Appends a rectangle or rectangles to the current path, in
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the same manner as rectfill, rectclip, etc. Only
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defined if the dps option is selected.
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Filters
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-------
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Ghostscript supports all standard filters except DCTEncode and
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DCTDecode. Ghostscript does not support the use of a procedure as a
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data source or sink, only a file or a string. In addition,
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Ghostscript supports two non-standard filters:
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<file|string> <seed_integer> /eexecDecode filter <file>
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Creates a filter for decrypting data that has been
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encrypted using eexec encryption as described in the
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Adobe Type 1 Font Format documentation. The
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seed_integer must be 55665 for proper operation.
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<file|string> <hex_boolean> /PFBDecode filter <file>
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Creates a filter that decodes data in .PFB format, the
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usual semi-binary representation for Type 1 font files
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on IBM PC and compatible systems. If hex_boolean is true,
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binary packets are converted to hex; if false, binary
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packets are not converted.
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Miscellaneous operators
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-----------------------
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- currenttime <number>
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Returns the current value of a continuously-running timer,
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in minutes. The initial value of this timer is undefined.
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<string> getenv <string> true or false
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Looks up a name in the shell environment. If the name is
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found, returns the corresponding value and true; if the
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name is not found, returns false.
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<name> <array> makeoperator <operator>
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Constructs and returns a new operator that is actually the
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given procedure in disguise. The name is only used for
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printing. The operator has the executable attribute.
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<string> <boolean> setdebug -
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If the Ghostscript interpreter was built with the DEBUG
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flag set, sets or resets any subset of the debugging
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flags normally controlled by -Z in the command line.
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Has no effect otherwise.
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Device operators
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----------------
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<device> copydevice <device>
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Copies a device.
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<index> getdevice <device>
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Returns a device from the set of devices known to the
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system. The first device, which is default, is numbered
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0. If the index is out of range, causes a rangecheck
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error.
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<matrix> <width> <height> <palette> makeimagedevice <device>
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Makes a new device that accumulates an image in memory.
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matrix is the initial transformation matrix: it must be
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orthogonal (i.e., [a 0 0 b x y] or [0 a b 0 x y]).
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palette is a string of 2^N or 3*2^N elements, specifying
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how the 2^N possible pixel values will be interpreted.
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Each element is interpreted as a gray value, or as RGB
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values, multiplied by 255. For example, if you want
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a monochrome image for which 0=white and 1=black, the
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palette should be <ff 00>; if you want a 3-bit deep
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image with just the primary colors and their complements
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(ignoring the fact that 3-bit images are not supported),
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the palette might be <000000 0000ff 00ff00 00ffff
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ff0000 ff00ff ffff00 ffffff>. At present,
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the palette must contain exactly 2 or 256 entries,
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and must contain an entry for black and an entry
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for white; if it contains any entries that aren't black,
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white, or gray, it must contain at least the six primary
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colors (red, green, blue, and their complements cyan,
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magenta, and yellow); aside from this, its contents are
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arbitrary. (4-entry or 16-entry palettes, corresponding
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to 2- or 4-bit pixels, may be supported eventually.)
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Alternatively, palette can be null. This is interpreted
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as 32-bit-per-pixel color, where the four bytes of each
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pixel are respectively unused, R, G, and B.
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Note that one can also make an image device (with the same
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palette as an existing image device) by copying a device
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using the copy operator.
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<device> <index> <string> copyscanlines <substring>
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Copies one or more scan lines from an image device into a
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string, starting at a given scan line in the image.
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The data is in the same format as for the image
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operator. Error if the device is not an image device or
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if the string is too small to hold at least one complete
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scan line. Always copies an integral number of scan
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lines.
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<device> setdevice -
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Sets the current device to the specified device. Also
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resets the transformation and clipping path to the
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initial values for the device.
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- currentdevice <device>
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Gets the current device from the graphics state.
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<device> devicename <string>
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Gets the name of a device.
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<device> <matrix> deviceinitialmatrix <matrix>
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Gets the initial matrix of a device, i.e., the one that
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defaultmatrix would return if the device were the
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current device.
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<device> getdeviceprops <mark> <name1> <value1> ... <namen> <valuen>
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Gets all the properties of a device. Currently defined
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names and values for all devices are:
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HWResolution [<float> <float>]
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X and Y resolution in pixels/inch.
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HWSize [<integer> <integer>]
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X and Y size in pixels.
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InitialMatrix [<6 floats>]
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Initial transformation matrix.
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Name <string>
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Read-only. The device name.
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For printers, the following are also defined:
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BufferSpace <integer>
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Buffer space for band lists, if the bitmap
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is too big to fit in RAM.
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MaxBitmap <integer>
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Maximum space for a full bitmap in RAM.
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OutputFile <string>
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() means send to printer directly,
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otherwise specifies the file name for
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output; a %d is replaced by the page #;
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on Unix systems, (|command) writes to a pipe
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PageCount <integer>
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Read-only. Counts the number of pages
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printed on the device.
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<mark> <name1> <value1> ... <namen> <valuen> <device>
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putdeviceprops <device>
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Sets properties of a device. May cause undefined,
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typecheck, rangecheck, or limitcheck errors.
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- flushpage -
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On displays, flushes any buffered output, so that it
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is guaranteed to show up on the screen; on printers,
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has no effect.
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Character operators
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-------------------
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<string> type1addpath -
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Adds the description of a character to the current path,
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and then optionally renders the character. The string
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argument is a scalable description encoded in Adobe Type
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1 format. This operator is only valid in the context of
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a show operator, like setcharwidth and setcachedevice.
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It uses information from the current font, in addition
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to the argument.
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<font> <char> Type1BuildChar -
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This is not a new operator: rather, it is a name known
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specially to the interpreter. Whenever the interpreter
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needs to render a character (during a ...show,
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stringwidth, or charpath), it looks up the name
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BuildChar in the font dictionary to find a procedure to
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run. If it does not find this name, and if the FontType
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is 1, the interpreter instead uses the value (looked up
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on the dictionary stack in the usual way) of the name
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Type1BuildChar.
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The standard definition of Type1BuildChar is in gs_fonts.ps.
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Users should not need to redefine Type1BuildChar, except
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perhaps for tracing or debugging.
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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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PostScript is a trademark of Adobe Systems, Incorporated.
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