NAME

PostScript::File - Base class for creating Adobe PostScript files

SYNOPSIS

    use PostScript::File qw(check_tilde check_file
		    incpage_label incpage_roman);

At its simplest, an 'hello world' program:

    use PostScript::File;

    my $ps = new PostScript::File();
    
    $ps->add_to_page( <<END_PAGE );
	/Helvetica findfont 
	12 scalefont 
	setfont
	72 300 moveto
	(hello world) show
    END_PAGE
    
    $ps->output( "~/test" );
    

DESCRIPTION

This module provides the outline for an Adobe PostScript file. Functions allow access to each of Adobe's Document Structuring Convention (DSC) sections and control how the pages are constructed. It is possible to construct and output files in either normal PostScript (*.ps files) or as Encapsulated Postscript (*.epsf or *.epsi files). By default a minimal file is output, but support for font encoding, postscript error reporting and debugging can be built in if required.

Documents can typically be built using only these functions:

new		  The constructor, with many options
add_function  Add postscript functions to the prolog
add_to_page	  Add postscript to construct each page 
newpage	  Begins a new page in the document
output	  Construct the file and saves it

The rest of the module involves fine-tuning this. Some settings only really make sense when given once, while others can control each page independently. See new for the functions that duplicate option settings, they all have get_ counterparts. The following provide additional support.

get/set_bounding_box
get/set_page_bounding_box
get/set_page_clipping
get/set_page_landscape
set_page_margins
get_ordinal
get_pagecount
draw_bounding_box
clip_bounding_box

The functions which insert entries into each of the DSC sections all begin with 'add_'. They also have get_ counterparts.

add_comment
add_preview
add_default
add_resource
add_function
add_setup
add_page_setup
add_to_page
add_page_trailer
add_trailer

Finally, there are a few stand-alone functions. These are not methods and are available for export if requested.

check_tilde 
check_file 
incpage_label 
incpage_roman

CONSTRUCTOR

new( options )

Create a new PostScript::File object, either a set of pages or an Encapsulated PostScript (EPS) file. Options are hash keys and values. All values should be in the native postscript units of 1/72 inch.

Example

    $ref = new PostScript::File ( 
		eps => 1,
		landscape => 1,
                width => 216,
                height => 288,
		left => 36,
		right => 44,
		clipping => 1 );

This creates an encapsulated postscript document, 4 by 3 inch pages printing landscape with left and right margins of around half an inch. The width is always the shortest side, even in landscape mode. 3*72=216 and 4*72=288. Being in landscape mode, these would be swapped. The bounding box used for clipping would then be from (50,0) to (244,216).

options may be a single hash reference instead of an options list. This is more convenient when used as a base class.

In addition, the following keys are recognized. First, four options which control how much gets put into the resulting file.

headings

Enable PostScript comments such as the date of creation and user's name.

errors

By default postscript fails silently. Setting this to 1 prints fatal error messages on the bottom left of the paper. For user functions, a postscript function report_error is defined. This expects a message string on the stack, which it prints before stopping.

debug

undef

No debug code is added to the file. Of course there must be no calls to debug functions in the postscript code.

0

db_ functions are replaced by dummy functions which do nothing.

1

A range of functions are added to the file to support debugging postscript. This switch is similar to the 'C' NDEBUG macro in that debugging statements may be left in the postscript code but their effect is removed.

Of course, being an interpreted language, it is not quite the same as the calls still takes up space - they just do nothing. See "POSTSCRIPT DEBUGGING SUPPORT" for details of the functions.

2

Loads the debug functions and gives some reassuring output at the start and a stack dump at the end of each page.

A mark is placed on the stack at the beginning of each page and 'cleartomark' is given at the end, avoiding potential invalidrestore errors. Note, however, that if the page does not end with a clean stack, it will fail when debugging is turned off.

reencode

Requests that a font re-encode function be added and that the 13 standard PostScript fonts get re-encoded in the specified encoding. The only recognized value so far is 'ISOLatin1Encoding' which selects the iso8859-1 encoding and fits most of western Europe, including the Scandinavia.

