Add lcms2 interface

configure.ac: Add boilerplate for configuring and detecting liblcms2.
etc/NEWS: Mention new configure option and color-distance change.
src/Makefile.in: Add references to lcms.c and liblcms.
src/emacs.c: Define lcms2 symbols.
src/lcms.c: New file.
src/lisp.h: Add declaration for lcms2.
src/xfaces.c: Add optional METRIC argument.

5 files changed, 205 insertions, 7 deletions

diff --git a/src/Makefile.in b/src/Makefile.in
index dde3f1d3fb4..a98ad9c5ebd 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -234,6 +234,8 @@ LIBXML2_CFLAGS = @LIBXML2_CFLAGS@
 
 GETADDRINFO_A_LIBS = @GETADDRINFO_A_LIBS@
 
+LIBLCMS2 = @LIBLCMS2@
+
 LIBZ = @LIBZ@
 
 ## system-specific libs for dynamic modules, else empty
@@ -389,7 +391,7 @@ base_obj = dispnew.o frame.o scroll.o xdisp.o menu.o $(XMENU_OBJ) window.o \
         syntax.o $(UNEXEC_OBJ) bytecode.o \
         process.o gnutls.o callproc.o \
         region-cache.o sound.o atimer.o \
-        doprnt.o intervals.o textprop.o composite.o xml.o $(NOTIFY_OBJ) \
+        doprnt.o intervals.o textprop.o composite.o xml.o lcms.o $(NOTIFY_OBJ) \
         $(XWIDGETS_OBJ) \
         profiler.o decompress.o \
         thread.o systhread.o \
@@ -490,7 +492,7 @@ LIBES = $(LIBS) $(W32_LIBS) $(LIBS_GNUSTEP) $(LIBX_BASE) $(LIBIMAGE) \
    $(LIBXML2_LIBS) $(LIBGPM) $(LIBS_SYSTEM) $(CAIRO_LIBS) \
    $(LIBS_TERMCAP) $(GETLOADAVG_LIBS) $(SETTINGS_LIBS) $(LIBSELINUX_LIBS) \
    $(FREETYPE_LIBS) $(FONTCONFIG_LIBS) $(LIBOTF_LIBS) $(M17N_FLT_LIBS) \
-   $(LIBGNUTLS_LIBS) $(LIB_PTHREAD) $(GETADDRINFO_A_LIBS) \
+   $(LIBGNUTLS_LIBS) $(LIB_PTHREAD) $(GETADDRINFO_A_LIBS) $(LIBLCMS2) \
    $(NOTIFY_LIBS) $(LIB_MATH) $(LIBZ) $(LIBMODULES) $(LIBSYSTEMD_LIBS)
 
 ## FORCE it so that admin/unidata can decide whether these files
diff --git a/src/emacs.c b/src/emacs.c
index 44f6285795a..668711a5ab9 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -1546,6 +1546,10 @@ Using an Emacs configured with --with-x-toolkit=lucid does not have this problem
       syms_of_xml ();
 #endif
 
