java qr code app PGPLOT devices in Java

Creating QR Code 2d barcode in Java PGPLOT devices

The pgopen() call takes one argument: the device to write to. A device specification is made up of two parts: optionally, the name of the device or file and the device type,

Version 5.0.0 was released in December 1994, and the current version, 5.2.0, was released in June 1997.

preceded by a slash (/). If the device or file name contains slashes, it should be enclosed in double quotes:

my $device_id = pgopen('"/tmp/file.ps"/PS');

If the device or filename is left off, PGPLOT will use a default name. Which devices are available to you depends on how your local copy of the library has been compiled. The distribution ships with code for a large number of devices, some of which are shown in table 5.2.

Table 5.2 The devices that can be used in PGPLOT programs, by specifying them as an argument to pgopen(). The device names starting with a V cause the output to be vertically oriented, the others have a horizontal orientation. For the devices that output to a file, a nondefault file name can be specified between double quotes before the slash. Type GIF file HPGL plotters Portable pixel map PostScript X Windows Null device (no output) LaTeX picture environment Type specifications /GIF /VGIF , /HPGL, /VHPGL /PPM, /VPPM /PS, /CPS, /VPS, /VCPS /XWINDOW, /XSERVE /NULL /LATEX pgplot.tex Default device pgplot.gif pgplot.hpgl pgplot.ppm pgplot.ps default X display

The device names that start with a V plot their output in portrait (vertical) mode, the other ones plot in landscape mode. For example: to plot a GIF file in landscape mode, use /GIF. To plot in portrait mode, use /VGIF. The PostScript drivers with a C in the name will output color PostScript. Each device can be controlled by setting environment variables which are described in the user manual. If you want to specify a different width, height or resolution than is the default for the driver, you would set the appropriate environment variables. For example, to set the width and height of a GIF output file, you would do something like:

$ENV{PGPLOT_GIF_WIDTH} = 640; $ENV{PGPLOT_GIF_HEIGHT} = 480; pgopen('"/tmp/resized.gif"/GIF');

The user manual contains an appendix with a full description of each driver, including all the environment variables that affect the output for that driver. There are a number of device drivers available for specific printers, plotters, terminals and special applications, such as tcl/tk widgets. 5.3.2 Example: A simple X-Y plot PGPLOT produces simple X-Y plots with a minimum of fuss, but there is a certain methodology that needs to be followed. 77

Figure 5.6 This graph illustrates how to use PGPLOT to plot data points with their respective error bars, a function to fit the data, and a visual label for this function s line.

Let s walk through the code that produced figure 5.6:

use PGPLOT; my my my my @x = (-0.5, 0, 1, 2, 3, 5); @y = (0.35, 0.1, 1.2, 3.3, 9.5, 23); @y_err = (0.6, 0.3, 0.8, 1.6, 2.0, 3); $num = @x;

First, the PGPLOT module is included, which exports all the functionality we need into the current name space, hence we can use the functions just as described in the PGPLOT user s manual. We then set up some data to plot. Most of the PGPLOT calls require an array of X values and an array of Y values of the same length. Since we want to draw error bars as well, we define an array containing the error in the measurements in both the upward and downward directions, i.e., the total error is twice as large as the elements of the array. These arrays will be used later in the program in calls to pgpt() and pgerry(). It s now time to open a device to write to, and set up the environment:

$ENV{PGPLOT_PS_WIDTH} = 4000; $ENV{PGPLOT_PS_HEIGHT} = 3000; my $dev_id = pgopen('pgplot1.eps/VPS'); die "Couldn't open plot" if $dev_id <= 0; pgslw(2); pgsch(1.5); pgenv(-1, 5.5, -5, 30, 0, 0);

The pgopen() function is called to open a PostScript file for output. If this fails, pgopen() will return a false value, allowing us to check for success in the same way that we would with a regular open(). You will occasionally see a call to pgbeg() instead of pgopen(). This is a sign that you re looking at an older program, since pgbeg() is deprecated nowadays, and only available for compatibility with existing programs. 78