Pie Chart class

<?php /* -*- C -*- */
/*
** $Id: piechart.phl,v 1.2 1998/02/03 16:55:06 borud Exp $
**
** PHP Class for creating pie charts using the GD library functions.
**
** There is a bug in the GD library somewhere that seems to kick in
** when you try to return images that are larger than 4K. We probably
** need a workaround for this...
**
** Pie charts look a bit shabby. There seems to be one or more
** roundoff errors lurking about making life hard for us. To fix this
** we should perhaps investigate how the Arc-drawing thingey works and
** try to find out how it gets the endpoints. Also the flood-filler
** doesn't quite cope with filling the pieces very well.
**
** Authors: Bjørn Borud, Guardian Networks AS, <borud@guardian.no>
*/
/* {{{ piechart */
/*
** This is a class for creating pie charts. Generally you just have
** to instantiate it, and then make a call to the "init" method to
** set the size and transfer the data.
**
** The data is an array of arrays that consist the following data:
**  o numeric value
**  o value legend
**  o red \
**  o green > the RGB values for the color of the slice/legend
**  o blue /
**
*/
class piechart {
/* {{{ attributes */
 var $im;
 var $width, $height;
 var $data;
 var $colors;
 var $angles;
 var $left=10;
 var $right=200;
 var $top=100;
 var $bottom=10;
 var $head_top=10;
 var $head_space=5;
 var $legend_left=20;
 var $center_x;
 var $center_y;
 var $diameter;
 /* sum of values */
 var $sum;
 /* font sizes */
 var $fx, $fy;
 var $legend_num = "";
/* }}} */
/* {{{ constants */
 var $PI = 3.1415926535897931; 
/* }}} */
/* {{{ roundoff */
 /* 
 ** PHP has no function for rounding off doubles to the nearest
 ** integer so we have to roll our own.
 */
 function roundoff ($v) {
  if ( $v - floor($v) >= 0.5) {
   return(ceil($v));
  } else {
   return(floor($v));
  }
 }
/* }}} */
/* {{{ deg2rad */
 /*
 ** The built-in trig functions use radians and there's no
 ** function in PHP to convert between degrees and radians
 */
 function deg2rad ($degrees) {
  return (($this->PI * $degrees) / doubleval(180));
 }
/* }}} */
/* {{{ get_xy_factors */
 /*
 ** Calculate the directional vector for the sides of the
 ** piece of pie.
 */
 function get_xy_factors ($degrees) {
  $x = cos($this->deg2rad($degrees));
  $y = sin($this->deg2rad($degrees));
  return (array($x, $y));
 }
/* }}} */
/* {{{ init */
 /*
 ** Initialize the object and draw the pie. This would be the
 ** constructor in an ordinary OO scenario -- just that we haven't
 ** got constructors in PHP, now do we? ;-)
 */
 function init ($w, $h, $d) {
  $this->im  = ImageCreate($w, $h);
  $this->width = $w;
  $this->height = $h;
  $this->data = $d;
  $this->da_width = ($this->width - $this->left - $this->right);
  $this->da_height = ($this->height - $this->top - $this->bottom);
  $this->center_x = intval($this->left + ($this->da_width / 2));
  $this->center_y = intval($this->top + ($this->da_height / 2));

  /* font sizes */
  $this->fx = array(0, 5,6,7,8,9);
  $this->fy = array(0, 7,8,10,14,11);
  /* decide the diameter of the pie */
  if ($this->da_height > $this->da_width) {
   $this->diameter = $this->da_width;
  } else {
   $this->diameter = $this->da_height;
  }
  $this->white = ImageColorAllocate($this->im, 255, 255, 255);
  $this->black = ImageColorAllocate($this->im,  0,  0,  0);
  $n = count($this->data);
  for ($i = 0; $i < $n; $i++) {
   $this->colors[$i] = ImageColorAllocate($this->im, $this->data[$i][2],  
                    $this->data[$i][3],
                    $this->data[$i][4]);
   $this->sum += $this->data[$i][0];
  }
  $from = 0;  $to = 0;
  for ($i = 0; $i < $n; $i++) {
   $this->angles[$i] = $this->roundoff(($this->data[$i][0] * 360) 
                     / doubleval($this->sum));
   $to = $from + $this->angles[$i];
   $col = $this->colors[$i];
   
