dnrops
/
gimp
mirror of https://github.com/GNOME/gimp.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Clamp Addition and Subtract so that we acheieve consistent blending 

* app/gegl/gimpoperationpointlayermode.c: Clamp Addition and
Subtract so that we acheieve consistent blending results. Also,
our Addition is fine, it is the formula for 'plus' in the SVG 1.2
draft that is wrong as far as I can see.

svn path=/trunk/; revision=27421
This commit is contained in:
Martin Nordholts 2008-10-26 19:28:47 +00:00
parent 65714a8ceb
commit 5bb194a21d
2 changed files with 37 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
ChangeLog
View File

@ -1,3 +1,10 @@
2008-10-26 Martin Nordholts <martinn@svn.gnome.org>
* app/gegl/gimpoperationpointlayermode.c: Clamp Addition and
Subtract so that we acheieve consistent blending results. Also,
our Addition is fine, it is the formula for 'plus' in the SVG 1.2
draft that is wrong as far as I can see.
2008-10-26 Martin Nordholts <martinn@svn.gnome.org>
* app/gegl/gimpoperationpointlayermode.c: Continue the quest of

43
app/gegl/gimpoperationpointlayermode.c
View File

@ -40,13 +40,13 @@
#define outC out[c]
#define outA out[A]
#define BLEND(mode, expr) \
#define BLEND(mode, expr) \
case (mode): \
for (c = RED; c < ALPHA; c++) \
{ \
expr; \
} \
break;
break;
enum
{
@ -277,22 +277,39 @@ gimp_operation_point_layer_mode_process (GeglOperation *operation,
outC = (inC * layA + (sqrt (inC / inA) * inA - inC) * (2 * layC - layA)) + layC * (1 - inA) + inC * (1 - layA);
});
/* To be more mathematically correct we would have to either
* adjust the formula for the resulting opacity or adapt the
* other channels to the change in opacity. Compare to the
* 'plus' compositing operation in SVG 1.2.
/* Custom SVG 1.2:
*
* Since this doesn't matter for completely opaque layers, and
* since consistency in how the alpha channel of layers is
* interpreted is more important than mathematically correct
* results, we don't bother.
* if Dc + Sc >= 1
* f(Sc, Dc) = 1
* otherwise
* f(Sc, Dc) = Dc + Sc
*/
BLEND (GIMP_ADDITION_MODE,
outC = inC + layC);
if (layC * inA + inC * layA >= layA * inA)
{
outC = layA * inA + layC * (1 - inA) + inC * (1 - layA);
}
else
{
outC = inC + layC;
});
/* Derieved from SVG 1.2 formulas, f(Sc, Dc) = Dc - Sc */
/* Custom SVG 1.2:
*
* if Dc - Sc <= 0
* f(Sc, Dc) = 0
* otherwise
* f(Sc, Dc) = Dc - Sc
*/
BLEND (GIMP_SUBTRACT_MODE,
outC = inC + layC - 2 * layC * inA);
if (inC * layA - layC * inA <= 0)
{
outC = layC * (1 - inA) + inC * (1 - layA);
}
else
{
outC = inC + layC - 2 * layC * inA;
});
/* Derieved from SVG 1.2 formulas, f(Sc, Dc) = Dc - Sc + 0.5 */
BLEND (GIMP_GRAIN_EXTRACT_MODE,