[gegl] Add a illuminant adjustment to negative-darkroom operation

[Øyvind "pippin" Kolås <ok src gnome org>]

commit 5feae5792538c61d6fd57400cda80cdd59f07f99
Author: JonnyRobbie <marcodv seznam cz>
Date:   Mon Jun 7 15:29:55 2021 +0200

    Add a illuminant adjustment to negative-darkroom operation

 operations/common/negative-darkroom.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)
---
diff --git a/operations/common/negative-darkroom.c b/operations/common/negative-darkroom.c
index b7277ef47..54c1d282e 100644
--- a/operations/common/negative-darkroom.c
+++ b/operations/common/negative-darkroom.c
@@ -57,7 +57,7 @@ property_double (boost, _("Density boost"), 1.0)
 property_double (contrast, _("Contrast boost"), 1.0)
        description(_("Increase contrast for papers with fixed contrast (usually color papers)"))
        value_range (0.25, 4)
-       ui_range (0.5, 2)
+       ui_range (0.75, 1.5)
        ui_gamma (2)
 
 property_double (dodge, _("Dodge/burn multiplier"), 1.0)
@@ -83,6 +83,16 @@ property_double (flashY, _("Blue preflash"), 0)
        value_range (0, 0.05)
        ui_meta("visible", "preflash")
 
+property_boolean (illum, _("Illuminant adjustment"), FALSE)
+       description (_("Show illuminamt controls"))
+property_double (illumX, _("X multiplier"), 0.965)
+       description(_("Adjust the X tristimulus value for output"))
+       value_range (0.7, 1.3)
+       ui_meta("visible", "illum")
+property_double (illumZ, _("Z multiplier"), 0.829)
+       description(_("Adjust the Z tristimulus value for output"))
+       value_range (0.7, 1.3)
+       ui_meta("visible", "illum")
 #else
 
 #define GEGL_OP_POINT_COMPOSER
@@ -340,13 +350,13 @@ process (GeglOperation       *operation,
                // the CIEXYZ tramsmittance back
                out[0] = (1 / pow(10, r * curves[o->curve].cdens.X)) *
                         (1 / pow(10, g * curves[o->curve].mdens.X)) *
-                        (1 / pow(10, b * curves[o->curve].ydens.X));
+                        (1 / pow(10, b * curves[o->curve].ydens.X)) * o->illumX;
                out[1] = (1 / pow(10, r * curves[o->curve].cdens.Y)) *
                         (1 / pow(10, g * curves[o->curve].mdens.Y)) *
                         (1 / pow(10, b * curves[o->curve].ydens.Y));
                out[2] = (1 / pow(10, r * curves[o->curve].cdens.Z)) *
                         (1 / pow(10, g * curves[o->curve].mdens.Z)) *
-                        (1 / pow(10, b * curves[o->curve].ydens.Z));
+                        (1 / pow(10, b * curves[o->curve].ydens.Z)) * o->illumZ;
                /*printf("XYZ output %f %f %f\n", out[0], out[1], out[2]);*/
 
                in   += 3;