public function testValues()
 {
     $values = [MonoImageFilter::CCITT_FAX_ENCODE, MonoImageFilter::FLATE_ENCODE, MonoImageFilter::RUN_LENGTH_ENCODE];
     $this->assertEquals($values, MonoImageFilter::values());
 }
 /**
  * Set monochrome image filter
  *
  * @param string $monoImageFilter
  *
  * @throws \InvalidArgumentException
  *
  * @return $this
  */
 public function setMonoImageFilter($monoImageFilter)
 {
     $monoImageFilter = ltrim($monoImageFilter, '/');
     if (!in_array($monoImageFilter, MonoImageFilter::values())) {
         throw new \InvalidArgumentException('Invalid monochrome image filter argument');
     }
     $this->setArgument(sprintf('-dMonoImageFilter=/%s', $monoImageFilter));
     return $this;
 }