WordPress: Prevent large image uploads by dimension

filter_large_image_dimensions.php

<?php

add_filter( 'wp_handle_upload_prefilter', 'gga_filter_large_image_dimensions' );

function gga_filter_large_image_dimensions( $file ) {

	$maxsize = 2000;

	if ( false !== strpos($file['type'], 'image/') ) {
		$size = getimagesize( $file['tmp_name'] );
		if ( !empty( $size ) && count( $size ) > 1 ) {
			if ( ($size[0] > 0 && $size[0] > $maxsize ) || ($size[1] > 0 && $size[1] > $maxsize ) ) {
				$file['error'] = 'Image width or height cannot exceed ' . $maxsize . ' pixels.';
				return $file;
			}
		}
	}

	return $file;
}