   $foo = $this->angles[$i];
   $this->draw_slice($this->center_x, 
            $this->center_y, 
            $from, 
            $to, 
            $this->colors[$i]);
   $from += $this->angles[$i];
  }
 }
/* }}} */
/* {{{ set_legend_percent */
/* utility function to set an attribute so we display percentages */ 
 function set_legend_percent () {
  $this->legend_num = "p";
 }
/* }}} */
/* {{{ set_legend_value */
 /* utility function to set an attribute so we display values */ 
 function set_legend_value () {
  $this->legend_num = "v";
 }
/* }}} */
/* {{{ draw_point */
 /*
 ** This function is just here for debugging purposes. It is
 ** sometimes very useful to be able to draw an X to check
 ** coordinates.
 */
 function draw_point($x, $y) {
  ImageLine($this->im, $x-4, $y-4, $x+4, $y+4, $this->black);
  ImageLine($this->im, $x-4, $y+4, $x+4, $y-4, $this->black);
 }
/* }}} */
/* {{{ draw_margins */
 /*
 ** Also a debugging function to show where the margins are at
 */
 function draw_margins () {
  ImageLine($this->im, 0, $this->top, $this->width, 
       $this->top, 
       $this->black);  
  ImageLine($this->im, 0, $this->height - $this->bottom, 
       $this->width, $this->height - $this->bottom, 
       $this->black);
  ImageLine($this->im, $this->left, 0, $this->left, 
       $this->height, $this->black);
  ImageLine($this->im, $this->width - $this->right, 
       0, $this->width - $this->right, 
       $this->height, $this->black);
 }
/* }}} */
/* {{{ draw_legends */
 /*
 ** Draw legends at the right side of the pie chart. This function
 ** accepts a fontsize and gathers all the other information from
 ** the multilevel data array
 */
 function draw_legends ($fontsize) {
  $n = count($this->data);
  $x1 = $this->width - $this->right + $this->legend_left;
  $x2 = $x1 + $this->fy[$fontsize];;
  for ($i = 0; $i < $n; $i++) {
   /* determine Y coordinates */
   $y1 = ($i * $this->fy[$fontsize] * 1.5) + $this->top;
   $y2 = $y1 + $this->fy[$fontsize];
   /* draw the legend color rectangle */
   ImageFilledRectangle($this->im, $x1, $y1, $x2, $y2, $this->colors[$i]);
   ImageRectangle($this->im, $x1, $y1, $x2, $y2, $this->black);
   $legend = $this->data[$i][1];
   /* decide what to show after legend */
   switch ($this->legend_num) {
   case "v":
    $legend .= sprintf(" (%.2f)", $this->data[$i][0]);
    break;
   case "p":
    $legend .= sprintf(" (%.2f%%)", 
              ($this->data[$i][0] 
              * 100 / doubleval($this->sum)));
    break;
   }
   ImageString($this->im, $fontsize, $x2 + 5, $y1, 
         $legend, $this->black);
  }
 }
/* }}} */
/* {{{ draw_heading */
 /*
 ** This function accepts an array of arrays containing (in order):
 ** o The text of the heading as a string
 ** o The fontsize as an integer
 ** o The justification ("c"=center)
 **
 */
 function draw_heading($head_data) {
  $n = count($head_data);
  $y = $this->head_top;
  for ($i = 0; $i < $n; $i++) {
   
   switch($head_data[$i][2]) {
   case "c":
    $x = ($this->width - $this->fx[$head_data[$i][1]] 
       * strlen($head_data[$i][0])) / 2;
    break;
   case "r": /* uses left margin here... */
    $x = $this->width - $this->left -
     ($this->fx[$head_data[$i][1]] * strlen($head_data[$i][0]));
    break;
   default:
    $x = $this->left;
    break;

   }
   ImageString($this->im, $head_data[$i][1], $x, $y, $head_data[$i][0],
         $this->black);
   $y += ($this->fy[$head_data[$i][1]] + $this->head_space);   
  }
 }
/* }}} */
/* {{{ draw_slice */
 /*
 ** This function draws a piece of pie centered at x,y starting at
 ** "from" degrees and ending at "to" degrees using the specified color.
 */
 function draw_slice ($x, $y, $from, $to, $color) {
  # Awful Kludge!!!
  if ($to > 360) {
   $to = 360;
  }
  ImageArc($this->im, $this->center_x, $this->center_y,
       $this->diameter, $this->diameter, $from, $to, $color);
  /* First line */
  $axy2 = $this->get_xy_factors($from);
  $ax2 = floor($this->center_x + ($axy2[0] * ($this->diameter /2)));
  $ay2 = floor($this->center_y + ($axy2[1] * ($this->diameter /2)));
  ImageLine($this->im, $this->center_x, $this->center_y, $ax2, $ay2, $color);
  /* Second line */
  $bxy2 = $this->get_xy_factors($to);
  $bx2 = ceil($this->center_x + ($bxy2[0] * ($this->diameter /2)));
  $by2 = ceil($this->center_y + ($bxy2[1] * ($this->diameter /2)));
  ImageLine($this->im, $this->center_x, $this->center_y, $bx2, $by2, $color);

  /* decide where to start filling, then fill */
  $xy2 = $this->get_xy_factors((($to - $from) / 2) + $from);
  $x2 = floor($this->center_x + ($xy2[0] * ($this->diameter /3)));
  $y2 = floor($this->center_y + ($xy2[1] * ($this->diameter /3)));
  ImageFillToBorder($this->im, $x2, $y2, $color, $color);
 }
/* }}} */
/* {{{ display */
 /*
 ** Make sure the legends are drawn, then output the image to the
 ** client
 */
 function display() {
  $this->draw_legends(2);
#  $this->draw_margins();
  ImageGif($this->im, "/tmp/pie.gif");
  Header("Content-type: image/gif");
  ImageGif($this->im);
 }
/* }}} */
};
/* }}} */

/* {{{ Test code */
$vals = array(
       array(100, "First value", 190, 0 ,0),
       array(100, "Second value", 0, 190, 0),
       array(100, "Third value", 0, 0 ,190),
       array(100, "Fourth value", 0, 190 ,190),
       array(301.2437, "Fifth value", 204, 0 ,204),
       array(308, "Sixth value", 204,204,0)
       );

$heads = array(
        array("First line (centered)", 4, "c"),
        array("Second line (left justified)", 4, "l"),
        array("Third line (right justified)", 4, "r")
        );

$pie = new piechart;
$pie->init(400, 300, $vals);
$pie->draw_heading($heads);
$pie->set_legend_percent();
$pie->display();
/* }}} */
/*
 * Local Variables:
 * tab-width: 3
 * End: */
?>