pslib v3.2 - A PostScript based plotting library

pslib was created to make the generation of PostScript page description code easier. It is a library that contains a series of tools that can be used to create plots. The resulting PostScript code is ASCII text and can be edited using any text editor. Thus, it is fairly easy to modify a plot file even after it has been created, e.g., to change text strings, set new gray shades or colors, experiment with various penwidths etc. pslib is written in C but now includes FORTRAN bindings (thanks to John Goff, WHOI) and can therefore be called from both C and FORTRAN programs. To use this library, you must link your plotting program with pslib.a. pslib is the core of the GMT SYSTEM and XY graphics programs. pslib output conforms to the Adobe Encapsulated PostScript File Specification Version 3.0 (EPSL), and may be used as EPS files and inserted into, say, a Word document on a Mac. See Appendix F in the Technical Reference for detailed instructions.

Before any pslib calls can be issued, the plotting system must be initialized. This is done by calling ps_plotinit, which defines macros, sets up the plot-coordinate system, scales, and [optionally] opens a file where all the PostScript code will be written. Normally, the plot code is written to stdout. The measure unit for sizes and positions can be set to be centimeter, inch, or m. When all plotting is done, you must terminate the plotting system by calling ps_plotend.

pslib uses the direct color model where red, green, and blue are given separately, each must be in the range from 0-255. If red < 0 then no fill operation takes place. Most plot-items can be plotted with or without outlines. If outline is desired (i.e., set to 1), it will be drawn using the current linewidth and pattern. pslib uses highly optimized macro substitutions and scales the coordinates depending on the resolution of the hardcopy device so that the output file is kept as compact as possible.

A wide variety of output devices that support PostScript exist, including laserwriters (color or monochrome) and workstations running PostScript based window systems like SUNs OpenWindows. xnews (part of OpenWindows) or ghostscript (public domain) can be used to create rasterfiles at a user-defined resolution (DPI), making it possible to render PostScript on a Versatec and other non-PostScript raster devices. Regular SUN rasterfiles created under NeWS from PostScript files can be sent to a variety of color hardcopy units. Check the devices available on your network.

The following is a list of available functions and a short description of what they do and what parameters they expect. All floating point variables are expected to be double (i.e., 8 bytes), whereas all integers are assumed to be 4 bytes long. All plotting functions are declared as functions returning an int. Currently, the return value is undefined.

void ps_arc (x, y, radius, angle1, angle2, status)

double x, y, radius, angle1, angle2;

int status; Draws a circular arc centered on (x,y) from angle angle1 to angle2. Angles must be given in decimal degrees. If angle1 > angle2, a negative arc is drawn. status is a value from 0 through 3. 1 means set new anchor point, 2 means stroke the circle, 3 means both, 0 means none of the above.

void ps_axis (xpos, ypos, length, startval, stopval, tickval, label, anotpointsize, side)

double xpos, ypos, length, startval, stopval, tickval;

int anotpointsize, side;

char *label; Plots an axis with tickmarks, annotation, and label. xpos, ypos, and length are in inches (or cm or meters), anotpointsize in points (72 points = 1 inch), else data units are used. side can be 0, 1, 2, or 3, which selects lower x-axis, right y-axis, upper x-axis, or left y-axis, respectively. labelpointsize = 1.5 * anotpointsize. A negative tickval will reverse the sense of positive direction, e.g., to have the y-axis be positive down.

void ps_circle (xcenter, ycenter, diameter, rgb, outline)

double xcenter, ycenter, diameter;

int rgb[3], outline; Plots a circle and fills it with the specified color. If outline == 1, the outline will be drawn using current pen-width and -pattern.

void ps_clipoff () Resets the clip path to what it was before the last call to clipon.

void ps_clipon (xarray, yarray, npoints, rgb, flag)

double xarray[], yarray[];

int npoints, rgb[3], flag; Sets up a user-definable clip path. Plotting outside this polygon will be clipped until ps_clipoff is called. If red >= 0 the inside of the path is filled with the specified color. flag is used to create complex clip paths consisting of several disconnected regions, and takes on values 0-3. flag = 1 means this is the first path in a multi-segment clip path. flag = 2 means this is the last segment. Thus, for a single path, flag = 3.

void ps_colorimage (xpos, ypos, xlength, ylength, buffer, nx, ny)

double xpos, ypos, xlength, ylength;

unsigned char buffer[];

int nx, ny; Plots a 24-bit true color image using rgb colors. Similar to ps_image except bits is fixed to be 8. The rgb triplets are stored in buffer as rgbrgbrgb... This functions sets up a call to the PostScript colorimage operator which is not implemented in all drivers.

