<?php
	/**
	 * Copyright 2000, 2001, 2002 Philipp von Klitzing
	 * Copyright 2003, 2004, 2005, 2006, 2007, 2008, 2009 Wim van Ravesteijn
	 *
	 * This file is part of AEGEE-Europe Statutory Event Applications.
	 *
	 * AEGEE-Europe Statutory Event Applications is free software: you can
	 * redistribute it and/or modify it under the terms of the GNU General
	 * Public License as published by the Free Software Foundation, either
	 * version 3 of the License, or (at your option) any later version.
	 *
	 * AEGEE-Europe Statutory Event Applications is distributed in the hope
	 * that it will be useful, but WITHOUT ANY WARRANTY; without even the
	 * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
	 * PURPOSE.  See the GNU General Public License for more details.
	 *
	 * You should have received a copy of the GNU General Public License
	 * along with AEGEE-Europe Statutory Event Applications.  If not, see
	 * <http://www.gnu.org/licenses/>.
	 */
	class Chart {
		private $title;
		private $data;
		private $padding;
		private $tmpdir;
		private $size;
		private $color;

		/*
		 * Constructor
		 * - parameters:
		 *   - $title: the title of the Chart. Printed at top.
		 *   - $data: an array of values to be printed in the chart. The keys are the X-values, the array values the Y-values
		 *   - $padding: the padding around the different parts. Only one padding is used between items.
		 *   - $tmpdir: the temp directory which can be used to write temporally files to
		 * - return value:
		 *   [void]
		 */
		public function __construct($title, $data, $padding=10, $tmpdir="/tmp/") {
			$this->title = $title;
			$this->data = $data;
			$this->padding = $padding;
			$this->tmpdir = $tmpdir;
			$this->size = array();
			$this->color['background'] = array(245, 245, 245);
			$this->color['outline'] = array(0, 0, 0);
			$this->color['text'] = array(0, 0, 0);
			$this->color['footer'] = array(100, 100, 100);
			$this->color['grid'] = array(204, 204, 204);
			$this->color['grid_mark'] = array(0, 0, 255);
			$this->color['label'] = array(0, 0, 0);
			$this->color['label_mark'] = array(0, 0, 255);
			if( count($data)>=1 ) $this->color['data'][0] = array(255, 0, 0);
			if( count($data)>=2 ) $this->color['data'][1] = array(255, 0, 255);
			if( count($data)>=3 ) $this->color['data'][2] = array(0, 0, 255);
			if( count($data)>=4 ) $this->color['data'][3] = array(0, 255, 255);
			if( count($data)>=5 ) $this->color['data'][4] = array(0, 255, 0);
			if( count($data)>=6 ) $this->color['data'][5] = array(255, 255, 0);
			if( count($data)>=7 ) $this->color['data'][6] = array(127, 0, 0);
			if( count($data)>=8 ) $this->color['data'][7] = array(127, 0, 127);
			if( count($data)>=9 ) $this->color['data'][8] = array(0, 0, 127);
			if( count($data)>=10 ) $this->color['data'][9] = array(0, 127, 127);
			if( count($data)>=11 ) $this->color['data'][10] = array(0, 127, 0);
			if( count($data)>=12 ) $this->color['data'][11] = array(127, 127, 0);
			for( $i=12; $i<count($data); $i++ ) $this->color['data'][$i] = array(255*mt_rand(), 255*mt_rand(), 255*mt_rand());
		}

		/*
		 * Destructor
		 * - parameters:
		 *   [none]
		 * - return value:
		 *   [void]
		 */
		public function __destruct() {
		}

		/*
		 * Change a default color into another value
		 * - parameters:
		 *   - $type: the color of which item should be changed
		 *   - $color: an array with 3 values denoting the R, G, B color ('array(255, 0, 0)' for red).
		 *   - $index: in case the color of the data elements is changed, the color to be set. Only for 'pie' it makes sense to change anything else than element 0.
