1Pstopnm User Manual(0) Pstopnm User Manual(0)
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6 pstopnm - convert a PostScript file to a PNM image
7
10 pstopnm
11 [-stdout]
13 [-forceplain]
15 [-help]
17 [-dpi=dpi]
19 [-xsize=pixels] [-ysize=pixels]
21 [-xborder=frac] [-yborder=frac] [-landscape]
23 [-portrait]
25 [-nocrop]
27 [-pbm
29 |-pgm
31 |-ppm]
33 [-llx=s] [-lly=s] [-urx=s] [-ury=s]
35 [-verbose]
37 [-xmax=pixels] [-ymax=pixels]
39 [-textalphabits={1,2,4}]
41 psfile[.ps]
44
47 Minimum unique abbreviation of option is acceptable. You may use dou‐
48 ble hyphens instead of single hyphen to denote options. You may use
49 white space in place of the equals sign to separate an option name from
50 its value.
51
54 This program is part of Netpbm(1).
55 pstopnm reads a PostScript file as input and produces PBM, PGM, or PPM
57 images as output. This program simply uses GhostScript to render a
58 PostScript file with its PNM device drivers. If you don't have Ghost‐
59 Script installed or the version you have installed was not built with
60 the relevant PNM device drivers, pstopnm will fail. You can see if you
61 have the proper environment by issuing the command gs --help . If it
62 responds and lists under "Available Devices" pbm, pbmraw, pgm, pgmraw,
63 pnm, pnmraw, ppm, or ppmraw, you're in business.
64 It's important to understand that pstopnm is a Netpbm image file format
66 converter only in the broadest sense of the word, because Postscript is
67 far from an image file format. What pstopnm really is is a Postscript
68 renderer - an image generator. One place you'll notice the difference
69 is where you expect pstopnm | pnmtops to be idempotent (which is not
70 the case). There are details on this kind of conversion below.
71 pstopnm uses the value of the GHOSTSCRIPT environment variable as the
73 file name for the Ghostscript program. If GHOSTSCRIPT is not set,
74 pstopnm searches your PATH for a regular file named gs. If it doesn't
75 find one, it assumes Ghostscript is in the file /usr/bin/gs.
76 pstopnm does not use the Netpbm libraries to generate the output files,
78 so may not be entirely consistent with most Netpbm programs.
79 psfile[.ps] is the name of the input file. pstopnm will add the ps to
81 the end of the name you specify if no file exists by the exact name you
82 specify, but one with added does. For Standard Input, use - or just
83 don't give any argument.
84 If you use the -stdout option or your input is from Standard Input,
86 pstopnm outputs images of all the pages as a multi-image file to Stan‐
87 dard Output. Otherwise, pstopnm creates one file for each page in the
88 Postscript input. The files are named as follows: If the input file is
89 named psfile.ps, the name of the files will be psfile001.ppm,
90 psfile002.ppm, etc. The filetype suffix is .ppm, .pgm, or .pbm,
91 depending on which kind of output you choose with your invocation
92 options. If the input file name does not end in .ps, the whole file
93 name is used in the output file name. For example, if the input file
94 is named psfile.old, the output file name is psfile.old001.ppm, etc.
95 Note that the output file selection is inconsistent with most Netpbm
97 programs, because it does not default to Standard Output. This is for
98 historical reasons, based on the fact that the Netpbm formats did not
99 always provide for a sequence of images in a single file.
100 When your input is from Standard Input, you may feed multiple Encapsu‐
102 lated Postscript documents, one after another, and pstopnm converts
103 every document and places it in the Standard Output stream as an image.
104 But if your input is from a named file, pstopnm expects the file to be
105 an Encapsulated Postscript file, which means it contains only one Enap‐
106 sulated Postscript document. If the file contains multiple concate‐
107 nated documents, pstopnm ignores every document but the first. This
108 distinction does not exist for non-EPSF Postscript input - pstopnm gen‐
109 erates an output image for each page of the input regardless of whether
110 the input is from Standard Input or from a named file.