void ps_colortiles (x0, y0, xlength, ylength, buffer, nx, ny)

double x0, y0, xlength, ylength;

int nx, ny;

unsigned char buffer[]; Plots a true color image based on individual color tiles. x0, y0 is the location of the lower left corner of the image in inches. xlength, ylength is the image size in inches. buffer contains rgb triplets stored as rgbrgbrgb... nx, ny is the image size in pixels.

void ps_command (text)

char *text;

Writes a raw PostScript command to the PostScript output file, e.g. "1 setlinejoin".

void ps_comment (text)

char *text; Writes a comment (text) to the PostScript output file, e.g. "Start of graph 2".

void ps_cross (xcenter, ycenter, diameter)

double xcenter, ycenter, diameter; Plots a cross at the specified point using current pen-width and -pattern that fits inside a circle of given diameter.

void ps_diamond (xcenter, ycenter, diameter, rgb, outline)

double xcenter, ycenter, diameter;

int rgb[3], outline; Plots a diamond and fills it with the specified color. If outline == 1, the outline will be drawn using current pen-width and -pattern. The symbol will fit inside a circle of given diameter.

void ps_ellipse (xcenter, ycenter, angle, major, minor, rgb, outline)

double xcenter, ycenter, angle, major, minor;

int rgb[3], outline; Plots a ellipse with its major semiaxis rotated by angle degrees and fills it with the specified color. If outline == 1, the outline will be drawn using current pen-width and -pattern.

void ps_flush () Flushes the output buffer.

void ps_hexagon (xcenter, ycenter, diameter, rgb, outline)

double xcenter, ycenter, diameter;

int rgb[3], outline; Plots a hexagon and fills it with the specified color. If outline == 1, the outline will be drawn using current pen-width and -pattern. The symbol will fit inside a circle of given diameter.

void ps_image (xpos, ypos, xlength, ylength, buffer, nx, ny, bits)

double xpos, ypos, xlength, ylength;

unsigned char buffer[];

int nx, ny, bits; Plots a bit-mapped image using grayshades. Specify position of lower left corner and size (in inches) of image. buffer is an unsigned character array with gray shade values (0 - 255) where 0 is black, 255 is white. bits is number of bits pr pixel (8, 4, or 1). nx,ny refers to the number of pixels in image. The rowlength of buffer must be an integral number of 8/bits. buffer[0] is upper left corner. E.g. if bits = 4, then buffer[j]/16 gives shade for pixel[2j-1] and buffer[j]%16 (mod 16) gives shade for pixel[2j]. buffer values are stored as columns, starting at the lower left corner and ending at the upper right corner. See the Adobe Systems PostScript Reference Manual for more details.

void ps_imagefill (x, y, n, image, imagefile, invert, imagedpi, outline, template, r_rgb, b_rgb)

double x[], y[], x0, y0;

int n, image, invert, imagedpi, outline, template, f_rgb[3], b_rgb[3];

char imagefile; Similar to ps_polygon, but fills the area with an image pattern rather than a color or grayshade. x and y hold the arrays of n points. 90 predefined patterns are available (See GMT Appendix E). image gives the image number (1-90). If set to 0, imagefile must be the name to the user's image, which must be stored as a' SUN 1-, 8-, or 24-bit rasterfile. 1-bit images only: (i) If invert is TRUE (1), the black and white pixels are interchanged before plotting. (ii) If template is TRUE (1), the set pixels are colored using the RGB combination in f_rgb, while the unset are painted with b_rgb. The unit size of the image is controlled by imagedpi. If set to zero, the image is plotted at the device resolution. If outline is TRUE, the current penwidth is used to draw the polygon outline.

void ps_imagemask (xpos, ypos, xlength, ylength, buffer, nx, ny, polarity, rgb)

double xpos, ypos, xlength, ylength;

unsigned char buffer[];

int nx, ny, polarity, rgb[3]; Plots a transparent 1-bit image mask using the given rgb color. Specify position of lower left corner and size (in inches) of image. buffer is an unsigned character array with 8 pixels per byte. nx,ny refers to the number of pixels in image. The rowlength of buffer must be an integral number of 8. buffer[0] is upper left corner. buffer values are stored as columns, starting at the lower left corner and ending at the upper right corner. If polarity is 0 then the bits that are 0 are painted with the rgb color, else the bits that are 1 are colored. See the Adobe Systems PostScript Reference Manual for more details.

