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![]() Web-based graphsThis page contains notes related to use of ploticus to produce data displays that are viewable on web pages. There are a number of web sites that are using ploticus .Ploticus can generate the following types of graphics that web browsers can display: PNG, JPEG, WBMP, pseudo-GIF, and SVG. Some of these types are more compact than others (smaller is faster). Here's a comparison, done on gallery example stock:
As of version 2.02 ploticus can also generate HTML clickmaps to accompany images. PNG, JPEG, WBMP, and pseudo-GIFs are generated using the GD image generation library from boutell.com . Ploticus is bundled with portions of GD 1.3 (pseudo-GIF) 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).
SVG
is a relatively new vector-based format that looks
good. Browsers display SVG via a plug-in.
Ploticus (version 2.01 or later, all builds) can produce
SVG
graphics.
Creating PNGTo create a PNG image, use ploticus with the -png option.
To incorporate a PNG image into an HTML web page, use the
HTML construct:
<img src="mygraph.png">
PNG 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 xv. To see if your
current web browser can display PNG, try
this page.
See also the PNG home page
Creating pseudo-GIFTo create pseudo-GIF (not available in the Debian package), use ploticus with the -gif option.
To incorporate a GIF image into an HTML web page, use the HTML
construct:
<img src="mygraph.gif">
GIF format has been around for a long while, is fairly universal, and can be viewed on any graphical web browser or image viewing tool. Ploticus 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. The RLE GIF images that ploticus produces are viewable via any graphical web browser or image viewer that supports GIF.
More on GIF LZW patent and licensing issues
Creating SVGThis is discussed hereTransparent background![]()
Images may be created with 'transparent' background by setting
the background color to transparent. This allows the ploticus
graphs to be "overlayed" against the existing background color of
the web page.
Web page exampleHere is an example HTML page that is viewable using any web browser: <html> <center> Here is an image. <img src="lineplot1.gif"> </html>
Suppose the above is in a file called /home/steve/firsttry.html.
If you don't have a web server running, you can view the file by
entering the following URL into your web browser:
file:///home/steve/firsttry.html
Clickmap supportAs of version 2.02 ploticus can also generate HTML clickmaps to accompany images.CGI controlAs of version 2.00, ploticus may be directly invoked as a CGI program . 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).
A
perl script
which implements a web interface to ploticus was
contributed by Tom McClure.
See also
Controlling Ploticus from Other Programs
.
Image importPloticus includes the capability to import PNG images into graphs, and can use small images as scatterplot points and symbols. GIF import is not supported. Ploticus can also be used to reduce, enlarge, and crop images; see the gallery example pngresizeThumbnail and button imagesThumbnail images (tiny renditions of a plot for icon or selection uses) may be rendered using the -scale command line option. For example: -scale 0.15. Very small text is rendered as lines.Ploticus can also be used to make simple buttons for web pages. See the gallery example button ![]() Example HTML code for making a thumbnail or button that will take a user to a new page when clicked upon: <a href="newpage.html"><img src="mybutton.gif"></a> |
![]() data display engine Copyright Steve Grubb ![]() |