Document sws_getIdentityVec().

git-svn-id: file:///var/local/repositories/mplayer/trunk/libswscale@28533 b3059339-0415-0410-9bf9-f77b7e298cf2

swscale.h

@@ -141,6 +141,11 @@ SwsVector *sws_getGaussianVec(double variance, double quality);
  * with the same value \p c.
  */
 SwsVector *sws_getConstVec(double c, int length);
+
+/**
+ * Allocates and returns a vector with just one coefficient, with
+ * value 1.0.
+ */
 SwsVector *sws_getIdentityVec(void);
 
 /**