PostScriptLight — GMT 6.5.0 documentation

# PostScriptLight

PSL 6.0 - A PostScript based plotting library

## Description

PSL (PostScriptLight) was created to make the generation of PostScript page description code easier. PS is a page description language developed by the Adobe for specifying how a printer should render a page of text or graphics. It uses a reverse Polish notation that puts and gets items from a stack to draws lines, text, and images and even performs calculations. PSL is a self-contained library that presents a series of functions that can be used to create plots. The resulting PostScript code is ASCII text (with some exceptions for images if so desired) and can thus be edited using any text editor. Thus, it is possible 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 pen widths, etc. Furthermore, various tools exist that can parse PostScript and let you make such edits via a graphical user interface (e.g., Adobe Illustrator). PSL is written in C but includes FORTRAN bindings and can therefore be called from both C and FORTRAN programs. To use this library, you must link your plotting program with PSL. PSL is used by the GMT graphics programs to generate PS. PSL output is freeform PostScript that conforms to the Adobe PostScript File Specification Version 3.0.

Before any PSL calls can be issued, the plotting system must be initialized. This is done by calling PSL_beginsession, which initializes a new PSL session; then call PSL_setdefaults which sets internal variables and default settings, accepts settings for measurement units and character encoding, and returns a pointer to a struct PSL_CTRL which must be passed as first argument to all other PSL functions. The measure unit for sizes and positions can be set to be centimeter (c), inch (i), meter (m), or points (p). A PSL session is terminated by calling PSL_endsession. You may create one or more plots within the same session. A new plot is started by calling PSL_beginplot, which defines macros, sets up the plot-coordinate system, scales, and [optionally] opens a file where all the PS code will be written. Normally, the plot code is written to stdout. When all plotting to this file is done, you finalize the plot by calling PSL_endplot.

A wide variety of output devices that support PostScript exist, including many printers and large-format plotters. Many tools exists to display PostScript on a computer screen. Open source tools such as ghostscript can be used to convert PostScript into PDF or raster images (e.g., TIFF, JPEG) at a user-defined resolution (DPI). In particular, the GMT tool psconvert is a front-end to ghostscript and pre-selects the optimal options for ghostscript that will render quality PDF and images.

The PSL is fully 64-bit compliant. Integer parameters are here specified by the type long to distinguish them from the 32-bit int. Note that under standard 32-bit compilation they are equivalent. Users of this library under 64-bit mode must make sure they pass proper long variables (under Unix flavors) or __int64 under Windows 64.

## Units

PSL can be instructed to use centimeters, inches, meters or points as input units for the coordinates and sizes of elements to be plotted. Any dimension that takes this setting as a unit is specified as user units or plot units in this manual. Excluded from this are line widths and font sizes which are always measured in points. The user units can be further refined by calling PSL_beginaxes, giving the user the opportunity to specify any linear coordinate frame. Changing the coordinate frame only affects the coordinates of plotted material indicated as measured in plot units, not the sizes of symbols (which remain in user units), nor line widths or font sizes (which remain in points).

## Color

PSL uses the direct color model where red, green, and blue are given separately, each must be in the range from 0-1. If red = -1 then no fill operation takes place. If red = -3, then pattern fill will be used, and the green value will indicate the pattern to be used. 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 line width and pattern. PSL 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.

## Justification

Text strings, text boxes and images can be “justified” by specifying the corner to which the x and y coordinates of the subroutine call apply. Nine different values are possible, as shown schematically in this diagram:

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

>     |                             |

>     5              6              7

>     |                             |

>     1 ------------ 2 ------------ 3

The box represents the text or image. E.g., to plot a text string with its center at (x, y), you must use justify == 6. justify == 0 means “no justification”, which generally means (x, y) is at the bottom left. Convenience values PSL_NONE, PSL_BL, PSL_BC, PSL_BR, PSL_ML, PSL_MC, PSL_MR, PSL_TL, PSL_TC and PSL_TR are available.