void ps_itriangle (xcenter, ycenter, diameter, rgb, outline)

double xcenter, ycenter, diameter;

int rgb[3], outline; Plots an inverted and fills it with the specified color. If outline == 1, the outline will be drawn using current pen-width and -pattern. The symbol will fit inside a circle of given diameter.

void ps_line (xarray, yarray, npoints, type, close, split)

double xarray[], yarray[];

int npoints, type, close, split; Draw a continuous line from the positions in the x-y arrays. If close == 1, the first and last point will automatically be closed by the PostScript driver. If this is the first segment in a multi-segment path, set type == 1. To end the segments and have the line(s) drawn, set type == 2. Thus, for a single segment, type must be 3. The line is drawn using the current penwidth. Only if split is TRUE may ps_line use multiple strokes to draw lines longer that MAX_PATH. ps_polygon will call ps_line with split = FALSE since the path must be continuous. If split is FALSE and the pathlength exceeds MAX_PATH a warning will be issued.

unsigned char *ps_loadraster (fp, header, invert, monochrome, template, f_rgb, b_rgb)

FILE *fp;

struct rasterfile *header;

BOOLEAN invert, monochrome, template;

int f_rgb[], b_rgb[]; Reads the image contents of the Sun rasterfile pointed to by the open filepointer fp. The header must first be obtained with ps_read_rasheader. If invert is TRUE then 1-bit images will be bit-reversed. If monochrome is TRUE then color images are converted to grayimages using the TV YIQ translation. If template is TRUE then 1-bit images will be colorized using the for- and background colors provided in f_rgb and b_rgb. The routine can handle 1-, 8-, 24-, or 32-bit files in old, standard, run-length encoded, or RGB-style Sun format.

void ps_patch (xarray, yarray, npoints, rgb, outline)

double xarray[], yarray[];

int npoints, rgb[3], outline; Identical to ps_polygon except polygon must be < 20 points long and there will be no attempt to shorten the path by discarding unnecessary intermediate points along straight segments. Primarily used when painting large number of small polygons and not waste output space.

void ps_pie (xcenter, ycenter, radius, azimuth1, azimuth2, rgb, outline)

double xcenter, ycenter, radius, azimuth1, azimuth2;

int rgb[3], outline; Plots a sector of a circle and paints it with the specified RGB combination. If outline == 1, the outline will be drawn using current pen-width and -pattern.

void ps_plot (xabs, yabs, kpen)

double xabs, yabs;

int kpen; Absolute move (kpen=3) or draw (kpen=2), using current linewidth.

void ps_plotend (last_page)

int last_page; Terminates the plotting sequence and closes plot file (if other than stdout). If last_page == 1, then a PostScript showpage command is issued, which initiates the printing process on hardcopy devices.

void ps_plotinit (plotfile, overlay, mode, xoff, yoff, xscl, yscl, ncopies, dpi, unit, pagesize, rgb, eps)

char *plotfile;

int overlay, mode, ncopies, dpi, unit;

double xoff, yoff, xscl, yscl;

int pagesize[2], rgb[3]; struct EPS * eps; Initializes the plotting. If plotfile == NULL (or ""), then output is sent to stdout, else output is sent to plotfile. overlay should be 1 only if you plan to append it to some existing PostScript file. mode contains three flags in the three lowest bits. The lowest bit controls the plot orientation and can be 0 (Landscape) or 1 (Portrait). The next bit, if set to 1, will re-encode the fonts to include European accented characters. The third bit controls the format used to write PostScript images: 0 means binary, 1 means hexadecimal. Most printers needs the latter while some can handle binary which are 50% smaller and therefore execute faster. xoff,yoff are used to move the origin from the default position in the lower left corner. xscl,yscl are used to scale the entire plot (Usually set to 1.0, 1.0). Set ncopies to get more than 1 copy. dpi sets the hardcopy resolution in dots pr units. For optimum plot quality and processing speed, choose dpi to match the intended plotter resolution. Examples are 300 for most laserwriters, 2540 for Linotype-300, and ~85 for SUN screens. When in doubt, use 300. unit can be any of 0 (CM), 1 (INCH), or 2 (M), telling the plot system what units are used for distance and sizes. Note that, regardless of choice of unit, dpi is still in dots-pr-inch. pagesize means the physical width and height of the plotting media in points, (typically 612 by 792 for Letter or 595 by 842 for A4 laserwriter plotters. The rgb array holds the color of the page (usually white = 255,255,255). The EPS structure is defined in the pslib.h include file and contains information that will make up the comments header of a EPS file. Programmers who plan to call pslib routines should read the comments in pslib.h first. Note that the FORTRAN binding does not expect this last argument.

