Modern Linux distros featuring either GNOME, Unity or KDE offer fairly easy configuration of color management, this system level configuration mostly pertains to the handling of an ICC display profile.

If you have set a display profile via your system configuration tool (The Color applet in System Settings for GNOME or Unity), there are a few things to keep in mind.

An ICC display profile consists of two main parts. First the so-called "vcgt", which corrects for whitepoint (this is most noticeable on laptops which shift from being very blueish to a bit more yellowish) and gamma. The "vcgt" is loaded into X11 and applied to your whole screen, so all applications automatically benefit. On a GNOME or Unity desktop this is done by GNOME Settings Daemon during login.

The second is the rest of the ICC profile, and this has to be processed in color management enabled application (typically via liblcms2). So we need a mechanism to pass the actual ICC profile to our applications without having to configure them all individually.

The oldest mechanism is the _ICC_PROFILE atom, which allows a single display profile to be defined for your system (this obviously fails for dual head configurations). You can check if a profile is setup like so:

$ xprop -display :0.0 -len 14 -root _ICC_PROFILE

On a GNOME or Unity system the _ICC_PROFILE is setup by GNOME Setting Daemon during login.

On some systems there may be a _ICC_PROFILE_1 and _ICC_PROFILE_2 atom to facilitate dual head configurations. While darktable should pick up on those, I'm not sure how well other applications support this mechanism.

The another relatively new mechanism is colord by Richard Hughes, which is an infrastructure daemon, which by it self does very little, as it's mostly just an information/configuration store. But modern GNOME, Unity or KDE desktops store their display profile setups in colord, so applications can query colord which profile to apply depending on which screen they are displayed on (in case of a dual head configuration). Currently few applications are colord aware however. darktable is one of those few.

If you haven't setup a display profile yourself that doesn't per-se mean there is no display profile active. Modern desktops actually query the display (via EDID) itself about its advertised color coverage, from which an automatic display profile is generated. An easy way to check if such an automatic profile was generated:

# ls -l ~/.local/share/icc/edid-*.icc

For more in-depth information the following articles are highly recommended:

• http://blog.pcode.nl/2013/04/14/display-profiles-generated-from-edid/
• http://blog.pcode.nl/2012/01/29/color-management-on-linux/

darktable's current (1.0/1.1/1.2) implementation

First off I want to make something very clear, darktable's darkroom mode is fully color managed and should always be used in situations where you are evaluating color. Since darktable is colord enabled (and if colord is properly setup) it should even render correct color in dual head configurations.

In darktable's lighttable mode there are however a few things you need to be aware of. When importing new RAW photos into darktable, it will display the RAWs embedded thumbnail (which has been fully processed by the camera software) and the display profile is currently NOT being applied to these embedded thumbnails. Keep in mind, that these thumbnails have been processed by the proprietary firmware of the camera, so even if we applied the display profile it would still not match the processing that is done by darktable by default. It is however possible to disable the use of these embedded thumbnails altogether in darktable's preferences, forcing all RAWs to be processed by darktable's own imaging pipeline. This will slow down thumbnail generation by a few orders of magnitude, which is why this isn't our default behavior.

Once you've entered darkroom mode for a RAW, the image has been processed in darktable's imaging pipeline including the application of the display profile, so this result is now kept as an accurate thumbnail for that particular RAW.

If you've read that well, you might have noticed that we currently keep the display profile pre-applied in our thumbnail cache. Which is good for performance, and works just fine in most use-cases, but can result in ugly behavior for example when you change/replace your display, since darktable will still show thumbnails applied with the display profile of your previous display. In such a case you can forcibly remove the thumbnail cache like so:

$ rm -Iv ~/.cache/darktable/mipmaps-*

example

let take this photo as an example.Here, we will get rid of the fluorescent orange wall. We will use the color zone module to desaturate reds, but doing so would also desaturate the lighthouse railings. We will use masks to avoid that.we now add a masks to limit the effect of the module to the wall only. Using the masks combobox from the module, we add a curve shape :And here is our final image :

masking interfaces

The masks combobox inside modules let you add new shapes, reuse existing shapes. But if you want to perform more complex tasks, you will have to use the masks manager which is in the left panel:Right-clicking on a shapes will open a popup menu with all the possible actions.