## Initialization

These functions initialize or terminate the PSL system. We use the term PSL session to indicate one instance of the PSL system (a complicated program could run many PSL sessions concurrently as each would operate via its own control structure). During a single session, one or more plots may be created. Here are the functions involved in initialization:

struct PSL_CTRL *New_PSL_Ctrl (char *session)

> This is the first function that must be called as it creates a new PSL session. Specifically, it will allocate a new PSL control structure and initialize the session default parameters. The pointer that is returned must be passed to all subsequent PSL functions.

long *PSL_beginsession (struct PSL_CTRL *PSL, long search, char *sharedir, char *userdir)

> This is the second function that must be called as it initializes the new PSL session. Here, search is an integer that is passed as 0 in GMT but should be 1 for other users. If so we will search for the environmental parameters PSL_SHAREDIR and PSL_USERDIR should the corresponding arguments sharedir and userdir be NULL.

long PSL_endsession (struct PSL_CTRL *PSL)

> This function terminates the active PSL session; it is the last function you must call in your program. Specifically, this function will deallocate memory used and free up resources.

struct PSL_CTRL *PSL_beginlayer (struct PSL_CTRL *PSL, long layer)

> Adds a DSC comment by naming this layer; give a unique integer value. Terminate layer with PSL_endlayer

struct PSL_CTRL *PSL_endlayer (struct PSL_CTRL *PSL)

> Terminate current layer with a DSC comment.

long PSL_fopen (char *file, char *mode)

> This function simply opens a file, just like fopen. The reason it is replicated here is that under Windows, file pointers must be assigned within the same DLL as they are being used. Yes, this is retarded but if we do not do so then PSL will not work well under Windows. Under non-Windows this functions is just a macro that becomes fopen.

void PSL_copy (struct PSL_CTRL *PSL, char *text);

> This functions simply adds the given test as is to the output PostScript stream (or internal buffer). It is used when the text may exceed the internal 4096 buffer used in PSL_command (which is implemented as a printf function and hence a buffer of fixed size is used.)

void PSL_free (void *ptr)

> This function frees up the memory allocated inside PSL. Programmers using C/C++ should now this is a macro and there is no need to cast the pointer to void * as this will be done by the macro. FORTRAN programmers should instead call PSL_freefunction.

void PSL_beginaxes (struct PSL_CTRL *PSL, double llx, double lly, double width, double height, double x0, double y0, double x1, double y1)

> This function sets up the mapping that takes the users data coordinates and converts them to the positions on the plot in PostScript units. This should be used when plotting data coordinates and is terminated with PSL_endaxes, which returns PSL to the default measurement units and scaling. Here, llx and lly sets the lower left position of the mapping region, while width and height sets the dimension of the plot area in user units. Finally, x0, x1 and y0, y1 indicate the range of the users x- and y-coordinates, respectively. Specify a reverse axis direction (e.g., to let the y-axis be positive down) by setting y0 larger than y1, and similarly for an x-axis that increases to the left.

void PSL_endaxes (struct PSL_CTRL *PSL)

> Terminates the map scalings initialized by PSL_beginaxes and returns PSL to standard scaling in measurement units.

long PSL_beginplot (struct PSL_CTRL *P, FILE *fp, long orientation, long overlay, long color_mode, char origin[], double offset[], double page_size[], char *title, long font_no[])

> Controls the initiation (or continuation) of a particular plot within the current session. Pass file pointer fp where the PostScript code will be written; if NULL then the output is written to stdout. The FORTRAN interface always sends to stdout. If you want to receive the PostScript back in memory then you need to add PSL_MEMORY to orientation and call PSL_getplot to retrieve the plot after you finish the plot with PSL_endplot. The orientation may be landscape (PSL_LANDSCAPE or 0) or portrait (PSL_PORTRAIT or 1). Set overlay to PSL_OVERLAY (0) if the following PostScript code should be appended to an existing plot; otherwise pass PSL_INIT (1) to start a new plot. Let colormode be one of PSL_RGB (0), PSL_CMYK (1), PSL_HSV (2) or PSL_GRAY (3); this setting controls how colors are presented in the PostScript code. The origin setting determines for x and y separately the origin of the specified offsets (next argument). Each of the two characters are either r for an offset relative to the current origin, a for a temporary adjustment of the origin which is undone during BD(PSL_endplot), f for a placement of the origin relative to the lower left corner of the page, c for a placement of the origin relative to the center of the page. The array offset specifies the offset of the new origin relative to the position indicated by origin. page_size means the physical width and height of the plotting media in points (typically 612 by 792 for Letter or 595 by 842 for A4 format). The character string title can be used to specify the %%Title: header in the PostScript file (or use NULL for the default). The array font_no specifies all fonts used in the plot (by number), or use NULL to leave out the %%DocumentNeededResources: comment in the PostScript file.

long PSL_endplot (struct PSL_CTRL *P, long last_page)

> Terminates the plotting sequence and closes plot file (if other than stdout). If last_page == PSL_FINALIZE (1), then a PostScript showpage command is issued, which initiates the printing process on hardcopy devices. Otherwise, pass PSL_OVERLAY (0).

long PSL_setorigin (struct PSL_CTRL *P, double xorigin, double yorigin, double angle, long mode)

> Changes the coordinate system by translating by (xorigin,yorigin) followed by a angle-degree rotation (mode=PSL_FWD or 0) or alternatively the rotation followed by translation (mode=PSL_INV or 1).

