diff --git a/cogl-color.h b/cogl-color.h
index 0cbc479a4..73de891de 100644
--- a/cogl-color.h
+++ b/cogl-color.h
@@ -228,6 +228,18 @@ float     cogl_color_get_blue        (const CoglColor *color);
  */
 float     cogl_color_get_alpha       (const CoglColor *color);
 
+/**
+ * cogl_color_premultiply:
+ * @color: the color to premultiply
+ *
+ * Converts a non-premultiplied color to a pre-multiplied color. For
+ * example, semi-transparent red is (1.0, 0, 0, 0.5) when non-premultiplied
+ * and (0.5, 0, 0, 0.5) when premultiplied.
+ *
+ * Since: 1.0
+ */
+void cogl_color_premultiply (CoglColor *color);
+
 G_END_DECLS
 
 #endif /* __COGL_COLOR_H__ */
diff --git a/common/cogl-color.c b/common/cogl-color.c
index 306005f2f..df338fcc4 100644
--- a/common/cogl-color.c
+++ b/common/cogl-color.c
@@ -153,6 +153,14 @@ cogl_color_get_alpha (const CoglColor *color)
   return  ((float) color->alpha / 255.0);
 }
 
+void
+cogl_color_premultiply (CoglColor *color)
+{
+  color->red = (color->red * color->alpha + 128) / 255;
+  color->green = (color->green * color->alpha + 128) / 255;
+  color->blue = (color->blue * color->alpha + 128) / 255;
+}
+
 void
 cogl_set_source_color4ub (guint8 red,
                           guint8 green,