Question

Is there a way when uploading images (JPEG) to check the DPI?

I would like to integrate it into a form, so as a validator.

Answer 1

You have to open the image with Imagick (or Gmagick) and then call getImageResolution.

$image = new Imagick($path_to_image);
var_dump($image->getImageResolution());

result:

Array
(
    [x]=>75
    [y]=>75
)

Edit:

For an integration into symfony, you can use a custom validator for that. You extends the default one to validate a file and add the DPI restriction.

Create this one into /lib/validator/myCustomValidatorFile .class.php:

<?php

class myCustomValidatorFile extends sfValidatorFile
{
  protected function configure($options = array(), $messages = array())
  {
    parent::configure($options, $messages);

    $this->addOption('resolution_dpi');
    $this->addMessage('resolution_dpi', 'DPI resolution is wrong, you should use image with %resolution_dpi% DPI.');
  }

  protected function doClean($value)
  {
    $validated_file = parent::doClean($value);

    $image      = new Imagick($validated_file->getTempName());
    $resolution = $image->getImageResolution();

    if (empty($resolution))
    {
      throw new sfValidatorError($this, 'invalid');
    }

    if ((isset($resolution['x']) && $resolution['x'] < $this->getOption('resolution_dpi')) || (isset($resolution['y']) && $resolution['y'] < $this->getOption('resolution_dpi')))
    {
      throw new sfValidatorError($this, 'resolution_dpi', array('resolution_dpi' => $this->getOption('resolution_dpi')));
    }

    return $validated_file;
  }
}

Then, inside your form, use this validator for your file:

$this->validatorSchema['file'] = new myCustomValidatorFile(array(
  'resolution_dpi' => 300,
  'mime_types'     => 'web_images',
  'path'           => sfConfig::get('sf_upload_dir'),
  'required'       => true
));