[PATCH] lcms2 (was Re: Emacs 26.1 release branch created)

[Mark Oteiza <mvoteiza@udel.edu>]

On 16/09/17 at 05:58pm, Eli Zaretskii wrote:
> > Date: Sat, 16 Sep 2017 10:51:12 -0400
> > From: Mark Oteiza <mvoteiza@udel.edu>
> > Cc: emacs-devel@gnu.org
> > 
> > > > I'm working on more utilities and tests for lcms.c, where should I
> > > > commit those?
> > > 
> > > On emacs-26, I guess.  How many more utilities do you envision?
> > > (Tests are okay to add to emacs-26 regardless.)
> > 
> > Dividing the internals of lcms-cam02-ucs into C functions, and from that
> > making the Lisp functions:
> > 
> > lcms-xyz->jch
> > lcms-jch->jab
> > lcms-jab->jch
> > lcms-jch->xyz
> > 
> > and adding a Lisp variable `lcms-d65-xyz' as the default whitepoint for
> > all the functions in lcms.c that need one.  That should be two commits
> > if I can get all the Windows build stuff correct.
> 
> That can certainly go to emacs-26.
> 
> > I plan to add more, but I can wait for an emacs-26 -> master merge and
> > continue to work on master.
> 
> If you consider the feature fairly complete for a first release, then
> that's fine.  Otherwise we could consider adding more of your code to
> emacs-26, unless you think the development will take a considerable
> time.  In general, once the first pretest is out (which will be
> probably a week or 2 from now), no new features should be added.

Here is the patch I thought I would not get done.

From 98a0ff92120f7c23f716dc98b381660004b37a8c Mon Sep 17 00:00:00 2001
From: Mark Oteiza <mvoteiza@udel.edu>
Date: Tue, 26 Sep 2017 17:13:36 -0400
Subject: [PATCH] Add CAM02 JCh and CAM02-UCS J'a'b' conversions

* src/lcms.h: New file.
* src/lcms.c (rad2deg, parse_jch_list, parse_jab_list, xyz_to_jch):
(jch_to_xyz, jch_to_jab, jab_to_jch): New functions.
(lcms-jch->xyz, lcms-jch->xyz, lcms-jch->jab, lcms-jab->jch): New Lisp
functions.
(lcms-cam02-ucs): Refactor.
(syms_of_lcms2): Declare new functions.
* test/src/lcms-tests.el (lcms-roundtrip, lcms-ciecam02-gold):
(lcms-jmh->cam02-ucs-silver): New tests.
---
 src/lcms.c             | 291 +++++++++++++++++++++++++++++++++++++++++++------
 src/lcms.h             |  30 +++++
 test/src/lcms-tests.el |  44 ++++++++
 3 files changed, 332 insertions(+), 33 deletions(-)
 create mode 100644 src/lcms.h

diff --git a/src/lcms.c b/src/lcms.c
index a5e527911e..24b4f22ed1 100644
--- a/src/lcms.c
+++ b/src/lcms.c
@@ -24,6 +24,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include <math.h>
 
 #include "lisp.h"
+#include "lcms.h"
 
 #ifdef WINDOWSNT
 # include <windows.h>
@@ -145,6 +146,12 @@ deg2rad (double degrees)
   return M_PI * degrees / 180.0;
 }
 
+static double
+rad2deg (double radians)
+{
+  return 180.0 * radians / M_PI;
+}
+
 static cmsCIEXYZ illuminant_d65 = { .X = 95.0455, .Y = 100.0, .Z = 108.8753 };
 
 static void
@@ -180,6 +187,46 @@ parse_xyz_list (Lisp_Object xyz_list, cmsCIEXYZ *color)
   return true;
 }
 
