[Digikam-devel] [Bug 140131] No zoom in image preview

[Arnd Baecker]

Wow - that zooming looks absolutely great!!!!

Some observations and comments:
- I also observe artefacts at different zoom-levels
  (eg. at 92 % and at 397%, but these values differ from image to
  image; also this only seems to happen when using CTRL+ and CTRL-,
  but not the slider?)
- pressing F4 to open the image editor: the zoom in the album view
   is undone (however, moving the slider afterwards shows, that it is
   still zoomed in)
- maybe related: somehow the previous zoom-level is memorized:
  F3 for an image and zoom in (e.g. 1000%)
  ESC to leave
  F3 again: the image is displayed to fit the available space,
  but the slider is still on 1000%.
- the zoom percentages do not seem to match with the values in
  the image editor (but maybe I am wrong): I.e.,
  shouldn't 100% mean that one image pixel corresponds one
  display pixel?
- Maybe just a personal problem: I always find my to press CTRL-Q
  to leave the large view (obviously because of the large display
  some corner of my brain thinks that this must be the image editor),
  but this does leave digikam (which does indeed leave the large view,
  but not in the way I wanted ...)
- And another one: I happen to press the left-mouse
  (having panning in mind) quite frequently, which brings
  me back to the thumbnail view (which I did not want;-) - not sure
  if this is optimal from the useability point of view
  (I know that the "return-on-left-click" was a wish brought
   up a while ago...;-)

Some wishes:
- When zoomed in: a pan-window widget in the lower-right corner
  where the scroll-bars meet
  (as in the image editor) would be nice
- it would be nice if the position of the mouse would be
  the center around which the zoom is done
  (I also mentioned this as a wish for the image editor zoom,
   but did not yet manage to look into the logic there, should
   be fairly easy to implement...)

There is maybe one very important point:
the zoom as it is presently done, uses a reduced-size version of the
underlying image, right?
So while it is nice to be able to zoom in, it does not allow for
a judgement of the image quality (in contrast to the image editor).
Do you think that there is a way to use the actual image
(maybe from a certain zoom-level on?) But that would (quite
certainly?) slow things down...

In particular for the upcoming light-table I think it is important
to compare the real images, not just up-scaled ones

Uups: I just realized that for zooming in, the image editor also
some interpolation is done, so that that one does not see the single
pixels, but some nicely interpolated version?

OK, that's all for the moment...

Best, Arnd