Contrôler le traitement des images.

traitement de l’image

always use LittleCMS 2 to apply output color profile
If this option is activated, Ansel will use the LittleCMS 2 system library to apply the output color profile instead of its own internal routines. This is significantly slower than the default but might give more accurate results in some cases.

Remarque : Si l’ICC donné est basé sur une LUT ou contient à la fois une LUT et une matrice, Ansel utilisera LittleCMS2 pour rendre les couleurs quelle que soit la valeur de ce paramètre (par défaut désactivé).

pixel interpolator (warp)
The pixel interpolator used for rotation, lens correction, liquify, crop and final scaling.

Chaque fois que nous redimensionnons ou déformons une image, nous devons choisir un algorithme d’interpolation de pixels (voir wikipedia  pour plus de détails). Pour les modules de déformation, Ansel propose les méthodes : bilinéaire, bicubique ou lanczos2. Dans la plupart des cas bicubique est une option sûre, c’est la valeur par défaut.

interpolations des pixels (mise à l’échelle)
L’interpolateur de pixels utilisé pour la mise à l’échelle. Les mêmes options sont fournies que pour les modules de déformation, mais avec lanczos3 en plus.

lanczos3 peut provoquer des dépassements de pixels conduisant à des artefacts mais donne parfois un aspect plus net. Cette option n’est donc fournie que pour les algorithmes de transformation (mise à l’échelle) et c’est la valeur par défaut.

3D lut root folder
Define the root folder (and sub-folders) containing Lut files used by the lut 3D module

CPU, GPU, Memory

Settings

CPU cores
Number of CPU cores (physical and virtual) in use. -1 will use all detected cores (physical and virtual). Depending on your hardware, you may want to try setting this value equal to the number of physical cores of your CPU, which may speed-up memory I/O, since memory transfer usually is our bottleneck in image processing. This will be irrelevant for most users, aside from debugging issues. This value does not affect modules using OpenCL when OpenCL is enabled.
Background workers
Number of background threads used to process thumbnail rendering pipelines, import, export, etc. Increasing this value will not increase memory usage proportionnaly, because only one pipeline at a time is allowed to run, but it may help hiding filesystem I/O latencies when loading image files. The maximum value here is defined by your operating system, and is typically 1024 or 2048.
Memory headroom for OS/applications (MiB)
This is the amount of RAM space that Ansel will never use, and leave to the operating system and other applications. To set it, you can reboot your computer and open a system monitoring application, then measure how much RAM space the idle OS is using. If you like to play videos or music in background, while retouching in Ansel, you will need to plan for this too and include the RAM usage of your player into this headroom. Setting this value too low will result in crashes of the application because the OS will kill the Ansel process when it reaches RAM saturation.
Memory reserved for lighttable thumbnail cache (MiB)
This is the amount of RAM space that Ansel will allocate to rendered thumbnails displayed in the lighttable and filmstrip. You should set this value according to the typical number of images you have in a folder and how large they appear in the lighttable :
  • a 360×225 px image uses 0.35 MiB,
  • a 720×450 px image uses 1.24 MiB,
  • a 1440×900 px image uses 5 MiB,
  • a 6000×4000 px image uses 92 MiB
The default value of 1000 MiB can hold 2800 small thumbnails, or 805 medium thumbnails, or 200 large thumbnails, or 10 images at 24 Mpx full resolution (for full-resolution preview in lighttable).
Maximum RAW resolution to edit
Set this value to the resolution of your best camera. Ansel will then reserve at all time a sufficient RAM space to hold 4 internal full-resolution buffers, which will be enough to avoid tiling in most modules using intermediate copies (when not using OpenCL).
Pipe recompute timeout
When doing value changes on sliders and comboxes, in darkroom modules, the changes are sent to the pixel pipeline to re-render the output once every N milliseconds. N is the pipe recompute timeout. It will ensure that intermediate value changes (when dragging a cursor) don’t trigger a new (computationnaly-expensive) recomputation, at the expense of making the GUI feel more or less laggy or responsive. Powerful hardware can tolerate values as low as 50 ms, but weak hardware (or battery mode) may benefit from values as high as 200 ms to spare useless intermediate recomputations.
Enable disk backend for thumbnail cache
Saves rendered lighttable thumbnails to the disk cache, in the current user’s home folder. This will prevent recomputing them on the next startup, but may create privacy issues if you are editing private pictures on a publicly shared computer.
Activate OpenCL support
Process darkroom modules that support it on the GPU using OpenCL. This option will be available only if an OpenCL driver and device were found on your system.
GPU vRAM headroom (MiB)
Amount of video RAM that Ansel will never use on the GPU, and leave to other applications using hardware graphics acceleration (OpenGL, Vulkan, VDPAU, CUDA, etc.).
System library with OpenCL runtime
Ansel will typically detect automatically the OpenCL drivers on your system, so you can leave this option empty. But if you have several conflicting OpenCL libraries, or your runtime is installed in an unusual place, you can define here the path to the OpenCL runtime to load.

Testing your configuration

  • To diagnose OpenCL issues, start ansel -d opencl
  • To benchmark performance and test different memory configurations, start ansel -d perf,
  • To diagnose memory and cache size issues, start ansel -d memory -d cache -d pipe

Libraw

Ansel uses the Rawspeed library by default to decode raw image files. Rawspeed is flawlessly integrated in Ansel, but does not support Canon .CR3 files yet. For this reason, a basic support of Libraw has been implemented such that owners of recent Canon cameras can still decode their files. Libraw also tends to support new formats faster than Rawspeed.

The options of this section allow users to force the use of Libraw for any picture they want, using rules based on file extension and camera/vendor EXIF metadata. The feature is brittle and unsafe in general because we don’t check and sanitize every possible flavour of encoding.

Supported files
  • Canon .CR3
Files that seem to be working
  • Olympus .ORF
  • Hasselblad .3FR
  • Nikon .NEF non-compressed
Files that definitely don’t work and make the software crash
  • Nikon sRAW and compressed .NEF
  • Phase One .IIQ
Raw file extensions to load through Libraw
case-insensitive, coma-separated list of the file extensions. Default : cr3.
Camera models to load through Libraw
case-insensitive, coma-separated list of the camera models as they appear in the Display metadata module, under the model field. You may have to enable this field using the preferences of the module if it does not appear in the widget.
Camera makers to load through Libraw
case-insensitive, coma-separated list of the camera manufacturers as they appear in the Display metadata module, under the maker field. You may have to enable this field using the preferences of the module if it does not appear in the widget.

To debug this feature : 

  1. Start Ansel in command line using ansel -d imageio. For each loaded image, it will tell which library was used to decode it,
  2. If the settings you input make the software crash at startup, remove the libraw/extensions, libraw/models, libraw/makers configuration keys in the anselrc configuration file, located in ~./config/ansel folder on Linux and Mac, or APPDATA\.config\ansel on Windows.