+static bool
+parse_jch_list (Lisp_Object jch_list, cmsJCh *color)
+{
+#define PARSE_JCH_LIST_FIELD(field)					\
+  if (CONSP (jch_list) && NUMBERP (XCAR (jch_list)))			\
+    {									\
+      color->field = XFLOATINT (XCAR (jch_list));			\
+      jch_list = XCDR (jch_list);					\
+    }									\
+  else									\
+    return false;
+
+  PARSE_JCH_LIST_FIELD (J);
+  PARSE_JCH_LIST_FIELD (C);
+  PARSE_JCH_LIST_FIELD (h);
+
+  if (! NILP (jch_list))
+    return false;
+  return true;
+}
+
+static bool
+parse_jab_list (Lisp_Object jab_list, lcmsJab_t *color)
+{
+#define PARSE_JAB_LIST_FIELD(field)					\
+  if (CONSP (jab_list) && NUMBERP (XCAR (jab_list)))			\
+    {									\
+      color->field = XFLOATINT (XCAR (jab_list));			\
+      jab_list = XCDR (jab_list);					\
+    }									\
+  else									\
+    return false;
+
+  PARSE_JAB_LIST_FIELD (J);
+  PARSE_JAB_LIST_FIELD (a);
+  PARSE_JAB_LIST_FIELD (b);
+
+  return true;
+}
+
 static bool
 parse_viewing_conditions (Lisp_Object view, const cmsCIEXYZ *wp,
                           cmsViewingConditions *vc)
@@ -216,6 +263,204 @@ parse_viewing_conditions (Lisp_Object view, const cmsCIEXYZ *wp,
   return true;
 }
 
