.. index:: ! postscriptlight *************** postscriptlight *************** .. only:: not man PSL 5.1 - 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 :doc:`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_BL, 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_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 <#toc6>`_ ---------------------------- 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_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_setpattern** to select a pattern as current paint color. For PDF transparency, set *rgb*\ [3] to a value between 0 (opaque) and 1 (fully transparent). **long PSL_setpattern** (**struct PSL_CTRL** *\*P*, **long** *image_no*, **char** *\*imagefile*, **long** *dpi*, **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. 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 two remaining settings 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_setpattern**. **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. **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_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 <#toc7>`_ -------------------------------------- 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 <#toc8>`_ --------------------------- 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 <#toc9>`_ -------------------------- 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_loadimage** (**struct PSL_CTRL** *\*P*, **FILE** *\*fp*, **struct imageinfo** *\*header*, **unsigned char** *\*\*image*) Reads the image contents of the EPS file or a raster image pointed to by the open file pointer *fp*. The routine can handle Encapsulated PostScript files or 1-, 8-, 24-, or 32-bit raster images in old, standard, run-length encoded, or RGB-style Sun format. Non-Sun rasters are automatically reformatted to Sun rasters via a system call to GraphicsMagick's or ImageMagick's **convert**, if installed. The image is returned via the *image* pointer. 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 hight 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 <#toc12>`_ ----------------------------------- 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 -------- :doc:`psconvert` References ---------- Adobe Systems Inc., 1990, PostScript language reference manual, 2nd edition, Addison-Wesley, (ISBN 0-201-18127-4).