touch-packages team mailing list archive

[Albert Astals Cid <albert.astals@xxxxxxxxxxxxx>]

> I don't quite understand why you need to know the aspect ratio beforehand. 
> Surely, there must be some display size into which the thumbnail is expected to fit?

Ok, let's give you an example.

I know i have to fit my image in something that is 100 width x 100
height and i am using the PreserveAspectCrop fill format meaning the
image is scaled uniformly to fill, cropping if necessary

If i don't know the aspect ratio of the image that i have to draw which
size do i request?

If the image is portrait i have to request (100, 0)

If the image is landscape i have to request (0, 100)

See http://paste.ubuntu.com/12197917/ using
http://i.imgur.com/xiP0k4T.jpg as landscape.jpg and
http://i.imgur.com/A2M6bnF.jpg as portrait.jpg and you'll see
http://i.imgur.com/f5sEMhe.png. You can see there why we need to know
the aspect ratio to achive the best quality. In the first row "Source
Size Width" has the best quality while in the second row "Source Size
Height" has the best quality.

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You received this bug notification because you are a member of Ubuntu
Touch seeded packages, which is subscribed to thumbnailer in Ubuntu.
https://bugs.launchpad.net/bugs/1467740

Title:
  Lots of thumbnail requests with invalid size

Status in thumbnailer package in Ubuntu:
  New
Status in unity8 package in Ubuntu:
  New

Bug description:
  When using scopes, the thumbnailer gets loads of requests with
  QSize(-1,-1) from the shell. For example, with a bunch of videos
  recorded, run up the video scope and go to "My Videos". The shell asks
  for a thumbnail at QSize(-1,-1) for the tiny thumbnail that appears to
  the left of each list entry.

  The problem with this is that the thumbnailer interprets this to mean
  "give me the largest size you can (limited to a 1920x1920 bounding
  box). That's very expensive, especially in terms of disk space,
  because that 1920 "thumbnail" ends up going into the cache, needlessly
  hogging space.

  We are about to add a qWarning message to the QML side that reports
  invalid QSize requests. For now, we are going to retain the old
  behavior, but this will turn into an error soon.

  The most effective way to use the thumbnailer is to simply ask for an
  image in the desired size, with neither width nor height of -1. The
  thumbnailer will efficiently produce a thumbnail for that. (We do lots
  of internal caching to avoid extracting or downloading a thumbnail
  unnecessarily.)

  The thumbnailer may deliver a thumbnail that is smaller than what was
  asked for (because it never up-scales) so, if asked for a thumbnail of
  size 256, it's guaranteed not to be larger, but might be smaller (if
  the original image is smaller than what was asked for).

  Could you please adjust the shell behavior to ask for specific, valid
  sizes only?

  Running a tail -f on ~/.cache/upstart/dbus.log allows you to see the
  requests as they are made. Each request shows the size that was asked
  for.

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