## Memory Output

Normally, PSL will write all PostScript to the designated file stream set in PSL_beginplot. Alternatively, PSL can write all the PostScript to an internal char * buffer which can be retrieved at the end of the plotting. This mode can be enabled on a plot-by-plot basis by adding the flag PSL_MEMORY to the variable orientation passed to PSL_beginplot. Once we reach the end of the plot with PSL_endplot the buffer will be available (see below). One function provide the functionality for memory output.

char * PSL_getplot (struct PSL_CTRL *P)

> Retrieves the pointer to the PostScript plot that is kept in memory when PSL_beginplot was instructed to use memory rather than stream output. Note: It is the responsibility of the programmer to ensure that the object retrieved is duplicated or written or otherwise processed before the next call to PSL_beginplot or PSL_endsession either of which will destroy the memory pointed to.

## Changing Settings

The following functions are used to change various PSL settings and affect the current state of parameters such as line and fill attributes.

long PSL_define_pen (struct PSL_CTRL *P, char *name, long width, char *style, double offset, double rgb[])

> Stores the specified pen characteristics in a PostScript variable called name. This can be used to place certain pen attributes in the PostScript file and then retrieve them later with PSL_load_pen. This makes the stored pen the current pen.

long PSL_define_rgb (struct PSL_CTRL *P, char *name, double rgb[])

> Stores the specified color in a PostScript variable called name. This can be used to place certain color values in the PostScript file and then retrieve them later with PSL_load_rgb. This makes the stored color the current color.

long PSL_setexec (struct PSL_CTRL *P, long mode)

> If mode = 1 then we tell PSL to execute a custom PostScript procedure named PSL_completion at the start of the next overlay. Once executed, the function is reset to a dummy null procedure. Experts may define their own procedure called PSL_completion and insert it into the PostScript stream. Changing the mode can then be used to have some tasks complete prior to the new overlay being generated.

long PSL_setcolor (struct PSL_CTRL *P, double rgb[], long mode)

> Sets the current color for all stroked (mode = PSL_IS_STROKE (0)) or filled (mode = PSL_IS_FILL (1)) material to follow (lines, symbol outlines, text). rgb is a triplet of red, green and blue values in the range 0.0 through 1.0. Set the red color to -3.0 and the green color to the pattern number returned by PSL_setimage to select an image pattern as current paint color. For PDF transparency, set rgb[3] to a value between 0 (opaque) and 1 (fully transparent).

long PSL_setcurrentpoint (struct PSL_CTRL *P, double x, double y)

> Sets the current point to the location given by (x, y).

long PSL_setimage (struct PSL_CTRL *P, long image_no, char *imagefile, unsigned char *image, long dpi, long dim[3], **double f_rgb[], double b_rgb[])

> Sets up the specified image pattern as the fill to use for polygons and symbols. Here, image_no is the number of the standard PSL fill patterns (1-90; use a negative number when you specify an image filename instead and pass the image data vector and the dimensions of the image via the dim array (width, height, and bit-depth). The scaling (i.e., resolution in dots per inch) of the pattern is controlled by the image dpi; if set to 0 it will be plotted at the device resolution. The last two arguments apply to 1-bit images only and are otherwise ignored: You may replace the foreground color (the set bits) with the f_rgb color and the background color (the unset bits) with b_rgb. Alternatively, pass either color with the red component set to -1.0 and we will instead issue an image mask that is see-through for the specified fore- or background component. To subsequently use the pattern as a pen or fill color, use PSL_setcolor or DB(PSL_setfill) with the a color rgb code made up of r = -3, and b = the pattern number returned by PSL_setimage.

long PSL_setdash (struct PSL_CTRL *P, char *pattern, double offset)

> Changes the current pen style attributes. The character string pattern contains the desired pattern using a series of lengths in points specifying the alternating lengths of dashes and gaps in points. E.g., “4 2” and offset = 1 will plot like

> > x ---- ---- ----

> where x is starting point of a line (The x is not plotted). That is, the line is made up of a repeating pattern of a 4 points long solid line and a 2 points long gap, starting 1 point after the x. To reset to solid line, specify pattern = NULL (“”) and offset = 0.

long PSL_setfill (struct PSL_CTRL *P, double rgb[], long outline)

> Sets the current fill color and whether or not outline is needed for symbols. Special cases are handled by passing the red color as -1.0 (no fill), -2.0 (do not change the outline setting) or -3.0 (select the image pattern indicated by the second (green) element of rgb). For PDF transparency, set rgb[3] to a value between 0 (opaque) and 1 (fully transparent). Set outline to PSL_OUTLINE (1) to draw the outlines of polygons and symbols using the current pen, 0 to turn outline off, and -2 to leave existing setting as is.