editing shapes :

Advanced tips

Cloning :

Warning :

• there is no brush painting. masks are currently limited to curves
• very complex, self-intersecting curves might not render correctly

The general aim of the module is transferring the look and feel of one image onto another. You can use it if you intend to harmonize the image's colors of a photo series - or you may want to completely change the atmoshpere of an image, maybe even into an unnatural, surrealistic look. As its purpose is mainly an artistic one, the new module was put into the effect group.

Mathematically "color mapping" uses an enhanced model of the groundbreaking work of Eric Reinhard et.al. [0]. The basic idea is to make a statistical match of lightness and colors between images by mapping their mean and variance values in an Lab-like color space. Our enhanced version analyses the color space of the images in form of color clusters to allow for a more fine-grained match of colors. In addition we use histogram equalization for lightness matching instead of the simpler mean/variance method.

To use this module two steps are required:

• First you open the source image in darkroom mode and acquire its color characteristics by pressing the "acquire as source" button. A set of color clusters is generated and displayed in the source clusters area. Each cluster is represented by a set of nine color swatches with the mean value in the center surrounded by swatches indicating the color variance within that cluster. The clusters are sorted in ascending order by their weight, which reflects the relative number of pixels that contribute to the clusters.
• Next you open your target image in darkroom mode. darktable has remembered the previously collected source clusters; if they are not yet displayed, press the reset button in the module's expander bar. You now press the "acquire as target" button to generate a corresponding set of color clusters for your target image. It is displayed in the target clusters area.

When both source and target clusters are collected an automatic color mapping is applied to the target image. In its default settings the overall effect can be quite exaggerated. A set of sliders gives you control of the effect's strength. You can also use blending operator "normal" to tame the effect. As the color mapping module comes early in the pixelpipe, you have a lot of freedom to further finetune the colors with modules like tone curve or color correction.

The number of color clusters to apply - from 1 to 5 - is a central parameter. In the most simple case only one color cluster is applied to all colors of the target image. This will provide a color cast as if the scene was illuminated with a light in the corresponding color. Sometimes this is what you aim for but frequently the situation is more complex. Often the source and target image contain different dominant colors and you want them to be mapped in a more smooth way.

Let's look at an example. We will take the following image as our target image. It shows a scene of Valencia's Ciudad de las Artes y de las Ciencias.

First we go for a grotesque case with strong color shifts to make the effects obvious. I want to transfer the greenish color atmosphere of this image (an abandoned cold war shelter's washroom) to our target image.

If I only take one cluster I get the following output.

All colors are shifted towards the dominant green tint of the source image. The picture changes a bit if I take two clusters.

Within the source image a first cluster now represents the greens, the second cluster the more neutral tones. In our target image one cluster represents the more blueish colors and the second the more reddish ones. The cluster mapping will apply the green tones of the source image onto the blue tones of the target image leaving the other colors neutral. This gives the overall impression of a sky with poisoned green clouds. And here finally the image if we take five clusters:

Now the color variety of the target image is much better preserved. Still the greenish tint of the source image has found its way into the target. The overall result is more credible but also less pronounced as in the previous two examples. Generally a higher number of clusters leads to a less pronounced effect.

The mapping between source and target clusters is done automatically. Parameter "color dominance" gives you a level of control. If this parameter is set to zero, clusters are mapped according to color proximity. Each target cluster is checked against each source cluster and the color adjustment is done with the closest match. Depending on the source and target image this can lead to different target clusters being mapped to the same source cluster. If "color dominance" is set to its maximum 100%, the mapping is based on cluster weight. Instead of color proximity now the number of pixels contributing to a cluster plays the major role. The dominant color of the target image will be mapped to the dominant color of the source image. This is a bit similar to using a lower number of color clusters but allows a flexible adjustment without the need to recollect clusters in both source and target image.

