When "Auto-rotate/flip image" is checked on import, photos are rotated automatically according to their EXIV tag which is fine. Unfortunately this seems to be done in a lossy manner, meaning rotating the image and saving it anew. This should be done using a lossless rotation instead. Reproducible: Always
Which image format are you referring to?
Autorotation is performed by JPEG Loss Less methods, provided by libjpeg... https://projects.kde.org/projects/extragear/graphics/digikam/repository/revisions/master/entry/libs/jpegutils/jpegutils.h#L84 Gilles Caulier
Yes, I'm referring to JPEG. But how do you explain that those pictures are about 20% smaller after the import? I know JPEGs can often be optimized but I cannot explain a change from 900k to 700k...?
BTW: When loading them into GIMP, setting the second image to "difference" and boosting the curves way up, I can actually see, that there's a difference between those two pictures. So it cannot be a lossless rotation imo.
Can you share 'before' and 'after' JPEG images to check diff. I don't know how you compare both image into gimp, but i'm sure that you need to rotate one image to check color channel contents. Rotation can change image color data... This can be not lossless, depending of algorithm used in background. The file sizes diff can become from metadata where digiKam will record information. This operation do not touch image data ! Gilles Caulier
Do you see my previous comment. Without images samples it will be difficult to investigate. Gilles Caulier
New digiKam 4.11.0 is available : https://www.digikam.org/node/740 Can you reproduce the problem with this release ? Gilles Caulier
digiKam 4.12.0 is out : https://www.digikam.org/node/741 We need a fresh feedback using this release please... Thanks in advance.
With digiKam 5.0.0, I cannot reproduce this problem. I close this file now. Don't hesitate to re-open if necessary. Gilles Caulier