		 * - return value:
		 *   - boolean: true in case color is changed, false otherwise
		 */
		public function set_color($type, $color, $index=-1) {
			if( $type=="data" ) {
				if( check_color($color) AND $index>=0 AND $index<=count($this->data) ) {
					$this->color[$type][$index] = $color;
					return true;
				}else {
					return false;
				}
			}else {
				if( check_color($color) AND array_key_exists($type, $this->color) ) {
					$this->color[$type] = $color;
					return true;
				}else {
					return false;
				}
			}
		}

		/*
		 * Get the height of the last generated graph of a certain type
		 * - parameters:
		 *   - $graph: the type of graph for which height should be returned. Can be 'bar', 'line' or 'pie'
		 * - return value:
		 *   - int: height of the whole image in pixels, or false otherwise
		 */
		public function get_height($graph) {
			if( isset($this->size[$graph]['height']) ) return $this->size[$graph]['height'];
			else return false;
		}

		/*
		 * Get the width of the last generated graph of a certain type
		 * - parameters:
		 *   - $graph: the type of graph for which width should be returned. Can be 'bar', 'line' or 'pie'
		 * - return value:
		 *   - int: width of the whole image in pixels, or false otherwise
		 */
		public function get_width($graph) {
			if( isset($this->size[$graph]['width']) ) return $this->size[$graph]['width'];
			else return false;
		}

		/*
		 * Create a bar chart
		 * - parameters:
		 *   - $x_size: width of the chart itself
		 *   - $y_size: height of the chart itself
		 *   - $x_labels: interval of showing labels on X axis (0 for none, -1 for auto)
		 *   - $y_labels: interval of showing labels on Y axis (0 for none, -1 for auto)
		 *   - $x_grid: interval of showing grid on X axis (0 for none, -1 for auto)
		 *   - $y_grid: interval of showing grid on Y axis (0 for none, -1 for auto)
		 *   - $x_grid_mark: array of x-values that should be marked with different color grid line
		 *   - $y_grid_mark: array of y-values that should be marked with different color grid line
		 *   - $x_label_mark: array of x-values where the label should be marked with different color
		 *   - $y_label_mark: array of y-values where the label should be marked with different color
		 * - return value:
		 *   a PNG image, or 'false' in case of error
		 */
		public function bar($x_size, $y_size, $x_labels=-1, $y_labels=-1, $x_grid=-1, $y_grid=-1, $x_grid_mark=array(), $y_grid_mark=array(), $x_label_mark=array(), $y_label_mark=array()) {
			$k = array_keys($this->data);
			$x_max_len = 0;
			for( $i=0; $i<count($k); $i++ ) $x_max_len = max($x_max_len, strlen($k[$i]));
			$y_max = 0;
			for( $i=0; $i<count($k); $i++ ) $y_max = max($y_max, $this->data[ $k[$i] ]);
			$textpadding = 3;
			// Check parameters
			if( $x_size<(imagefontwidth(1) * strlen("[created ".date("H\hi T d.m.Y")."]") - 2 * $this->padding) OR $x_size>10000 ) return false;
			if( $y_size<(imagefontwidth(1) * strlen("[created ".date("H\hi T d.m.Y")."]") - 2 * $this->padding) OR $y_size>10000 ) return false;
			if( $x_labels<-1 OR $x_labels>100 ) return false;
			if( $y_labels<-1 OR $y_labels>10000 ) return false;
			if( $x_grid<-1 OR $x_grid>100 ) return false;
			if( $y_grid<-1 OR $y_grid>10000 ) return false;
			if( !is_array($x_grid_mark) ) return false;
			if( !is_array($y_grid_mark) ) return false;
			if( !is_array($x_label_mark) ) return false;
			if( !is_array($y_label_mark) ) return false;
			// Calculate values for auto parameters