Next, there are a few initialization settings that are only relevant when the file object is constructed.

eps

Set to 1 to produce Encapsulated PostScript. get_eps returns the value set here. (Default: 0)

paper

Set the paper size of each page. A document can be created using a standard paper size without having to remember the size of paper using PostScript points. Valid choices are currently A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, B0, B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, Executive, Folio, 'Half-Letter', Letter, 'US-Letter', Legal, 'US-Legal', Tabloid, 'SuperB', Ledger, 'Comm #10 Envelope', 'Envelope-Monarch', 'Envelope-DL', 'Envelope-C5', 'EuroPostcard'. (Default: "A4")

This also sets width and height. get_paper returns the value set here.

width

height

Set the page width and height. The height is the longest edge of the paper. (Default taken from paper)

The paper size is set to "Custom". get_width and get_height return the values set here.

left

bottom

right

top

These are margins in from the paper edges to specify non-printable areas on the paper. They are all positive offsets, so left=36 and right=36 will leave a half inch no-go margin on each side of the page. Remember to specify clipping if that is what is wanted.

landscape

Set whether the page is oriented horizontally (1) or vertically (0). (Default: 0)

In landscape mode the coordinates are rotated 90 degrees and the origin moved to the bottom left corner. Thus the coordinate system appears the same to the user, with the origin at the bottom left.

clipping

Set whether printing will be clipped to the file's bounding box. (Default: 0)

clipcmd

The bounding box is used for clipping if this is set to "clip" or is drawn with "stroke". This also makes the whole page area available for debugging output. (Default: "clip").

fontsuffix

This string is appended to each font name as it is reencoded. (Default: "-iso")

The standard fonts are named Courier, Courier-Bold, Courier-BoldOblique, Courier-Oblique, Helvetica, Helvetica-Bold, Helvetica-BoldOblique, Helvetica-Oblique, Times-Roman, Times-Bold, Times-BoldItalic, Times-Italic, and Symbol. The string value is appended to these to make the new names.

Example

    $ps = new PostScript::File( 
		fontsuffix => "-iso",
		reencode => "ISOLatin1Encoding"
	    );
	    

"Courier" still has the standard mapping while "Courier-iso" includes the additional European characters.

Debugging support makes most sense in the postscript code rather than perl. However, it is convenient to be able to set defaults for the output position and so on. See "POSTSCRIPT DEBUGGING SUPPORT" for further details.

db_ytop

The top line of debugging output. Defaults to 6 below the top of the page.

db_base

Debug printing will not occur below this point. (Default: 6)

db_xpos

The left edge, where debug output starts. (Default: 6)

db_xtab

The amount indented by db_indent. (Default: 10)

db_xgap

Typically, the output comprises single values such as a column showing the stack contents. db_xgap specifies the width of each column. By default, this is calculated to allow 4 columns across the page.

db_color

This is the whole postscript command (with any parameters) to specify the colour of the text printed by the debug routines. (Default: "0 setgray")

db_font

The name of the font to use. (Default: "Courier")

db_fontsize

The size of the font. Postscript uses its own units, but they are almost points. (Default: 10)

db_bufsize

The size of string buffers used. Output must be no longer than this. (Default: 256)

db_active

Set to 0 to temporarily suppress the debug output. (Default: 1)

If errors is set, the position of any fatal error message can be controlled with the following options. Each value is placed into a postscript variable of the same name, so they can be overridden from within the code if necessary.

errx =head3 erry

Position of the error message on the page. (Default: (72, 72))

errmsg

The error message comprises two lines. The second is the name of the postscript error. This sets the first line. (Default: "ERROR:")

errfont

errsize

Font name and font size of the error message. (Default: "Courier-Bold", 12)

There are options which only affect the DSC comments. They all have get_ functions which return the values set here, e.g. get_title returns the value given to the title option.

title

Set the document's title as recorded in PostScript's Document Structuring Conventions. (No default)

version

Set the document's version as recorded in PostScript's Document Structuring Conventions. This should be a string with a major, minor and revision numbers. For example "1.5 8" signifies revision 8 of version 1.5. (No default)

langlevel

Set the PostScript language level. (No default)

extensions

Declare and PostScript language extensions that need to be available. (No default)

order

Set the order the pages have been defined. It should one of "ascend", "descend" or "special" if a document manager must not reorder the pages. (No default)

Finally, a few that may be changed between pages.

page

Set the label (text or number) for the initial page. See "set_page_label". (Default: "1")

incpage_handler

Set the initial value for the function which increments page labels. See "set_incpage_handler".

strip

Set whether the postscript code is filtered. space strips leading spaces so the user can indent freely without increasing the file size. comments remove lines beginning with '%' as well. (Default: "space")

MAIN METHODS

newpage( [page] )

Generate a new PostScript page, unless in a EPS file when it is ignored.

