Small change in image-dired.el

Small change in image-dired.el

[Mathias Dahl]

When cleaning my mailbox I found an old request from Stefan Reichör
asking if tumme (as it was called back then) could preserve the
timestamp of rotated original files. He sent a patch which I
implemented (although slightly changed) today. I made it customizable
and by default it works as before, i.e. not preserving timestamp.

If people are OK with the change, could someone check this in for me
(it was a long time since I did any CVS commit and I don't want to
mess up)?

diff -c /home/mathias/image-dired.el /home/mathias/prj/emacs/lisp/image-dired.el
*** /home/mathias/image-dired.el	2008-03-29 20:46:03.000000000 +0100
--- /home/mathias/prj/emacs/lisp/image-dired.el	2008-03-29
20:58:28.000000000 +0100
***************
*** 516,521 ****
--- 516,528 ----
    :type 'integer
    :group 'image-dired)

+ (defcustom image-dired-rotate-original-preserve-timestamp nil
+   "If non-nil, try to preserve the timestamp of the image file.
+ Used by `image-dired-rotate-original'.  Requires the `touch'
+ program to work."
+   :type 'boolean
+   :group 'image-dired)
+
  (defun image-dired-dir ()
    "Return the current thumbnails directory (from variable `image-dired-dir').
  Create the thumbnails directory if it does not exist."
***************
*** 1923,1929 ****
  		      "Rotate to temp file OK.  Overwrite original image? "))
                  (not image-dired-rotate-original-ask-before-overwrite))
              (progn
!               (copy-file image-dired-temp-rotate-image-file file t)
                (image-dired-refresh-thumb))
            (image-dired-display-image file))))))

--- 1930,1942 ----
  		      "Rotate to temp file OK.  Overwrite original image? "))
                  (not image-dired-rotate-original-ask-before-overwrite))
              (progn
!               (let ((time-stamp (dired-touch-initial (list file)))
!                     touch-program)
!                 (copy-file image-dired-temp-rotate-image-file file t)
!                 (when (and image-dired-rotate-original-preserve-timestamp
!                            (setq touch-program (executable-find "touch")))
!                     (call-process shell-file-name nil nil nil
shell-command-switch
!                                   (format "touch -t %s \"%s\""
time-stamp file))))
                (image-dired-refresh-thumb))
            (image-dired-display-image file))))))


Diff finished.  Sat Mar 29 21:01:35 2008

/Mathias

Re: Small change in image-dired.el

[Stefan Monnier]

> When cleaning my mailbox I found an old request from Stefan Reichör
> asking if tumme (as it was called back then) could preserve the
> timestamp of rotated original files. He sent a patch which I
> implemented (although slightly changed) today. I made it customizable
> and by default it works as before, i.e. not preserving timestamp.

What is the rationale for such a "feature"?  Generally, modifying a file
and then changing its timestamp back to what it was is a good way to get
in trouble (many programs assume that if the timestamp hasn't changed,
then the file hasn't changed).

Maybe some other feature can provide the same end result?  E.g. maybe
the file's content should hold the timestamp (in its metadata) instead?

> If people are OK with the change, could someone check this in for me
> (it was a long time since I did any CVS commit and I don't want to
> mess up)?

I'm not necessarily opposed to it, but I'd first like a compelling
evidence that this is really the right way to solve the
original problem.


        Stefan

Re: Small change in image-dired.el

[Reiner Steib]

On Sat, Mar 29 2008, Stefan Monnier wrote:

>> When cleaning my mailbox I found an old request from Stefan Reichör
>> asking if tumme (as it was called back then) could preserve the
>> timestamp of rotated original files. [...]
>
> What is the rationale for such a "feature"?  

When a picture from a digital camera has the wrong orientation, it
might be useful to preserve the time stamp when fixing it.  Not all
programs honor the EXIF info or the camera might do it wrong (due to
misconfiguration?).  I don't know what the rationale was for Stefan R.
 
Bye, Reiner.
-- 
       ,,,
      (o o)
---ooO-(_)-Ooo---  |  PGP key available  |  http://rsteib.home.pages.de/

Re: Small change in image-dired.el

[Stefan Monnier]

>>> When cleaning my mailbox I found an old request from Stefan Reichör
>>> asking if tumme (as it was called back then) could preserve the
>>> timestamp of rotated original files. [...]
>> What is the rationale for such a "feature"?  
> When a picture from a digital camera has the wrong orientation, it
> might be useful to preserve the time stamp when fixing it.  Not all
> programs honor the EXIF info or the camera might do it wrong (due to
> misconfiguration?).

