Hi all
I would like to display several charts on a webpage. I have designed a class that would draw each chart using GD and based on data set by a public method. Unfortunately instead of charts being drawn I get an error message:
The image ... cannot be displayed because it contains errors
I have googled and checked similar threads here on DW but nothing helped. I think I do not have any output sent before headers (checked with if(headers_sent())) which is usually the cause for this error. Maybe my class is coded incorrectly. The same code works fine if put in an ordinary php file, but I would prefer to have a class for this purpose. If anybody coud have a look at the code and give me a hint I would really appreciate it.
The Chart class (simplified, but does not work):
<?php
class Chart
{
// data for drawing the chart
protected $chart_data = array();
public function __construct()
{
}
public function set_chart_data($data)
{
$this->chart_data = $data;
}
public function draw_chart()
{
header("Content-type: image/png");
$width = $this->chart_data['width'];
$height = $this->chart_data['height'];
// create image
$image=imagecreatetruecolor($width, $height)
or die('Cannot iInitialize new GD image stream');;
// define colors
$fill_color=imagecolorallocate($image, 127, 127, 127);
// draw a filled rectangle
imagefilledrectangle($image, 0, 0, $width, $height, $fill_color);
// output image and destroy it
imagepng($image);
imagedestroy($image);
}
}
?>
And the php file to display the chart (simplified):
<?php
require_once('Chart.php');
$ch = new Chart;
// set data for the chart
$w = 250; $h = 250;
$ch->set_chart_data( array('width' => $w,'height' => $h));
echo '<html><head></head><body>';
echo '<p>Test GD</p>';
// display the chart
echo "<p><img src=\"{$ch->draw_chart()}\" width=\"$w\" height=\"$h\" /></p>";
echo '</body></html>';
?>
