screenshot: allow taking screenshots with subtitles

This adds a new screenshot mode "subtitles", which basically takes the
video frame as decoded, and renders subtitles into it.

This may fail for some pixel formats, because libswscale sucks. If this
becomes ever a real problem, the code could be changed to convert the
image to RGBA first (or whatever the image writer wants), and then
render the subtitles into it. This would avoid the additional image
copy needed with vo_xv too. But for now, it seems better to go with the
current method in the common case: vo_opengl creates an image copy
anyway, and drawing bitmaps to yv12 is better, as no color space
conversion is involved in draw_bmp.c's up/downsampling conversion.

1 files changed, 2 insertions, 0 deletions

diff --git a/libvo/video_out.h b/libvo/video_out.h
index ffb5c0c4f3..1c48b5fb06 100644
--- a/libvo/video_out.h
+++ b/libvo/video_out.h
@@ -105,6 +105,8 @@ struct voctrl_screenshot_args {
     // image data directly.
     // Is never NULL. (Failure has to be indicated by returning VO_FALSE.)
     struct mp_image *out_image;
+    // Whether the VO rendered OSD/subtitles into out_image
+    bool has_osd;
 };
 
 typedef struct {