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  <td><br><h2>making web-based graphs</h2></td>
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  <small>
  <a href="../doc/Welcome.html"><img src="../doc/ploticus.gif" border=0></a><br>
  <a href="../doc/Welcome.html">Welcome</a> &nbsp; &nbsp;
  <a href="../gallery/index.html">Gallery</a> &nbsp; &nbsp;
  <a href="../doc/Contents.html">Handbook</a> 
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.TH making_web-based_graphs PL "23-AUG-2001   PL www.sgpr.net"

.ig >>
<center>
<img src="../gallery/stock.gif"><br>
</center>
.>>

.SH WEB-BASED GRAPHS
This page contains notes related to use of ploticus to produce
data displays that are viewable on web pages.
There are a number of
.ig >>
<a href="../gallery/gall.real.html">
.>>
\0web sites that are using ploticus
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</a>
.>>
\0.

.LP
Ploticus utilizes the GD image generation library from 
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<a href="http://www.boutell.com">
.>>
\0boutell.com
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</a>
.>>
\0.  Ploticus is bundled
with portions of GD 1.3 (run-length encoded psuedo-GIF images)
and GD 1.6 (PNG images).  Of, if you prefer, ploticus may be
built by linking it with your own copy of GD 1.8.4 or higher,
for PNG, PJEG, WBMP, and FreeType2 support (see GD18 in the Makefile).


.SH CREATING PNG
To create a PNG image, use pl or pltab with the \fC-png\fR option.
.LP
To incorporate a PNG image into an HTML web page, use the
HTML construct:
.ce
\fC<img src="mygraph.png">\fR
.LP
\fBPNG\fR is a newer image format that has superior compression 
(hence the images are smaller and faster to transmit).  
The images can be viewed using the newer versions of web browsers 
(Netscape 4.04 or higher, Explorer 4.0 or higher)
and image viewing tools such as \fBxv\fR.  To see if your
current web browser can display PNG, try
.ig >>
<a href="../thumbpng/index.html">this page</a>.
See also <a href="http://www.libpng.org/pub/png">the PNG home page</a>
.>>


.SH CREATING GIF
To create GIF, use pl or pltab with the \fC-gif\fR option.
.LP
To incorporate a GIF image into an HTML web page, use the HTML
construct:
.ce
\fC<img src="mygraph.gif">\fR
.LP
\fBGIF\fR format has been around for a long while, is fairly universal, and
can be viewed on any graphical web browser or image viewing tool.
\fIPloticus does not read GIF files.
Ploticus writes run-length-encoded (RLE) GIF files. 
Our understanding is that these RLE GIF files do not 
use patented LZW compression.\fR
The RLE GIF images that ploticus produces are viewable via
any graphical web browser or image viewer that supports GIF.
.LP
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<a href="../doc/gifpatent.html">
.>>
More on GIF LZW patent and licensing issues
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</a>
.>>




.SH TRANSPARENT BACKGROUND
.ig >>
<a href="../gallery/transparent.htm"><img src="../gallery/transparent.gif" border=0></a>
.>>
.LP
Images may be created with 'transparent' background by setting
the background color to \fCtransparent\fR.  This allows the ploticus
graphs to be "overlayed" against the existing background color of
the web page.
.br
.br

.SH WEB PAGE EXAMPLE
.LP
Here is an example HTML page that is viewable using any web browser:
.nf
.ft C
<html>
<center>
Here is an image.
<img src="lineplot1.gif">
</html>
.ft R
.fi
.LP
Suppose the above is in a file called \fC/home/steve/firsttry.html\fR.  
If you don't have a web server running, you can view the file by 
entering the following URL into your web browser:
.ce
\fBfile:///home/steve/firsttry.html\fR
This assumes that your web browser is running on the same computer
that the HTML file is located upon.

.SH CGI CONTROL
As of version 2.00, pl may be
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<a href="cgi.html">
.>>
\0directly invoked as a CGI program
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</a>
.>>
\0.
Another way to use ploticus via CGI is to 1) generate a unique temp file name; 2) invoke ploticus via shell or system()
and build a PNG or GIF file using the unique name; 3) reference that file in an <IMG> tag;
4) clean up temp PNG / GIF files regularly using a find command run by cron.
In my applications I use a static ploticus script with several @variables that I pass to it; 
it would also be possible to dynamically build a ploticus script (as step 1a above).
.LP
A 
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<a href="../download/ploticus.perl">
.>>
perl script 
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</a>
.>>
which implements a web interface to ploticus was
contributed by Tom McClure.
See also
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<a href="controlling.html">
.>>
Controlling Ploticus from Other Programs
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</a>
.>>
 .

.SH IMAGE IMPORT
\fBPloticus\fR includes the capability to import PNG images 
into graphs, and can use small images as scatterplot points and symbols.
GIF import is not supported.
\fBPloticus\fR can also be used to reduce, enlarge, and crop images;
see the gallery example
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<a href="../gallery/pngresize.htm">
.>>
pngresize 
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</a>
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.SH THUMBNAIL AND BUTTON IMAGES
Thumbnail images (tiny renditions of a plot for icon or selection uses) may be
rendered using the -scale command line option.  For example: \fC-scale 0.15\fR.
Very small text is rendered as lines.  
.LP
\fBPloticus\fR can also be used to make simple buttons for web pages.
See the gallery example 
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<a href="../gallery/button.htm">
.>>
button 
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</a>
<center>
<img src="../gallery/button.gif">
</center>
.>>
.LP
Example HTML code for making a thumbnail or button that will take a user to
a new page when clicked upon:
.nf
.ft C
<a href="newpage.html"><img src="mybutton.gif"></a>
.ft R
.fi


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<a href="Welcome.html">
<img src="../doc/ploticus.gif" border=0></a><br><small>data display engine &nbsp; <br>
<a href="../doc/Copyright.html">Copyright Steve Grubb</a>
<br>
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<center>
<img src="../gallery/all.gif">
</center>
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</table>
.>>
