Contents

License Notice

Introduction

Getting Started

• Installation
• A simple example
• More examples
• Fortran interface
• Perl interface

g2 Function Reference

• Device Functions
• Drawing Functions
• General
• Pixels and QuasiPixels
• Lines
• Triangles, Rectangles, Polygons
• Circles, Ellipses, Arcs
• Text
• Images

• Style Functions
• Colors
• Line Styles
• Text

• Other Functions

g2 Device Support

Developing new devices

Known Bugs and ToDo

Appendix

• PostScript paper sizes

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License Notice

Introduction

Short version (if you are in hurry):

• 2D graphic library
• Simple to use
• Supports several types of output devices (currently X11, PostScript, devices supported by gd (PNG, JPEG) and MS Windows windows)
• Concept allows easy implementation of new device types
• Virtual devices allow to send output simultaneously to several devices
• User definable coordinate system
• Written in ANSI-C
• Tested under Digital Unix, AIX, Linux, VMS and Windows NT
• Perl support
• Fortran interface

g2 is a simple to use graphics library for 2D graphical applications written in Ansi-C. This library provides a comprehensive set of functions for simultaneous generation of graphical output on different types of devices. Presently, following devices are currently supported by g2: X11, gd (PNG and JPEG), PostScript (xfig is in developement).
One major feature of the g2_library is the concept of virtual devices. An arbitrary number of physical devices (such as PostScript, or X11) can be grouped to create a so-called virtual device. Commands sent to such a virtual devices will automatically issued to all attached physical devices. This allows for example simultaneous output to a PNG file and a Postscript file. A virtual device in turn can be attached to another virtual device, allowing to construct trees of devices.
Virtual devices can also be useful when using different user-coordinate systems. E.g. one X11 window showing an overview of a graphical output, and a second window showing a zoom of a more detailed area of the graphic. Drawing in both windows is performed by one single command to the virtual device.

                                   /-------> PNG:   g2_attach(id_PNG,..
            ----------------------- 
g2_plot---> | Virtual device: id  |--------> X11:   g2_attach(id_X11,...
            -----------------------
                                   \-------> PS:    g2_attach(id_PS,...

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Getting Started

• PNG and JPEG support

g2 uses the gd library by Thomas Boutell to generate PNG files. This package is freeware (however not GPL) and can be downloaded at http://www.boutell.com/gd/.
Linux users might prefer to install a pre-compiled gd rpm package which should be available at your local RedHat mirrorsite.
NT users should install the gd source package in a subdirectory named "gd" which should be located in the same directory as the g2 subdirectory (but not in the g2 directory itself). Otherwise file locations for gd must be modified in the g2 project workspace.
Unix and VMS users will have to build and install gd according to the instructions found in the gd distribution.

Installation

LINUX

• Either install RPM packet with binaries, or compile as described in the UNIX section

• Extract package with gzip -dc g2-xxxx.tar.gz | tar xvf -
• Run './configure'
• Optionally run 'make depend'
• Run 'make'
• Run 'make install' or copy libg2.a and g2.h, g2_X11.h, g2_gd.h, anf g2_PS.h to the default locations for library and include files.
• Optional: run 'make demo' to compile demo applications

• Extract package using either the .tar.gz or the .zip distribution
• MS Visual C++ users can build both library and demos with the supplied project file: g2.dsw (To obtain an icon and use menu functions you must also build the g2res project in g2.dsw)
• users of gcc or other commandline based compilers with make support continue as in Unix example
• It is also possible to compile g2 on winNT/95 using the free cygwin32 library and a X-windows library for windows. Theoretically it should be possible to support both X-windows and native NT/95 windows at the same time.

• Change to directory g2_perl
• Perform following steps
• perl Makefile.PL
• make
• make test
• make install
• See the perl interface section for more information
• swig is also supported, more details are comming ...

