18. Advanced Prefs¶
The Advanced Prefs option on the File menu give access to a dialog with some of SPIERS’ more esoteric settings. These are global (rather than per-dataset) settings; some only take effect when datasets are opened (e.g. maximum memory for undo and cache).
Maximum memory for undo: Controls the maximum size of the undo stack. As the stack is wiped every time a multi-slice operation is executed, this is normally limited to the changes to a single slice anyway, and thus the default of 512 Mb is ample. For computers with limited RAM this can safely be reduced, although of course this means that fewer Undo’s will be possible.
Undo Timer Interval: Determines how many seconds’ worth of actions are clumped into a single undo event. If the amount of memory for the undo stack is reduced, it may be worth increasing this value to allow bigger undo steps and hence to allow stepping further back in time.
Maximum memory for cache: SPIERSedit keeps copies of all files it loads (source images, working images etc) in a ‘cache’. Use of this cache greatly speeds subsequent access to files. The maximum size for the cache is set here; it is recommended that it should be set as high as the system reasonably allows; approximately one half of total system RAM might be a good guideline. Be aware that this may make the opening of multiple copies of SPIERSedit problematic.
Tune Cache for Rendering: If ticked, the cache preferentially stores working images, mask data etc rather than source images. If the latter are relatively large (e.g. colour images at twice resolution of working images) this can give substantial performance increases while rendering, as it may enable the entire dataset to fit within the cache. The downside is that it will reduce performance for ‘leafing through’ the dataset.
File compression: Controls how working images, mask data and lock/selection data are written to disk. Setting to ‘off’ produces large files, but normally results in faster disk operations. If set to ‘low’ or ‘high’ these files are compressed when written back to disk (i.e. the compression only happens if/when they change). ‘low’ compression offers substantial space savings over ‘none’ (typically a factor of 5-10), ‘high’ may increase compression factor a little over ‘low’. High settings produce extra processor load (compression/decompressing data), so will normally slow many operations down. The default setting of ‘low’ will be best in most cases.
(Re)compress source files now: Allows the user to recompress the source images; this is the only exception to SPIERSedit’s rule that it never changes source images, so should be used with caution. Behaviour is controlled by the file compression slider - if this is ‘off’ then this button converts all source images to ‘.bmp’ format. If slider is set to ‘low’ images are converted to ‘.png’ format (normally around one half of the size of ‘.bmp’ files. If the slider is set to ‘high’ images are converted to ‘.jpg’ format, which will be substantially smaller again. ‘.jpg’ images are saved at maximum fidelity, so artefacts should be negligible; repeated conversion back and forward between high and low/off is not recommended though, as this could build up artefacts with each conversion. Compression of source images to ‘jpg’ format is not normally recommended, but may be an acceptable means of saving disk space once the user is confident that all generation operations have been completed.
(Re)compress working files now: Applies the current file compression level (see above) to all working files.
Cache compression: SPIERSedit can compress files when storing them in its internal cache (see above). This trades off processing speed against memory usage, but it may enable the entire dataset to fit in the cache, which can in itself increase performance substantially. If cache compression is set to low around 4-5 times more files will fit in the cache – it set to high this figure will reach perhaps 7-8 times. Note that if you set cache compression to ‘high’ then colour images are cached using the lossy JPEG algorithm - there may be slight artefacts which can in theory (though probably not in practice) make their way into your datasets via slice-generation. Cache Compression should normally be turned off, but may be worth trying on machines with limited memory. Note that changing this setting empties the cache, so will not provide an instant performance increase!
Autosave frequency: Controls how often the SPIERSedit settings file (.spe) is written out.
Clear Recent Files List: This button removes everything from the Open Recent list on the File menu.