If page is not specified the page number is increased each time a new page is requested.

page can be a string or a number. If anything other than a simple integer, you probably should register your own counting function with set_incpage_handler. Of course there is no need to do this if a page string is given to every newpage call.

output( [filename [, dir]] )

Writes the current PostScript out to file. It is printed to STDOUT if no filename has been given either here, to new or set_filename.

Use this option whenever output is required to disk. The current PostScript document in memory is not cleared, and can still be extended.

ACCESS METHODS

Use these get_ and set_ methods to access a PostScript::File object's data.

get_filename()

set_filename( file, [dir] )

file

An optional fully qualified path-and-file, a simple file name, or "" which stands for the special file File::Spec->devnull().

dir

An optional directory dir. If present (and file is not already an absolute path), it is prepended to file.

Specify the root file name for the output file(s) and ensure the resulting absolute path exists. This should not include any extension. .ps will be added for ordinary postscript files. EPS files have an extension of .epsf without or .epsi with a preview image.

If eps has been set, multiple pages will have the page label appendend to the file name.

Example

    $ps->new PostScript::File( eps => 1 );
    $ps->set_filename( "pics", "~/book" );
    $ps->newpage("vi");
	... draw page
    $ps->newpage("7");
	... draw page
    $ps->newpage();
	... draw page
    $ps->output();

The three pages for user 'chris' on a unix system would be:

/home/chris/book/pics-vi.epsf
/home/chris/book/pics-7.epsf
/home/chris/book/pics-8.epsf

It would be wise to use set_page_bounding_box explicitly for each page if using multiple pages in EPS files.

get_strip

set_strip( "none" | "space" | "comments" )

Determine whether the postscript code is filtered. space strips leading spaces so the user can indent freely without increasing the file size. comments remove lines beginning with '%' as well.

get_page_landscape( [page] )

set_page_landscape( [[page,] landscape] )

Inspect and change whether the page specified is oriented horizontally (1) or vertically (0). The default is the global setting as returned by get_landscape. If page is omitted, the current page is assumed.

get_page_clipping( [page] )

set_page_clipping( [[page,] clipping] )

Inspect and change whether printing will be clipped to the page's bounding box. (Default: 0)

get_page_label()

set_page_label( [page] )

Inspect and change the number or label for the current page. (Default: "1")

This will be automatically incremented using the function set by set_incpage_hander.

get_incpage_handler()

set_incpage_handler( [handler] )

Inspect and change the function used to increment the page number or label. The following suitable values for handler refer to functions defined in the module:

\&PostScript::File::incpage_label
\&PostScript::File::incpage_roman

The default (incpage_label) increments numbers and letters, the other one handles roman numerals up to 39. handler should be a reference to a subroutine that takes the current page label as its only argument and returns the new one. Use this to increment pages using roman numerals or custom orderings.

get_bounding_box()

set_bounding_box( x0, y0, x1, y1 )

Inspect or change the bounding box for the whole document, showing only the area inside.

Clipping is enabled. Call with set_clipping with 0 to stop clipping.

get_page_bounding_box( [page] )

set_page_bounding_box( [page], x0, y0, x1, y1 )

Inspect or change the bounding box for a specified page. If page is not specified, the current page is assumed, otherwise it should be a page label already given to newpage or set_page_label. The page bounding box defaults to the paper area.

Note that this automatically enables clipping for the page. If this isn't what you want, call set_page_clipping with 0.

set_page_margins( [page], left, bottom, right, top )

An alternative way of changing a single page's bounding box. Unlike the options given to new, the parameters here are the gaps around the image, not the paper. So left=36 will set the left side in by half an inch, this might be a short side if landscape is set.

Note that this automatically enables clipping for the page. If this isn't what you want, call set_page_clipping with 0.

get_ordinal( [page] )

Return the internal number for the page label specified. (Default: current page)

Example

Say pages are numbered "i", "ii", "iii, "iv", "1", "2", "3".

get_ordinal("i") == 0
get_ordinal("iv") == 3
get_ordinal("1") == 4

get_pagecount()

Return the number of pages currently known.

CONTENT METHODS

get_comments()

add_comment( comment )

Most of the required and recommended comments are set directly, so this function should rarely be needed. It is provided for completeness so that comments such as DocumentNeededResources: can be added. The comment should be the bare PostScript DSC name and value, with additional lines merely prefixed by +.

