PHP implementation of stackblur algorithm available?

Question

I am trying to blur an image and need a faster solution.

This is my current attempt which is much too slow for large images and I do not want to use imagick.

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Answer 1

The simple solution is to scale the image down before you apply the blur filter. Here are some examples:

Original image:

20× Gaussian Blur (2.160 seconds):

{
  $start = microtime(true);
  for ($x=0; $x<20; $x++) {
    imagefilter($image, IMG_FILTER_GAUSSIAN_BLUR);
  }
  $end =  microtime(true);
  $howlong = $end - $start;
}

Combination of scaling and Gaussian blur (0.237 seconds):

{
  $start = microtime(true);

  /* Scale by 25% and apply Gaussian blur */
  $s_img1 = imagecreatetruecolor(160,120);
  imagecopyresampled($s_img1, $image, 0, 0, 0, 0, 160, 120, 640, 480);
  imagefilter($s_img1, IMG_FILTER_GAUSSIAN_BLUR);

  /* Scale result by 200% and blur again */
  $s_img2 = imagecreatetruecolor(320,240);
  imagecopyresampled($s_img2, $s_img1, 0, 0, 0, 0, 320, 240, 160, 120);
  imagedestroy($s_img1);
  imagefilter($s_img2, IMG_FILTER_GAUSSIAN_BLUR);

  /* Scale result back to original size and blur one more time */
  imagecopyresampled($image, $s_img2, 0, 0, 0, 0, 640, 480, 320, 240);
  imagedestroy($s_img2);
  imagefilter($image, IMG_FILTER_GAUSSIAN_BLUR);
  $end =  microtime(true);
  $howlong = $end - $start;
}