+static void
+xyz_to_jch (const cmsCIEXYZ *xyz, cmsJCh *jch, const cmsViewingConditions *vc)
+{
+  cmsHANDLE h;
+
+  h = cmsCIECAM02Init (0, vc);
+  cmsCIECAM02Forward (h, xyz, jch);
+  cmsCIECAM02Done (h);
+}
+
+static void
+jch_to_xyz (const cmsJCh *jch, cmsCIEXYZ *xyz, const cmsViewingConditions *vc)
+{
+  cmsHANDLE h;
+
+  h = cmsCIECAM02Init (0, vc);
+  cmsCIECAM02Reverse (h, jch, xyz);
+  cmsCIECAM02Done (h);
+}
+
+static void
+jch_to_jab (const cmsJCh *jch, lcmsJab_t *jab, double FL, double c1, double c2)
+{
+  double Mp = 43.86 * log (1.0 + c2 * (jch->C * sqrt (sqrt (FL))));
+  jab->J = 1.7 * jch->J / (1.0 + (c1 * jch->J));
+  jab->a = Mp * cos (deg2rad (jch->h));
+  jab->b = Mp * sin (deg2rad (jch->h));
+}
+
+static void
+jab_to_jch (const lcmsJab_t *jab, cmsJCh *jch, double FL, double c1, double c2)
+{
+  jch->J = jab->J / (1.0 + c1 * (100.0 - jab->J));
+  jch->h = atan2 (jab->b, jab->a);
+  double Mp = sqrt (jab->a * jab->a + jab->b * jab->b);
+  jch->h = rad2deg (jch->h);
+  if (jch->h < 0.0)
+    jch->h += 360.0;
+  jch->C = (exp (c2 * Mp) - 1) / (c2 * sqrt (sqrt (FL)));
+}
+
+DEFUN ("lcms-xyz->jch", Flcms_xyz_to_jch, Slcms_xyz_to_jch, 1, 3, 0,
+       doc: /* Convert CIE CAM02 JCh to CIE XYZ.
+COLOR is a list (X Y Z), with Y scaled about unity.
+Optional arguments WHITEPOINT and VIEW are the same as in `lcms-cam02-ucs',
+which see.  */)
+  (Lisp_Object color, Lisp_Object whitepoint, Lisp_Object view)
+{
+  cmsViewingConditions vc;
+  cmsJCh jch;
+  cmsCIEXYZ xyz, xyzw;
+
+#ifdef WINDOWSNT
+  if (!lcms_initialized)
+    lcms_initialized = init_lcms_functions ();
+  if (!lcms_initialized)
+    {
+      message1 ("lcms2 library not found");
+      return Qnil;
+    }
+#endif
+
+  if (!(CONSP (color) && parse_xyz_list (color, &xyz)))
+    signal_error ("Invalid color", color);
+  if (NILP (whitepoint))
+    xyzw = illuminant_d65;
+  else if (!(CONSP (whitepoint) && parse_xyz_list (whitepoint, &xyzw)))
+    signal_error ("Invalid white point", whitepoint);
+  if (NILP (view))
+    default_viewing_conditions (&xyzw, &vc);
+  else if (!(CONSP (view) && parse_viewing_conditions (view, &xyzw, &vc)))
+    signal_error ("Invalid viewing conditions", view);
+
+  xyz_to_jch(&xyz, &jch, &vc);
+  return list3 (make_float (jch.J), make_float (jch.C), make_float (jch.h));
+}
+
+DEFUN ("lcms-jch->xyz", Flcms_jch_to_xyz, Slcms_jch_to_xyz, 1, 3, 0,
+       doc: /* Convert CIE XYZ to CIE CAM02 JCh.
+COLOR is a list (J C h), where lightness of white is equal to 100, and hue
+is given in degrees.
+Optional arguments WHITEPOINT and VIEW are the same as in `lcms-cam02-ucs',
+which see.  */)
+  (Lisp_Object color, Lisp_Object whitepoint, Lisp_Object view)
+{
+  cmsViewingConditions vc;
+  cmsJCh jch;
+  cmsCIEXYZ xyz, xyzw;
+
+#ifdef WINDOWSNT
+  if (!lcms_initialized)
+    lcms_initialized = init_lcms_functions ();
+  if (!lcms_initialized)
+    {
+      message1 ("lcms2 library not found");
+      return Qnil;
+    }
+#endif
+
+  if (!(CONSP (color) && parse_jch_list (color, &jch)))
+    signal_error ("Invalid color", color);
+  if (NILP (whitepoint))
+    xyzw = illuminant_d65;
+  else if (!(CONSP (whitepoint) && parse_xyz_list (whitepoint, &xyzw)))
+    signal_error ("Invalid white point", whitepoint);
+  if (NILP (view))
+    default_viewing_conditions (&xyzw, &vc);
+  else if (!(CONSP (view) && parse_viewing_conditions (view, &xyzw, &vc)))
+    signal_error ("Invalid viewing conditions", view);
+
+  jch_to_xyz(&jch, &xyz, &vc);
+  return list3 (make_float (xyz.X / 100.0),
+                make_float (xyz.Y / 100.0),
+                make_float (xyz.Z / 100.0));
+}
+
+DEFUN ("lcms-jch->jab", Flcms_jch_to_jab, Slcms_jch_to_jab, 1, 3, 0,
+       doc: /* Convert CIE CAM02 JCh to CAM02-UCS J'a'b'.
+COLOR is a list (J C h) as described in `lcms-jch->xyz', which see.
+Optional arguments WHITEPOINT and VIEW are the same as in `lcms-cam02-ucs',
+which see.  */)
+  (Lisp_Object color, Lisp_Object whitepoint, Lisp_Object view)
+{
+  cmsViewingConditions vc;
+  lcmsJab_t jab;
+  cmsJCh jch;
+  cmsCIEXYZ xyzw;
+  double FL, k, k4;
+
+#ifdef WINDOWSNT
+  if (!lcms_initialized)
+    lcms_initialized = init_lcms_functions ();
+  if (!lcms_initialized)
+    {
+      message1 ("lcms2 library not found");
+      return Qnil;
+    }
+#endif
+
+  if (!(CONSP (color) && parse_jch_list (color, &jch)))
+    signal_error ("Invalid color", color);
+  if (NILP (whitepoint))
+    xyzw = illuminant_d65;
+  else if (!(CONSP (whitepoint) && parse_xyz_list (whitepoint, &xyzw)))
+    signal_error ("Invalid white point", whitepoint);
+  if (NILP (view))
+    default_viewing_conditions (&xyzw, &vc);
+  else if (!(CONSP (view) && parse_viewing_conditions (view, &xyzw, &vc)))
+    signal_error ("Invalid viewing conditions", view);
+
+  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);
+  jch_to_jab (&jch, &jab, FL, 0.007, 0.0228);
+  return list3 (make_float (jab.J), make_float (jab.a), make_float (jab.b));
+}
+
+DEFUN ("lcms-jab->jch", Flcms_jab_to_jch, Slcms_jab_to_jch, 1, 3, 0,
+       doc: /* Convert CAM02-UCS J'a'b' to CIE CAM02 JCh.
+COLOR is a list (J' a' b'), where white corresponds to lightness J equal to 100.
+Optional arguments WHITEPOINT and VIEW are the same as in `lcms-cam02-ucs',
+which see.  */)
+  (Lisp_Object color, Lisp_Object whitepoint, Lisp_Object view)
+{
+  cmsViewingConditions vc;
+  cmsJCh jch;
+  lcmsJab_t jab;
+  cmsCIEXYZ xyzw;
+  double FL, k, k4;
+
+#ifdef WINDOWSNT
+  if (!lcms_initialized)
+    lcms_initialized = init_lcms_functions ();
+  if (!lcms_initialized)
+    {
+      message1 ("lcms2 library not found");
+      return Qnil;
+    }
+#endif
+
+  if (!(CONSP (color) && parse_jab_list (color, &jab)))
+    signal_error ("Invalid color", color);
+  if (NILP (whitepoint))
+    xyzw = illuminant_d65;
+  else if (!(CONSP (whitepoint) && parse_xyz_list (whitepoint, &xyzw)))
+    signal_error ("Invalid white point", whitepoint);
+  if (NILP (view))
+    default_viewing_conditions (&xyzw, &vc);
+  else if (!(CONSP (view) && parse_viewing_conditions (view, &xyzw, &vc)))
+    signal_error ("Invalid viewing conditions", view);
+
+  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);
+  jab_to_jch (&jab, &jch, FL, 0.007, 0.0228);
+  return list3 (make_float (jch.J), make_float (jch.C), make_float (jch.h));
+}
+
 /* References:
    Li, Luo et al. "The CRI-CAM02UCS colour rendering index." COLOR research
    and application, 37 No.3, 2012.
@@ -239,10 +484,9 @@ The default viewing conditions are (20 100 1 1).  */)
 {
   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;
+  lcmsJab_t jab1, jab2;
+  double FL, k, k4;
 
