I am trying to optimize my images when uploading to website. I trying to write plugin, that will use hook 'add_attachment' and after attachment uploaded do image converting.

add_action( 'add_attachment', 'optimize_psio', 0);
// Action for optimizing on upload
function optimize_psio( $post_ID){
    require_once plugin_dir_path( __FILE__ ) . 'includes/class-ps-image-optimizer-converter.php';
    $converter = new Ps_Image_Optimizer_Converter($post_ID);

The optimize_psio function works great when working standalone. But when I trying to register hook and upload image, I getting error:

Post-processing of the image failed likely because the server is busy or does not have enough resources. Uploading a smaller image may help. Suggested maximum size is 2500 pixels.

Image uploading, but not cropped and not converted. What am I doing wrong?

  • the code for Ps_Image_Optimizer_Converter is missing!
    – Tom J Nowell
    Jan 22, 2022 at 18:02
  • There only converting to webp function there and it was tested without action and worked.
    – Denny
    Jan 22, 2022 at 19:52
  • 1
    You still need to share the class, all of the relevant code to answering the question is contained inside that class. You must edit your question to include it. I know you do not believe it is relevant, but you're also trying to figure out a problem and have come here and asked, so humour us, after all if it is indeed irrelevant it will be clear from the code and nobody will ask again
    – Tom J Nowell
    Jan 23, 2022 at 1:46
  • Thank you @TomJNowell I found what is my error. Hook fires before image was cropped and that is why I can't optimize images that not exists.
    – Denny
    Jan 24, 2022 at 12:45

1 Answer 1


Hook add_attachment fires before images cropped via wp_ajax_crop_image(). That's why Wordpress trying to work with files, that is not existed for now.

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