WordPress get_intermediate_image_sizes Function: A Comprehensive Guide with Usage and Filter Examples

In WordPress, managing images is an essential aspect of building a visually appealing website. The get_intermediate_image_sizes function is a powerful tool that allows developers to retrieve a list of registered image sizes, providing flexibility and control over image resizing. In this comprehensive guide, we will explore the capabilities of get_intermediate_image_sizes in detail, along with practical usage examples and insights into utilizing filters to enhance its functionality.

Understanding the get_intermediate_image_sizes Function: The get_intermediate_image_sizes function is a built-in WordPress function that returns an array of intermediate image sizes registered in your WordPress installation. Intermediate image sizes are additional image variations generated by WordPress during the upload process. These sizes complement the default image sizes (thumbnail, medium, large, and full).

Usage Examples:

1. Retrieving and Displaying Image Sizes: To obtain an array of registered intermediate image sizes, simply call the get_intermediate_image_sizes function in your code:

$image_sizes = get_intermediate_image_sizes();

// Display the image sizes
foreach ($image_sizes as $size) {
    echo $size . '<br>';
}

This code snippet retrieves all the registered image sizes and displays them on the screen.

2. Customizing Image Size Output: You can also customize the output of the image sizes by utilizing the image_size_names_choose filter. This filter allows you to modify the names of the image sizes displayed in the Media Uploader’s size dropdown.

function custom_image_sizes($sizes) {
    // Add a custom image size
    $sizes['custom-size'] = __('Custom Size');

    // Remove unwanted image sizes
    unset($sizes['medium_large']);

    return $sizes;
}
add_filter('image_size_names_choose', 'custom_image_sizes');

In this example, we add a new custom image size named “Custom Size” and remove the “medium_large” size from the dropdown options in the Media Uploader.

Filtering Examples: The get_intermediate_image_sizes function can be further enhanced by leveraging filters provided by WordPress. Filters enable developers to modify the default behavior of functions and customize their output.

1. Filtering Image Sizes: The intermediate_image_sizes filter allows you to modify the array of intermediate image sizes before it is returned by the get_intermediate_image_sizes function. This filter opens up possibilities for manipulating the sizes based on specific requirements.

function modify_image_sizes($sizes) {
    // Add a custom image size
    $sizes[] = 'custom-size';

    // Remove unwanted image sizes
    unset($sizes['thumbnail']);

    return $sizes;
}
add_filter('intermediate_image_sizes', 'modify_image_sizes');

Here, we add a custom image size and remove the default thumbnail size from the array of intermediate image sizes.

2. Filtering Image Attributes: The wp_get_attachment_image_attributes filter can be used to modify the attributes of the image HTML output. By utilizing this filter in conjunction with get_intermediate_image_sizes, you can customize the image attributes based on specific image sizes.

function modify_image_attributes($attr, $attachment, $size) {
    if ($size === 'custom-size') {
        $attr['class'] = 'custom-image';
    }

    return $attr;
}
add_filter('wp_get_attachment_image_attributes', 'modify_image_attributes', 10, 3);

In this example, when the “custom-size” is requested, we add a CSS class of “custom-image” to the image attributes.

Conclusion: The get_intermediate_image_sizes function in WordPress empowers developers to retrieve and manipulate registered intermediate image sizes with ease. By utilizing this function, along with filters like image_size_names_choose, intermediate_image_sizes, and wp_get_attachment_image_attributes, you can customize image sizes, control their availability, and modify image attributes according to your specific requirements. This comprehensive guide has equipped you with the knowledge and examples to master the potential of get_intermediate_image_sizes and enhance your WordPress website’s image management capabilities.