URL:
<http://gna.org/bugs/?20157>
Summary: [wish] 'overlay' and 'soft light' layer blending
Mode.
Project: MyPaint
Submitted by: deevad
Submitted on: sam. 08 sept. 2012 12:13:15 GMT
Severity: 1 - Wish
Priority: 5 - Normal
Status: None
Privacy: Public
Assigned to: None
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Release: 1.0.0Git+
Planned Release: None
Operating System: Kubuntu 12.04
_______________________________________________________
Details:
= Intro =
I come for the request of 2 'new' layers blending modes for Mypaint. Those
modes are named on other softwares 'overlay' and 'soft light'. I use those
layers in my digital comics to paste over a paper texture. Those blending
modes are good for textures ; the bright data as well as the dark data on the
layer influence the pixel under. It simulate well bump ( bright) and crease
(dark ) of a paper texture. Perfect grey ( 50% ) is transparent. Many other
use are also possible to do with them.
= Formula =
To quote wikipedia article about Blend mode, here is the pseudo formula :
Overlay : Result Color = if (Bottom Color < 128) then (2 * Top Color * Bottom
Color / 255) else (255 - 2 * (255 - Top Color) * (255 - Bottom Color) / 255)
Softlight : This is a softer version of Overlay. Applying pure black or white
does not result in pure black or white.
_( source : http://en.wikipedia.org/wiki/Blend_modes#Overlay )_
_( other link : http://inlandstudios.com/en/?p=851 )_
= Open raster (*.ora) compatibiltiy =
Gimp as well as Krita export inside the open raster stack xml file the
information of layer mode. The 2 softwares agree on this markup :
for overlay :
<layer composite-op="svg:overlay" name="Layer" opacity="1.0"
src="data/000.png" visibility="visible" x="0" y="0"/>
for soft-light :
<layer composite-op="svg:soft-light" name="Layer" opacity="1.0"
src="data/000.png" visibility="visible" x="0" y="0"/>
Test files to download :
2 mini open raster files with both blending mode, for test :
http://david.revoy.free.fr/forums/Mypaint/openraster_softlight-overlay.zip
= Misc infos =
A famous bug unsolved on Gimp since 2004 made Gimp use the same formula for
"Soft-light" and "overlay" , making "overlay" wrong and inexistant in all Gimp
since almost a decade. Users complain on forums, mailing list , on bug
tracker, but after a research developpers sounds to wait for GEGL
implementation to fix that since years. ( bug link
:https://bugzilla.gnome.org/show_bug.cgi?id=162395 , mailing list :
https://mail.gnome.org/archives/gimp-developer-list/2012-September/msg00037.html
, etc ... ). Just for informations if test are done to re-open a *.ora on
Gimp. Krita will give an accurate rendering. I hope Mypaint too.
Thanks in advance !
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<http://gna.org/bugs/?20157>
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