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Re: tumme directory

From: Juri Linkov
Subject: Re: tumme directory
Date: Sun, 12 Feb 2006 19:45:47 +0200
User-agent: Gnus/5.110004 (No Gnus v0.4) Emacs/22.0.50 (gnu/linux)

>> The thumbnail PNG file sizes are much smaller than generated by other
>> programs, but still are readable by them.
> Are they still conforming to the standard?

Yes.  `pngcrush' can add textual chunks (either compressed or not) with
the prefix `Thumb::Image::' that make generated thumbnails perfectly
readable by other programs.

However, there is one problem with textual chunks added by `convert'.
Its `-set attr value' command option adds only compressed textual chunks,
and GQview (a GTK image viewer) can't read compressed chunks.  So if
`pngcrush' is not installed on the system, then thumbnails we can produce
with `convert' will be unreadable by GQview.  This is not a problem
since when GQview can't recognize the thumbnail it overwrites it with its
own version.  A later versions of GQview might fix this shortcoming.
And Gimp reads compressed chunks just fine.

>> But when I regenerate them with a set of PNG optimizing utilities,
>> it reads them instantly.  And disk space saving is almost three-fold
>> which is significant with a large thumbnail collection.
> It seems to me that you should dive into tumme.el and start hacking :)

Well.  I've added support for the Thumbnail Managing Standard to tumme.el.
It adds all required attributes, but still misses some additional attributes
(like original dimensions).  Since the same attributes should be displayed
in the *tumme* buffer, I expect more discussion how to extract these
attributes from original images.  I'd like to add

(defcustom tumme-cmd-read-info-program
  "*Executable used to get information about original images.
Used together with `tumme-cmd-read-info-options'."
  :type 'string
  :group 'tumme)

(defcustom tumme-cmd-read-info-options
  "%p -format \"%%f %%wx%%h %%b\n\" %f"
  "*Format of command used to get information about original images.
Available options are %p which is replaced by
`tumme-cmd-read-info-program', %f which is replaced by the file name
of the original image."
  :type 'string
  :group 'tumme)

and use it to extract image information.

Juri Linkov

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