Try to extract either the tar.gz or the zip distribution (whatever is easier for you)

type mms to compile library (descrip.mms file is suplied)

run mms in demo directory to compile demo applications

A simple example

#include <g2.h>
#include <g2_PS.h>

main()
{
    int id;
    id = g2_open_PS("rect.ps", g2_A4, g2_PS_land); 
    g2_rectangle(id,20,20,150,150); 
    g2_close(id);
}

2.) Open devices using g2_open functions. The open function returns a device id of type int, which you need to refer to the device.

3.) use g2 functions for drawing, changing drawing styles, or doing other stuff

4.) call g2_close to close device
 

You want to draw a PNG file instead of a PostScript file ?

replace the PS header file with

#include <g2_gd.h>

id = g2_open_gd("rect.png",300,200,g2_gd_png);

Here we use the concept of virtual devices. Open a PNG and PostScript device, then open a virtual device and attach both the PNG and PostScript device to the virtual device. Plot commands to the virtual device will be issued to both PNG and PostScript device. You can attach and detatch further devices at any time.

#include <g2.h>
#include <g2_PS.h>
#include <g2_gd.h>

main()
{
    int id_PS,id_PNG,id;

    id_PS  = g2_open_PS("rect.ps", g2_A4, g2_PS_land);
    id_PNG = g2_open_gd("rect.png",300,200,g2_gd_png);
    id     = g2_open_vd();

    g2_attach(id,id_PS);
    g2_attach(id,id_PNG);

    g2_rectangle(id,20,20,150,150);
    g2_circle(id,50,60,100);

    g2_close(id);
}

More examples

Fortran interface

The Fortran interface for g2 is currently tested for Linux and Digital Unix/OSF. Function names for Fortran are the same as in C, however following differences exist:

• all variables including device IDs are of type REAL
• void functions are implemented as subroutines and must be called with CALL
• constants defined by #define in C (e.g. g2_A4) do not work. Get corresponding values from the apropriate header files.

        program demo
        real d,color
        d=g2_open_PS('demo_f.ps', 4.0, 1.0)
        call g2_plot(d, 50.0, 50.0)
        call g2_string(d, 25.0, 75.0, 'TEST ')
        color=g2_ink(d, 1.0, 0.0, 0.0)
        write (6,*) color
        call g2_pen(d, color)
        call g2_circle(d, 20.0, 20.0, 10.0)
        call g2_flush(d)
        call g2_close(d)
        stop
        end

Perl interface (old info)

The perl interface for g2 is currently tested for Linux and Digital Unix/OSF. Function names in perl are the same as in C, however the device itself is implemented object orientated, i.e. the device argument is ommited in all functions.
E.g., following simple perl script:

use G2;

$d = newX11 G2::Device(100,100);
$d->circle(10, 10, 20);
$d->string(20, 40, "Hello World");

print "\nDone.\n[Enter]\n";
getc(STDIN);

$d->close()

The creator functions are newX11, newGIF, newPS, etc. and accept the same arguments as the open functions in the C version.
See the perl documentation (perldoc G2) for more details and the test.pl script for a more extensive example.

g2 Function Reference

Device Functions

int g2_open_X11(int width, int height)

open an X11 window
width,height: width and height of X11 window in pixels
returns : device id of new X11 device.

int g2_open_X11X(int width, int height, int x, int y, char *window_name, char *icon_name, char *icon_data, int icon_width, int icon_height);

open an X11 window supporting additional features as icons and window title.
width,height: width and height of X11 window in pixels
x,y: position of window on screen
window_name: \0 terminated string of name of window
icon_name:
icon_data:
icon_width,icon_height:
returns : device id of new X11 device.

int g2_open_PS(const char *file_name, enum g2_PS_paper paper, enum g2_PS_orientation orientation)

open a new PostScript device
file_name: name of PostScript file
paper: Paper size (e.g. g2_A4, g2_Letter). See PostScript paper sizes for a full list of supported sizes.
orientation: paper orientation. Either g2_PS_land for landscape or g2_PS_port for portrait
returns : device id of new PostScript device.

