[Koha-devel] Cover image 'thumbnail' size is bigger than 'imagefile' size

[Andreas Roussos]

Hi Paul, Jonathan,

Thank you both for your prompt replies and your feedback.
I have now opened a new bug report here:
https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=21987

Andreas

On Wed, 12 Dec 2018 at 14:53, Paul Poulain <paul.poulain at biblibre.com>
wrote:

> Hi Andreas,
>
> (and if you can't provide a patch, please file a bug on buzilla, this
> description is perfect ! )
>
> Le 12/12/2018 à 13:49, Jonathan Druart a écrit :
> > Hi Andreas,
> >
> > This module has never been enhanced much and as you noticed there is
> > room for such enhancements :)
> > All of what you describe in your email makes sense to me, and I am
> > sure the changes will be accepted if a patch is provided.
> >
> > Cheers,
> > Jonathan
> > Le mer. 12 déc. 2018 à 06:42, Andreas Roussos <arouss1980 at gmail.com> a
> écrit :
> >> Dear Developers,
> >>
> >> We use local cover images in our setup, and also resize the covers
> >> we scan to a width of 160px before uploading and attaching them to
> >> a Koha bibliographic record (we upload one cover per biblio).
> >>
> >> While using phpMyAdmin to view the contents of the 'biblioimages'
> >> table (relevant screenshot here: https://imgur.com/a/cSEVLBI), we
> >> noticed that the size of the BLOBs for the 'thumbnail' column was in
> >> some cases twice as big as that of the 'imagefile' column. In fact,
> >> this happens for more than 50% of uploaded covers as you can see
> >> from the output of the SQL queries below:
> >>
> >> mysql> SELECT COUNT( * ) AS count
> >>           FROM biblioimages
> >>          WHERE LENGTH( thumbnail ) > ( LENGTH( imagefile ) * 2 ) ;
> >> +-------+
> >> | count |
> >> +-------+
> >> |  1356 |
> >> +-------+
> >>
> >> mysql> SELECT COUNT( * ) AS count,
> >>                SUM( LENGTH( imagefile ) ) AS images_size,
> >>                SUM( LENGTH( thumbnail ) ) AS thumbnails_size
> >>           FROM biblioimages ;
> >> +-------+-------------+-----------------+
> >> | count | images_size | thumbnails_size |
> >> +-------+-------------+-----------------+
> >> |  2347 |    68323933 |       115839686 |
> >> +-------+-------------+-----------------+
> >>
> >> It would appear that for each 160px-wide JPG with 24-bit depth that
> >> we have uploaded, the 'imagefile' column has been populated with an
> >> PNG of 8 bit depth with the same dimensions as the uploaded file,
> >> whereas the 'thumbnail' column contains a 24-bit PNG image with a
> >> width reduced to 140 pixels.
> >>
> >> I've tracked down the creation of resized 24-bit PNGs to this code:
> >>
> https://github.com/Koha-Community/Koha/blob/master/C4/Images.pm#L182-L183
> >>
> >> Do thumbnails for covers need to be true colour (24-bit) images?
> >>
> >> Also, why is it that _scale_image() returns an image of 8-bit depth
> >> if the source image's dimensions are less than 600x800? (i.e. when
> >> no resizing is performed)
> >>
> >> Thank you in advance for your time.
> >>
> >> Kind regards,
> >> Andreas
> >> _______________________________________________
> >> Koha-devel mailing list
> >> Koha-devel at lists.koha-community.org
> >> http://lists.koha-community.org/cgi-bin/mailman/listinfo/koha-devel
> >> website : http://www.koha-community.org/
> >> git : http://git.koha-community.org/
> >> bugs : http://bugs.koha-community.org/
> > _______________________________________________
> > Koha-devel mailing list
> > Koha-devel at lists.koha-community.org
> > http://lists.koha-community.org/cgi-bin/mailman/listinfo/koha-devel
> > website : http://www.koha-community.org/
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> > bugs : http://bugs.koha-community.org/
>
> --
> Paul Poulain, Associé-gérant / co-owner
> BibLibre, Services en logiciels libres pour les bibliothèques
> BibLibre, Open Source software and services for libraries
>
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