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=cut
TITLE=dataimage.cgi
DESCRIPTION=generates images from live data
KEYWORDS=dataimage.cgi
DOCTOP=index
DOCPREV=availability-report.cgi
DOCNEXT=datapage.cgi
=pod
=head1 dataimage.cgi - create images driven by live data
=head2 Usage:
<IMG SRC="@@HTMLURL@@/dataimage.cgi?imagename">
=head2 Description:
C<Dataimage.cgi> reads an image definition from
C<@@INSTALLDIR@@/datapage/imagename.image>. Some of the commands are in common
with L<datapage.cgi|datapage-cgi.html#common_commands> and are documented
there:
oid, rrd, status, eval, debug, macro, macroend and *EOD*
These retrieve and manipulate data. There are also commands to create
images:
image, colordef, color, linewidth, line, rectangle, circle,
fill, font, text, out, flow
=head1 Image Commands
=head2 image
The image command has two formats. The first looks like:
image WIDTH HEIGHT
This creates a blank image of the size specified. Sometimes you'll want a
background for the image, and you can use the second form to specify
a file to read for the background:
image BGFILE
This will create the new image the same size as the one in C<BGFILE>,
by reading C<BGFILE> and using its contents as the background. N.B., the
image must be a PNG graphic.
The C<image> command also defines a few colors (see C<colordef> below):
C<black>, C<white> and C<transparent>, sets the current color to
C<black>, fills the image with C<white> and sets the C<linewidth> to 1.
=head2 colordef
[It can also be spelled C<colourdef>.]
This defines a new colour and names it. The command looks like:
colordef COLORNAME RED GREEN BLUE
where C<RED>, C<GREEN> and C<BLUE> specify the level of each of those colours
to be mixed to define the colour referred to in the script as C<COLORNAME>.
=head2 color
[It can also be spelled C<colour>.]
This sets the current colour, to be used by those commands that don't specify
a colour. It is used as simply:
color COLORNAME
=head2 linewidth
This sets the width of lines. It isn't honoured by all other commands,
unfortunately, but so far this hasn't been a problem for me. It looks like:
linewidth WIDTH
=head2 line
This just draws a line in the current C<color> and C<linewidth>:
line X1 Y1 X2 Y2
=head2 rectangle
This is a way to draw a rectangle, without useing C<line> 4 times:
rectangle X1 Y1 X2 Y2 [filled]
The co-ordinates (C<X1>, C<Y1>) and (C<X2>, C<Y2>) define oposite corners
of the rectangle. If the keyword C<filled> is added to the end, the
rectangle will be filled with the current colour as well.
=head2 circle
Here you get a circle:
circle X Y RADIUS [filled]
The circle will be centered on (C<X>, C<Y>) with a radius of C<RADIUS>.
If the keyword C<filled> is added to the end, the
circle will be filled with the current colour as well.
=head2 fill
This command permits you to fill arbitrary regions:
fill X Y [COLORNAME]
The C<COLORNAME> is optional.
=head2 text
The C<text> command sets text into the image, for labelling things:
text X Y TEXT
=head2 font
This changes the font for the C<text> command:
font (giant|large|mediumbold|medium|small|tiny)
=head2 out
This permits the script to output additional information to an auxiliary
file. I added this for doing image-maps automatically, which can be
automatically loaded by a L<datapage.cgi|datapage-cgi> web-page.
The syntax is:
out TEXT
=head2 flow
This draws a strange double-headed, bi-coloured arrow. Think of it as two
half arrows, split lengthwise, one in each direction. The colour and width
of each half arrow indicates the flow in that direction. I use it for
indicating network traffic flow, which usually isn't the same in both
directions. It looks like:
flow X1 Y1 X2 Y2 INFLOW OUTFLOW
The co-ordinates (C<X1>, C<Y1>), (C<X2>, C<Y2>) indicate the ends of the
flow. C<INFLOW> and C<OUTFLOW> indicate the level in each direction,
relative to (C<X1>, C<Y1>).
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