long PSL_setfont (struct PSL_CTRL *P, long 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, 34 = ZapfDingbats, 35 = Ryumin-Light-EUC-H, 36 = Ryumin-Light-EUC-V, 37 = GothicBBB-Medium-EUC-H, and 38 = GothicBBB-Medium-EUC-V. If fontnr is outside this range, it is reset to 0.

long PSL_setfontdims (struct PSL_CTRL *P, double supsub, double scaps, double sup, double sdown)

> Changes the settings for a variety of relative font sizes and shifts pertaining to sub-scripts, super-scripts, and small caps. Default settings are given in brackets. Here, supsub sets the relative size of sub- and super-scripts [0.58], scaps sets the relative size of small caps [0.8], sup indicates the upward baseline shift for placement of super-scripts [0.33], while sdown sets the downward baseline shift for sub-scripts [0.33].

long PSL_setformat (struct PSL_CTRL *P, long n_decimals)

> Sets the 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.

long PSL_setlinewidth (struct PSL_CTRL *P, double linewidth)

> Changes the current line width in points. Specifying 0 gives the thinnest line possible, but this is implementation-dependent (seems to work fine on most PostScript printers).

long PSL_setlinecap (struct PSL_CTRL *P, long cap)

> Changes the current line cap, i.e., what happens at the beginning and end of a line segment. PSL_BUTT_CAP (0) gives butt line caps [Default], PSL_ROUND_CAP (1) selects round caps, while PSL_SQUARE_CAP (2) results in square caps. Thus, the two last options will visually lengthen a straight line-segment by half the line width at either end.

long PSL_setlinejoin (struct PSL_CTRL *P, long join)

> Changes the current linejoin setting, which handles how lines of finite thickness are joined together when the meet at different angles. PSL_MITER_JOIN (0) gives a mitered joint [Default], PSL_ROUND_JOIN (1) makes them round, while PSL_BEVEL_JOIN (2) produces bevel joins.

long PSL_setmiterlimit (struct PSL_CTRL *P, long limit)

> Changes the current miter limit used for mitered joins. PSL_MITER_DEFAULT (35) gives the default PS miter; other values are interpreted as the cutoff acute angle (in degrees) when mitering becomes active.

long PSL_settextmode (struct PSL_CTRL *P, long mode)

> Changes between the two modes PSL_TXTMODE_MINUS and PSL_TXTMODE_HYPHEN. When the minus mode is active we assume we are plotting annotation strings with numbers and all hyphens are translated to minus codes which differs based on char sets. Likewise, in hyphen mode any minus character is typeset as a hyphen in the current char set.

long PSL_settransparency (struct PSL_CTRL *P, double *transparency)

> Changes the current PDF transparency value for both fill and stroke.

long PSL_settransparencies (struct PSL_CTRL *P, double transparencies)

> Changes the current PDF transparency values for fill and stroke separately.

long PSL_settransparencymode (struct PSL_CTRL *P, char *mode)

> Changes the current PDF transparency rendering mode [Default is Normal]. Choose among Color, ColorBurn, ColorDodge, Darken, Difference, Exclusion, HardLight, Hue, Lighten, Luminosity, Multiply, Normal, Overlay, Saturation, SoftLight, and Screen.

long PSL_setdefaults (struct PSL_CTRL *P, double xyscales[], double pagergb[], char *encoding)

> Allows changes to the PSL session settings and should be called immediately after PSL_beginsession. The xyscales array affect an overall magnification of your plot [1,1]. This can be useful if you design a page-sized plot but would then like to magnify (or shrink) it by a given factor. Change the default paper media color [white; 1/1/1] by specifying an alternate page color. Passing zero (or NULL for pagergb) will leave the setting unchanged. Finally, pass the name of the character set encoding (if NULL we select Standard).

long PSL_defunits (struct PSL_CTRL *P, char *name, double value)

> Creates a PostScript variable called name and initializes it to the equivalent of value user units.

long PSL_defpoints (struct PSL_CTRL *P, char *name, double fontsize)

> Creates a PostScript variable called name and initializes it to the value that corresponds to the font size (in points) given by fontsize.

