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Re: thumbs.el and transparency

From: Juri Linkov
Subject: Re: thumbs.el and transparency
Date: Sun, 05 Feb 2006 22:36:29 +0200
User-agent: Gnus/5.110004 (No Gnus v0.4) Emacs/22.0.50 (gnu/linux)

> I would like to have some feedback on the changes, but it seems I won't
> get some, so I better test some more myself first.

Well, the basic thing both thumbs packages are still missing is proper
integration with dired.  The first thing I expect from a thumbs package
is to display a dired buffer with thumbnail images in it.

This can be very easily done with iimage.el, i.e. just open a dired buffer
and type M-x iimage-mode RET and you will see, for example:

PNG image

This doesn't look right yet.  With a simple fix it could preserve file
names in the dired buffer:

--- lisp/iimage.el      6 Aug 2005 22:13:43 -0000       1.6
+++ lisp/iimage.el      5 Feb 2006 20:28:32 -0000
@@ -133,12 +133,43 @@
-                 (add-text-properties (match-beginning 0) (match-end 0)
-                                      (list 'display (create-image file)))
-               (remove-text-properties (match-beginning 0) (match-end 0)
-                                       '(display)))))))
+                 (let ((ov (make-overlay (match-beginning 0) (match-end 0))))
+                   (overlay-put ov 'evaporate t)
+                   (overlay-put ov 'before-string
+                                (propertize " "
+                                            'display
+                                            (create-image file))))
+               (remove-overlays (match-beginning 0) (match-end 0)
+                                'display))))))

After that, images get added before the file name part in the dired
buffer like:

PNG image

This is much better, but still doesn't work for large images.  This can be
improved with another fix:

--- lisp/iimage.el      6 Aug 2005 22:13:43 -0000       1.6
+++ lisp/iimage.el      5 Feb 2006 20:29:32 -0000
@@ -133,1 +133,1 @@
-                               (create-image file))))
+                               (create-image (my-make-thumbnail file)))))

and a new function:

(defun my-make-thumbnail (file)
  (let* ((image-file (concat "file://" (expand-file-name file)))
         (thumb-file (expand-file-name (concat "~/.thumbnails/normal/" (md5 
image-file) ".png")))
         (file-attrs (file-attributes file))
         (modif-time (float-time (nth 5 file-attrs))))
    (unless (file-exists-p thumb-file)
         (format "\"%s\"" file)
         (format "-set \"Description\" \"Thumbnail of %s\"" image-file)
         (format "-set \"Software\" \"ImageMagick, GNU Emacs %s\"" 
         (format "-set \"Thumb::URI\" \"%s\"" image-file)
         (format "-set \"Thumb::MTime\" \"%.0f\"" modif-time)
         "-set \"Thumb::Size\" \"%b\""
         "-set \"Thumb::Image::Width\" \"%w\""
         "-set \"Thumb::Image::Height\" \"%h\""
         "-set \"Thumb::Image::Mimetype\" \"image/jpeg\""
         "-resize 128x128"
         "+profile \"*\""
         "-type TrueColorMatte"
         (format "png:\"%s\"" thumb-file))
        " ")))

This function generates thumbnail files exactly as specified by the
Thumbnail Managing Standard.  It constructs the thumbnail filename,
fills all required attributes, resizes the image, removes EXIF data
and uses -type TrueColorMatte to force the encoder to write an
alpha channel as specified by the standard.  I think this function
should be adopted for all Emacs thumbnail packages.

Given that, the result on large files will look like:

PNG image

Isn't this nice?  I think it is.

This is just one thing that would make Emacs thumbnail packages
more useful.

Juri Linkov

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