Typically the colorizing effect at 0% is rather subtle whereas it is quite bold at 100%. In-between values lead to a transition between the extremes. This transition is incremental - the mapping flips at certain threshold values which depend on the source/target images.

Let's take a new source image: one of the Gehry buildings in Düsseldorf's Medienhafen shot shortly after sunset.

Obviously the image has two dominant colors: blue and orange. So let's take two color clusters. Here is the result if we set parameter "color dominance" to 0%.

The same source and target clusters, now applied with a color dominance of 100% give a much stronger effect.

In the last two cases I set parameter "histogram equalization" to 80%. This parameter controls how strong the tonal contrast of the source image is transferred onto the target image.

You need to do some experiments with the number of clusters and the other parameters of this module by yourself to find the best suited settings for your aim. The current status of this module can be found in darktable's master branch and will be part of darktable's next feature release.

[0] Erik Reinhard, Michael Ashikhmin, Bruce Gooch, Peter Shirley, "Color Transfer between Images", IEEE Computer Graphics and Applications, September/October 2001

source tarball

user manual

macintosh disk image

as a feature release, it comes with a lot of new goodies:

• profiled denoising: adapt to the properties of your camera's sensor (72 cameras already profiled for you).
• lightroom import: convert some basic edits from your lightroom collection to darktable operations.
• multi instance support: duplicate your modules and apply them more than one time with different settings.
• improved usability for distorting modules (streamline spot removal in the presence of crop/rotate for example).
• selective copy/paste of image processing.
• new more intuitive keystone correction tool.
• jpeg2000 support.
• graphics magick import (support virtually all input image formats).
• much faster thumbnail loading (if you can live with crappy embedded thumbnails).
• incredibly lengthy list of small bug fixes, performance enhancements, and usability improvements.
• new camera support (decode and color matrices).
• dithering against banding.
• sharper thumbnails in lighttable mode.
• new oauth2 based picasa uploader.
• updated translations.
• and a thoroughly overhauled user manual, proof read by natives (thanks heaps guys!).

this is the list of cameras supported for profiled denoising in this tarball:

• canon eos-1d mark iv
• canon eos-1ds mark ii
• canon eos 20d
• canon eos 30d
• canon eos 350d
• canon eos 400d
• canon eos 40d
• canon eos 450d
• canon eos 50d
• canon eos 550d
• canon eos 5d
• canon eos 5d mark ii
• canon eos 5d mark iii
• canon eos 600d
• canon eos 60d
• canon eos 650d
• canon eos 6d
• canon eos 7d
• canon eos rebel t1i
• canon eos rebel t3i
• canon eos rebel t4i
• canon powershot g10
• canon powershot g12
• canon powershot s90
• konica minolta dynax 5d
• nikon d200
• nikon d300
• nikon d300s
• nikon d3100
• nikon d5000
• nikon d5100
• nikon d600
• nikon d700
• nikon d7000
• nikon d80
• nikon d800
• nikon d800e
• nikon d90
• olympus e-30
• olympus e-400
• olympus e-420
• olympus e-m5
• olympus e-pl1
• olympus e-pl5
• olympus xz-1
• olympus xz-2
• panasonic dmc-fz18
• panasonic dmc-g2
• panasonic dmc-g3
• panasonic dmc-g5
• panasonic dmc-gf1
• panasonic dmc-gh2
• panasonic dmc-gx1
• pentax k100d
• pentax k10d
• pentax k200d
• pentax k-5
• pentax k-5 ii s
• pentax k-7
• pentax k-m
• pentax k-r
• pentax k-x
• samsung nx100
• sony dsc-rx100
• sony dslr-a200
• sony dslr-a230
• sony dslr-a550
• sony dslr-a700
• sony nex-3
• sony nex-5n
• sony nex-6
• sony nex-7
• sony nex-c3
• sony slt-a55v
• sony slt-a65v
• sony slt-a77v

these are all community contributed noise profiles, we're quite happy about this great response!

