rename negative to invert (mirror y) and add negative that reverses (mirror x)

Signed-off-by: Mattias Andrée <maandree@operamail.com>

3 files changed, 36 insertions, 4 deletions

diff --git a/examples/comprehensive b/examples/comprehensive
index 9b9bf36..bcb20c1 100644
--- a/examples/comprehensive
+++ b/examples/comprehensive
@@ -3,7 +3,8 @@
 # This example is complete with exceptions for less normal colour
 # curve modifiers: nothing else than CIE 1964 10 degree CMF for
 # colour temperature, not use of temporarly linear RGB curves,
-# negative image, sigmoid correction, or free function modifier.
+# negative image, inverted image, sigmoid correction, or free
+# function modifier.
 
 
 # Geographical coodinates.
diff --git a/info/blueshift.texinfo b/info/blueshift.texinfo
index d32aba6..0360956 100644
--- a/info/blueshift.texinfo
+++ b/info/blueshift.texinfo
@@ -321,13 +321,27 @@ and @code{b} on the red, green and blue curves,
 respectively.
 
 @item negative()
-Inverts the all values on the colour curves.
+Reverse the colour curves on the encoding axis.
+This creates a negative image with preserved gamma.
 
 @item negative(rgb)
-Inverts the all values on the colour curves
+Reverse the colour curves on the encoding axis
 if @code{rgb} is @code{True}.
 
 @item negative(r, g, b)
+Reverse the red, green and blue curves on the
+encoding axis if @code{r}, @code{g} and @code{b}
+are @code{True}, respectively.
+
+@item invert()
+Inverts the all values on the colour curves.
+This creates a negative image with inverted gamma.
+
+@item invert(rgb)
+Inverts the all values on the colour curves
+if @code{rgb} is @code{True}.
+
+@item invert(r, g, b)
 Inverts the all values on the red, green and
 blue curves if @code{r}, @code{g} and @code{b}
 are @code{True}, respectively.
diff --git a/src/curve.py b/src/curve.py
index 6446a2a..001108f 100644
--- a/src/curve.py
+++ b/src/curve.py
@@ -336,7 +336,24 @@ def gamma(r, g = None, b = None):
     
 def negative(r = True, g = None, b = None):
     '''
-    Invert the colour curves (negative image)
+    Revese the colour curves (negative image with gamma preservation)
+    
+    @param  r:bool   Whether to invert the red curve
+    @param  g:bool?  Whether to invert the green curve, defaults to `r` if `None`
+    @param  b:bool?  Whether to invert the blue curve, defaults to `r` if `None`
+    '''
+    if g is None:  g = r
+    if b is None:  b = r
+    for (curve, setting) in curves(r, g, b):
+        if setting:
+            for i in range(i_size // 2):
+                j = i_size - 1 - i
+                curve[i], curve[j] = curve[j], curve[i]
+
+
+def invert(r = True, g = None, b = None):
+    '''
+    Invert the colour curves (negative image with gamma invertion)
     
     @param  r:bool   Whether to invert the red curve
     @param  g:bool?  Whether to invert the green curve, defaults to `r` if `None`