+#ifdef HAVE_LCMS2
+      syms_of_lcms2 ();
+#endif
+
 #ifdef HAVE_ZLIB
       syms_of_decompress ();
 #endif
diff --git a/src/lcms.c b/src/lcms.c
new file mode 100644
index 00000000000..120ef769810
--- /dev/null
+++ b/src/lcms.c
@@ -0,0 +1,182 @@
+/* Interface to Little CMS
+   Copyright (C) 2017 Free Software Foundation, Inc.
+
+This file is part of GNU Emacs.
+
+GNU Emacs is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or (at
+your option) any later version.
+
+GNU Emacs is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+#ifdef HAVE_LCMS2
+
+#include <lcms2.h>
+#include <math.h>
+
+#include "lisp.h"
+
+static bool
+parse_lab_list (Lisp_Object lab_list, cmsCIELab *color)
+{
+#define PARSE_LAB_LIST_FIELD(field)                                     \
+  if (CONSP (lab_list) && NUMBERP (XCAR (lab_list)))                    \
+    {                                                                   \
+      color->field = XFLOATINT (XCAR (lab_list));                       \
+      lab_list = XCDR (lab_list);                                       \
+    }                                                                   \
+  else                                                                  \
+    return false;
+
+  PARSE_LAB_LIST_FIELD (L);
+  PARSE_LAB_LIST_FIELD (a);
+  PARSE_LAB_LIST_FIELD (b);
+
+  return true;
+}
+
+/* http://www.ece.rochester.edu/~gsharma/ciede2000/ciede2000noteCRNA.pdf> */
+
+DEFUN ("lcms-cie-de2000", Flcms_cie_de2000, Slcms_cie_de2000, 2, 5, 0,
+       doc: /* Compute CIEDE2000 metric distance between COLOR1 and COLOR2.
+Each color is a list of L*a*b* coordinates, where the L* channel ranges from
+0 to 100, and the a* and b* channels range from -128 to 128.
+Optional arguments KL, KC, KH are weighting parameters for lightness,
+chroma, and hue, respectively. The parameters each default to 1. */)
+  (Lisp_Object color1, Lisp_Object color2,
+   Lisp_Object kL, Lisp_Object kC, Lisp_Object kH)
+{
+  cmsCIELab Lab1, Lab2;
+  cmsFloat64Number Kl, Kc, Kh;
+
+  if (!(CONSP (color1) && parse_lab_list (color1, &Lab1)))
+    signal_error ("Invalid color", color1);
+  if (!(CONSP (color2) && parse_lab_list (color2, &Lab2)))
+    signal_error ("Invalid color", color1);
+  if (NILP (kL))
+    Kl = 1.0f;
+  else if (!(NUMBERP (kL) && (Kl = XFLOATINT(kL))))
+    wrong_type_argument(Qnumberp, kL);
+  if (NILP (kC))
+    Kc = 1.0f;
+  else if (!(NUMBERP (kC) && (Kc = XFLOATINT(kC))))
+    wrong_type_argument(Qnumberp, kC);
+  if (NILP (kL))
+    Kh = 1.0f;
+  else if (!(NUMBERP (kH) && (Kh = XFLOATINT(kH))))
+    wrong_type_argument(Qnumberp, kH);
+
+  return make_float (cmsCIE2000DeltaE (&Lab1, &Lab2, Kl, Kc, Kh));
+}
+
+/* FIXME: code duplication */
+
+static bool
+parse_xyz_list (Lisp_Object xyz_list, cmsCIEXYZ *color)
+{
+#define PARSE_XYZ_LIST_FIELD(field)                                     \
+  if (CONSP (xyz_list) && NUMBERP (XCAR (xyz_list)))                    \
+    {                                                                   \
+      color->field = 100.0 * XFLOATINT (XCAR (xyz_list));               \
+      xyz_list = XCDR (xyz_list);                                       \
+    }                                                                   \
+  else                                                                  \
+    return false;
+
+  PARSE_XYZ_LIST_FIELD (X);
+  PARSE_XYZ_LIST_FIELD (Y);
+  PARSE_XYZ_LIST_FIELD (Z);
+
+  return true;
+}
+
+DEFUN ("lcms-cam02-ucs", Flcms_cam02_ucs, Slcms_cam02_ucs, 2, 3, 0,
+       doc: /* Compute CAM02-UCS metric distance between COLOR1 and COLOR2.
+Each color is a list of XYZ coordinates, with Y scaled to unity.
+Optional argument is the XYZ white point, which defaults to illuminant D65. */)
+  (Lisp_Object color1, Lisp_Object color2, Lisp_Object whitepoint)
+{
+  cmsViewingConditions vc;
+  cmsJCh jch1, jch2;
+  cmsHANDLE h1, h2;
+  cmsCIEXYZ xyz1, xyz2, xyzw;
+  double Jp1, ap1, bp1, Jp2, ap2, bp2;
+  double Mp1, Mp2, FL, k, k4;
+
+  if (!(CONSP (color1) && parse_xyz_list (color1, &xyz1)))
+    signal_error ("Invalid color", color1);
+  if (!(CONSP (color2) && parse_xyz_list (color2, &xyz2)))
+    signal_error ("Invalid color", color1);
+  if (NILP (whitepoint))
+    {
+      xyzw.X = 95.047;
+      xyzw.Y = 100.0;
+      xyzw.Z = 108.883;
+    }
+  else if (!(CONSP (whitepoint) && parse_xyz_list(whitepoint, &xyzw)))
+    signal_error("Invalid white point", whitepoint);
+
+  vc.whitePoint.X = xyzw.X;
+  vc.whitePoint.Y = xyzw.Y;
+  vc.whitePoint.Z = xyzw.Z;
+  vc.Yb = 20;
+  vc.La = 100;
+  vc.surround = AVG_SURROUND;
+  vc.D_value = 1.0;
+
+  h1 = cmsCIECAM02Init (0, &vc);
+  h2 = cmsCIECAM02Init (0, &vc);
+  cmsCIECAM02Forward (h1, &xyz1, &jch1);
+  cmsCIECAM02Forward (h2, &xyz2, &jch2);
+  cmsCIECAM02Done (h1);
+  cmsCIECAM02Done (h2);
+
+  /* Now have colors in JCh, need to calculate J'a'b'
+
+     M = C * F_L^0.25
+     J' = 1.7 J / (1 + 0.007 J)
+     M' = 43.86 ln(1 + 0.0228 M)
+     a' = M' cos(h)
+     b' = M' sin(h)
+
+     where
+
+     F_L = 0.2 k^4 (5 L_A) + 0.1 (1 - k^4)^2 (5 L_A)^(1/3),
+     k = 1/(5 L_A + 1)
+  */
+  k = 1.0 / (1.0 + (5.0 * vc.La));
+  k4 = k * k * k * k;
+  FL = vc.La * k4 + 0.1 * (1 - k4) * (1 - k4) * cbrt (5.0 * vc.La);
+  Mp1 = 43.86 * log (1.0 + 0.0228 * (jch1.C * sqrt (sqrt (FL))));
+  Mp2 = 43.86 * log (1.0 + 0.0228 * (jch2.C * sqrt (sqrt (FL))));
+  Jp1 = 1.7 * jch1.J / (1.0 + (0.007 * jch1.J));
+  Jp2 = 1.7 * jch2.J / (1.0 + (0.007 * jch2.J));
+  ap1 = Mp1 * cos (jch1.h);
+  ap2 = Mp2 * cos (jch2.h);
+  bp1 = Mp1 * sin (jch1.h);
+  bp2 = Mp2 * sin (jch2.h);
+
+  return make_float (sqrt ((Jp2 - Jp1) * (Jp2 - Jp1) +
+                           (ap2 - ap1) * (ap2 - ap1) +
+                           (bp2 - bp1) * (bp2 - bp1)));
+}
+
+
+/* Initialization */
+void
+syms_of_lcms2 (void)
+{
+  defsubr (&Slcms_cie_de2000);
+  defsubr (&Slcms_cam02_ucs);
+}
+
+#endif /* HAVE_LCMS2 */
diff --git a/src/lisp.h b/src/lisp.h
index 81f8d6a24b5..19594e7830d 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -4396,6 +4396,11 @@ extern void syms_of_xml (void);
 extern void xml_cleanup_parser (void);
 #endif
 