so string freeze is over! that means we'll have cool new stuff in git for you to check out soon :)

as always, thanks to everybody who made this possible. all the developers, translators, proof readers, battle testers and the guys who maintain the great libraries we depend on. you know who you are!

https://sourceforge.net/projects/darktable/files/darktable/1.2/darktable-1.2~rc2.tar.xz/download

here is the macintosh disk image:

http://sourceforge.net/projects/darktable/files/darktable/1.2/darktable-1.2~rc2.dmg/download

and this time it comes with an updated usermanual:

http://sourceforge.net/projects/darktable/files/darktable/1.2/darktable-usermanual.pdf/download

• the changes on top of rc1 are minor, some details:
• fixed a spurious crash/deadlock when switching images in filmstrip mode
• fixed a couple of exif strings for profiled denoising
• fixed gcc 4.8.0 build
• new noise profiles
• fixed gphoto 2.5 issues
• updated translations
• updated user manual!

thanks all, and enjoy the release!

source tarball

mac disk image

as a feature release, it comes with a lot of new goodies:

• profiled denoising: adapt to the properties of your camera's sensor (72 cameras already profiled for you).
• lightroom import: convert some basic edits from your lightroom collection to darktable operations.
• multi instance support: duplicate your modules and apply them more than one time with different settings.
• improved usability for distorting modules (streamline spot removal in the presence of crop/rotate for example).
• selective copy/paste of image processing.
• new more intuitive keystone correction tool.
• jpeg2000 support.
• graphics magick import (support virtually all input image formats).
• much faster thumbnail loading (if you can live with crappy embedded thumbnails).
• incredibly lengthy list of small bug fixes, performance enhancements, and usability improvements.
• new camera support (decode and color matrices).
• dithering against banding.
• sharper thumbnails in lighttable mode.
• new oauth2 based picasa uploader.
• and the final release 1.2 will contain a thoroughly overhauled user manual, proof read by natives (thanks heaps guys!).

translations:
ca: 253 translated messages, 394 fuzzy translations, 912 untranslated messages.
cs: 1457 translated messages, 63 fuzzy translations, 39 untranslated messages.
de: 1558 translated messages, 1 fuzzy translation.
es: 1554 translated messages, 5 fuzzy translations.
fi: 623 translated messages, 515 fuzzy translations, 421 untranslated messages.
fr: 1558 translated messages, 1 fuzzy translation.
gl: 406 translated messages, 561 fuzzy translations, 592 untranslated messages.
it: 1458 translated messages, 61 fuzzy translations, 40 untranslated messages.
ja: 1548 translated messages, 10 fuzzy translations, 1 untranslated message.
nl: 1554 translated messages, 5 fuzzy translations.
pl: 1454 translated messages, 62 fuzzy translations, 43 untranslated messages.
pt_BR: 1549 translated messages, 6 fuzzy translations, 4 untranslated messages.
pt_PT: 1554 translated messages, 5 fuzzy translations.
ro: 726 translated messages, 453 fuzzy translations, 380 untranslated messages.
ru: 1139 translated messages, 230 fuzzy translations, 190 untranslated messages.
sq: 1553 translated messages, 6 fuzzy translations.
sv: 1558 translated messages, 1 fuzzy translation.
th: 171 translated messages, 203 fuzzy translations, 1185 untranslated messages.
uk: 1538 translated messages, 14 fuzzy translations, 7 untranslated messages.
zh_CN: 1083 translated messages, 254 fuzzy translations, 222 untranslated messages.

there is a new point release with a couple of smaller updates. The source tarball and OSX image can be found here:

http://sourceforge.net/projects/darktable/files/darktable/1.1/darktable-1.1.4.tar.xz/download
http://sourceforge.net/projects/darktable/files/darktable/1.1/darktable-1.1.4.dmg/download
And the usermanual is still the same.

