add tests, fixes errors, and improve percision

Signed-off-by: Mattias Andrée <maandree@kth.se>

2 files changed, 5 insertions, 14 deletions

diff --git a/doc/info/chap/colour-spaces.texinfo b/doc/info/chap/colour-spaces.texinfo
index eb26ba0..a214feb 100644
--- a/doc/info/chap/colour-spaces.texinfo
+++ b/doc/info/chap/colour-spaces.texinfo
@@ -403,21 +403,8 @@ function is available for your use:
 @table @code
 @item double libcolour_srgb_encode(double x)
 Applies the sRGB transfer function.
-It's full code is
-@example
-return x <= 0.0031306684425217108
-       ? 12.92 * x
-       : 1.055 * pow(x, 1 / 2.4) - 0.055;
-@end example
-
 @item double libcolour_srgb_decode(double x)
 Unapplies the sRGB transfer function.
-It's full code is
-@example
-return x <= 0.040448236277380506 
-       ? x / 12.92
-       : pow((x + 0.055) / 1.055, 2.4);
-@end example
 @end table
 
 
diff --git a/doc/info/chap/functions.texinfo b/doc/info/chap/functions.texinfo
index b47a584..9ddefdf 100644
--- a/doc/info/chap/functions.texinfo
+++ b/doc/info/chap/functions.texinfo
@@ -18,7 +18,11 @@ Described in @ref{sRGB}.
 
 @item int libcolour_delta_e(const libcolour_colour_t*, const libcolour_colour_t*, double*)
 Calculates the @math{\Delta E^*_{ab}} distance
-(the distance in CIE L*a*b*) of two colours.
+(the distance in CIE L*a*b*) of two colours,
+and outputs it to the last parameter.
+Returns 0 on success and @math{-1} one error.
+This function fails if and only if
+@code{libcolour_convert} fails.
 
 @item int libcolour_proper(libcolour_colour_t*)
 Sets any member or submember that may be