Each image in the current collection is represented by a thumbnail in the lighttable view and filmstrip module. A cache of the most recently used thumbnails is stored in a file on disk and loaded into memory at startup. The size of this cache can be adjusted in Preferences > Processing > CPU, GPU, Memory.
Thumbnail creation
Ein Vorschaubild wird erstellt, wenn ein Bild zum ersten Mal in Ansel geladen wird, nachdem das Bildes in der Dunkelkammer geändert wurde, oder wenn ein Bild erneut betrachtet wird, dessen Vorschaubild nicht mehr verfügbar ist.
When an image is imported for the first time Ansel can either try to extract an embedded thumbnail from the input image (most raw files contain these, usually in JPEG format) or process the raw image itself using default settings. Choose how Ansel obtains its thumbnails from the global menu Display 🡒 Thumbnail source — always process the RAW, use embedded JPG if unedited, or always use embedded JPG. This can be changed at runtime.
Das Extrahieren eines eingebetteten Vorschaubildes aus den Raw-Daten führt dazu, dass diese sehr schnell geschieht. Diese Vorschaubilder wurden jedoch vom Raw-Konverter der Kamera erzeugt und unterscheiden sich von der “Darstellung” des Ansel-Bildes. Der Unterschied wird sichtbar, sobald das Bild in der Dunkelkammer geöffnet wird. Ansel ersetzt dann das eingebettete Vorschaubild durch ein eigenes.
After import Ansel automatically generates thumbnails for new images as they are needed. When importing a large set of new images, thumbnail generation can slow down navigation in the lighttable view. Alternatively you may terminate Ansel and generate the thumbnail cache separately by running ansel-generate-cache. This program will generate all missing thumbnails in one go.
As the thumbnail cache has a pre-defined maximum size it will eventually get filled up. If new thumbnails are subsequently added, old thumbnails are dropped from the cache. However, Ansel will keep all thumbnails on disk if the corresponding disk backend option is activated in Preferences > Processing > CPU, GPU, Memory. Access to the thumbnails in this secondary cache is slower than the primary cache, but still much faster than reprocessing thumbnails from scratch. The size of the secondary cache is limited only by the available disk space.
You can pre-render or purge cached thumbnails for the selected images at runtime from the global menu Run 🡒 Preload selected thumbnails in cache and Purge selected thumbnails from cache.
Thumbnails are never removed automatically from the secondary cache. You can manually clean it by recursively deleting all images in the $HOME/.cache/ansel/mipmaps-xyz.d folder (where xyz denotes an alphanumeric identifier of the cache). After clearing the secondary cache you can simply let Ansel re-generate thumbnails as needed, or generate them all in one go with ansel-generate-cache.
If you choose not to activate the disk backend and select too small a cache size, Ansel may become unresponsive, you may experience continuous regeneration of thumbnails when you navigate your collection or flickering of thumbnail images. A good choice of cache size is 512MB or higher (see Memory and performance tuning for more information).
All thumbnails are fully color managed. Colors are rendered accurately on screen as long as your system is properly set up to hand over the right monitor profile to Ansel. For more information see the color management section.
Skulls
If for some reason Ansel is unable to generate a thumbnail, it displays an image of a skull instead. Don’t panic!
Hierfür gibt es drei wesentliche Gründe.
Missing image file: Ansel remembers all images it has ever imported, as long as they have not been removed from your database. If Ansel wants to create a thumbnail but is not able to open the input file, a skull is displayed instead. Users are advised to remove images from the database using the selected images module before physically removing them from disk. Alternatively you may occasionally run the script
purge_non_existing_images.shfrom Ansel’s toolset to clean-up your database.Invalid image format: While the extension of an image may seem to be supported by Ansel, its contents could be either an unsupported image format or a corrupt file.
Low memory: If Ansel runs out of memory while generating a thumbnail, it will warn you and display a skull. This can happen if Ansel is run with sub-optimal settings, especially on a 32-bit system. See memory and performance tuning for more information.