Example

$ps->add_comment("ProofMode: NotifyMe");
$ps->add_comment("Requirements: manualfeed");
$ps->add_comment("DocumentNeededResources:");
$ps->add_comment("+ Paladin");
$ps->add_comment("+ Paladin-Bold");

get_preview()

add_preview( width, height, depth, lines, preview )

Use this to add a Preview in EPSI format - an ASCII representation of a bitmap. If an EPS file has a preview it becomes an EPSI file rather than EPSF.

get_defaults()

add_default( default )

Use this to add any PostScript DSC comments to the Defaults section. These would be typically values like PageCustomColors: or PageRequirements:.

get_resources()

add_resource( type, name, params, resource )

type

A string indicating the DSC type of the resource. It should be one of Document, Resource, File, Font, ProcSet or Feature (case sensitive).

name

An arbitrary identifier of this resource.

params

Some resource types require parameters. See the Adobe documentation for details.

resource

A string containing the postscript code. Probably best provided a 'here' document.

Use this to add fonts or images. add_function is provided for functions.

Example

    $ps->add_resource( "File", "My_File1", 
		       "", <<END_FILE1 );
	...postscript resource definition
    END_FILE1

Note that get_resources returns all resources added, including those added by any inheriting modules.

get_functions()

add_function( name, code )

Add user defined functions to the PostScript prolog. Despite the name, it is better to add related functions in the same code section. name is an arbitrary identifier of this resource. Best used with a 'here' document.

Example

    $ps->add_function( "My_Functions", <<END_FUNCTIONS );
	% postscript code can be freely indented
	% as leading spaces and blank lines 
	% (and comments, if desired) are stripped
	
	% foo does this...
	/foo {
	    ... definition of foo
	} bind def

	% bar does that...
	/bar {
	    ... definition of bar
	} bind def
    END_FUNCTIONS

Note that get_functions (in common with the others) will return all user defined functions possibly including those added by other classes.

has_function( name )

This returns true if name has already been included in the file. The name should identical to that given to "add_function".

get_setup()

set_setup( code )

Direct access to the %%Begin(End)Setup section. Use this for setpagedevice, statusdict or other settings that initialize the device or document.

get_page_setup()

set_page_setup( code )

Code added here is output before each page. As there is no special provision for %%Page... DSC comments, they should be included here.

Note that any settings defined here will be active for each page seperately. Use add_setup if you want to carry settings from one page to another.

get_page( [page] )

add_to_page( [page], code )

The main function for building the postscript output. page can be any label, typically one given to set_page_label. (Default: current page)

If page is not recognized, a new page is added with that label. Note that this is added on the end, not in the order you might expect. So adding "vi" to page set "iii, iv, v, 6, 7, 8" would create a new page after "8" not after "v".

Examples

    $ps->add_to_page( <<END_PAGE );
	...postscript building this page
    END_PAGE
    
    $ps->add_to_page( "3", <<END_PAGE );
	...postscript building page 3
    END_PAGE
    

The first example adds code onto the end of the current page. The second one either adds additional code to page 3 if it exists, or starts a new one.

get_page_trailer()

set_page_trailer( code )

Code added here is output after each page. It may refer to settings made during set_page_setup or add_to_page.

get_trailer()

set_trailer( code )

Add code to the PostScript %%Trailer section. Use this for any tidying up after all the pages are output.

POSTSCRIPT DEBUGGING SUPPORT

This section documents the postscript functions which provide debugging output. Please note that any clipping or bounding boxes will also hide the debugging output which by default starts at the top left of the page. Typical new options required for debugging would include the following.

    $ps = PostScript::File->new ( 
	    errors => "page",
	    debug => 2,
	    clipcmd => "stroke" );

The debugging output is printed on the page being drawn. In practice this works fine, especially as it is possible to move the output around. Where the text appears is controlled by a number of postscript variables, most of which may also be given as options to new.

The main controller is db_active which needs to be non-zero for any output to be seen. It might be useful to set this to 0 in new, then at some point in your code enable it.

/db_active 1 def
(this will now show) db_show

At any time, the next output will appear at db_xpos and db_ypos. These can of course be set directly. However, after most prints, the equivalent of a 'newline' is executed. It moves down db_fontsize and left to db_xpos. If, however, that would take it below db_ybase, db_ypos is reset to db_ytop and the x coordinate will have db_xgap added to it, starting a new column.

The positioning of the debug output is changed by setting db_xpos and db_ytop to the top left starting position, with db_ybase guarding the bottom. Extending to the right is controlled by not printing too much! Judicious use of db_active can help there.