+#ifdef HAVE_LCMS2
+/* Defined in lcms.c.  */
+extern void syms_of_lcms2 (void);
+#endif
+
 #ifdef HAVE_ZLIB
 /* Defined in decompress.c.  */
 extern void syms_of_decompress (void);
diff --git a/src/xfaces.c b/src/xfaces.c
index 86bb9b0b496..32a5bd5f60b 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -4088,12 +4088,14 @@ color_distance (XColor *x, XColor *y)
 }
 
 
-DEFUN ("color-distance", Fcolor_distance, Scolor_distance, 2, 3, 0,
+DEFUN ("color-distance", Fcolor_distance, Scolor_distance, 2, 4, 0,
        doc: /* Return an integer distance between COLOR1 and COLOR2 on FRAME.
 COLOR1 and COLOR2 may be either strings containing the color name,
-or lists of the form (RED GREEN BLUE).
-If FRAME is unspecified or nil, the current frame is used.  */)
-  (Lisp_Object color1, Lisp_Object color2, Lisp_Object frame)
+or lists of the form (RED GREEN BLUE), each in the range 0 to 65535 inclusive.
+If FRAME is unspecified or nil, the current frame is used.
+If METRIC is unspecified or nil, a modified L*u*v* metric is used.  */)
+  (Lisp_Object color1, Lisp_Object color2, Lisp_Object frame,
+   Lisp_Object metric)
 {
   struct frame *f = decode_live_frame (frame);
   XColor cdef1, cdef2;
@@ -4107,7 +4109,10 @@ If FRAME is unspecified or nil, the current frame is used.  */)
            && defined_color (f, SSDATA (color2), &cdef2, false)))
     signal_error ("Invalid color", color2);
 
-  return make_number (color_distance (&cdef1, &cdef2));
+  if (NILP (metric))
+    return make_number (color_distance (&cdef1, &cdef2));
+  else
+    return call2 (metric, color1, color2);
 }