From 22018122f86e40c6e8909fa0fca8ea622b6950e7 Mon Sep 17 00:00:00 2001
From: Cristy <mikayla-grace@urban-warrior.org>
Date: Fri, 28 Feb 2020 13:40:20 -0500
Subject: [PATCH] Support Lab colorspace when color thresholding

---
 MagickCore/colorspace.c  | 12 ------------
 MagickCore/gem-private.h |  2 ++
 MagickCore/gem.c         | 39 +++++++++++++++++++++++++++++++++++++++
 MagickCore/threshold.c   | 10 ++++++++--
 4 files changed, 49 insertions(+), 14 deletions(-)

diff --git a/MagickCore/colorspace.c b/MagickCore/colorspace.c
index daf2d06bdd..ac9f7e91b4 100644
--- a/MagickCore/colorspace.c
+++ b/MagickCore/colorspace.c
@@ -197,18 +197,6 @@ static void ConvertRGBToLMS(const double red,const double green,
   ConvertXYZToLMS(X,Y,Z,L,M,S);
 }
 
-static void ConvertRGBToLab(const double red,const double green,
-  const double blue,double *L,double *a,double *b)
-{
-  double
-    X,
-    Y,
-    Z;
-
-  ConvertRGBToXYZ(red,green,blue,&X,&Y,&Z);
-  ConvertXYZToLab(X,Y,Z,L,a,b);
-}
-
 static void ConvertRGBToLuv(const double red,const double green,
   const double blue,double *L,double *u,double *v)
 {
diff --git a/MagickCore/gem-private.h b/MagickCore/gem-private.h
index e15f74106f..68439caa71 100644
--- a/MagickCore/gem-private.h
+++ b/MagickCore/gem-private.h
@@ -69,6 +69,8 @@ extern MagickPrivate void
     double *),
   ConvertRGBToHWB(const double,const double,const double,double *,double *,
     double *),
+  ConvertRGBToLab(const double,const double,const double,double *,double *,
+    double *),
   ConvertRGBToLCHab(const double,const double,const double,double *,double *,
     double *),
   ConvertRGBToLCHuv(const double,const double,const double,double *,double *,
diff --git a/MagickCore/gem.c b/MagickCore/gem.c
index 8dccbb9534..5767b574b3 100644
--- a/MagickCore/gem.c
+++ b/MagickCore/gem.c
@@ -1273,6 +1273,45 @@ MagickPrivate void ConvertRGBToHWB(const double red,const double green,
 %                                                                             %
 %                                                                             %
 %                                                                             %
+%   C o n v e r t R G B T o L a b                                             %
+%                                                                             %
+%                                                                             %
+%                                                                             %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%
+%  ConvertRGBToLab() transforms a (red, green, blue) to a (L, a, b) triple.
+%
+%  The format of the ConvertRGBToLCHab method is:
+%
+%      void ConvertRGBToLCHab(const double red,const double green,
+%        const double blue,double *L,double *a,double *b)
+%
+%  A description of each parameter follows:
+%
+%    o red, green, blue: A Quantum value representing the red, green, and
+%      blue component of a pixel.
+%
+%    o L, a, b: A pointer to a double value representing a component of the
+%      Lab color space.
+%
+*/
+MagickPrivate void ConvertRGBToLab(const double red,const double green,
+  const double blue,double *L,double *a,double *b)
+{
+  double
+    X,
+    Y,
+    Z;
+
+  ConvertRGBToXYZ(red,green,blue,&X,&Y,&Z);
+  ConvertXYZToLab(X,Y,Z,L,a,b);
+}
+
+/*
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%                                                                             %
+%                                                                             %
+%                                                                             %
 %   C o n v e r t R G B T o L C H a b                                         %
 %                                                                             %
 %                                                                             %
diff --git a/MagickCore/threshold.c b/MagickCore/threshold.c
index 335d0f5552..194813c572 100644
--- a/MagickCore/threshold.c
+++ b/MagickCore/threshold.c
@@ -1289,6 +1289,14 @@ MagickExport MagickBooleanType ColorThresholdImage(Image *image,
         &stop.red,&stop.green,&stop.blue);
       break;
     }
+    case LabColorspace:
+    {
+      ConvertRGBToLab(start_color->red,start_color->green,start_color->blue,
+        &start.red,&start.green,&start.blue);
+      ConvertRGBToLab(stop_color->red,stop_color->green,stop_color->blue,
+        &stop.red,&stop.green,&stop.blue);
+      break;
+    }
     default:
     {
       start.red*=QuantumScale;
@@ -1307,8 +1315,6 @@ MagickExport MagickBooleanType ColorThresholdImage(Image *image,
   stop.green*=QuantumRange;
   stop.blue*=QuantumRange;
   progress=0;
-/* convert start/stop colorspace to the same as image colorspace */
-/* for hsv() will need ConvertRGBToHSV() and them compare in HSV */
   image_view=AcquireAuthenticCacheView(image,exception);
 #if defined(MAGICKCORE_OPENMP_SUPPORT)
   #pragma omp parallel for schedule(static) shared(progress,status) \