XnViewMP - thumbnails - understanding quality/size

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user0
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XnViewMP - thumbnails - understanding quality/size

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INFO
Browser tab of XnView MP may display cached/live thumbnails from different sources (image/embedded thumbnail) with few quality adjustments, depending on the following settings:

1. Thumbnail source
1.1. live/cache
  • is Catalog and Thumbnails caching enabled (Settings > Catalog)
    ☑ will be generated from file when folder is opened for the first time (WxH and compression set in Settings > Catalog)
    ☐ will be generated from file each time folder is opened
1.2. image/embedded thumbnail
  • is Use embedded thumbnails enabled (Settings > Thumbnails)
    ☑ • does image have embedded thumbnail
           ☑ • is Create from original image if embedded thumbnail is smaller than thumbnail size enabled (Settings > Thumbnails)
                  when this setting is in use related overlay icon will disappear from image
                  ☑ • is embedded thumb size > thumb rendering size (Browser > View > Thumbnails size)
                         ☑ embedded thumb will be used
                         ☐ will be generated from image
                  ☐ will be generated from image
           ☐ will be generated from image
    ☐ will be generated from image

2. Thumbnail rendering
2.1. rendering size (Browser > View > Thumbnails size)
  • is image/embedded thumb size > thumb rendering size
    ☑ source will be shrunk to rendered size
    ☐ source will have original size
2.2. rendering quality (Settings > Thumbnails)
  • Create high quality thumbnail (bilinear filter)
  • Use alpha
  • Use sharpen
  • Use gamma correction


Thumbnails can be rebuild/deleted manually:
  • rebuilding
    • embedded
      - selected files via EXIF thumbnail - Rebuild (Browser > Metadata > EXIF thumbnail)
    • live
      - selected files via Rebuild thumbnails (Browser > View)
    • cached
      - selected files via Rebuild thumbnails (Browser > View)
      - all files via Rebuild thumbnails (Settings > Catalog)
  • deleting
    • embedded
      - selected files via EXIF thumbnail - Rebuild (Browser > Metadata > Clean)
    • cached
      - per folder via Delete/Delete all (Settings > Catalog)
      - all files via Purge all thumbnails (Settings > Catalog > Maintenance)


USE CASE
Thumbnails quality decreased (became blurry) in Browser when you increased their size from default 128x96 to, eg, 500x500.

Fix depends on the thumbnail caching setting
  • ☑ Thumbnail caching (default)
    1. in Settings > Thumbnail
    - uncheck Use embedded thumbnail OR
    - check Create from original image if embedded thumbnail is smaller than thumbnail [rendering] size
    2. in Settings > Catalog
    - change Thumbnail caching size to match new rendering size (500x500) or slightly exceed it
    - press Rebuild thumbnails button
    3. reopen Browser tab or restart app
  • ☐ Thumbnail caching
    option A
    1. in Settings > Thumbnail
    - uncheck Use embedded thumbnail OR
    - check Create from original image if embedded thumbnail is smaller than thumbnail [rendering] size
    2. press OK

    option B
    1. delete embedded thumbnails from files (JPEG only)
    - select files
    - select EXIF Thumbnail in Browser > Metadata > Clean.. dialog
    2. press OK


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