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Álvaro Ramírez

Álvaro Ramírez

06 October 2023 Displaying image details in mode line

A benefit of running Emacs as a GUI app, is that you can view images from your beloved editor. This is super handy to take a quick peek at any image.

Sometimes, I'd like a little more than just viewing the image. I'd like to see basic image details like type, dimensions, and file size. The imagemagick identify utility is pretty handy for that.

identify -format "%m %wx%h %b" path/to/image.png
PNG 2387x1055 2.28454MB

I could easily invoke shell-command for this or even create a dwim-shell-command function (maybe I will), but if this info was proactively displayed in the mode line, I wouldn't have to fetch it myself.

Since I know I can use the identify command for this, I may as well see if I can plug it into the mode line.

Turns out this wasn't too bad by setting setting mode-line-format. I added a little logic to only include image details while in image-mode and rely on process-lines to fetch the details. This function returns a list, which is a happy coincidence since mode-line-format also expects a list.

(setq-default mode-line-format
              '(" "
                 (when (eq major-mode 'image-mode)
                   ;; Needs imagemagick installed.
                   (process-lines "identify" "-format" "[%m %wx%h %b]" (buffer-file-name))))
                " "
                (vc-mode vc-mode)
                (multiple-cursors-mode mc/mode-line)
                " " mode-line-modes


I'd love to hear if there's a pure elisp alternative (mastodon/twitter). I gave (image-size (image-get-display-property) :pixels) a try, but that seemed to return the display size in buffer rather than actual file size.