Color Management Status
The color management status of the loaded image is indicated by the Color Management status icon in the bottom left hand corner of the window. The icon is fully saturated when the image is color managed, and desaturated when the image is not color managed. The tooltip provides more detailed status information if the image is color managed: it shows the working space and monitor profiles.
Left clicking the status button accesses the Color Management Dialog. Right clicking the tool toggles the ISO 12646 color assessment display mode. Both are described in more detail below.
Just above the color management status button is a new menu for image checks. This includes the existing cut check for highlighting pixels that exceed the gui hi slider, and adds a new gamut check, which highlights pixels that are out of gamut for the soft proofing profile in bright magenta.
Color Management Dialog
The Color Management tool is accessed by clicking on the Color Management status icon. (It can also be accessed via the Tools menu.)
The tool itself is shown below.
The top part of the tool shows information about the current ICC profile assigned to the image. The description, manufacturer details and copyright notice are shown.
Underneath this are choosers that allow you to choose a different profile, either one of the built-in profiles using the drop-down menu on the left or any ICC profile you wish to load from a file using the filechooser on the right.
Warning
When loading a profile from a file, the profile type must be either RGB or Gray to match the loaded image. Assigning or converting images to other color spaces such as XYZ, CIE La*b* or CMYK is not supported, however color spaces such as CIE La*b* may be used internally by some image operations where required.
Tip
You can convert a RGB image to a Gray profile. This will result in a mono image with the appropriate tone response curve (TRC) transform and contributions from the 3 R, G and B channels determined by the white points of the two profiles. Converting a Gray image to a RGB profile will result in a 3-channel image with the appropriate TRC transform and all pixel components equal.
At the bottom of the window, the tool shows the same kind of information for the target profile that it does for the original profile at the top of the window. This helps in checking you've loaded the right one.
Toolbar
The Export button simply exports the current image profile to a file in the working directory.
The Remove button removes the ICC profile from an image.
The Assign button assigns the selected ICC profile to the image, without performing a color space conversion. This is useful if the image has an incorrect color profile embedded.
The Convert button converts the image to the selected ICC profile and assigns the profile to the image. This is useful if you wish to transform the image from its current color space to a different one.
Warning
Use of the Remove, Assign or Convert buttons (or the Siril commands icc_remove, icc_assign or icc_convert_to) will clear any ROI that is set.
ISO 12646 Image Assessment Mode
ISO 12646 defines optimum viewing conditions for assessing color. In summary, to get the best assessment of the colors in your image the best viewing conditions are provided by a uniform neutral gray background called D50. Technically this should even extend to the walls in your room, but Siril can't control that! Siril does provide an image assessment mode that approximates ISO 12646 recommendations, however. It is available by right clicking on the color management button in the bottom-left of the screen, and does not require the image to be color managed to use it.
This mode is intended as a final check of the colors of your image, so it sets the preview mode to linear with the sliders at 0 and 65535 (full range). It also hides the panel and sets the zoom so that the full image is visible and centered with an ample border around it, and sets a moderate white border around the image to provide a visual white reference, surrounded by a background of D50 gray.
Ideally you should also choose a neutral gray GTK theme, such as the excellent Equilux theme.
This mode automatically disables itself if the zoom is changed or the panel made visible again, and it can be toggled off by right clicking a second time on the color management button. The view will revert to its previous zoom settings and panel state.
Commands
Most Siril commands do not engage with color management except that they do not prevent existing color profiles from being preserved in an image.
The exceptions are three specific color management commands that can be used to assign, convert or delete the ICC profile in an image.
Siril command line
icc_assign profile
Siril command line
icc_convert_to profile [intent]
Siril command line
icc_remove