[qcms] Allow negative XYZ for display profiles on the APPLE port

third_party/qcms/src/iccread.c

Index: third_party/qcms/src/iccread.c
diff --git a/third_party/qcms/src/iccread.c b/third_party/qcms/src/iccread.c
index b62f127dad4ef824fe66ae105c57afdaae65e643..0e34bad8bf21236b9e5c7ddaba569f908e43c391 100644
--- a/third_party/qcms/src/iccread.c
+++ b/third_party/qcms/src/iccread.c
@@ -253,82 +253,93 @@ static struct tag_index read_tag_table(qcms_profile *profile, struct mem_source
 	return index;
 }
 
-// Checks a profile for obvious inconsistencies and returns
-// true if the profile looks bogus and should probably be
-// ignored.
+/* Checks a profile for obvious inconsistencies and return true if the
+ * profile looks bogus and should probably be ignored.
+ */
 qcms_bool qcms_profile_is_bogus(qcms_profile *profile)
 {
-       float sum[3], target[3], tolerance[3];
-       float rX, rY, rZ, gX, gY, gZ, bX, bY, bZ;
-       bool negative;
-       unsigned i;
+        float rX, rY, rZ, gX, gY, gZ, bX, bY, bZ;
+        float target[3], tolerance[3], sum[3];
+        unsigned i;
 
-       // We currently only check the bogosity of RGB profiles
-       if (profile->color_space != RGB_SIGNATURE)
-	       return false;
+        // We currently only check the bogosity of RGB profiles.
+        if (profile->color_space != RGB_SIGNATURE)
+               return false;
 
-       if (qcms_supports_iccv4 && (profile->A2B0 || profile->B2A0))
+        if (qcms_supports_iccv4 && (profile->A2B0 || profile->B2A0))
                return false;
 
-       rX = s15Fixed16Number_to_float(profile->redColorant.X);
-       rY = s15Fixed16Number_to_float(profile->redColorant.Y);
-       rZ = s15Fixed16Number_to_float(profile->redColorant.Z);
+        rX = s15Fixed16Number_to_float(profile->redColorant.X);
+        rY = s15Fixed16Number_to_float(profile->redColorant.Y);
+        rZ = s15Fixed16Number_to_float(profile->redColorant.Z);
 
-       gX = s15Fixed16Number_to_float(profile->greenColorant.X);
-       gY = s15Fixed16Number_to_float(profile->greenColorant.Y);
-       gZ = s15Fixed16Number_to_float(profile->greenColorant.Z);
+        gX = s15Fixed16Number_to_float(profile->greenColorant.X);
+        gY = s15Fixed16Number_to_float(profile->greenColorant.Y);
+        gZ = s15Fixed16Number_to_float(profile->greenColorant.Z);
 
-       bX = s15Fixed16Number_to_float(profile->blueColorant.X);
-       bY = s15Fixed16Number_to_float(profile->blueColorant.Y);
-       bZ = s15Fixed16Number_to_float(profile->blueColorant.Z);
+        bX = s15Fixed16Number_to_float(profile->blueColorant.X);
+        bY = s15Fixed16Number_to_float(profile->blueColorant.Y);
+        bZ = s15Fixed16Number_to_float(profile->blueColorant.Z);
 
-       // Check if any of the XYZ values are negative (see mozilla bug 498245)
-       // CIEXYZ tristimulus values cannot be negative according to the spec.
-       negative =
-	       (rX < 0) || (rY < 0) || (rZ < 0) ||
-	       (gX < 0) || (gY < 0) || (gZ < 0) ||
-	       (bX < 0) || (bY < 0) || (bZ < 0);
+        // Build our target vector: CIE D50 white. See also mozilla bug 460629,
+        // and http://www.color.org/whyd50.xalter "Why is the media white point
+        // of a display profile always D50?"
 
-       if (negative)
-	       return true;
+        target[0] = (float) 0.96420;
+        target[1] = (float) 1.00000;
+        target[2] = (float) 0.82491;
 
+        // Our tolerance vector - Recommended by Chris Murphy [1] based on
+        // conversion from the L*a*b space criterion of no more than 3 in any
+        // one channel. This is similar to, but slightly more tolerant than
+        // Adobe's criterion. [1] https://bugzil.la/460629#c10
 
-       // Sum the values; they should add up to something close to white
-       sum[0] = rX + gX + bX;
-       sum[1] = rY + gY + bY;
-       sum[2] = rZ + gZ + bZ;
+        tolerance[0] = (float) 0.02;
+        tolerance[1] = (float) 0.02;
+        tolerance[2] = (float) 0.04;
 
-#if defined (_MSC_VER)
-#pragma warning(push)
-/* Disable double to float truncation warning 4305 */
-#pragma warning(disable:4305)
-#endif
-       // Build our target vector (see mozilla bug 460629)
-       target[0] = 0.96420;
-       target[1] = 1.00000;
-       target[2] = 0.82491;
-
-       // Our tolerance vector - Recommended by Chris Murphy based on
-       // conversion from the LAB space criterion of no more than 3 in any one
-       // channel. This is similar to, but slightly more tolerant than Adobe's
-       // criterion.
-       tolerance[0] = 0.02;
-       tolerance[1] = 0.02;
-       tolerance[2] = 0.04;
-
-#if defined (_MSC_VER)
-/* Restore warnings */
-#pragma warning(pop)
+        // Sum the XYZ values: they should add to D50 white, within tolerance.
+
+        // FIXME: this test assumes the TRC RGB curves equal 1.0 for the white
+        // input (255,255,255) RGB test color. For user display profiles, that
+        // is the normal case. Profiles with abnormal TRC exist. A better test
+        // would transform 255,255,255 white through the profile to either XYZ
+        // or L*a*b color and compare the result to D50 in XYZ or L*a*b color.
+
+        sum[0] = rX + gX + bX;
+        sum[1] = rY + gY + bY;
+        sum[2] = rZ + gZ + bZ;
+
+        for (i = 0; i < 3; ++i) {
+            if (!(((sum[i] - tolerance[i]) <= target[i]) &&
+                  ((sum[i] + tolerance[i]) >= target[i]))) {
+                return true; // out of tolerance: bogus
+            }
+        }
+
+#ifndef __APPLE__
+
+        // Check if any of the XYZ values are negative (see mozilla bug 498245)
+        // CIEXYZ tristimulus values cannot be negative according to the spec.
+
+        bool negative =
+            (rX < 0) || (rY < 0) || (rZ < 0) ||
+            (gX < 0) || (gY < 0) || (gZ < 0) ||
+            (bX < 0) || (bY < 0) || (bZ < 0);
+
+        if (negative)
+            return true; // bogus
+#else
+        // Chromatic adaption to D50 can result in negative XYZ, but the white
+        // point D50 tolerance test has passed. Accept negative values herein.
+        // See https://bugzilla.mozilla.org/show_bug.cgi?id=498245#c18 onwards
+        // for discussion about whether profile XYZ can or cannot be negative,
+        // per the spec. Also the https://bugzil.la/450923 user report.
+
+        // FIXME: allow this relaxation on all ports?
 #endif
-       // Compare with our tolerance
-       for (i = 0; i < 3; ++i) {
-           if (!(((sum[i] - tolerance[i]) <= target[i]) &&
-                 ((sum[i] + tolerance[i]) >= target[i])))
-               return true;
-       }
-
-       // All Good
-       return false;
+        // All good.
+        return false;
 }
 
 #define TAG_bXYZ 0x6258595a