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| -rw-r--r-- | piechart.php | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/piechart.php b/piechart.php new file mode 100644 index 0000000..42b29f9 --- /dev/null +++ b/piechart.php @@ -0,0 +1,114 @@ +<?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; +} + +?> |