			if( $x_labels==-1 ) $x_labels = max(1, ceil(count($k) / ($x_size / imagefontheight(2))));
			if( $y_labels==-1 ) $y_labels = max(1, ceil($y_max / ($y_size / imagefontheight(2))));
			if( $x_grid==-1 ) $x_grid = $x_labels; #max(1, round(count($k) / ($x_size / 10)));
			if( $y_grid==-1 ) $y_grid = $y_labels; #max(1, round($y_max / ($y_size / 25)));
			// Find the biggest font size for the title that still fits in the image (max 5)
			$titlefontsize = 1;
			for( $i=1; $i<=5; $i++ ) if( imagefontwidth($i)*strlen($this->title)<($x_size + strlen($y_max) * imagefontwidth(2)) ) $titlefontsize = $i;
			// Create image
			$im = imagecreate(2 * $this->padding + $x_size + strlen($y_max) * imagefontwidth(2) + $textpadding,
						3 * $this->padding + imagefontheight($titlefontsize) + $y_size + $x_max_len * imagefontwidth(2) + imagefontheight(1) + $textpadding);
			$this->size['bar']['height'] = 3 * $this->padding + imagefontheight($titlefontsize) + $y_size + $x_max_len * imagefontwidth(2) + imagefontheight(1) + $textpadding;
			$this->size['bar']['width'] = 2 * $this->padding + $x_size + strlen($y_max) * imagefontwidth(2) + $textpadding;
			// Initialize colors
			$c = array_keys($this->color);
			for( $i=0; $i<count($c); $i++ ) {
				if( $c[$i]!="data" ) {
					$color[ $c[$i] ] = imagecolorallocate($im, $this->color[ $c[$i] ][0], $this->color[ $c[$i] ][1], $this->color[ $c[$i] ][2]);
				}else {
					for( $j=0; $j<count($this->color[ $c[$i] ]); $j++ )
						$color[ $c[$i] ][$j] = imagecolorallocate($im, $this->color[ $c[$i] ][$j][0], $this->color[ $c[$i] ][$j][1], $this->color[ $c[$i] ][$j][2]);
				}
			}
			// Draw title
			imagestring($im, $titlefontsize,
						$this->padding + .5 * $textpadding + .5 * ($x_size + strlen($y_max) * imagefontwidth(2)) - .5 * strlen($this->title) * imagefontwidth($titlefontsize),
						$this->padding,
						$this->title, $color['text']);
			// Draw footer
			$footer = "[created ".date("H\hi T d.m.Y")."]";
			imagestring($im, 1,
						2 * $this->padding + $x_size + strlen($y_max) * imagefontwidth(2) + $textpadding - strlen($footer) * imagefontwidth(1),
						3 * $this->padding + imagefontheight($titlefontsize) + $y_size + $textpadding + $x_max_len * imagefontwidth(2),
						$footer, $color['footer']);
			// Draw axis
			imageline($im,
						$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding,
						2 * $this->padding + imagefontheight($titlefontsize),
						$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding,
						2 * $this->padding + imagefontheight($titlefontsize) + $y_size,
						$color['outline']);
			imageline($im,
						$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding,
						2 * $this->padding + imagefontheight($titlefontsize) + $y_size,
						$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding + $x_size,
						2 * $this->padding + imagefontheight($titlefontsize) + $y_size,
						$color['outline']);
			// Draw X labels
			if( $x_labels>0 ) for( $i=0; $i<count($k); $i+=$x_labels )
				imagestringup($im, 2,
							$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding + ($x_size / count($k)) * ($i + .5) - .5 * imagefontheight(2),
							2 * $this->padding + imagefontheight($titlefontsize) + $y_size + $textpadding + strlen($k[$i]) * imagefontwidth(2),
							$k[$i], (in_array($k[$i], $x_label_mark)?$color['label_mark']:$color['label']));
			// Draw Y labels
			if( $y_labels>0 ) for( $i=0; $i<=$y_max; $i+=$y_labels )
				imagestring($im, 2,
