Annotation of OpenXM_contrib/gnuplot/docs/psdoc/ps_file.doc, Revision 1.1.1.1
1.1 maekawa 1: A short guide to PostScript files created by gnuplot's "postscript" terminal
2:
3: by Dick Crawford, aka rccrawford@lanl.gov
4:
5: Before we begin, let me say a few words about PostScript. It is highly ver-
6: satile, but with versatility comes complexity. Syntax is extremely important;
7: a misplaced command can do unexpected things. Thus the adventurous soul who
8: wishes to alter the PostScript but has not been initiated into the arcana of
9: PostScript would be well-advised to change only those items (like numerical
10: values, font names or heights, or the letters defining symbols) that are
11: fairly obvious as to their meaning.
12:
13: PostScript is stack-oriented and works in Reverse Polish notation:
14: 'a b add' takes 'a' and 'b' off of the stack and replaces them with 'a+b'.
15:
16: The 'stroke' command actually draws lines on the page. It uses whatever line
17: width and style are currently defined. Thus if we specify a bunch of commands
18: like 'LT1 1 2 moveto 3 4 lineto LT3 stroke' [LT1 and LT3 are line type defi-
19: nitions, 'x y moveto' moves the (virtual) pen to (x,y) and 'x y lineto' draws
20: a line from wherever the pen was to (x,y)], the line connecting points (1,2)
21: and (3,4) will be in type LT3.
22:
23: PostScript is case-sensitive.
24:
25: The sample file below has been pruned of repeated commands, just to keep its
26: length down. Comment lines begin with '%'. Lines beginning with '%%' are
27: inserted for "encapsulated PostScript" -- these lines are read by applications
28: that import PostScript. Lines beginning with '%#' have been added to the
29: sample by me for explanatory purposes.
30:
31: I have merged files created by the postscript terminal with no options, with
32: the "eps" option and with the "enhanced" option. The differences will be
33: clearly pointed out when appropriate.
34:
35: Here we go.
36:
37: %!PS-Adobe-2.0
38: %%Title: psgenh
39: %%Creator: gnuplot 3.5 (pre 3.6) patchlevel beta 338
40: %%CreationDate: Fri Jan 16 13:18:18 1998
41: %%DocumentFonts: (atend)
42: %%BoundingBox: 50 50 554 770
43: %%Orientation: Landscape
44: %# In 'eps' mode, the preceding two lines would look like:
45: %# %%BoundingBox: 50 50 410 302
46: %# %%Orientation: Portrait
47: %%Pages: (atend)
48: %%EndComments
49: %#
50: %# The 'dictionary' contains stuff defined by the user.
51: %#
52: /gnudict 120 dict def
53: gnudict begin
54: %#
55: %# The following switch toggles between color and monochromatic.
56: %#
57: /Color false def
58: %#
59: %# The following switch toggles between solid and dot-dash lines.
60: %#
61: /Solid false def
62: %#
63: %# The following parameter scales all linewidths in the plot.
64: %#
65: /gnulinewidth 5.000 def
66: /userlinewidth gnulinewidth def
67: %#
68: %# The following parameter specifies the vertical displacement of the labels
69: %# and titles (it is used in the 'show' commands defined below). It should
70: %# be about 1/3 of the font height.
71: %#
72: /vshift -46 def
73: %#
74: %# The following parameter scales the lengths of all dot-dash patterns.
75: %#
76: /dl {10 mul} def
77: %#
78: %# The following two parameters scale the horizontal and vertical sizes of
79: %# the symbols used by 'plot with points'.
80: %#
81: /hpt_ 31.5 def
82: /vpt_ 31.5 def
83: /hpt hpt_ def
84: /vpt vpt_ def
85: %#
86: %# The following four commands are aliases of the four 'pen movement'
87: %# commands. Use of these aliases significantly shortens the file. Note
88: %# that the first two are 'absolute' movements and the latter two are
89: %# 'relative'. M and R move to the specified position; L and V draw a
90: %# straight line (from the current position) to it.
91: %#
92: /M {moveto} bind def
93: /L {lineto} bind def
94: /R {rmoveto} bind def
95: /V {rlineto} bind def
96: %#
97: %# These are a couple more parameters used in plotting symbols. Why
98: %# they are here instead of up with 'hpt' and 'vpt' I know not.
99: %#
100: /vpt2 vpt 2 mul def
101: /hpt2 hpt 2 mul def
102: %#
103: %# The 'show' command writes out a character string. The following three
104: %# varieties do so as left-, right-, and center-justified. [Remember,
105: %# we're still in the dictionary--the font doesn't need to be specified
106: %# until we actually use one of these.]
107: %#
108: /Lshow { currentpoint stroke M
109: 0 vshift R show } def
110: /Rshow { currentpoint stroke M
111: dup stringwidth pop neg vshift R show } def
112: /Cshow { currentpoint stroke M
113: dup stringwidth pop -2 div vshift R show } def
114: %#
115: %# The following commands define the various line types (normal, bold,
116: %# dashed, etc.) used by gnuplot.
