Extend color syntax, make it accept an alpha component specifier.

Originally committed as revision 23835 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 9 insertions, 1 deletions

diff --git a/libavfilter/parseutils.h b/libavfilter/parseutils.h
index 8ad7b8b5e6..f699e9d34a 100644
--- a/libavfilter/parseutils.h
+++ b/libavfilter/parseutils.h
@@ -46,7 +46,15 @@ char *av_get_token(const char **buf, const char *term);
  * Puts the RGBA values that correspond to color_string in rgba_color.
  *
  * @param color_string a string specifying a color. It can be the name of
- * a color (case insensitive match) or a 0xRRGGBB[AA] sequence.
+ * a color (case insensitive match) or a 0xRRGGBB[AA] sequence,
+ * possibly followed by "@" and a string representing the alpha
+ * component.
+ * The alpha component may be a string composed by "0x" followed by an
+ * hexadecimal number or a base-10 number between 0 and 255, or a
+ * decimal number between 0.0 and 1.0, which represents the opacity
+ * value (0/0x00/0.0 means completely transparent, 255/0xff/1.0
+ * completely opaque).
+ * If the alpha component is not specified then 255 is assumed.
  * The string "random" will result in a random color.
  * @return >= 0 in case of success, a negative value in case of
  * failure (for example if color_string cannot be parsed).