Index: image.php
===================================================================
--- image.php	(revision 6400)
+++ image.php	(working copy)
@@ -17,7 +17,7 @@
  * If PHP does not have the functionality to save in a file of the same format, the thumbnail will be created as a jpeg.
  */
 function wp_create_thumbnail( $file, $max_side, $deprecated = '' ) {
-	if ( ctype_digit( $file ) ) // Handle int as attachment ID
+	if ( is_numeric( $file ) ) // Handle int as attachment ID
 		$file = get_attached_file( $file );
 
 	$image = wp_load_image( $file );
@@ -88,7 +88,7 @@
  *
  */
 function wp_crop_image( $src_file, $src_x, $src_y, $src_w, $src_h, $dst_w, $dst_h, $src_abs = false, $dst_file = false ) {
-	if ( ctype_digit( $src_file ) ) // Handle int as attachment ID
+	if ( is_numeric( $src_file ) ) // Handle int as attachment ID
 		$src_file = get_attached_file( $src_file );
 
 	$src = wp_load_image( $src_file );
@@ -172,7 +172,7 @@
  *
  */
 function wp_load_image( $file ) {
-	if ( ctype_digit( $file ) )
+	if ( is_numeric( $file ) )
 		$file = get_attached_file( $file );
 
 	if ( ! file_exists( $file ) )