void ps_plotr (xrel, yrel, kpen)

double xrel, yrel;

int kpen; Move (kpen = 3) or draw (kpen = 2) relative to current point (see ps_plot).

void ps_polygon (xarray, yarray, npoints, rgb, outline)

double xarray[], yarray[];

int npoints, rgb[3], outline; Creates a colored polygon from the positions in the x-y arrays. Polygon will automatically be closed by the PostScript driver. If outline == 0, no outline is drawn. If outline == 1, the outline is drawn using current penwidth.

int ps_read_rasheader (fp, header)

FILE *fp;

struct rasterfile *header; Using the pointer fp to the open file, return the header structure of the Sun rasterfile. This call is portable as it operates on the byte level. Once the header is returned you may obtain the raster image with ps_loadraster.

void ps_rect (x1, y1, x2, y2, rgb, outline)

double x1, y1, x2, y2;

int red, green, blue, outline; Plots a colored rectangle. (x1,y1) and (x2,y2) are any two corners on a diagonal. If outline == 1, the outline will be drawn using current pen-width and -pattern.

void ps_rotatetrans (x, y, angle)

double x, y, angle; Rotates the coordinate system by angle degrees, then translates origin to (x,y).

void ps_setdash (pattern, offset)

char *pattern;

int offset; Changes the current dashpattern. The character string pattern is set to the desired pattern. E.g., "4 2" and offset = 1 will plot like: x ---- ---- ---- etc, where x is starting point (The x is not plotted). That is, the line is made up of a repeating pattern of a 4 units long line and a 2 unit long gap, starting 1 unit after the x. To reset to solid line, specify pattern = NULL ("") and offset = 0. Units are in dpi units.

void ps_setfont (fontnr)

int fontnr; Changes the current font number to fontnr. The fonts available are: 0 = Helvetica, 1 = H. Bold, 2 = H. Oblique, 3 = H. Bold-Oblique, 4 = Times, 5 = T. Bold, 6 = T. Italic, 7 = T. Bold Italic, 8 = Courier, 9 = C. Bold, 10 = C Oblique, 11 = C Bold Oblique, 12 = Symbol, 13 = AvantGarde-Book, 14 = A.-BookOblique, 15 = A.-Demi, 16 = A.-DemiOblique, 17 = Bookman-Demi, 18 = B.-DemiItalic, 19 = B.-Light, 20 = B.-LightItalic, 21 = Helvetica-Narrow, 22 = H-N-Bold, 23 = H-N-Oblique, 24 = H-N-BoldOblique, 25 = NewCenturySchlbk-Roman, 26 = N.-Italic, 27 = N.-Bold, 28 = N.-BoldItalic, 29 = Palatino-Roman, 30 = P.-Italic, 31 = P.-Bold, 32 = P.-BoldItalic, 33 = ZapfChancery-MediumItalic. If fontnr is outside this range, it is set to 0.

void ps_setformat (n_decimals)

int n_decimals; Sets number of decimals to be used when writing color or gray values. The default setting of 3 gives 1000 choices per red, green, and blue value, which is more than the 255 choices offered by most 24-bit platforms. Choosing a lower value will make the output file smaller at the expense of less color resolution. Still, a value of 2 gives 100 x 100 x 100 = 1 million colors, more than most eyes can distinguish. For a setting of 1, you will have 10 nuances per primary color and a total of 1000 unique combinations.

void ps_setline (linewidth)

int linewidth; Changes the current linewidth in DPI units. 0 gives thinnest line, but the use of 0 is implementation-dependent (Works fine on most laserwriters).

void ps_setpaint (rgb)

int rgb[3]; Changes the current RGB setting for pens and text.

void ps_square (xcenter, ycenter, diameter, rgb, outline)

double xcenter, ycenter, diameter;

int rgb[3], outline; Plots a square and fills it with the specified color. If outline == 1, the outline will be drawn using current pen-width and -pattern. The symbol will fit inside a circle of given diameter.

void ps_star (xcenter, ycenter, diameter, rgb, outline)

double xcenter, ycenter, diameter;

int rgb[3], outline; Plots a star and fills it with the specified color. If outline == 1, the outline will be drawn using current pen-width and -pattern. The symbol will fit inside a circle of given diameter.

void ps_text (x, y, pointsize, text, angle, justify, form)

double x, y, angle;

char *text;

int pointsize, justify, form; The text is plotted starting at (x,y), and will make an angle with the horizontal. The point (x,y) maps onto different points of the textstring by giving various values for justify. It is used as follows:

