Hello...

I am photographer and I use Krita for photo editing, becouse Krita has 16bit mode, LAB colour space and many other features for professional work.
I know that Krita is painting software but I have no other software for Linux with this features.
Well..
Some of photos need editing of single channel, for example:
1. We convert layer to LAB colour space,
2. invert (or paint) colors of "b" channel
....
and in this moment Krita invert all channels (not single b channel )...

This is very important feauture for proffesional photo editing which make this program will be a real tool for professionals (speed up is very important too)

Hi,
Actually we have a way to split channels to different layers (menu image - separate image; make sure to use output to color option). Then for each layer leave only the respective channel activated in their properties. This way you can easily edit channels separatly. Though I never tried it with lab, only with RGB and CMYK, but it should work as well.

"This is a very important feature for professional photo editing which make this program will be a real tool for professionals"

While applying an action on a single channel is something we'd like to have, I do want to restate that Krita is not a tool for photo editing; matte painting has some of the same requirements, but Krita is not meant for professional photo editing. I do not recommend Krita for photo editing.

Hello mmoransky,

You might want to take a look at the G'MIC filters (with Krita 2.9.4. you get the 1.6.1.0 version of them).
Perhaps some of these G'MIC filters might be handy for what you are looking for...
For instance, G'MIC > Colors > Curves (Curves interactive, curves rgb mixer, curves lab mixer etc)

boudewijn wrote:While applying an action on a single channel is something we'd like to have, I do want to restate that Krita is not a tool for photo editing; matte painting has some of the same requirements, but Krita is not meant for professional photo editing. I do not recommend Krita for photo editing.

But in Linux We have only Krita with 16bit color space and else advanced editing options. Gimp in beta version have high bit depth but don't have Lab space, and other feautures for real photo editing.. When Krita will be faster it will be real alternative for Adobe Photoshop..

Silvio Grosso wrote:Hello mmoransky,

You might want to take a look at the G'MIC filters (with Krita 2.9.4. you get the 1.6.1.0 version of them).
Perhaps some of these G'MIC filters might be handy for what you are looking for...
For instance, G'MIC > Colors > Curves (Curves interactive, curves rgb mixer, curves lab mixer etc)

I know G'Mic, but curves in Lab mode in Krita are very good too. But most amazing effects require more advanced layer operations.

Animtim wrote:Hi,
Actually we have a way to split channels to different layers (menu image - separate image; make sure to use output to color option). Then for each layer leave only the respective channel activated in their properties. This way you can easily edit channels separatly. Though I never tried it with lab, only with RGB and CMYK, but it should work as well.

Thank You for this tips. I try this with LAB..

Is it possible to combine the layers back into a single layer after you've extracted them using Separate Image? I'm trying to combine normal maps (videogame textures) which involves modifying the channels separately.

This is already possible through blending modes:

If you have channel r, g, and b, with r as lowest, just set g and b to 'addition'. This blending mode is done per channel, so it'll require having the greyscale converted to the full color of the channel.

If you did set them to greyscale: do not loose hope! If you set the channel-image in question to 'copy -channel name-' (under misc) it'll mix fine.
So in a stack with from bottom to top: R, G, B, set G to 'copy green', and B to 'copy Blue'.



I hope this helps!

Oh excellent, thanks for the help, it looks like this should be possible! Though... I'm still not quite able to wrap my head around getting the layers in the correct order/blending mode to make it work right. Here's what I'm trying to do: https://vimeo.com/8025133 (sorry, the video's kinda long for what it is!)

Actually I think I might have gotten it! Separated 2 copies of the detail normal map into color channels. This layer order seems to give me the same result as the tutorial:

Group 1 (set to overlay)
Green (copy green)
Red (copy red)
Blue (normal blend mode) - this layer is neutralized with 50% gray

Group 2 (set to multiply)
Blue (copy blue)
Green (copy green) - this layer is neutralized with 100% white
Red (normal blend mode) - this layer is neutralized with 100% white

Original Normal Map (normal blend mode)