117: %#
118: %# UP, DL, and UL are busywork commands used by others here
119: %#
120: /UP { dup vpt_ mul /vpt exch def hpt_ mul /hpt exch def
121: /hpt2 hpt 2 mul def /vpt2 vpt 2 mul def } def
122: /DL { Color {setrgbcolor Solid {pop []} if 0 setdash }
123: {pop pop pop Solid {pop []} if 0 setdash} ifelse } def
124: /BL { stroke gnulinewidth 2 mul setlinewidth } def %# twice the linewidth
125: /AL { stroke gnulinewidth 2 div setlinewidth } def %# half the linewidth
126: /UL { gnulinewidth mul /userlinewidth exch def } def
127: /PL { stroke userlinewidth setlinewidth } def %# normal linewidth
128: /LTb { BL [] 0 0 0 DL } def
129: /LTa { AL [1 dl 2 dl] 0 setdash 0 0 0 setrgbcolor } def
130: /LT0 { PL [] 0 1 0 DL } def
131: /LT1 { PL [4 dl 2 dl] 0 0 1 DL } def
132: %#
133: %# ...and a bunch more.
134: %# In the LT's, the first command ('PL' for LT1) sets the linewidth,
135: %# the stuff in [...] defines the dot-dash pattern, and the three numbers
136: %# define the rgb color.
137: %#
138: %# The following commands define the symbols used to plot data points.
139: %#
140: /Pnt { stroke [] 0 setdash
141: gsave 1 setlinecap M 0 0 V stroke grestore } def
142: /Dia { stroke [] 0 setdash 2 copy vpt add M
143: hpt neg vpt neg V hpt vpt neg V
144: hpt vpt V hpt neg vpt V closepath stroke
145: Pnt } def
146: %#
147: %# ...and a bunch (dozens) more.
148: %#
149: %# The 'MF...' commands are used to handle the 'enhanced' syntax. If the
150: %# 'enhanced' mode is not invoked, these commands won't appear in the file.
151: %#
152: /MFshow {{dup dup 0 get findfont exch 1 get scalefont setfont
153: [ currentpoint ] exch dup 2 get 0 exch rmoveto dup dup 5 get exch 4 get
154: {show} {stringwidth pop 0 rmoveto}ifelse dup 3 get
155: {2 get neg 0 exch rmoveto pop} {pop aload pop moveto}ifelse} forall} bind def
156: /MFwidth {0 exch {dup 3 get{dup dup 0 get findfont exch 1 get scalefont setfont
157: 5 get stringwidth pop add}
158: {pop} ifelse} forall} bind def
159: /MLshow { currentpoint stroke M
160: 0 exch R MFshow } bind def
161: /MRshow { currentpoint stroke M
162: exch dup MFwidth neg 3 -1 roll R MFshow } def
163: /MCshow { currentpoint stroke M
164: exch dup MFwidth -2 div 3 -1 roll R MFshow } def
165: end
166: %#
167: %# The dictionary is now complete. We activate it, save what went before
168: %# (the 'gsave' command saves everything on a different stack) and begin.
169: %#
170: %%EndProlog
171: %%Page: 1 1
172: gnudict begin
173: gsave
174: %#
175: %# First we position the plot on the page and scale it.
176: %#
177: %# The 'translate' command moves the origin to the specified position.
178: %# [The PostScript default origin is near the lower left-hand corner.]
179: %# The 'scale' command changes the units used in the plot.
180: %# [The PostScript default unit is the point: 72 points equal one inch.]
181: %# The 'rotation' command rotates the coordinates clockwise through the
182: %# specified angle (degrees).
183: %# [The PostScript default orientation is profile.]
184: %#
185: %# This sample changes the orientation to landscape (the gnuplot default)
186: %# and the unit to tenths of a point. Note that if the first two commands
187: %# were interchanged, the translation would be only five points in each
188: %# direction, instead of fifty.
189: %#
190: %# If this had been generated in 'eps' mode, the "90 rotate" and "0 -5040
191: %# translate" commands would not appear and the units would be 0.050 instead
192: %# of 0.100.
193: %#
194: %# If you want to change the size or the position of the plot, this is where
195: %# to do it.
196: %#
197: 50 50 translate
198: 0.100 0.100 scale
199: 90 rotate
200: 0 -5040 translate
201: 0 setgray
202: newpath
203: %#
204: %# Define the default font. The number is the height. As usual, fonts
205: %# used primarily for text have characters only about 70% the specified
206: %# height, because spacing between lines is built-in. The Symbol font and
207: %# others that are normally not used for text produce characters that are
208: %# more nearly the specified height. Thus if you want to intersperse, for
209: %# example, Greek and Roman letters (as you might when writing an equation),
210: %# you'll need to play with the heights of the two fonts in order for them
211: %# to look reasonably proportioned.
