How to use image_downsize filter in WordPress

Hey! So, you’re diving into the world of WordPress hooks, huh? Let’s talk about the image_downsize filter. This one is pretty nifty. When you return a ‘truthy’ value from this filter, you essentially bypass the down-sizing of the image, giving you back that value instead. It’s like a shortcut, and who doesn’t love a good shortcut, right?

To get started with the image_downsize filter, you’ll need to register it using add_filter. You can pop this code into your theme’s functions.php file or, as we prefer at WePlugins, create a custom WordPress Plugin. That way, when you update your theme, nothing breaks. Pretty smart, eh?

Sometimes, you’ll need to remove a registered hook. For that, remove_filter is your best friend.

Live Example 1: Basic Usage

Here’s a straightforward example of how to use this hook.

    function weplugins_modify_image_downsize_defaults($downsize, $id, $size) { 
        // Update the $downsize variable according to your website requirements and return this variable. You can modify the $downsize variable conditionally too if you want.
        return $downsize; 
    }
    // add the filter
    add_filter("image_downsize", "weplugins_modify_image_downsize_defaults", 10, 3);
    

Live Example 2: Removing the Filter

To remove a hook callback, use the example below. Make sure to match the callback function name, priority, and number of arguments.

    remove_filter("image_downsize", "weplugins_modify_image_downsize_defaults", 10, 3);
    

Live Example 3: Conditional Modification

Modify the $downsize variable conditionally based on your requirements.

    function weplugins_modify_image_downsize_conditional($downsize, $id, $size) {
        if (is_admin()) {
            $downsize = true;
        }
        return $downsize;
    }
    add_filter("image_downsize", "weplugins_modify_image_downsize_conditional", 15, 3);
    

Parameters: There are three key parameters you need when using this hook:

• $downsize: (bool|array) Whether to short-circuit the image downsize.
• $id: (int) Attachment ID for the image.
• $size: (string|int[]) Requested image size. Can be any registered image size name, or an array of width and height values in pixels (in that order).