avfilter/drawutils: allow drawing opaque text on transparent background

Signed-off-by: Paul B Mahol <onemda@gmail.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/libavfilter/drawutils.h b/libavfilter/drawutils.h
index 1fb3e4f256..cf53635456 100644
--- a/libavfilter/drawutils.h
+++ b/libavfilter/drawutils.h
@@ -55,6 +55,7 @@ typedef struct FFDrawContext {
     uint8_t vsub[MAX_PLANES];  /*< vertical subsampling */
     uint8_t hsub_max;
     uint8_t vsub_max;
+    unsigned flags;
 } FFDrawContext;
 
 typedef struct FFDrawColor {
@@ -67,11 +68,16 @@ typedef struct FFDrawColor {
 } FFDrawColor;
 
 /**
+  * Process alpha pixel component.
+  */
+#define FF_DRAW_PROCESS_ALPHA 1
+
+/**
  * Init a draw context.
  *
  * Only a limited number of pixel formats are supported, if format is not
  * supported the function will return an error.
- * No flags currently defined.
+ * flags is combination of FF_DRAW_* flags.
  * @return  0 for success, < 0 for error
  */
 int ff_draw_init(FFDrawContext *draw, enum AVPixelFormat format, unsigned flags);