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Screen resolution of large thumbnails

Posted: Tue Nov 15, 2016 4:03 pm
by Stuart444
Can anyone tell me why the thumbnails shown on my computer in XnView MP appear at very low resolution? They don't look bad at small sizes, but at say 192 x 144 and bigger they are very blurred. The originals are all about 5000x4000px. How can I get them to appear clearly?

Re: Screen resolution of thumbnails

Posted: Tue Nov 15, 2016 8:02 pm
by helmut
Why are the thumbnails blur?

First some basic info regarding thumbnails: XnView MP has a "view thumbnail size" and a "cache thumbnail size".
  • In View>Thumbnail size you set the view size, i.e. the size the thumbnail is displayed, but not the size the thumbnail is created and cached.
  • By default, XnView MP uses a maximum "cache thumbnail size" of 192x144 for caching thumbnails.
  • By default, XnView MP uses the EXIF thumbnails embedded in your image files. The embedded EXIF thumbnails can be read very quickly but the size (width x height) is limited, e.g. something like 150x150 pixels. If you make your thumbnails larger than the size of the embedded thumbnail, they will look blur.
How to get sharp, large thumbnails
You can force XnView MP to...
1.) ...calculate the thumbnail from the original image if the embedded thumbnail is not large enough and not sufficient.
2.) ...use larger thumbnails in the thumbnail cache.

WARNING: Creating thumbnails from the full image (not the embedded thumbnail) may result in a big slow down of XnView.

You have been warned, if you still want large thumbnails you:
1. Select "Tools > settings..." menu
2. Select "Browser > thumbnail" category
3. On tab "Misc" you will find the setting "Use embedded thumbnail". And underneath there is the setting "Create from original image if embedded thumbnail is smaller than thumbnail size". Check this setting (not recommended, see above warning).
4. Select "Browser > Catalog" category
5. In "Thumbnail caching" panel, set a size for your thumbnails. All thumbnails will be created and stored in the thumbnail cache using this size.
Please check this setting and save your changed settings with "OK".

Your changes in the setting will apply when creating new thumbnails. This means: At first, nothing will happen, because the thumbnails have been built already and are read from the thumbnail cache. Select "View rebuild" thumbnails to force XnView to rebuild the thumbnails and you will see your thumbnails at high resolution.

Note: If you want XnView to apply some sharpening, then check the setting "Sharpen thumbnail" in the settings (Browser > Thumbnail" category, tab "Misc".).

Re: Screen resolution of thumbnails

Posted: Tue Nov 15, 2016 11:33 pm
by Stuart444
Thanks, Helmut. I don't really want to slow down the program, so I'll heed your advice. I thought that the sharpening might be useful though, but when I tick "sharpen thumbnail" and then "Rebuild thumbnails", the process runs until it gets to a particular folder on my PC then is seems to stop. I've tried excluding this folder but it still stops at that point. The green progress indicator is still moving across but the folder shown stops changing. Do you know why that is?

Re: Screen resolution of thumbnails

Posted: Wed Mar 27, 2019 6:53 pm
by dma_k
helmut wrote: Tue Nov 15, 2016 8:02 pm First some basic info regarding thumbnails: XnView MP has a "view thumbnail size" and a "cache thumbnail size".
Thanks for this information. In my case I had too small values in "Catalog" → "Width"/"Height". Unless I pressed "Get thumbnail size" and "Rebuild thumbnails" I couldn't get what is wrong with thumbnails. Actually had to read few posts (1, 2, 3) before I found this very post. Maybe this can be somehow automated:
  • once a view size is increased, then suggest the user to rebuild a thumbnail cache
  • or once a view size is increased, then have an option to invalidate thumbnail cache, so it is refreshed when I jump to a directory (i.e. the cache is populated with thumbnails of correct size on demand)

Re: Screen resolution of large thumbnails

Posted: Sat Apr 20, 2019 5:37 am
by CenoZoic_Jurassic
I increased the size of the thumbnails so I can sort through images much faster. Sometimes it's the details that matter, right?

I have years worth of tool-assisted image gathering to sort and re-sort if my current filing system isn't capable of handling what I'm throwing at it (and it probably isn't), so I'm trying to avoid having XnView build a thumbnail cache for all my image folders. I downloaded it for the purpose of sorting those images, so I'm still having trouble with the automatically registered tags/categories when the program sees an image for the first time. That's the only possible snag I see with making thumbnails take longer to register.

Re: Screen resolution of large thumbnails

Posted: Sun Apr 21, 2019 11:52 pm
by CenoZoic_Jurassic
Update: XnView took forever to start up when I started it after my last post. I think it's because I was partially using it as a file browser to navigate between different image folders. I also moved a bunch of folders and files around with another program, which probably game the program a lot of broken links to work with.

My current setup in the Settings menu is as follows:
  • Create HQ thumbnail
  • Use embedded thumbnail
    • Create from original image if embedded thumbnail is smaller than thumbnail size
  • Custom thumbnail size is NOT checked
  • Enable Catalog
  • Enable thumbnail caching
    • Compression: None
    • W:278 H:229 [I think I might need to tweak this. I want to have a clear view of multiple images on screen at a time, with the folder/categories tab on the side.]
  • No maximum size for cached thumbnails
  • Memory usage for database engine: 2000MiB (I don't really know what this does, but the max cache size in the range given by cache maintenance was getting close to 2 gigs before I trimmed it. I'm just trying to change this number to be higher than the cache size because I suspect that if it isn't, then I'll get slowdown. I'll read up on what this does at some point, I'm sure.)
  • Check integrity of catalog at startup. This was the big one, I think. I have a lot of pictures that it was sorting through.
I think I've changed the thumbnail cache size to have no pre-set maximum that it'll load (meaning faster searching or search results if I understand that right). I've gotten rid of any compression on the thumbnail caching, which I assume means that it doesn't have to unpack or unzip anything when it accesses the cache. The performance impact of that is not known to me. I also disabled checking the integrite of the catalog on startup. I assume that'll be what caused the majority of the really slow startup.

Assuming I have some idea of what I'm doing, I've set things up so that the program will load and work faster, with the compromise being that it takes more storage space and RAM to do the job. I'm a little worried that setting it to create a high quality thumbnail AND use the embedded thumbnail will interfere with each other, but I'm a little nervous about messing with any thumbnail settings based on how much of a lag it was before. Actually, on second thought, I'll turn the embedded thumbnail and "create from original image" thing off. I assume this will create thumbnails from the images themselves at whatever size I'm working with right now, whenever I open or access the folder.