							$this->padding + (strlen($y_max) - strlen($i)) * imagefontwidth(2),
							2 * $this->padding + imagefontheight($titlefontsize) + $y_size - ($y_size / $y_max) * $i - .5 * imagefontheight(2),
							$i, (in_array($i, $y_label_mark)?$color['label_mark']:$color['label']));
			// Draw graph
			for( $i=0; $i<count($k); $i++ )
				if( $this->data[ $k[$i] ]>0 ) imagefilledrectangle($im,
							$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding + ($x_size / count($k)) * ($i) + 1,
							2 * $this->padding + imagefontheight($titlefontsize) + $y_size - ($y_size / $y_max) * $this->data[ $k[$i] ],
							$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding + ($x_size / count($k)) * ($i + 1),
							2 * $this->padding + imagefontheight($titlefontsize) + $y_size - 1,
							$color['data'][0]);
			// Draw Y grid
			if( $y_grid>0 ) for( $i=$y_grid; $i<=$y_max; $i+=$y_grid )
				imageline($im,
							$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding + 1,
							2 * $this->padding + imagefontheight($titlefontsize) + $y_size - ($y_size / $y_max) * $i,
							$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding + $x_size,
							2 * $this->padding + imagefontheight($titlefontsize) + $y_size - ($y_size / $y_max) * $i,
							(in_array($i, $y_grid_mark)?$color['grid_mark']:$color['grid']));
			// Store image, read, and return it
			$tmpfile = tempnam($this->tmpdir, "phpchart");
			imagepng($im, $tmpfile);
			imagedestroy($im);
			$image = file_get_contents($tmpfile);
			unlink($tmpfile);
			return $image;
		}

		/*
		 * Create a line chart
		 * - parameters:
		 *   - $x_size: width of the chart itself
		 *   - $y_size: height of the chart itself
		 *   - $x_labels: interval of showing labels on X axis (0 for none, -1 for auto)
		 *   - $y_labels: interval of showing labels on Y axis (0 for none, -1 for auto)
		 *   - $x_grid: interval of showing grid on X axis (0 for none, -1 for auto)
		 *   - $y_grid: interval of showing grid on Y axis (0 for none, -1 for auto)
		 *   - $x_grid_mark: array of x-values that should be marked with different color grid line
		 *   - $y_grid_mark: array of y-values that should be marked with different color grid line
		 *   - $x_label_mark: array of x-values where the label should be marked with different color
		 *   - $y_label_mark: array of y-values where the label should be marked with different color
		 * - return value:
		 *   a PNG image, or 'false' in case of error
		 */
		public function line($x_size, $y_size, $x_labels=-1, $y_labels=-1, $x_grid=-1, $y_grid=-1, $x_grid_mark=array(), $y_grid_mark=array(), $x_label_mark=array(), $y_label_mark=array()) {
			$k = array_keys($this->data);
			$x_max_len = 0;
			for( $i=0; $i<count($k); $i++ ) $x_max_len = max($x_max_len, strlen($k[$i]));
			$y_max = 0;
			for( $i=0; $i<count($k); $i++ ) $y_max = max($y_max, $this->data[ $k[$i] ]);
			$textpadding = 3;
			// Check parameters
			if( $x_size<(imagefontwidth(1) * strlen("[created ".date("H\hi T d.m.Y")."]") - 2 * $this->padding) OR $x_size>10000 ) return false;
			if( $y_size<(imagefontwidth(1) * strlen("[created ".date("H\hi T d.m.Y")."]") - 2 * $this->padding) OR $y_size>10000 ) return false;
			if( $x_labels<-1 OR $x_labels>100 ) return false;
			if( $y_labels<-1 OR $y_labels>10000 ) return false;
			if( $x_grid<-1 OR $x_grid>100 ) return false;
			if( $y_grid<-1 OR $y_grid>10000 ) return false;
			if( !is_array($x_grid_mark) ) return false;
			if( !is_array($y_grid_mark) ) return false;
			if( !is_array($x_label_mark) ) return false;
