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 <arouss1...@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
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--
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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