Fixes:

• keep the styles plugin usable after applying a style
• darktable should now be better able to import some of the data from .xmp's from other applications
• better redraw logic in darkroom mode
• it should be less likely to get blurry thumbnails in lighttable mode now
• on low end system use lower quality thumbnails
• work around some malformed icc profiles
• add a mandatory cprt tag to our embedded icc profiles
• prevent adobe rgb related trademark issue
• some fixes with regard to the colorpicker
• tooltips should now be more easily distinguisable
• fix build with new glib versions
• more assorted small fixes

Added preliminary camera support:

• Nikon coolpix p7100 blackpoint fix
• Leica basecurve should apply to more camera models now
• Pentax k-5 ii (s)
• Nikon 1 j3
• Nikon 1 s1
• Improved panasonic dmc-g5 support
• Improved panasonic dmc-lx7 support

Improved color rendition:
Olympus e-m5 enhanced color matrix (frederic crozat)

New white balance presets:

• Panasonic dmc-g5 (thouks)
• pentax k-5 ii (s) (jack bowling)
• sony slt-a77v
• nikon d3200
• nikon d800 update (wolfgang goetz)

darktable wouldn't be where it is now if we weren't able to depend on
the great work of others, in particular we'd like to thank:

klaus post (rawspeed), dave coffin (dcraw), andreas hugel (exiv2),
andrew zabolotny (lensfun), marti maria (lcms), niels kristian bech
jensen (ufraw).

the online user manual has been updated to reflect the latest release of darktable. This is the html version of the reworked user manual for darktable 1.1 which descibes all major features of darktables and serves as a reference for all image operation modules.

The user manual for the upcoming darktable 1.2 is almost finished and is being proofread right now. Still, any changes and additions for the post-1.2 era are more than welcome!

since March 3 we are in the string freeze phase for the upcoming darktable 1.2 release. This release will be a major new version introducing tons of new features (as you might have guessed by all the blog articles in the last months...).

Please don't push or provide patches with any new translatable strings to master or change them (that's the ones in _("...") ).

Modules that can be instantiated multiple times have a new icon in their header, next to the "reset" button. Clicking that icon will open a pop-up menu that allows you to create a new instance of the module, change the order in which the different instances are applied, or delete an instance of the module. Each instance can have its own parameters, can be activated or deactivates separately and can use presets. Note that the last instance of a module can't be deleted, it can only be deactivated.

Keeping with darktable's philosophy, you can only rearrange modules of the same kind. The order of modules of different kind is optimized by the darktable developers in order to minimize quality loss. The different modules are, as usual, applied from bottom to top.

first example

To illustrate this new feature, let's take a blake&white image :

Now we will add 2 new instances of graduated density. We now have three instances, including the first one.
We set up each instance with a different colored gradient.

Here is what can be achieve :

real life example

The previous example is nice, but apart for illustrating diffraction, it is not that useful.
Multi-instance really shows its power when used with selective adjustments and the next example will show you how to do that.

Darktable does not currently implement masks, but we have a very powerful alternative, conditional blending, that allows to select region based on their color and luminance rather than their position.
So here is another example using conditional blending :

Let's start from this simple image :
This image is nice but we want to saturate the sand a little more and turn the rest of the image into black and white.

First, let's work on the sand in the foreground. We will use the colorzone plugin to selectively increase the saturation of the yellow color. The result is shown below
Now that the sand is done, let's desaturate the background.

First we create a second instance of the colorzone plugin using the new icon next to the "reset" button.
Then we restring the area where that instance will be applied using blendif.

Our background is much darker than our foreground, so it is very easy to use blendif to select the background.

Now we simply desaturate the image by pulling down the saturation line. This gives us the following final image

presets, styles...

Each instance of a module can be considered like a completely independent module. In particular, each instance can have presets applied to it independently from the other presets.

A nice trick is to use a temporary preset to easily copy/paste the settings of a given instance to a new instance. A fine tuned blendif selection can thus be copied from one instance to another (and usually inverted right away) to easily apply different presets to different areas.

Styles, on the other hands are applied to images and not to modules. This means that styles contains the information on the number of instances used and how each instance was set. If you create a style from our first image you could easily apply our "diffraction effect" to any image you want

Note : great thanks to Jeremy Rosen for is help in the writing of this blog post