int g2_open_win32(int width, int height, const char *name, int type)

open a new Win32 device
width,height: width and height of win32 window in pixels
name: depending on the value of "type" (see below) either window title or name of the metafile.
type: Defines the output type of win32 device:
0: output to a window
1: output to an enhanced metafile (EMF)
returns : device id of new win32 device

int g2_open_gd( const char *filename, int width, int height, enum g2_gd_type gd_type)

open a new gd device
filename: name of the file.
width,height: width and height of the image in pixels
gd_type: corrently supported g2_gd_png and g2_gd_jpeg
returns : device id of new gd device

int g2_open_vd(void)

open a new virtual device
returns : device id of new virtual device.

void g2_detach(int vd_dev, int dev)
detach a device attached to a virtual device
vd_dev : device id of virtual device to detach from.
dev : device id of device to detach.

Device Functions

void g2_close(int dev)
close device
dev: device ID of device to close

void g2_set_auto_flush(int dev, int on_off);
switch on/off autoflush for specified device dev
on/off: 0 = off, 1 = on
void g2_set_coordinate_system(int dev, double x_origin, double y_origin, double x_mul, double y_mul)
set origin and scaling for the device dev
x,y: coordinates of origin
x_mul,y_mul: scaling factor for x- and y axis
void g2_flush(int dev)
flush device dev
void g2_save(int dev)
Applies to file devices only. Flush, save and close files of device dev. The device remains open. Use to generate valid intermediate output files.
void g2_ld()
Returns id of last accessed device (macro G2LD is defined as g2_ld() )

Drawing Functions

General

void g2_clear(int dev)
Clear device dev
void g2_set_background(int dev, int color)
Set background color for device dev
color: index of colorpalette for new background color
void g2_move(int dev, double x, double y)
set new current point for device dev
x,y: coordinates of new current point
void g2_move_r(int dev, double dx, double dy)
set new current point relative to current point for device dev
x,y: relative coordinates of new current point

Pixels and QuasiPixels

void g2_plot(int dev, double x, double y)

void g2_plot_r(int dev, double dx, double dy)

void g2_set_QP(int dev, double d, enum QPshape shape);

void g2_plot_QP(int dev, double x, double y);

Lines

void g2_line(int dev, double x1, double y1, double x2, double y2)
Draw a line on device dev
x1,y1: starting point
x2,y2: ending point

void g2_line_to(int dev, double x, double y)
Draw a line from current position on device dev
x,y: ending point

void g2_line_r(int dev, double dx, double dy)
Draw a line relative to the current position on device dev
dx,dy: relative coordinates of the ending point
void g2_poly_line(int dev, int N_pt, double *points)
Draw a polyline with N_pt corners on device dev
N_pt: Number of corners
points: Array of point coordinates (x1,y1,x2,y2,x3,y3 ....)

Triangles, Rectangles, Polygons

void g2_triangle(int dev, double x1, double y1, double x2, double y2, double x3, double y3)
draw a triangle on device dev
x1,y1,x2,y2,x3,y3: coordinates of the corners of the triangle

void g2_filled_triangle(int dev, double x1, double y1, double x2, double y2, double x3, double y3)
draw a filled triangle on device dev
x1,y1,x2,y2,x3,y3: coordinates of the corners of the triangle
void g2_rectangle(int dev, double x1, double y1, double x2, double y2)
draw a rectangle on device dev
x1,y1,x2,y2: coordinates of the corners of the rectangle

void g2_filled_rectangle(int dev, double x1, double y1, double x2, double y2)
draw a filled rectangle on device dev
x1,y1,x2,y2: coordinates of the corners of the rectangle

void g2_polygon(int dev, int N_pt, double *points)
Draw a polygon with N_pt corners on device dev
N_pt: Number of corners
points: Array of point coordinates (x1,y1,x2,y2,x3,y3 ....)
void g2_filled_polygon(int dev, int N_pt, double *points)
Draw a polygon with N_pt corners on device dev
N_pt: Number of corners
points: Array of point coordinates (x1,y1,x2,y2,x3,y3 ....)

