Currently, anytime Gwenview is used to save a non-JPEG file as a JPEG, or anytime JPEG file is saved or re-saved after performing a lossy edit (e.g. crop or red eye, but not rotation), the new file is saved with 75% quality level, resulting in a noticeable degradation in appearance.
This patch implements a user-selectable JPEG save/compression quality setting, which can be temporarily overridden in the Save As dialog when saving a file as a JPEG. The new default quality level is 90% -- same as Spectacle. This should prevent people from accdientally destroying their JPEGs.
As before, when saving an existing JPEG file with a new name or after performing a non-lossy edit (e.g. rotation, which only changes the EXIF rotation tag), the appearance of the file is not changed because no actual image manipulation is done.