D29397: KPreviewJob : Support for DeviceRatioPixel

[Stefan Brüns]

bruns added a comment.


  In D29397#663902 <https://phabricator.kde.org/D29397#663902>, @broulik wrote:
  
  > > At the risk of asking a stupid question, why?
  >
  > The text thumbnailer should be able to produce readable text on high dpi, or the folder thumbnailer should render the folder icon sharply and the picture frames non-pixelated
  
  
  The folder thumbnailer does not care for DPR, the folder backdrop is rendered at full native resolution, and the sub-thumnails are rendered with a scale ~0.45 on top.
  
  The text thumbnailer currently renders previews in the file list with a height of either 256 or 128, and then scales it down. For an icon size of e.g. 64 the 128px thumb is scaled down, so the effective DPR becomes nativeDpr * 0.5. Assuming a native DPR of 2.0 (HiDPI), should the text in this case be rendered with a DPR of 1.0 or 2.0? One will be blurry, and the other one will hardly contain any text at all (how many characters can you squeeze into 48x64px?).
  
  For dolphin, there is actually another reason for blurriness. The thumbnail icons are scaled so after adding the drop shadow the icon has the selected size - at 256px, the 256px thumbnail is scaled to 250px. For natural images (Photos, Video thumbnails, cover images ...) this is hardly visible, but very noticeable for text.

REPOSITORY
  R241 KIO

REVISION DETAIL
  https://phabricator.kde.org/D29397

To: meven, dfaure, broulik, #frameworks, ngraham
Cc: bruns, elvisangelaccio, kossebau, davidedmundson, kde-frameworks-devel, LeGast00n, cblack, michaelh, ngraham
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.kde.org/pipermail/kde-frameworks-devel/attachments/20200907/187084c4/attachment.htm>