			if( !is_array($y_label_mark) ) return false;
			// Calculate values for auto parameters
			if( $x_labels==-1 ) $x_labels = max(1, ceil(count($k) / ($x_size / imagefontheight(2))));
			if( $y_labels==-1 ) $y_labels = max(1, ceil($y_max / ($y_size / imagefontheight(2))));
			if( $x_grid==-1 ) $x_grid = $x_labels; #max(1, round(count($k) / ($x_size / 10)));
			if( $y_grid==-1 ) $y_grid = $y_labels; #max(1, round($y_max / ($y_size / 25)));
			// Find the biggest font size for the title that still fits in the image (max 5)
			$titlefontsize = 1;
			for( $i=1; $i<=5; $i++ ) if( imagefontwidth($i)*strlen($this->title)<($x_size + strlen($y_max) * imagefontwidth(2)) ) $titlefontsize = $i;
			// Create image
			$im = imagecreate(2 * $this->padding + $x_size + strlen($y_max) * imagefontwidth(2) + $textpadding,
						3 * $this->padding + imagefontheight($titlefontsize) + $y_size + $x_max_len * imagefontwidth(2) + imagefontheight(1) + $textpadding);
			$this->size['line']['height'] = 3 * $this->padding + imagefontheight($titlefontsize) + $y_size + $x_max_len * imagefontwidth(2) + imagefontheight(1) + $textpadding;
			$this->size['line']['width'] = 2 * $this->padding + $x_size + strlen($y_max) * imagefontwidth(2) + $textpadding;
			// Initialize colors
			$c = array_keys($this->color);
			for( $i=0; $i<count($c); $i++ ) {
				if( $c[$i]!="data" ) {
					$color[ $c[$i] ] = imagecolorallocate($im, $this->color[ $c[$i] ][0], $this->color[ $c[$i] ][1], $this->color[ $c[$i] ][2]);
				}else {
					for( $j=0; $j<count($this->color[ $c[$i] ]); $j++ )
						$color[ $c[$i] ][$j] = imagecolorallocate($im, $this->color[ $c[$i] ][$j][0], $this->color[ $c[$i] ][$j][1], $this->color[ $c[$i] ][$j][2]);
				}
			}
			// Draw title
			imagestring($im, $titlefontsize,
						$this->padding + .5 * $textpadding + .5 * ($x_size + strlen($y_max) * imagefontwidth(2)) - .5 * strlen($this->title) * imagefontwidth($titlefontsize),
						$this->padding,
						$this->title, $color['text']);
			// Draw footer
			$footer = "[created ".date("H\hi T d.m.Y")."]";
			imagestring($im, 1,
						2 * $this->padding + $x_size + strlen($y_max) * imagefontwidth(2) + $textpadding - strlen($footer) * imagefontwidth(1),
						3 * $this->padding + imagefontheight($titlefontsize) + $y_size + $textpadding + $x_max_len * imagefontwidth(2),
						$footer, $color['footer']);
			// Draw axis
			imageline($im,
						$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding,
						2 * $this->padding + imagefontheight($titlefontsize),
						$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding,
						2 * $this->padding + imagefontheight($titlefontsize) + $y_size,
						$color['outline']);
			imageline($im,
						$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding,
						2 * $this->padding + imagefontheight($titlefontsize) + $y_size,
						$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding + $x_size,
						2 * $this->padding + imagefontheight($titlefontsize) + $y_size,
						$color['outline']);
			// Draw X labels
			if( $x_labels>0 ) for( $i=0; $i<count($k); $i+=$x_labels )
				imagestringup($im, 2,
							$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding + ($x_size / (count($k) - 1)) * $i - .5 * imagefontheight(2),
							2 * $this->padding + imagefontheight($titlefontsize) + $y_size + $textpadding + strlen($k[$i]) * imagefontwidth(2),
							$k[$i], (in_array($k[$i], $x_label_mark)?$color['label_mark']:$color['label']));
			// Draw Y labels
