fix t_xyz2lab

CHANGES

@@ -1,3 +1,5 @@
+- fix t_xyz2lab - thanks @vadim-160102
+
 1.005 2020-09-17
 - eliminate // to keep 5.006 compat
 

lib/PDL/Transform/Color.pm

@@ -1539,9 +1539,7 @@ sub t_xyz2lab {
     my $wp_xyy = xyy_from_illuminant($me->{params}->{white});
     $me->{params}->{wp_xyz} = $wp_xyy->copy;
     $me->{params}->{wp_xyz}->slice('2') .= 1 - $wp_xyy->slice('0') - $wp_xyy->slice('1');
-    $me->{params}->{wp_xyz} *= $wp_xyy->slice('2');
-
-
+    $me->{params}->{wp_xyz} *= $wp_xyy->slice('2') / $wp_xyy->slice('1');
     # input is XYZ by the time it gets here
     $me->{func} = sub {
 	my($in,$opt) = @_;

t/color.t

@@ -167,11 +167,17 @@ ok(all( ($aa > $a -1e-10) & ($aa < $a + 1e-10) ),"decoding undoes coding");
 # (minimal testing)
 $a = xvals(101)/100;
 eval {$t = t_pc();};
-ok(($@ && $@=~m/^Usage\:/), "t_pc with no arguments died and threw out an info message");
+like $@, qr/^Usage\:/, "t_pc with no arguments died and threw out an info message";
 eval {$t = t_pc('sepia');};
 is $@, '', "t_pc('sepia') ran OK";
 eval {$b=$a->apply($t);};
 is $@, '', "t_pc applied OK";
 ok($b->ndims==2 && $b->dim(0)==3, "t_pc created an RGB output");
 
+eval {$t = t_xyz2lab();};
+is $@, '', "t_xyz2lab ran OK";
+eval {$b=pdl(1,1,1)->apply($t);};
+is $@, '', "t_xyz2lab applied OK";
+ok all(approx $b, pdl(100, 8.5841461, 5.5183538)), 't_xyz2lab right values' or diag "got=$b";
+
 done_testing;