Bug 394493

Summary: Multiple blending tool is not working
Product: [Applications] krita Reporter: kiawynne
Component: Filter LayersAssignee: Krita Bugs <krita-bugs-null>
Status: RESOLVED NOT A BUG    
Severity: normal CC: griffinvalley
Priority: NOR    
Version First Reported In: 4.0.3   
Target Milestone: ---   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description kiawynne 2018-05-20 21:01:56 UTC
When using the multiple layer it lightens the colour not darkens it? I've tried using it with multiple methods and none seem to be working.
Comment 1 wolthera 2018-05-20 21:07:56 UTC
Are you using it on a CMYK layer?
Comment 2 wolthera 2018-05-20 21:08:11 UTC
argh
Comment 3 kiawynne 2018-05-21 09:32:28 UTC
Yes I am! 

Sent from my iPhone

> On 20 May 2018, at 22:08, wolthera <bugzilla_noreply@kde.org> wrote:
> 
> https://bugs.kde.org/show_bug.cgi?id=394493
> 
> wolthera <griffinvalley@gmail.com> changed:
> 
>           What    |Removed                     |Added
> ----------------------------------------------------------------------------
>         Resolution|FIXED                       |WAITINGFORINFO
> 
> --- Comment #2 from wolthera <griffinvalley@gmail.com> ---
> argh
> 
> -- 
> You are receiving this mail because:
> You reported the bug.
Comment 4 wolthera 2018-05-21 11:24:31 UTC
Okay, so what is going on here is that CMYK in Krita does it's blending modes in CMYK, unlike photoshop, which does all blending modes in RGB regardless of colorspace. Because going between rgb and cmyk requires a conversion, it can mess up the image if you're not careful, and is at the least slower. So hence we don't do it.

In RGB the lowest value is black and the higher value is white, and multiply works as such that the values reduce, thus become darker. As for cmyk the lowest value is white and the highest value black, so multiply still makes the values lower, but they become brighter. Due this, it's recommended to do your image in RGB and only convert it to CMYK for some final touch ups when done.

So this is not a bug, but a technical difference, hence I am closing it as invalid.

https://docs.krita.org/Basic_Concepts#Colors
https://docs.krita.org/Color_Models#CMYK