## Plotting Lines And Polygons

Here are functions used to plot lines and closed polygons, which may optionally be filled. The attributes used for drawing and filling are set prior to calling these functions; see CHANGING SETTINGS above.

long PSL_plotarc (struct PSL_CTRL *P, double x, double y, double radius, double angle1, double angle2, long type)

> Draws a circular arc with its center at plot coordinates (x, y), starting from angle angle1 and end at angle2. Angles must be given in decimal degrees. If angle1 > angle2, a negative arc is drawn. The radius is in user units. The type determines how the arc is interpreted: PSL_MOVE (1) means set new anchor point, PSL_STROKE (2) means stroke the arc, PSL_MOVE + PSL_STROKE (3) means both, whereas PSL_DRAW (0) just adds to arc path to the current path.

long PSL_plotline (struct PSL_CTRL *P, double x, double y, long n, long type)

> Assemble a continuous line through n points whose the plot coordinates are in the x, y arrays. To continue an existing line, use type = PSL_DRAW (0), or if this is the first segment in a multisegment path, set type = PSL_MOVE (1). To end the segments and draw the lines, add PSL_STROKE (2). Thus, for a single segment, type must be PSL_MOVE + PSL_STROKE (3). The line is drawn using the current pen attributes. Add PSL_CLOSE (8) to type to close the first and last point by the PostScript operators; this is done automatically if the first and last point are equal.

long PSL_plotpoint (struct PSL_CTRL *P, double x, double y, long type)

> Moves the pen from the current to the specified plot coordinates (x, y) and optionally draws and strokes the line, depending on type. Specify type as either a move (PSL_MOVE, 1), or draw (PSL_DRAW, 2), or draw and stroke (PSL_DRAW + PSL_STOKE, 3) using current pen attributes. It the coordinates are relative to the current point add PSL_REL (4) to type.

long PSL_plotbox (struct PSL_CTRL *P, double x0, double y0, double x1, double y1)

> Creates a closed box with opposite corners at plot coordinates (x0,y1) and (x1,y1). The box may be filled and its outline stroked depending on the current settings for fill and pen attributes.

long PSL_plotpolygon (struct PSL_CTRL *P, double x, double y, long n)

> Creates a closed polygon through n points whose plot coordinates are in the x, y arrays. The polygon may be filled and its outline stroked depending on the current settings for fill and pen attributes.

long PSL_plotsegment (struct PSL_CTRL *P, double x0, double y0, double x1, double y1)

> Draws a line segment between the two points (plot coordinates) using the current pen attributes.

## Plotting Symbols

Here are functions used to plot various geometric symbols or constructs.

long PSL_plotaxis (struct PSL_CTRL *P, double tickval, char *label, double fontsize, long side)

> Plots a basic axis with tick marks, annotations, and label. Assumes that PSL_beginaxes has been called to set up positioning and user data ranges. Annotations will be set using the fontsize in points. side can be 0, 1, 2, or 3, which selects lower x-axis, right y-axis, upper x-axis, or left y-axis, respectively. The label font size is set to 1.5 times the fontsize.

long PSL_plotsymbol (struct PSL_CTRL *P, double x, double y, double size[], long symbol)

> Plots a simple geometric symbol centered on plot coordinates (x, y). The argument symbol selects the geometric symbol to use. Most symbols are scaled to fit inside a circle of diameter given as size[0], but some symbols take additional parameters. Choose from these 1-parameter symbols using the predefined self-explanatory integer values PSL_CIRCLE, PSL_DIAMOND, PSL_HEXAGON, PSL_INVTRIANGLE, PSL_OCTAGON, PSL_PENTAGON, PSL_SQUARE, PSL_STAR, and PSL_TRIANGLE; these may all be filled and stroked if PSL_setfill has been called first. In addition, you can choose several line-only symbols that cannot be filled. They are PSL_CROSS, PSL_DOT, PSL_PLUS, PSL_XDASH, and PSL_YDASH. Finally, more complicated symbols require more than one parameter to be passed via size. These are PSL_ELLIPSE (size is expected to contain the three parameter angle, major, and minor axes, which defines an ellipse with its major axis rotated by angle degrees), PSL_MANGLE (size is expected to contain the 10 parameters radius, angle1, and angle2 for the math angle specification, followed by tailwidth, headlength, headwidth, shape, status, trim1 and trim2 (see PSL_VECTOR below for explanation), PSL_WEDGE (size is expected to contain the three parameter radius, angle1, and angle2 for the sector specification), PSL_RECT (size is expected to contain the two dimensions width and height), PSL_RNDRECT (size is expected to contain the two dimensions width and height and the radius of the corners), PSL_ROTRECT (size is expected to contain the three parameter angle, width, and height, with rotation relative to the horizontal), and PSL_VECTOR (size is expected to contain the 9 parameters x_tip, y_tip, tailwidth, headlength, headwidth, shape, status, head1, head2, trim1, and trim2. Here (x_tip,y_tip) are the coordinates to the head of the vector, while (x, y) are those of the tail. shape 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. 0.0 gives a triangular head, 1.0 gives an arrow shaped head. The status value is a bit-flag being the sum of several possible contributions: PSL_VEC_RIGHT (2) = only draw right half of vector head, PSL_VEC_BEGIN (4) = place vector head at beginning of vector, PSL_VEC_END (8) = place vector head at end of vector, PSL_VEC_JUST_B (0) = align vector beginning at (x, y), PSL_VEC_JUST_C (16) = align vector center at (x, y), PSL_VEC_JUST_E (32) = align vector end at (x, y), PSL_VEC_JUST_S (64) = align vector center at (x, y), PSL_VEC_OUTLINE (128) = draw vector head outline using default pen, PSL_VEC_FILL (512) = fill vector head using default fill, PSL_VEC_MARC90 (2048) = if angles subtend 90, draw straight angle symbol (PSL_MANGLE only). The symbol may be filled and its outline stroked depending on the current settings for fill and pen attributes. The parameters head1 and head2 determines what kind of vector head will be plotted at the two ends (if selected). 0 = normal vector head, 1 = circle, 2 = terminal crossbar. Finally, trim1 and trim2 adjust the start and end location of the vector.

