(Resend in text mail format.)
Hi,

When opening a png file and toggle display from image to text by C-c
C-c, the `image-toggle-display-text` will be called twice in function
`image-toggle-display-text`.
The first call is from the major mode change hook, in the following
line will cause `change-major-mode-hook` be run and it’s
`image-toggle-display-text` for image-mode.
image-mode.el:730         (major-mode-restore '(image-mode image-mode-as-text))

The second call is from the direct call at
image-mode.el:736         (image-toggle-display-text)

Try debug-on-entry on `image-toggle-display-text`, then switch image
to text in image-mode by press C-c C-c to observe the issue.

And the patch tries to reduce calling for `image-toggle-display-text`.

Best Regards
Lin Sun