111 Note that you can generated both kinds of files - concatenated EPSF and
113 multi-page non-EPSF - with pnmtops, selecting with the -setpage option.
114 Each output image contains a rectangular area of the page to which it
116 pertains. See the Dimensions section ⟨#dimensions⟩ for details on
117 what part of the input image goes into the output image and how big it
118 is in the output and what borders and margins are in the output image.
119 It has been reported that on some Postscript Version 1 input, Ghost‐
121 script, and therefore pstopnm, produces no output. To solve this prob‐
122 lem, you can convert the file to Postscript Version 3 with the program
123 ps2ps. It is reported that the program pstops does not work.
124 Dimensions
127 This section describes what part of the input image gets used in the
128 output and the dimensions of the output, including borders and back‐
129 ground.
130 Note that an output image is associated with a single input page.
132 pstopnm starts by taking a rectangular area from the input page. That
134 is called the subject image.
135 pstopnm may add borders to the subject image to form what is called the
137 bordered subject image.
138 pstopnm places the bordered subject image in the center of the output
140 image and clips the edges as necessary to fit the computed output image
141 size.
142 The location of the subject image in the Postscript input page is
144 defined by four numbers, the lower left corner and the upper right cor‐
145 ner x and y coordinates. These coordinates are usually specified by
146 the BoundingBox DSC statement (a Postscript comment) in the PostScript
147 file, but they can be overridden by the user by specifying one or more
148 of the following options: -llx, -lly, -urx, and -ury.
149 The presence and thickness of a border to be added to the subject image
151 to form the bordered subject image is controlled by the options -xbor‐
152 der and -yborder. If pstopnm does not find a BoundingBox statement in
153 the input, and you don't specify image area coordinates on the command
154 line, pstopnm uses default values. If your input is from Standard
155 Input, pstopnm does not use the BoundingBox values (because of the
156 technical difficulty of extracting that information and still feeding
157 the file to Ghostscript), so you either have to specify the image area
158 coordinates or take the default.
159 The output image size is a confusing thing. In a Postscript file,
161 things have spatial dimensions. For example, a particular line may be
162 3 centimeters long. A Postscript printer is supposed to print the line
163 3 centimeters long, using however many pixels that takes, without
164 regard to how big the sheet of paper on which it is printing is. In a
165 PNM image, by contrast, there is no spatial dimension; there are only
166 pixels. You might have a line that is 100 pixels long, but the PNM
167 image says nothing about how long that line should be on a printed
168 page.
169 pstopnm fills the role of a Postscript printer. The PNM image is a
171 virtual printed page. pstopnm must determine how many pixels it will
172 use in the output image to represent an inch of input image, which is
173 the "output device resolution." Think of it as the number of dots per
174 inch the virtual printer prints on the virtual page.
175 The simplest thing is for you to tell pstopnm exactly what output
177 device resolution to use, using the -dpi option. If you say for exam‐
178 ple -dpi=300 and the bordered subject image is 2 inches by 3 inches,
179 the PNM output will be 600 pixels by 900 pixels. Using this method,
180 the output device resolution has to be the same in both directions.
181 Or you can set the output image dimensions with -xsize and -ysize. For
183 example, if you say -xsize=1200 -ysize=1800 and the bordered subject
184 image is 2 inches wide by 3 inches high, the output image is 1200 by
185 1800 pixels, with each pixel representing 1/600 inch of input image.
186 In the unlikely event that you want different output device resolutions
188 in the two directions, you could use -xsize and -ysize to do that. In
189 the above example, if you change -ysize to 900, a pixel still repre‐
190 sents 1/600 inch horizontally, but 1/300 inch vertically.
191 If you specify one of -xsize and -ysize and not the other, pstopnm
193 defaults the other such that the output device resolution is the same
194 in both directions.