			if( $y_labels>0 ) for( $i=0; $i<=$y_max; $i+=$y_labels )
				imagestring($im, 2,
							$this->padding + (strlen($y_max) - strlen($i)) * imagefontwidth(2),
							2 * $this->padding + imagefontheight($titlefontsize) + $y_size - ($y_size / $y_max) * $i - .5 * imagefontheight(2),
							$i, (in_array($i, $y_label_mark)?$color['label_mark']:$color['label']));
			// Draw X grid
			if( $x_grid>0 ) for( $i=$x_grid; $i<count($k); $i++ ) if( ($i%$x_grid)==0 OR in_array($k[ $i ], $x_grid_mark) )
				imageline($im,
							$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding + ($x_size / (count($k) - 1)) * $i,
							2 * $this->padding + imagefontheight($titlefontsize),
							$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding + ($x_size / (count($k) - 1)) * $i,
							2 * $this->padding + imagefontheight($titlefontsize) + $y_size - 1,
							(in_array($k[$i], $x_grid_mark)?$color['grid_mark']:$color['grid']));
			// Draw Y grid
			if( $y_grid>0 ) for( $i=$y_grid; $i<=$y_max; $i++ ) if( ($i%$y_grid)==0 OR in_array($i, $y_grid_mark) )
				imageline($im,
							$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding + 1,
							2 * $this->padding + imagefontheight($titlefontsize) + $y_size - ($y_size / $y_max) * $i,
							$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding + $x_size,
							2 * $this->padding + imagefontheight($titlefontsize) + $y_size - ($y_size / $y_max) * $i,
							(in_array($i, $y_grid_mark)?$color['grid_mark']:$color['grid']));
			// Draw graph
			for( $i=1; $i<count($k); $i++ )
				imageline($im,
							$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding + ($x_size / (count($k) - 1)) * ($i - 1),
							2 * $this->padding + imagefontheight($titlefontsize) + $y_size - ($y_size / $y_max) * $this->data[ $k[$i - 1] ],
							$this->padding + strlen($y_max) * imagefontwidth(2) + $textpadding + ($x_size / (count($k) - 1)) * $i,
							2 * $this->padding + imagefontheight($titlefontsize) + $y_size - ($y_size / $y_max) * $this->data[ $k[$i] ],
							$color['data'][0]);
			// Store image, read, and return it
			$tmpfile = tempnam($this->tmpdir, "phpchart");
			imagepng($im, $tmpfile);
			imagedestroy($im);
			$image = file_get_contents($tmpfile);
			unlink($tmpfile);
			return $image;
		}

		/*
		 * Create a pie chart
		 * - parameters:
		 *   - $diagonal: the diagonal of the pie.
		 * - return value:
		 *   a PNG image, or 'false' in case of error
		 */
		public function pie($diagonal) {
			$k = array_keys($this->data);
			// Check parameters
			if( $diagonal<50 OR $diagonal>10000 ) return false;
			// Calculate the total sum of values
			$sum = 0;
			for( $i=0; $i<count($k); $i++ ) $sum += $this->data[ $k[$i] ];
			// Find the biggest font size for the title that still fits in the image (max 5)
			$titlefontsize = 1;
			for( $i=1; $i<=5; $i++ ) if( imagefontwidth($i)*strlen($this->title)<$diagonal ) $titlefontsize = $i;
			// Create image
			$im = imagecreate(2 * $this->padding + $diagonal,
						4 * $this->padding + imagefontheight($titlefontsize) + $diagonal + 20 * count($k) + imagefontheight(1));
			$this->size['pie']['height'] = 4 * $this->padding + imagefontheight($titlefontsize) + $diagonal + 20 * count($k) + imagefontheight(1);
			$this->size['pie']['width'] = 2 * $this->padding + $diagonal;
			// Initialize colors
			$c = array_keys($this->color);
			for( $i=0; $i<count($c); $i++ ) {
				if( $c[$i]!="data" ) {
					$color[ $c[$i] ] = imagecolorallocate($im, $this->color[ $c[$i] ][0], $this->color[ $c[$i] ][1], $this->color[ $c[$i] ][2]);
