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<?php
/*
A small PHP program and function that draws a pie chart in SVG format.
Written by Branko Collin in 2008.
This code is hereby released into the public domain. In case this is not legally
possible: I, Branko Collin, hereby grant anyone the right to use this work for
any purpose, without any conditions, unless such conditions are required by law.
*/
/* Working with relative values confused me, so I worked with absolute ones
instead. Generally this should not be a problem, as the only relative values you
need are the chart's centre coordinates and its radius, and these are a linear
function of the bounding box size or canvas size. See the sample values for how
this could work out. */
/* Sample values */
$values[] = 14625;
$values[] = 644;
$width = 400; // canvas size
$height = 400;
$centerx = $width / 2; // centre of the pie chart
$centery = $height / 2;
$radius = min($centerx,$centery) - 10; // radius of the pie chart
if ($radius < 5) {
die("Your chart is too small to draw.");
}
/* Draw and output the SVG file. */
header('Content-type: image/svg+xml');
echo <<<END
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<svg xmlns:svg="http://www.w3.org/2000/svg" xmlns="http://www.w3.org/2000/svg"
version="1.0" width="$width" height="$height" id="svg2">
<title>Pie chart</title>
<desc>Picture of a pie chart</desc>
END;
print piechart($values,200,200,190);
print "\n</svg>\n";
/*
The piechart function
Arguments are an aray of values, the centre coordinates x and y, and
the radius of the piechart.
*/
function piechart($data, $cx, $cy, $radius) {
$chartelem = "";
$max = count($data);
// $colours = array('#4e9a06','#a40000','#204a87','#5c3566','#ce5c00');
$colours = array('#73d216','#cc0000','#3465a4','#75507b','#f57900');
// $colours = array('#8ae234','#ef2929','#729fcf','#ad7fa8','#fcaf3e');
$sum = 0;
foreach ($data as $key=>$val) {
$sum += $val;
}
$deg = $sum/360; // one degree
$jung = $sum/2; // necessary to test for arc type
/* Data for grid, circle, and slices */
$dx = $radius; // Starting point:
$dy = 0; // first slice starts in the East
$oldangle = 0;
/* Loop through the slices */
for ($i = 0; $i<$max; $i++) {
$angle = $oldangle + $data[$i]/$deg; // cumulative angle
$x = cos(deg2rad($angle)) * $radius; // x of arc's end point
$y = sin(deg2rad($angle)) * $radius; // y of arc's end point
$colour = $colours[$i];
if ($data[$i] > $jung) {
// arc spans more than 180 degrees
$laf = 1;
}
else {
$laf = 0;
}
$ax = $cx + $x; // absolute $x
$ay = $cy + $y; // absolute $y
$adx = $cx + $dx; // absolute $dx
$ady = $cy + $dy; // absolute $dy
$chartelem .= "\n";
$chartelem .= "<path d=\"M$cx,$cy "; // move cursor to center
$chartelem .= " L$adx,$ady "; // draw line away away from cursor
$chartelem .= " A$radius,$radius 0 $laf,1 $ax,$ay "; // draw arc
$chartelem .= " z\" "; // z = close path
$chartelem .= " fill=\"$colour\" stroke=\"#FFFFFF\" stroke-width=\"2\" ";
$chartelem .= " fill-opacity=\"1.0\" stroke-linejoin=\"round\" />";
$dx = $x; // old end points become new starting point
$dy = $y; // id.
$oldangle = $angle;
}
return $chartelem;
}
?>
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