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filter is not described

attachment_thumbnail_args filter-hook . WP 3.9.0

Filters the parameters for the attachment thumbnail creation.

Usage

add_filter( 'attachment_thumbnail_args', 'filter_function_name_5107', 10, 3 );
function filter_function_name_5107( $image_attachment, $metadata, $uploaded ){
	// filter...

	return $image_attachment;
}
$image_attachment(array)
An array of parameters to create the thumbnail.
$metadata(array)
Current attachment metadata.
$uploaded(array)
An array containing the thumbnail path and url.

Where the hook is called

wp_generate_attachment_metadata()
wp-admin/includes/image.php 196
$image_attachment = apply_filters( 'attachment_thumbnail_args', $image_attachment, $metadata, $uploaded );

Where the hook is used (in WP core)

Does not used.