195 The "x" and "y" of -xsize and -ysize refer to the image being printed
197 on the page, not the page. So if pstopnm prints it in landscape orien‐
198 tation, "x" would pertain to the vertical direction on the page, i.e.
199 the vertical direction in the output PNM image.
200 If you specify neither the output size nor the output device resolu‐
202 tion, pstopnm does some weird computation which exists mainly for his‐
203 torical reasons:
204 If you specify -nocrop, pstopnm uses the values of -xmax and -ymax for
206 the output image dimensions. These default to 612 and 792 pixels,
207 respectively.
208 The final case, the default, is where you don't specify any size or
210 resolution options or -nocrop. This is the most complicated case. In
211 this case, pstopnm first chooses an output device resolution that would
212 generate the number of pixels indicated by -xmax and -ymax from the
213 bordered subject image. Then, based on that resolution, it chooses an
214 output image size that is just large enough to accommodate the subject
215 image (no borders). Remember (above) that pstopnm trims the edges of
216 the bordered subject image to fit the computed output size.
217 Ghostscript Limitations
221 Tests done in 2013 with Ghostscript 8.71 indicate that Ghostscript's
222 pgmraw output driver has some kind of rounding error that causes the
223 pixel values to change slightly, and that means pstopnm generates
224 incorrect output when you have monochrome Postscript input. But with
225 color Postscript input, pstopnm uses Ghostscript's ppmraw output driver
226 and generates correct PPM output.
227 Usage Notes
231 There is some good advice on converting to and from Postscript, in the
232 document Postcript File Conversions" (1) by Andrew T. Young.
233 Reversible Conversion
235 If you're trying to do the equivalent of the naive pnmtops | pstopnm,
237 the following steps will do it.
238 $ pnmtops -nocenter -equalpixels -dpi 72 -noturn testimg.ppm > testimg.ps
240 $ pstopnm -xborder=0 -yborder=0 -xsize=XSIZE -ysize=YSIZE \
241 -portrait -stdout -quiet testimg.ps >testimg2.ppm
242 XSIZE and YSIZE above are the image dimensions, which you can get from
244 testimg.ps like in the following example (the grep, awk and echo com‐
245 mands are just to help demonstrate how the other commands work - you
246 wouldn't use those in a program).
247 $ grep "BoundingBox" testimg.ps
249 %%BoundingBox: 0 0 227 149
250 $ awk '/%%BoundingBox/ {print $4,$5}' testimg.ps
252 227 149
253 $ xysize=$(awk '/%%BoundingBox/ {print "-xsize="$4,"-ysize="$5}' testimg.ps)
255 $ echo $xysize
256 -xsize=227 -ysize=149
258 $ pstopnm -xborder=0 -yborder=0 $xysize -portrait ... testimg.ps
260 Note that Ghostscript bugs can keep this from doing a perfect
262 reversible conversion.
263
267 -forceplain
268 forces the output file to be in plain (text) format. Other‐
269 wise, it is in raw (binary) format. See pbm(1), etc.
270 -llx=bx
273 selects bx as the lower left corner x coordinate (in inches) on
274 the Postscript input page of the subject image. See the
275 Dimensions section ⟨#dimensions⟩ .
276 -lly=by
279 selects by as the lower left corner y coordinate (in inches) on
280 the Postscript input page of the subject image. See the
281 Dimensions section ⟨#dimensions⟩ .
282 -landscape
285 renders the image in landscape orientation.
286 If you specify neither -portrait nor -landscape, pstopnm chooses
288 the orientation that best fits the image on the output page.
289 Landscape means printed sideways on the page, not printed the
291 long way. Those are different things if the long edge of the
292 page is the top one.
293 -portrait
296 renders the image in portrait orientation.
