Resizing with GD outputs black images

Question

What can cause php gd to produce a black image after resizing? The following code always outputs a black image for every valid jpeg file.

<?php  $filename = 'test.jpg'; $percent = 0.5;  header('Content-Type: image/jpeg');  list($width, $height) = getimagesize($filename); $newwidth = $width * $percent; $newheight = $height * $percent;  $thumb = imagecreatetruecolor($newwidth, $newheight); $source = imagecreatefromjpeg($filename);  imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);  imagejpeg($thumb); imagedestroy($thumb); ?> 

output of gd_info():

  Array (     [GD Version] => bundled (2.1.0 compatible)     [FreeType Support] => 1     [FreeType Linkage] => with freetype     [T1Lib Support] =>      [GIF Read Support] => 1     [GIF Create Support] => 1     [JPEG Support] => 1     [PNG Support] => 1     [WBMP Support] => 1     [XPM Support] =>      [XBM Support] => 1     [JIS-mapped Japanese Font Support] =>  ) 

The code appeared working in other environments. Probably it is related to OS, installed packages, libraries, etc?

Answer 1

Research

Just tried to reproduce your situation. Running your code with out-of-the-box PHP and Apache displays the following

The image “http://localhost/” cannot be displayed because it contains errors.

Although browser tells you that there were some errors, they cannot be seen because of the headers returned in response were of Content-Type: image/jpeg thus forcing browser to interpret it as an image. By removing the header and setting the following will output errors.

ini_set('error_reporting', E_ALL); ini_set('display_errors', true); ... //header('Content-Type: image/jpeg'); ... 

Answer

What can cause php gd to produce a black image after resizing?

Since the gd_info output proves that the GD extension is loaded, check if the filename (linux is caseSensitive) and permissions are correct. If Apache is running as www-data (group)

sudo chown :www-data test.jpg && sudo chmod 660 test.jpg  

Code improvement / solution

ini_set('error_reporting', E_ALL); ini_set('display_errors', true);  if (extension_loaded('gd') && function_exists('gd_info')) {     $filename = 'test.jpg';      if (file_exists($filename) && is_readable($filename))     {         $percent = 0.5;          header('Content-Type: image/jpeg');          list($width, $height) = getimagesize($filename);         $newwidth = $width * $percent;         $newheight = $height * $percent;          $thumb = imagecreatetruecolor($newwidth, $newheight);         $source = imagecreatefromjpeg($filename);          imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);          imagejpeg($thumb);         imagedestroy($thumb);     }     else     {         trigger_error('File or permission problems');     } } else {     trigger_error('GD extension not loaded'); } 

Comments

This should be used as a temporary solution (development environment). IMHO, the errors should be handled by a central error handler, display_errors should be false in production. Also, the errors (in this case there would be Fatal error) are logged by default - check the logs for more (the frequent, the better). Also, on linux (with apt) the one-liner will install GD on your system:

sudo apt-get update && sudo apt-get install php5-gd && sudo /etc/init.d/apache2 restart