212: %#
213: %# The font defined here is used for the tick labels first, then the axis
214: %# labels and plot titles, and finally the key. If you want to change the
215: %# font, simply insert the modified line after you are done with the old one
216: %# (i.e. the last 'show' command to use it) but before the new one is needed.
217: %# Note that if you change the font height, you'll also want to change the
218: %# value of 'vshift' (it's near the top of the dictionary). I'll give an
219: %# example of this later on...
220: %#
221: (Helvetica) findfont 140 scalefont setfont
222: LTb
223: %#
224: %# Label and draw the ticks along the y-axis. I've given you three
225: %# y-tics in different formats...
226: %#
227: %# The tick length is 63 units.
228: %#
229: %# This first y-tic is in 'normal' mode:
230: %#
231: 728 560 M
232: 63 0 V
233: 6325 0 R
234: -63 0 V
235: 644 560 M
236: (-10) Rshow
237: %#
238: %# This y-tic is in 'enhanced' mode:
239: %#
240: 728 1645 M
241: 63 0 V
242: 6325 0 R
243: -63 0 V
244: stroke
245: 644 1645 M
246: [ [(Helvetica) 140.0 0.0 true true (-5)]
247: ] -46.7 MRshow
248: %#
249: %# This one is in 'normal' mode, but is rotated:
250: %#
251: 434 2730 M
252: 63 0 V
253: 6619 0 R
254: -63 0 V
255: -6759 0 R
256: currentpoint gsave translate 90 rotate 0 0 M
257: (0) Cshow
258: grestore
259: %#
260: %# Now the x-tics. Here's one:
261: %#
262: 728 560 M
263: 0 63 V
264: 0 4277 R
265: 0 -63 V
266: stroke
267: 728 420 M
268: [ [(Helvetica) 140.0 0.0 true true (-10)]
269: ] -46.7 MCshow
270: LTb
271: %#
272: %# Now draw the left and lower axes. Were this drawn by 'splot'
273: %# instead of 'plot', there might be some other axes drawn.
274: %#
275: 728 560 M
276: 6388 0 V
277: 0 4340 V
278: -6388 0 V
279: 728 560 L
280: stroke
281: %# Now come labels (both for the axes and those on "set label" commands)
282: %# and other titles. I just give you axis labels here, in 'enhanced' mode:
283: %#
284: 140 2730 M
285: currentpoint gsave translate 90 rotate 0 0 moveto
286: [ [(Helvetica) 140.0 0.0 true true (ylabel)]
287: ] -46.7 MCshow
288: grestore
289: 3922 210 M
290: [ [(Helvetica) 140.0 0.0 true true (xlabel)]
291: ] -46.7 MCshow
292: %#
293: %# We're finally ready to plot functions and/or data.
294: %#
295: %# The key is drawn just before the applicable data.
296: %#
297: %# Choose a line type and write the key.
298: %# In this sample, it is drawn with lines.
299: %#
300: 1.000 UL
301: LT0
302: 6465 4767 M (x) Rshow %# the function label in the key
303: 6549 4767 M %# the sample line in the key
304: 399 0 V
305: %#
306: %# Now the data (this is drawn with some combination of absolute and
307: %# relative lineto's and moveto's):
308: %#
309: 728 560 M
310: 2043 560 V
311: 4926 911 L
312: 2043 560 V
313: 7116 4900 L
314: %#
315: %# ...and more.
316: %#
317: %# We don't need to eplicitly 'stroke' to draw the lines for each function
318: %# because the 'stroke' command is included in the line-type definition
319: %# commands. Thus switching line types automatically 'strokes' previous
320: %# lines. Clever program, that gnuplot...
321: %#
322: %# We can now repeat commands for the key and data for as many items
323: %# as were specified on the "plot" or "splot" command.
324: %#
325: %# Here's a second function, plotted with dots:
326: %#
327: LT1
328: 6486 4486 M
329: (function 2) Rshow
330: 6654 4486 Pnt
331: %#
332: %# The data:
333: %#
334: 840 911 Pnt
335: 2883 2030 Pnt
336: 4926 2590 Pnt
337: 6969 3710 Pnt
338: %#
339: %# ...and more.
340: %#
341: %# Since we're now done, we 'stroke' the last lines, close the dictionary
342: %# and restore the previous settings (those saved by the 'gsave' at the top).
343: %# [The 'gsave'/'grestore' pair is included so that if this file is embedded
344: %# in another PostScript file, this patch won't mess up the other parts of
345: %# the picture. It's considered good PostScript style to do this.]
346: %#
347: stroke
348: grestore
349: end
350: %#
351: %# And, finally, we send the page to the printer. [If we do embed this
352: %# file into another PostScript file, we'd remove this 'showpage'. Unless,
353: %# of course, this was appended to the other file, in which case we'd
354: %# remove the 'showpage' from the end of that file.]
355: %#
356: %#
357: showpage
358: %%Trailer
359: %%DocumentFonts: Helvetica
360: %%Pages: 1
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