Circles, Ellipses, Arcs

void g2_circle(int dev, double x, double y, double r)
Draw a circle on device dev
x,y: center point
r: radius

void g2_filled_circle(int dev, double x, double y, double r)
Draw a filled circle on device dev
x,y: center point
r: radius

void g2_ellipse(int dev, double x, double y, double r1, double r2)
Draw an ellipse on device dev
x,y: center point
r1,r2: x and y radius
void g2_filled_ellipse(int dev, double x, double y, double r1, double r2)
Draw a filled ellipse on device dev
x,y: center point
r1,r2: x and y radius
void g2_arc(int dev, double x, double y, double r1, double r2, double a1, double a2)
Draw an arc on device dev
x,y: center point
r1,r2: x and y radius
a1,a2: starting and ending angle in radians
void g2_filled_arc(int dev, double x, double y, double r1, double r2, double a1, double a2)
Draw a filled arc on device dev
x,y: center point
r1,r2: x and y radius
a1,a2: starting and ending angle in radians

Text

void g2_string(int dev, double x, double y, char *text)
Draw a text string on device dev
x,y: Position of text
text: pointer to text string

Images

void g2_image(int dev, double x, double y, int x_size, int y_size, int *pens)
Draw a pen image on device dev
x,y: Position of image (lower left corner)
x_size,y_size: size of image
pens: integer array of size x_size x y_size specifying pen colors

Style Functions

Colors

int g2_ink(int dev, double red, double green, double blue)
create new pen color for device dev
red,green,blue: RGB value of new color, values can range from 0..1
returns: index of new color
void g2_pen(int dev, int color)
select new drawing color for device dev
color: index of new color to use.
void g2_reset_palette(int dev)
reset palette of device dev to default color palette
void g2_clear_palette(int dev)
clear palette of device dev

Line Styles

void g2_set_dash(int dev, int N, double *dashes)
set dash style for lines for device dev

void g2_set_line_width(int dev, double w)
set line width for device dev
width: width of line in ... units

Text

void g2_set_font_size(int dev, double size)
set font size for device dev
size: new font size

Other Functions

Query Pointer (mouse)

void g2_query_pointer(int dev, double *x, double *y, unsigned int *button)
query pointer (usually mouse) position for physical device dev
x, y: pointer coordinates
button: button status (device dependent)

Device Support

Legend:
x ............ Native support
E ........... Emulation of function
K ........... Kernel internal function

Function	PS	X11	gd	xfig	Win32
g2_close	x	x	x	x	x
g2_output_to	K	K	K	K	K
g2_set_auto_flush	K	K	K	K	K
g2_set_coordinate_system	K	K	K	K	K
g2_flush		x
g2_save			x

Drawing Functions

Developing new devices

(This section is obviously still in work. Please use copy-paste method to add new devices, i.e. copy code from an implemented device and replace function code with the code appropriate for your use case.)

Known bugs and problems

Win32:

• You may experience problems importing EMF to CorelDraw 8 and possibly other applications (e.g. dashed lines not working). This is a problem of the CorelDraw import filter and not a bug in g2 ! You can correctly view enhanced metafiles with the Microsoft program ENMETA.EXE (downloadable at several ftp sites) and also export placable WMF files with this tool.
• Dashed lines should not work with Win95 according to MS-VC++ documentation (not tested).

Perl:

• You cannot use a perl G2 device variable twice, i.e.


$d = newX11(100,100);
.....
$d->close();
$d = newX11(200,200);

will not work properly. This should be fixed in the next release.

ToDo

General:

• Implement additional devices: Xfig (in development), MacOS (help wanted !), other Bitmap output (e.g. PNG, JPEG, BMP), ...


• Documentation for implementing new physical devices.


• Implement native image support and image import functions.

Win32:

• Compile g2 as a pure DLL rather as a static library. This would allow the use of g2 from applications such as Word, Excel, Access, etc.

Appendix

PostScript paper sizes