[Gzz-commits] gzz/gfx libcolor/spaces.py util/papersampler.py

[Janne V. Kujala]

CVSROOT:        /cvsroot/gzz
Module name:    gzz
Changes by:     Janne V. Kujala <address@hidden>        03/03/09 05:39:17

Modified files:
        gfx/libcolor   : spaces.py 
        gfx/util       : papersampler.py 

Log message:
        Add gamma correction in the color space conversion so that the default 
(nonlinear) display gamma can be used

CVSWeb URLs:
http://savannah.gnu.org/cgi-bin/viewcvs/gzz/gzz/gfx/libcolor/spaces.py.diff?tr1=1.15&tr2=1.16&r1=text&r2=text
http://savannah.gnu.org/cgi-bin/viewcvs/gzz/gzz/gfx/util/papersampler.py.diff?tr1=1.26&tr2=1.27&r1=text&r2=text

Patches:
Index: gzz/gfx/libcolor/spaces.py
diff -u gzz/gfx/libcolor/spaces.py:1.15 gzz/gfx/libcolor/spaces.py:1.16
--- gzz/gfx/libcolor/spaces.py:1.15     Fri Feb 21 15:02:32 2003
+++ gzz/gfx/libcolor/spaces.py  Sun Mar  9 05:39:16 2003
@@ -155,6 +155,15 @@
 
 Wr,Wg,Wb = 0.3, 0.59, 0.11
 
+# Gamma correction used with the perceptual non-linearity in YtoL and LtoY
+# conversion functions.
+#
+gamma = 2
+#
+# Usually, the default display gamma of 1.0 actually yields an intensity
+# exponent of 0.5 so gamma correction of 2.0 here should result in linear
+# intensity. (The CIE L* computation assumes linear intensity).
+
 def YSTtoRGB(v):
     n = 1.0 / (Wr+Wg+Wb)
     mat =  [ [n, n*(Wg+Wb), n*(Wb - Wg)  / math.sqrt(3) ],
@@ -212,6 +221,7 @@
     Y: luminance between 0 and 1
     returns: lightness between 0 and 100
     """
+    Y = Y**gamma
     if Y <= (216./24389):
         return Y * (24389./27)
     else:
@@ -224,6 +234,6 @@
     returns: luminance between 0 and 1
     """
     if L <= 8:
-        return L * (27./24389)
+        return pow(L * (27./24389), 1.0 / gamma)
     else:
-        return pow((L + 16.0) / 116, 3)
+        return pow((L + 16.0) / 116, 3.0 / gamma)
Index: gzz/gfx/util/papersampler.py
diff -u gzz/gfx/util/papersampler.py:1.26 gzz/gfx/util/papersampler.py:1.27
--- gzz/gfx/util/papersampler.py:1.26   Wed Mar  5 05:23:05 2003
+++ gzz/gfx/util/papersampler.py        Sun Mar  9 05:39:17 2003
@@ -258,16 +258,16 @@
         w.setLocation(0,0,xs,ys)
 
         def star(vs):
-            putText(vs, 0, "*", x=xs*.5-10, y=ys*.6, h = 100)
+            putText(vs, 0, "*", x=xs*.5-10, y=ys*.6-100, h = 100)
 
         def space(vs):
-            putText(vs, 0, "Press space to start", x=xs*.5-350, y=ys*.6, h = 
100)
+            putText(vs, 0, "Press space to start", x=xs*.5-350, y=ys*.6-100, h 
= 100)
         
         doFrame(star, "tmp/star")
         doFrame(space, "tmp/space")
 
-       createPurePapers()
-       createTextPapers()
+       #createPurePapers()
+       #createTextPapers()
 
 
 gfxapi = GraphicsAPI.getInstance()