Postscript functions

x0 y0 x1 y1 cliptobox

This function is only available if 'clipping' is set. By calling the perl method draw_bounding_box (and resetting with clip_bounding_box) it is possible to use this to identify areas on the page.

    $ps->draw_bounding_box();
    $ps->add_to_page( <<END_CODE );
	...
	my_l my_b my_r my_t cliptobox
	...
    END_CODE
    $ps->clip_bounding_box();

msg report_error

If 'errors' is enabled, this call allows you to report a fatal error from within your postscript code. It expects a string on the stack and it does not return.

All the db_ variables (including function names) are defined within their own dictionary (debugdict). But this can be ignored by all calls originating from within code passed to add_to_page (usually including add_function code) as the dictionary is automatically put on the stack before each page and taken off as each finishes.

any db_show

The workhorse of the system. This takes the item off the top of the stack and outputs a string representation of it. So you can call it on numbers or strings and it will show them. Arrays are printed using db_array and marks are shown as '--mark--'.

n msg db_nshow

This shows top n items on the stack. It requires a number and a string on the stack, which it removes. It prints out msg then the top n items on the stack, assuming there are that many. It can be used to do a labelled stack dump. Note that if new was given the option debug = 2>, There will always be a '--mark--' entry at the base of the stack. See "debug".

count (at this point) db_nshow

db_stack

Prints out the contents of the stack. No stack requirements.

The stack contents is printed top first, the last item printed is the lowest one inspected.

array db_print

The closest this module has to a print statement. It takes an array of strings and/or numbers off the top of the stack and prints them with a space in between each item.

[ (myvar1=) myvar1 (str2=) str2 ] db_print

will print something like the following.

myvar= 23.4 str2= abc

When printing something from the stack you need to take into account the array-building items, too. In the next example, at the point '2 index' is given, the stack holds '222 111 [ (top=)' but '5 index' is required to get at 222 because the stack now holds '222 111 [ (top=) 111 (next=)'.

222 111
[ (top=) 2 index (next=) 5 index ] db_print

willl output this.

top= 111 next= 222

It is important that the output does not exceed the string buffer size. The default is 256, but it can be changed by giving new the option bufsize.

x y msg db_point

It is common to have coordinates as the top two items on the stack. This call inspects them. It pops the message off the stack, leaving x and y in place, then prints all three.

450 666
(starting point=) db_print
moveto

would produce:

starting point= ( 450 , 666 )

array db_array

Like "db_print" but the array is printed enclosed within square brackets.

db_newcol

Starts the next debugging column. No stack requirements.

db_down

Does a 'carriage-return, line-feed'. No stack requirements.

db_indent

Moves output right by db_xtab. No stack requirements. Useful for indenting output within loops.

db_unindent

Moves output left by db_xtab. No stack requirements.

EXPORTED FUNCTIONS

incpage_label( label )

The default function for set_incpage_handler which just increases the number passed to it. A useful side effect is that letters are also incremented.

incpage_roman( label )

An alternative function for set_incpage_handler which increments lower case roman numerals. It only handles values from "i" to "xxxix", but that should be quite enough for numbering the odd preface.

check_file( file, [dir, [create]] )

file

An optional fully qualified path-and-file or a simple file name. If omitted, the special file File::Spec->devnull() is returned.

dir

An optional directory dir. If present (and file is not already an absolute path), it is prepended to file.

create

If non-zero, ensure the file exists. It may be necessary to set dir to "" or undef.

This ensures the filename returned is valid and in a directory tree which is created if it doesn't exist.

Any leading '~' is expanded to the users home directory. If no absolute directory is given either as part of file, it is placed within the current directory. Intervening directories are always created. If create is set, file is created as an empty file, possible erasing any previous file of the same name.

File::Spec|File::Spec is used throughout so file access should be portable.

check_tilde( dir )

Expands any leading '~' to the home directory.

BUGS

When making EPS files, the landscape transformation throws the coordinates off. To work around this, avoid the landscape flag and set width and height differently.

Most of these functions have only had a couple of tests, so please feel free to report all you find.

AUTHOR

Chris Willmot, chris@willmot.org.uk

Thanks to Johan Vromans for the ISOLatin1Encoding.

SEE ALSO

PostScript Language Document Structuring Conventions Specification Version 3.0 published by Adobe, 1992.

Encapsulated PostScript File Format Specification Version 3.0 published by Adobe, 1992.

cpanm PostScript::File

perl -MCPAN -e shell
install PostScript::File