Annotation of OpenXM_contrib/gnuplot/docs/psdoc/ps_file.doc, Revision 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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