[Digikam-devel] ,image preview

Caulier Gilles caulier.gilles at kdemail.net
Sat Jul 15 07:33:25 BST 2006

Le Vendredi 14 Juillet 2006 21:51, Olivier a écrit :
> Hi,
> I tested digikam svn 0,9 and I see that when switching to the next preview
> I get a blinking "preview extration in progress". I do not think that it is
> a good idea. The blinking effect attract the attention to the exact thing
> you do not want the user to feel : it takes time ...

But it can take time is the picture do not have an embedded preview data to 
show. Let's me explain exactly how this part work:

Some picture file format use preview image embedded in metadata. RAW file like 
NEF, MRW, or CR2 use this in makernaote area. The preview is generaly a JPEG 
or TIF or PPM small image (1024*768 for example). It's not the Exif 
thumbnail ! It's a preview used by camera to show the image on a TV screen 
for slideshow. It's different.

This way is very fast to load image data instead the whole image...

In JPEG, the same way is used by camera (makernote preview).

About TIFF and PNG, there is generally no preview recorded. But with 
0.9.0-svn, digiKam use the IPTC preview tag to store a small JPEG preview 
image (800x600) to render preview extraction in a fast way. This is only done 
when you edit a picture, and your save it.

> The best implementation I have seen yet. is the one in eofg or showfoto
> with a progress bar, if is not pssible 

Is not possible because i don't have a progress feedback from the preview 
extractor kioslave. The Showfoto/Image Editor loading part is completly 
different and of course can do it.

> I would suggest writing the "preview 
> extraction in progress " under or over the image instead of taking the
> image away.

Hum this is my proposal : delayed the blink effect (for example 500ms). If a 
preview is found, nothing will appear. If no preview is available, the whole 
image is loaded and it can take a while. In this case the blink effect will 

 If you is agree with this rule, please make a new file in B.K.O, we will do 
it later the first beta1, because we have planed to do this release during 
next week with Marcel, and we try to fix the last know bugs actually.

> Concerning the "back to album" and edit". Why not... but what do you think
> of putting them as a toolbar on the top left as icon or ttext ? it would be
> more consistent with the rest of the interface (prev and next are at the
> top left in the properties sidebar and the toolbars are on the top too )

This need to be discuted with the rest of users/developpers. Make a new file 
in B.KO again about this point. 

Thanks in advance for your report.


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