				}else {
					for( $j=0; $j<count($this->color[ $c[$i] ]); $j++ )
						$color[ $c[$i] ][$j] = imagecolorallocate($im, $this->color[ $c[$i] ][$j][0], $this->color[ $c[$i] ][$j][1], $this->color[ $c[$i] ][$j][2]);
				}
			}
			// Draw title
			imagestring($im, $titlefontsize,
						$this->padding + .5 * $diagonal - .5 * strlen($this->title) * imagefontwidth($titlefontsize),
						$this->padding,
						$this->title, $color['text']);
			// Draw footer
			$footer = "[created ".date("H\hi T d.m.Y")."]";
			imagestring($im, 1,
						2 * $this->padding + $diagonal - strlen($footer) * imagefontwidth(1),
						4 * $this->padding + imagefontheight($titlefontsize) + $diagonal + 20 * count($k),
						$footer, $color['footer']);
			// Draw image
			$start = 0;
			$end = 0;
			for( $i=0; $i<count($k); $i++ ) {
				$start = $end;
				$end += $this->data[ $k[$i] ] / $sum * 360;
				// Draw index
				$label = $k[$i]." (".number_format(($end-$start)/3.6, 0)."%)";
				imagefilledrectangle($im,
							$this->padding,
							2 * $this->padding + imagefontheight($titlefontsize) + 20 * $i,
							$this->padding + 20,
							2 * $this->padding + imagefontheight($titlefontsize) + 20 * $i + 15,
							$color['data'][$i]);
				imagerectangle($im,
							$this->padding,
							2 * $this->padding + imagefontheight($titlefontsize) + 20 * $i,
							$this->padding + 20,
							2 * $this->padding + imagefontheight($titlefontsize) + 20 * $i + 15,
							$color['outline']);
				imagestring($im, 3,
							$this->padding + 25,
							2 * $this->padding + imagefontheight($titlefontsize) + 20 * $i + 2,
							$label, $color['label']);
				// Draw pie
				if( round($start)==0 AND round($end)==360 ) {
					imagefilledellipse($im,
								$this->padding + .5 * $diagonal,
								3 * $this->padding + 20 * count($k) + imagefontheight($titlefontsize) + .5 * $diagonal,
								$diagonal, $diagonal, $color['data'][$i]);
					imageellipse($im,
								$this->padding + .5 * $diagonal,
								3 * $this->padding + 20 * count($k) + imagefontheight($titlefontsize) + .5 * $diagonal,
								$diagonal, $diagonal, $color['outline']);
				}elseif( round($start)==round($end) ) {
					// do nothing, too small to be drawn
				}else {
					imagefilledarc($im,
								$this->padding + .5 * $diagonal,
								3 * $this->padding + 20 * count($k) + imagefontheight($titlefontsize) + .5 * $diagonal,
								$diagonal, $diagonal, (round($start) - 90) % 360, (round($end) - 90) % 360, $color['data'][$i], 4);
					imagefilledarc($im,
								$this->padding + .5 * $diagonal,
								3 * $this->padding + 20 * count($k) + imagefontheight($titlefontsize) + .5 * $diagonal,
								$diagonal, $diagonal, (round($start) - 90) % 360, (round($end) - 90) % 360, $color['outline'], 6);
				}
			}
			// Store image, read, and return it
			$tmpfile = tempnam($this->tmpdir, "phpchart");
			imagepng($im, $tmpfile);
			imagedestroy($im);
			$image = file_get_contents($tmpfile);
			unlink($tmpfile);
			return $image;
		}

		/*
		 * Check if the color is valid
		 * - parameters:
		 *   $color: an array with 3 values denoting the RGB color (0-255)
		 * - return value:
		 *   boolean: true for a correct color, false otherwise
		 */
		private function check_color($color) {
			if( is_array($color) AND count($color)==3 AND $color[0]>=0 AND $color[0]<=255 AND $color[1]>=0 AND $color[1]<=255 AND $color[2]>=0 AND $color[2]<=255 ) return true;
			else return false;
		}
	}
?>