9------------10----------- 11

| |

5 6 7

| |

1------------ 2------------ 3 The box represents the textstring. E.g., to plot a textstring with its center of gravity at (x,y), you must use justify == 6. If justify is negative, then all leading and trailing blanks are stripped before plotting. Certain character sequences (flags) have special meaning to ps_text. @~ toggles between current font and the Mathematical Symbols font. @%no% sets font to no; @%% resets to starting font. @- turns subscript on/off, @+ turns superscript on/off, @# turns small caps on/off, and @\ will make a composite character of the following two character. Give fontsize in points (72 points = 1 inch). Normally, the text is typed using solid characters. To draw outline characters, set form == 1.

void ps_textbox (x, y, pointsize, text, angle, justify, outline, dx, dy, rgb)

double x, y, angle, dx, dy;

char *text;

int pointsize, justify, outline, rgb[3]; This function is used in conjugation with ps_text when a box surrounding the text string is desired. Taking most of the arguments of ps_text, the user must also specify the color of the resulting rectangle, and whether its outline should be drawn. More room between text and rectangle can be obtained by setting dx and dy accordingly.

void ps_transrotate (x, y, angle)

double x, y, angle; Translates the origin to (x,y), then rotates the coordinate system by angle degrees.

void ps_triangle (xcenter, ycenter, diameter, rgb, outline)

double xcenter, ycenter, diameter;

int rgb[3], outline; Plots a triangle and paints it with the specified RGB combination. If outline == 1, the outline will be drawn using current pen-width and -pattern. The symbol will fit inside a circle of given diameter.

void ps_vector (xtail, ytail, xtip, ytip, tailwidth, headlength, headwidth, headshape, rgb, outline)

double xtail, ytail, xtip, ytip, tailwidth, headlength, headwidth, headshape;

int rgb[3], outline; Draws a vector of size and appearance as specified by the various parameters. headshape can take on values from 0-1 and specifies how far the intersection point between the base of a straight vector head and the vector line is moved toward the tip. 0 gives a triangular head, 1.0 gives an arrow shaped head. If outline == 1, the outline will be drawn using current penwidth.

void ps_words (x, y, text, n_words, line_space, par_width, par_just, font, font_size, angle, rgb, justify, draw_box, x_off, y_off, x_gap, y_gap, boxpen_width, boxpen_texture, boxpen_offset, boxpen_rgb, vecpen_width, vecpen_texture, vecpen_offset, vecpen_rgb, boxfill_rgb)

double x, y, line_space, par_width, angle, x_off, y_off, x_gap, y_gap;

int n_words, font, font_size, justify, draw_box, boxpen_width, boxpen_offset;

int boxpen_rgb[3], vecpen_width, vecpen_offset, vecpen_rgb[3], boxfill_rgb[3];

char **text, *boxpen_texture, *vecpen_texture; Typesets paragraphs of text. text is an array of the words to typeset, using the given line-spacing and paragraph width. The whole text block is positioned at x, y which is the anchor point on the box as indicated by justify (see ps_text). The whole block is then shifted by x_off, y_off. Inside the box, text is justified left, centered, right, or justified as governed by par_just (lcrj). draw_box contains 4 bit flags pertaining to the surrounding outline box. If on, the first (lowest) bit draws the box outline. The second bit fills the box interior. The third bit makes the outline box have rounded corners (unless x_gap, y_gap, which specifies the padding between the text and the box, are zero), while the forth bit draws a line from the original x, y point to the shifted position. The escape sequences described for ps_text applies here, as well as two additional commands: @;r/g/b; changes the font color (@;; resets it), and @:size: changes the font size (@:: resets it).

Paul Wessel, School of Ocean and Earth Science and Technology, 1680 East-West Road, Honolulu, Hawaii 96822, (808) 956-4778, Internet address: wessel@soest.hawaii.edu.

Caveat Emptor: The author is not responsible for any disasters, suicide attempts, or ulcers caused by correct or incorrect use of pslib. If you find bugs, please report them to the author by electronic mail. Be sure to provide enough detail so that I can recreate the problem.

Due to the finite memory of some output devices like Laserwriters, certain restrictions due to limitations of the PostScript interpreter apply: For now, the arrays passed to ps_clipon and ps_polygon must contain less than about 1350 points. Also, the buffer array passed to ps_image must be able to fit in the available memory. Check the specifications of the hardcopy device you are using. Note that some Raster Image Processors (RIPs) do not support direct color so that the colors you get may not be exactly the ones you wanted. This is a limitation of the RIP, not the underlying PostScript code generated by pslib.

Adobe Systems Inc., 1990, PostScript language reference manual, 2nd edition, Addison-Wesley, (ISBN 0-201-18127-4).