[gegl] newsprint: add black pullout property

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

commit 172324ffa9235d25a6dede86d04065cb894e9f8e
Author: Øyvind Kolås <pippin gimp org>
Date:   Wed Jul 17 18:28:59 2019 +0200

    newsprint: add black pullout property

 operations/common/newsprint.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
---
diff --git a/operations/common/newsprint.c b/operations/common/newsprint.c
index 80d307434..24e313092 100644
--- a/operations/common/newsprint.c
+++ b/operations/common/newsprint.c
@@ -159,6 +159,11 @@ property_double (twist, _("Black angle"), 75.0)
                  ui_meta ("bw-label",   _("Angle"))
                  ui_meta ("cmyk-label", _("Black angle"))
 
+property_double (black_pullout, _("Black pullout"), 1.0)
+                 value_range (0.0, 1.0)
+                 description (_("How much of common gray to pull out of CMY"))
+                 ui_meta ("visible", "color-model {cmyk}")
+
 property_int    (aa_samples, _("Anti-alias oversampling factor"), 16)
                  value_range (1, 128)
                  description (_("Number of samples that are averaged for antialiasing the result."))
@@ -492,7 +497,7 @@ process (GeglOperation       *operation,
            if (m < k) k = m;
            if (y < k) k = y;
 
-           k = k * 0.40; /* black pull out */
+           k = k * o->black_pullout; /* black pull out */
 
            if (k < 1.0)
            {