 #ifdef WINDOWSNT
   if (!lcms_initialized)
@@ -267,41 +511,18 @@ The default viewing conditions are (20 100 1 1).  */)
   else if (!(CONSP (view) && parse_viewing_conditions (view, &xyzw, &vc)))
     signal_error ("Invalid view conditions", view);
 
-  h1 = cmsCIECAM02Init (0, &vc);
-  h2 = cmsCIECAM02Init (0, &vc);
-  cmsCIECAM02Forward (h1, &xyz1, &jch1);
-  cmsCIECAM02Forward (h2, &xyz2, &jch2);
-  cmsCIECAM02Done (h1);
-  cmsCIECAM02Done (h2);
+  xyz_to_jch (&xyz1, &jch1, &vc);
+  xyz_to_jch (&xyz2, &jch2, &vc);
 
-  /* 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 (deg2rad (jch1.h));
-  ap2 = Mp2 * cos (deg2rad (jch2.h));
-  bp1 = Mp1 * sin (deg2rad (jch1.h));
-  bp2 = Mp2 * sin (deg2rad (jch2.h));
+  jch_to_jab (&jch1, &jab1, FL, 0.007, 0.0228);
+  jch_to_jab (&jch2, &jab2, FL, 0.007, 0.0228);
 
-  return make_float (sqrt ((Jp2 - Jp1) * (Jp2 - Jp1) +
-                           (ap2 - ap1) * (ap2 - ap1) +
-                           (bp2 - bp1) * (bp2 - bp1)));
+  return make_float (sqrt ((jab2.J - jab1.J) * (jab2.J - jab1.J) +
+                           (jab2.a - jab1.a) * (jab2.a - jab1.a) +
+                           (jab2.b - jab1.b) * (jab2.b - jab1.b)));
 }
 