## Plotting Images

Here are functions used to read and plot various images.

long PSL_plotbitimage (struct PSL_CTRL *P, double x, double y, double xsize, double ysize, int justify, unsigned char buffer, long nx, long ny, double f_rgb[], double b_rgb[])

> Plots a 1-bit image image at plot coordinates (x, y) justified as per the argument justify (see JUSTIFICATION for details). The target size of the image is given by xsize and ysize in user units. If one of these is specified as zero, the corresponding size is adjusted to the other such that the aspect ratio of the original image is retained. buffer is an unsigned character array in scanline orientation with 8 pixels per byte. nx, ny refers to the number of pixels in the image. The rowlength of buffer must be an integral number of 8; pad with zeros. buffer[0] is upper left corner. You may replace the foreground color (the set bits) with the f_rgb color and the background color (the unset bits) with b_rgb. Alternatively, pass either color with the red component set to -1.0 and we will instead issue an image mask that is see-through for the specified fore- or background component. See the Adobe Systems PostScript Reference Manual for more details.

long PSL_plotcolorimage (struct PSL_CTRL *P, double x, double y, double xsize, double ysize, int justify, unsigned char *buffer, long nx, long ny, long depth)

> Plots a 1-, 2-, 4-, 8-, or 24-bit deep image at plot coordinates (x, y) justified as per the argument justify (see JUSTIFICATION for details). The target size of the image is given by xsize and ysize in user units. If one of these is specified as zero, the corresponding size is adjusted to the other such that the aspect ratio of the original image is retained. This functions sets up a call to the PostScript colorimage or image operators. The pixel values are stored in buffer, an unsigned character array in scanline orientation with gray shade or r/g/b values (0-255). buffer[0] is the upper left corner. depth is number of bits per pixel (24, 8, 4, 2, or 1). nx, ny refers to the number of pixels in image. The rowlength of buffer must be an integral number of 8/Idepth. E.g. if depth = 4, then buffer[j]/16 gives shade for pixel[2j-1] and buffer[j%16 (mod 16) gives shade for pixel[2j]. When -depth is passed instead then “hardware” interpolation of the image is requested (this is implementation dependent). If -nx is passed with 8- (or 24-) bit images then the first one (or three) bytes of buffer holds the gray (or r/g/b) color for pixels that are to be masked out using the PS Level 3 Color Mask method. See the Adobe Systems PostScript Reference Manual for more details.

long PSL_plotepsimage (struct PSL_CTRL *P, double x, double y, double xsize, double ysize, int justify, unsigned char *buffer, long size, long nx, long ny, long ox, long oy)

> Plots an Encapsulated PostScript (EPS) image at plot coordinates (x, y) justified as per the argument justify (see JUSTIFICATION for details). The target size of the image is given by xsize and ysize in user units. If one of these is specified as zero, the corresponding size is adjusted to the other such that the aspect ratio of the original image is retained. The EPS file is stored in buffer and has size bytes. This function simply includes the image in the PostScript output stream within an appropriate wrapper. Specify position of lower left corner and size of image. nx, ny, ox, oy refers to the width, height and origin (lower left corner) of the BoundingBox in points.

long PSL_loadeps (struct PSL_CTRL *P, char *file, struct imageinfo *header, unsigned char **image)

> Reads the image contents of the EPS file given by the file name. The header is filled with dimensional information. If image is NULL we return just with header, otherwise we read and return the entire EPS content via image.

