Limit image resolution on upload

3 comments

1. The problem isn’t so much the uploading itself, as that is a network connection between the client and the server. It’s not what’s eating the server’s memory.

   When WordPress starts ‘cruncing’ the images, that is where PHP comes in and start resizing and cropping the uploaded images. It is before this moment you need to step in and perform a couple of checks before allowing PHP to eat up your memory.

   Using the wp_handle_upload_prefilter filter, you can hook a function that performs any check you’d like on the image that is about to be crunched:

   <?php 
   /* Marc Dingena Utilities
    * Test image resolution before image crunch
    */
   add_filter('wp_handle_upload_prefilter','mdu_validate_image_size');
   function mdu_validate_image_size( $file ) {
       $image = getimagesize($file['tmp_name']);
       $minimum = array(
           'width' => '400',
           'height' => '400'
       );
       $maximum = array(
           'width' => '2000',
           'height' => '2000'
       );
       $image_width = $image[0];
       $image_height = $image[1];
   
       $too_small = "Image dimensions are too small. Minimum size is {$minimum['width']} by {$minimum['height']} pixels. Uploaded image is $image_width by $image_height pixels.";
       $too_large = "Image dimensions are too large. Maximum size is {$maximum['width']} by {$maximum['height']} pixels. Uploaded image is $image_width by $image_height pixels.";
   
       if ( $image_width < $minimum['width'] || $image_height < $minimum['height'] ) {
           // add in the field 'error' of the $file array the message 
           $file['error'] = $too_small; 
           return $file;
       }
       elseif ( $image_width > $maximum['width'] || $image_height > $maximum['height'] ) {
           //add in the field 'error' of the $file array the message
           $file['error'] = $too_large; 
           return $file;
       }
       else
           return $file;
   }
   ?>
   

2. For a plugin, try http://wordpress.org/plugins/imsanity/ and that will help with keeping other site users from uploading images that are too large.

   Imsanity automatically resizes huge image uploads down to a size that
   is more reasonable for display in browser, yet still more than large
   enough for typical website use. The plugin is configurable with a max
   width, height and quality. When a contributor uploads an image that is
   larger than the configured size, Imsanity will automatically scale it
   down to the configured size and replace the original image.

3. It’s possible that your server has enough memory to do the task, but that the PHP memory limit setting is just too low for the job of converting very large images.

   Try setting memory_limit in php.ini higher.

   memory_limit=256M
   

   *Note: This might not be an appropriate solution in some hosting environments.

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