php - Resizing with GD outputs black images -


what can cause php gd produce black image after resizing? following code outputs black image 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] => 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. related os, installed packages, libraries, etc?

research

just tried reproduce situation. running code out-of-the-box php , apache displays following

the image “http://localhost/” cannot displayed because contains errors.

although browser tells there errors, cannot seen because of headers returned in response of content-type: image/jpeg forcing browser interpret image. removing header , setting following output errors.

ini_set('error_reporting', e_all); ini_set('display_errors', true); ... //header('content-type: image/jpeg'); ...
answer

what can cause php gd produce black image after resizing?

since gd_info output proves gd extension loaded, check if filename (linux casesensitive) , permissions correct. if apache running 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 used temporary solution (development environment). imho, errors should handled central error handler, display_errors should false in production. also, errors (in case there fatal error) logged default - check logs more (the frequent, better). also, on linux (with apt) one-liner install gd on system:

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

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