## Plotting Text

Here are functions used to read and plot text strings and paragraphs. This can be somewhat complicated since we rely on the PostScript interpreter to determine the exact dimensions of text items given the font chosen. For perfect alignment you may have to resort to calculate offsets explicitly using long PSL_deftextdim, PSL_set_height and others and issue calculations with PSL_setcommand.

long PSL_plottext (struct PSL_CTRL *P, double x, double y, double fontsize, char *text, double angle, long justify, long mode)

> The text is plotted starting at plot coordinates (x, y) and will make an angle with the horizontal. The point (x, y) maps onto different points of the text-string by giving various values for justify (see JUSTIFICATION for details). If justify is negative, then all leading and trailing blanks are stripped before plotting. Certain character sequences (flags) have special meaning to PSL_plottext. @~ toggles between current font and the Mathematical Symbols font. @%no% selects font no while @%% resets to the previous 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. @;r/g/b; changes the font color while @;; resets it [optionally append =transparency to change the transparency (0--100) of the text (the Default is opaque or 0)], @:size: changes the font size (@:: resets it), and @_ toggles underline on/off. If text is NULL then we assume PSL_plottextbox was called first. Give fontsize in points. Normally, the text is typed using solid characters in the current color (set by PSL_setcolor). To draw outlined characters, set mode == 1; the outline will get the current color and the text is filled with the current fill color (set by PSL_setfill). Use mode == 2 if the current fill is a pattern. Use mode == 3 to achieve the same as mode == 1, while preventing the outline from obsuring any filled text font; the outline will hence be reduced to half the selected width. If the text is not filled, mode == 3 operates the same as mode == 1. If fontsize is negative it means that the current point has already been set before PSL_plottext was called and that (x, y) should be ignored.

long PSL_plottextbox (struct PSL_CTRL *P, double x, double y, double fontsize, char *text, double angle, long justify, double offset[], long mode)

> This function is used in conjugation with PSL_plottext when a box surrounding the text string is desired. Taking most of the arguments of PSL_plottext, the user must also specify mode to indicate whether the box needs rounded (PSL_YES = 1) or straight (PSL_NO = 0) corners. The box will be colored with the current fill style set by PSL_setfill. That means, if an outline is desired, and the color of the inside of the box should be set with that routine. The outline will be drawn with the current pen color (and width). The offset array holds the horizontal and vertical distance gaps between text and the surrounding text box in distance units. The smaller of the two determined the radius of the rounded corners (if requested).

long PSL_deftextdim (struct PSL_CTRL *P, char *prefix, double fontsize, char *text)

> Computes the dimensions (width and height) required by the selected text given the current font and its fontsize (in points). The values are stored as PostScript variables called prefix_w and prefix_h, respectively. This function can be used to compute dimensions and, via BF(PSL_setcommand), calculate chances to position a particular item should be plotted. For instance, if you compute a position this way and wish to plot the text there, pass the coordinates to PSL_plottext as NaNs. If prefix is BF(-w), BF(-h), BF(-d) or BF(-b), no PostScript variables will be assigned, but the values of width, height, depth, or both width and height will be left on the PostScript stack.

long PSL_setparagraph (struct PSL_CTRL *P, double line_space, double par_width, long par_just)

> Initialize common settings to be used when typesetting paragraphs of text with PSL_plotparagraph. Specify the line spacing (1 equals the font size) and paragraph width (in distance units). Text can be aligned left (PSL_BL), centered (PSL_BC), right (PSL_BR), or justified (PSL_JUST) and is controlled by par_just.

long PSL_plotparagraphbox (struct PSL_CTRL *P, double x, double y, double fontsize, char *text, double angle, long justify, double offset[], long mode)

> Computes and plots the text rectangle for a paragraph using the specified fontsize (in points). Here, text is an array of the text to be typeset, using the settings initialized by PSL_setparagraph. The escape sequences described for PSL_plottext can be used to modify the text. Separate text into several paragraphs by appending \r to the last item in a paragraph. The whole text block is positioned at plot coordinates x, y, which is mapped to a point on the block specified by justify (see JUSTIFICATION for details). The whole block is then shifted by the amounts shift[]. The box will be plotted using the current fill and outline settings. The offset array holds the horizontal and vertical distance gaps between text and the surrounding text box in distance units. Use mode to indicate whether the box should be straight (PSL_RECT_STRAIGHT = 0), rounded (PSL_RECT_ROUNDED = 1), convex (PSL_RECT_CONVEX = 2) or concave (PSL_RECT_CONCAVE = 3).