If the program doesn't honor the EXIF info and uses the file's timestamp
as "the time the photo was taken", then there's not much we can do and
the time will often be wrong for whatever reason (e.g. you copied the
files).

So what we should do is check the EXIF info: if the photo's date is
missing, we should take the file's timestamp and put it as the
photo's date.  Then we can go on and change the file's time stamp all
we want.


        Stefan

Re: Small change in image-dired.el

[Mathias Dahl]

>  What is the rationale for such a "feature"?

See below.

>  Generally, modifying a file
>  and then changing its timestamp back to what it was is a good way to get
>  in trouble (many programs assume that if the timestamp hasn't changed,
>  then the file hasn't changed).

Yes, I agree, mostly.

>  I'm not necessarily opposed to it, but I'd first like a compelling
>  evidence that this is really the right way to solve the
>  original problem.

I think the only "problem" was that Stefan R was used to work in a
certain way with his photos, and the rotation messed up with his
scheme. I suspect for him that a rotation is an operation that can be
neglected from a change viewpoint.

Here is our original conversation:

----

from	Stefan Reichör
to	Mathias Dahl
date	Sat, Jun 17, 2006 at 10:31 PM
subject	Improvement for tumme-rotate-original
mailed-by	utanet.at
		
Hi Mathias!

I try to use tumme to organize/view my photo collection.
My photos all keep the timestamp when they were shot.

I modified tumme-rotate-original in a way that the time stamp is
preserved. It would be nice, if you could add this functionality!

Stefan.

[patch removed]

from	Mathias Dahl
to	Stefan Reichör
date	Sun, Jun 18, 2006 at 8:53 AM
subject	Re: Improvement for tumme-rotate-original
mailed-by	gmail.com
	
Thanks for the patch, I'll think about it. Personally I never trust
the timestamp of a file because I have found out too many times that
it has been modified in transit, when copying, moving, FTPing,
zipping, whatever... What I do instead is trust the EXIF data in it,
make sure that it is always preserved (tumme does that by default). I
also rename all the photos I take with my camera using the internal
timestamp so that the names will be unique and sorted in the correct
order in dired etc. Tumme has a command for this,
`tumme-copy-with-exif-file-name'. Maybe that is something you would
like to try?

Also, the touch command is not available on w32 so this would have to
be an option or we would have to find a suitable replacement command
that works there.

I suggest you keep your fix in your .emacs and I *might* try merge it
into tumme.el when I have the time.

Again, thanks for the suggestion!

from	Stefan Reichör
to	Mathias Dahl
date	Mon, Jun 19, 2006 at 6:23 AM
subject	Re: Improvement for tumme-rotate-original
	
Hi Mathias!

> Thanks for the patch, I'll think about it. Personally I never trust
> the timestamp of a file because I have found out too many times that
> it has been modified in transit, when copying, moving, FTPing,
> zipping, whatever... What I do instead is trust the EXIF data in it,
> make sure that it is always preserved (tumme does that by default). I
> also rename all the photos I take with my camera using the internal
> timestamp so that the names will be unique and sorted in the correct
> order in dired etc. Tumme has a command for this,
> `tumme-copy-with-exif-file-name'. Maybe that is something you would
> like to try?

Thanks for your ideas. I try to keep the date correct for my pictures.
And that works for me. Thanks for the hint about the EXIF data.

I also have a small python script to rename my pictures, using the
date. It is nice to see that date on the back of the pictures when I
order them from a photo shop.

> Also, the touch command is not available on w32 so this would have to
> be an option or we would have to find a suitable replacement command
> that works there.

You could try, if touch is available and use it only then. Something
like tumme-has-touch-command.

> I suggest you keep your fix in your .emacs and I *might* try merge it
> into tumme.el when I have the time.

That is fine with me. I think most users will prefer this behaviour.

----

As you can see, I too think EXIF should be trusted rather than the
timestamp. Still, I thought the feature sounded OK to have and should
not hurt anything, especially with the new variable
introduced. Granted, even if the change is quite small, it increases complexity,
so I won't argue about it being included.

/Mathias