297 See -landscape.
299 -nocrop
302 This option causes pstopnm to make the output image exactly the
303 dimensions of the bordered subject image. By default, pstopnm
304 makes the output image the dimensions specified by -xmax and
305 -ymax. See the Dimensions section ⟨#dimensions⟩ .
306 -pbm
309 -pgm
311 -ppm selects the format of the output file. By default, all files
313 are rendered as PPM.
314 -stdout
317 causes output to go to Standard Output instead of to regular
318 files, one per page (see description of output files above).
319 Use pnmsplit to extract individual pages from Standard Output.
320 -urx=tx
323 selects tx as the upper right corner x coordinate (in inches) on
324 the Postscript input page of the subject image. See the
325 Dimensions section ⟨#dimensions⟩ .
326 -ury=ty
329 selects ty as the upper right corner y coordinate (in inches) on
330 the Postscript input page of the subject image. See the
331 Dimensions section ⟨#dimensions⟩ .
332 -verbose
336 prints processing information to stdout.
337 -xborder=frac
340 specifies that the left and right borders added to the subject
341 image are to be frac times the subject image width. The default
342 value is 0.1. See the Dimensions section ⟨#dimensions⟩ .
343 -xmax=xmax
347 specifies that the output image is to be xmax pixels wide. The
348 default is 612. See the Dimensions section ⟨#dimensions⟩ .
349 -xsize=xsize
353 specifies that the output image is to be xsize pixels wide. See
354 the Dimensions section ⟨#dimensions⟩ .
355 -yborder=frac
358 specifies that the top and bottom borders added to the subject
359 image are to be frac times the subject image height. The
360 default value is 0.1. See the Dimensions section ⟨#dimensions⟩
361 .
362 -ymax=ymax
366 specifies that the output image is to be ymax pixels high. The
367 default is 792. See the Dimensions section ⟨#dimensions⟩ .
368 -ysize=ysize
371 specifies that the output image is to be ymax pixels high. See
372 the Dimensions section ⟨#dimensions⟩ .
373 -dpi=dpi
376 specifies the output device resolution, in dots per inch, of the
377 Postscript printer that pstopnm simulates. This is the number
378 of PNM pixels pstopnm generates for each inch of image. See the
379 Dimensions section ⟨#dimensions⟩ .
380 This option was new in Netpbm 10.21 (March 2004).
382 -textalphabits={1,2,4}
385 This controls subsample antialiasing of text. Antialiasing is a
386 form of smoothing that eliminates jagged edges on characters.
387 Subsample antialiasing is a kind of antialiasing that uses sub‐
388 pixels in a box, and the value of this option is the size of
389 that box. 4 gives you the best looking output, while 1 causes
390 no antialiasing. Smaller numbers make pnmtops use less CPU
391 time.
392 Pstopnm uses Ghostscript's TextAlphaBits parameter for this.
394 The default is 4.
396 This option was new in Netpbm 10.53 (December 2010). Older ver‐
398 sions of pstopnm do no antialiasing.
399
405 The program will produce incorrect results with PostScript files that
406 initialize the current transformation matrix. In these cases, page
407 translation and rotation will not have any effect. To render these
408 files, probably the best bet is to use the following options:
409 pstopnm -xborder 0 -yborder 0 -portrait -nocrop file.ps
411 Additional options may be needed if the document is supposed to be ren‐
413 dered on a medium different from letter-size paper.
414
417 gs, pnmtops(1), psidtopgm(1), pbmtolps(1), pbmtoepsi(1), pnmsplit(1),
418 pstofits
419
424 Copyright (c) 1992 Smithsonian Astrophysical Observatory
425 PostScript is a Trademark of Adobe Systems Incorporated.
427
431 Alberto Accomazzi, WIPL, Center for Astrophysics.
432
434 This manual page was generated by the Netpbm tool 'makeman' from HTML
435 source. The master documentation is at
436 http://netpbm.sourceforge.net/doc/pstopnm.html
438netpbm documentation 06 December 2013 Pstopnm User Manual(0)