Add CAM02 JCh and CAM02-UCS J'a'b' conversions

* 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.
* etc/NEWS: Mention new functions.

1 files changed, 44 insertions, 0 deletions

diff --git a/test/src/lcms-tests.el b/test/src/lcms-tests.el
index d6d1d16b9ad..cc324af68ba 100644
--- a/test/src/lcms-tests.el
+++ b/test/src/lcms-tests.el
@@ -94,6 +94,38 @@ B is considered the exact value."
     (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 @@ B is considered the exact value."
     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