long PSL_plotparagraph (struct PSL_CTRL *P, double x, double y, double fontsize, char *text, double angle, long justify, long mode)

> Typesets paragraphs of text using the specified fontsize (in points). Here, text is an array of the text to be typeset, using the settings initialized by PSL_setparagraph. The escape sequences described for PSL_plottext can be used to modify the text. Separate text into several paragraphs by appending \r to the last item in a paragraph. The whole text block is positioned at plot coordinates x, y, which is mapped to a point on the block specified by justify (see JUSTIFICATION for details). See PSL_plotparagraphbox for laying down the surrounding text rectangle first.

long PSL_plottextline (struct PSL_CTRL *P, double *xpath, double *ypath, long *np, long nseg, void *arg1, void *arg2, char *text[], double angle[], long n_per_seg[], double fontsize, **long* justify, double offset[], long mode)

> Please text along one or more path segments. The function does different things depending on the bit flags in mode. A key distinction occurs if the bit flag contains the bit PSL_TXT_CURVED (64) which means we wish to typeset the text along a variable and curved baseline given by the segments in xpath, ypath; otherwise we set straight text (possibly at an angle) and the xpath, ypath are not considered for text placement [If no line drawing is desired then these two arrays may be NULL]. We will describe the action taken for each bit value. Multiple values may be passed at the same time and we processes from low to high bit. PSL_TXT_INIT: When mode contains this bit (1) we will initialize all the required variables and store them in the PostScript file. PSL_TXT_SHOW: We wish to see the text strings (otherwise they may only serve as guides to set up clip paths). PSL_TXT_CLIP_ON: Use the text and the paths to set up clip paths. PSL_TXT_DRAW: Draw the lines defined by the xpath, ypath arrays. PSL_TXT_CLIP_OFF: Turn the text path clipping off. We pass the text strings via text. The locations of text plotting depends on whether PSL_TXT_CURVED is selected. If it is then you must pass as arg1 the node array indicating at which node in the xpath, ypath array the text will be plotted; let arg2 be NULL. For straight baselines you must instead pass another set of x, y coordinates with the locations of the text label placements via arg1, arg2. Each label has its own entry in the angle array. The text is an array of text pointers to the individual text items. The offset array holds the x and y distance gaps between text and the surrounding text box in user units (the clip path is the combination of all these text boxes). Use justify to specify how the text string relates to the coordinates (see BF(JUSTIFICATION) for details). PSL_TXT_FILLBOX (128) will fill the text box (this requires you to first define the text box rgb color with PSL_define_rgb by setting a local PostScript variable that must be called PSL_setboxrgb). PSL_TXT_DRAWBOX (256) will draw the text box outlines (this requires you to first define the text box pen with PSL_define_pen by setting a local PostScript variable that must be called PSL_setboxpen). Before calling this function you must also initialize a PSL array for line pens and text fonts.

## Clipping

Here are functions used to activate and deactivate clipping regions.

long PSL_beginclipping (struct PSL_CTRL *P, double x, double y, long n, double rgb[], long flag)

> Sets up a user-definable clip path as a series on n points with plot coordinates (x, y). Plotting outside this polygon will be clipped until PSL_endclipping is called. If rgb[0] = -1 the inside of the path is left empty, otherwise it 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 = PSL_PEN_MOVE_ABS (1) means this is the first path in a multisegment clip path. flag = PSL_PEN_DRAW_ABS (2) means this is the last segment. Thus, for a single path, flag = PSL_PEN_DRAW_AND_STROKE_ABS (3).

long PSL_endclipping (struct PSL_CTRL *P, long mode)

> Depending on the mode it restores the clip path. The mode values can be: -n will restore n levels of text-based clipping, n will restore n levels of polygon clipping, PSL_ALL_CLIP_TXT will undo all levels of text-based clipping, and PSL_ALL_CLIP_POL will undo all levels of polygon-based clipping.

## Miscellaneous Functions

Here are functions used to issue comments or to pass custom PostScript commands directly to the output PostScript file. In C these functions are declared as macros and they can accept a variable number of arguments. However, from FORTRAN only a single text argument may be passed.

long PSL_setcommand (struct PSL_CTRL *P, char *text)

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

long PSL_comment (struct PSL_CTRL *P, char *text)

  Writes a comment (text) to the PostScript output file, e.g., “Start of graph 20. The comment are prefixed with with %% .

## Authors

Paul Wessel, School of Ocean and Earth Science and Technology, http://www.soest.hawaii.edu.

Remko Scharroo, EUMETSAT, Darmstadt, Germany, http://www.eumetsat.int.

## Bugs

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

## See Also

psconvert

## References

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