 DEFUN ("lcms-temp->white-point", Flcms_temp_to_white_point, Slcms_temp_to_white_point, 1, 1, 0,
@@ -359,6 +580,10 @@ void
 syms_of_lcms2 (void)
 {
   defsubr (&Slcms_cie_de2000);
+  defsubr (&Slcms_xyz_to_jch);
+  defsubr (&Slcms_jch_to_xyz);
+  defsubr (&Slcms_jch_to_jab);
+  defsubr (&Slcms_jab_to_jch);
   defsubr (&Slcms_cam02_ucs);
   defsubr (&Slcms2_available_p);
   defsubr (&Slcms_temp_to_white_point);
diff --git a/src/lcms.h b/src/lcms.h
new file mode 100644
index 0000000000..6080de06ca
--- /dev/null
+++ b/src/lcms.h
@@ -0,0 +1,30 @@
+/* Definitions for data structures and routines for the
+   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 <https://www.gnu.org/licenses/>.  */
+
+#ifndef _LCMS_H
+#define _LCMS_H 1
+
+typedef struct
+{
+  double J;
+  double a;
+  double b;
+} lcmsJab_t;
+
+#endif /* lcms.h */
diff --git a/test/src/lcms-tests.el b/test/src/lcms-tests.el
index d6d1d16b9a..cc324af68b 100644
--- a/test/src/lcms-tests.el
+++ b/test/src/lcms-tests.el
@@ -94,6 +94,38 @@ lcms-rgb255->xyz
     (apply #'color-xyz-to-xyy (lcms-temp->white-point 7504))
     '(0.29902 0.31485 1.0))))
 
+(ert-deftest lcms-roundtrip ()
+  "Test accuracy of converting to and from different color spaces"
+  (skip-unless (featurep 'lcms2))
+  (should
+   (let ((color '(.5 .3 .7)))
+     (lcms-triple-approx-p (lcms-jch->xyz (lcms-xyz->jch color))
+                           color
+                           0.0001)))
+  (should
+   (let ((color '(.8 -.2 .2)))
+     (lcms-triple-approx-p (lcms-jch->jab (lcms-jab->jch color))
+                           color
+                           0.0001))))
+
+(ert-deftest lcms-ciecam02-gold ()
+  "Test CIE CAM02 JCh gold values"
+  (skip-unless (featurep 'lcms2))
+  (should
+   (lcms-triple-approx-p
+    (lcms-xyz->jch '(0.1931 0.2393 0.1014)
+                   '(0.9888 0.900 0.3203)
+                   '(18 200 1 1.0))
+    '(48.0314 38.7789 191.0452)
+    0.02))
+  (should
+   (lcms-triple-approx-p
+    (lcms-xyz->jch '(0.1931 0.2393 0.1014)
+                   '(0.9888 0.90 0.3203)
+                   '(18 20 1 1.0))
+    '(47.6856 36.0527 185.3445)
+    0.09)))
+
 (ert-deftest lcms-dE-cam02-ucs-silver ()
   "Test CRI-CAM02-UCS deltaE metric values from colorspacious."
   (skip-unless (featurep 'lcms2))
@@ -114,4 +146,16 @@ lcms-rgb255->xyz
     8.503323264883667
     0.04)))
 
+(ert-deftest lcms-jmh->cam02-ucs-silver ()
+  "Compare JCh conversion to CAM02-UCS to values from colorspacious."
+  (skip-unless (featurep 'lcms2))
+  (should
+   (lcms-triple-approx-p (lcms-jch->jab '(50 20 10))
+                         '(62.96296296 16.22742674 2.86133316)
+                         0.05))
+  (should
+   (lcms-triple-approx-p (lcms-jch->jab '(10 60 100))
+                         '(15.88785047 -6.56546789 37.23461867)
+                         0.04)))
+
 ;;; lcms-tests.el ends here
-- 
2.14.2