在emacs模式行上显示图片的尺寸

(add-hook 'image-mode-hook (lambda ()
                          "display image size on mode line."
                          (setq mode-name (format "Image[%s](%s*%s)" 
                                                  image-type 
                                                  (car (image-size (image-get-display-property) t)) 
                                                  (cdr (image-size (image-get-display-property) t))))))