videomixer: Add transparent background option for alpha channel formats

diff --git a/gst/videomixer/videomixer.c b/gst/videomixer/videomixer.c
index 1271d63216641669c286fe0c13a3c1077172e770..c7bc22404ee283d6463d199ddaba78204d85c282 100644 (file)
--- a/gst/videomixer/videomixer.c
+++ b/gst/videomixer/videomixer.c
@@ -533,6 +533,8 @@ gst_video_mixer_background_get_type (void)
     {VIDEO_MIXER_BACKGROUND_CHECKER, "Checker pattern", "checker"},
     {VIDEO_MIXER_BACKGROUND_BLACK, "Black", "black"},
     {VIDEO_MIXER_BACKGROUND_WHITE, "White", "white"},
+    {VIDEO_MIXER_BACKGROUND_TRANSPARENT,
+        "Transparent Background to enable further mixing", "transparent"},
     {0, NULL, NULL},
   };
 
@@ -1025,6 +1027,7 @@ gst_videomixer_setcaps (GstPad * pad, GstCaps * caps)
   GST_INFO_OBJECT (mixer, "set src caps: %" GST_PTR_FORMAT, caps);
 
   mixer->blend = NULL;
+  mixer->overlay = NULL;
   mixer->fill_checker = NULL;
   mixer->fill_color = NULL;
 
@@ -1034,114 +1037,133 @@ gst_videomixer_setcaps (GstPad * pad, GstCaps * caps)
   switch (mixer->fmt) {
     case GST_VIDEO_FORMAT_AYUV:
       mixer->blend = gst_video_mixer_blend_ayuv;
+      mixer->overlay = gst_video_mixer_overlay_ayuv;
       mixer->fill_checker = gst_video_mixer_fill_checker_ayuv;
       mixer->fill_color = gst_video_mixer_fill_color_ayuv;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_ARGB:
       mixer->blend = gst_video_mixer_blend_argb;
+      mixer->overlay = gst_video_mixer_overlay_argb;
       mixer->fill_checker = gst_video_mixer_fill_checker_argb;
       mixer->fill_color = gst_video_mixer_fill_color_argb;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_BGRA:
       mixer->blend = gst_video_mixer_blend_bgra;
+      mixer->overlay = gst_video_mixer_overlay_bgra;
       mixer->fill_checker = gst_video_mixer_fill_checker_bgra;
       mixer->fill_color = gst_video_mixer_fill_color_bgra;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_ABGR:
       mixer->blend = gst_video_mixer_blend_abgr;
+      mixer->overlay = gst_video_mixer_overlay_abgr;
       mixer->fill_checker = gst_video_mixer_fill_checker_abgr;
       mixer->fill_color = gst_video_mixer_fill_color_abgr;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_RGBA:
       mixer->blend = gst_video_mixer_blend_rgba;
+      mixer->overlay = gst_video_mixer_overlay_rgba;
       mixer->fill_checker = gst_video_mixer_fill_checker_rgba;
       mixer->fill_color = gst_video_mixer_fill_color_rgba;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_Y444:
       mixer->blend = gst_video_mixer_blend_y444;
+      mixer->overlay = mixer->blend;
       mixer->fill_checker = gst_video_mixer_fill_checker_y444;
       mixer->fill_color = gst_video_mixer_fill_color_y444;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_Y42B:
       mixer->blend = gst_video_mixer_blend_y42b;
+      mixer->overlay = mixer->blend;
       mixer->fill_checker = gst_video_mixer_fill_checker_y42b;
       mixer->fill_color = gst_video_mixer_fill_color_y42b;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_YUY2:
       mixer->blend = gst_video_mixer_blend_yuy2;
+      mixer->overlay = mixer->blend;
       mixer->fill_checker = gst_video_mixer_fill_checker_yuy2;
       mixer->fill_color = gst_video_mixer_fill_color_yuy2;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_UYVY:
       mixer->blend = gst_video_mixer_blend_uyvy;
+      mixer->overlay = mixer->blend;
       mixer->fill_checker = gst_video_mixer_fill_checker_uyvy;
       mixer->fill_color = gst_video_mixer_fill_color_uyvy;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_YVYU:
       mixer->blend = gst_video_mixer_blend_yvyu;
+      mixer->overlay = mixer->blend;
       mixer->fill_checker = gst_video_mixer_fill_checker_yvyu;
       mixer->fill_color = gst_video_mixer_fill_color_yvyu;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_I420:
       mixer->blend = gst_video_mixer_blend_i420;
+      mixer->overlay = mixer->blend;
       mixer->fill_checker = gst_video_mixer_fill_checker_i420;
       mixer->fill_color = gst_video_mixer_fill_color_i420;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_YV12:
       mixer->blend = gst_video_mixer_blend_yv12;
+      mixer->overlay = mixer->blend;
       mixer->fill_checker = gst_video_mixer_fill_checker_yv12;
       mixer->fill_color = gst_video_mixer_fill_color_yv12;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_Y41B:
       mixer->blend = gst_video_mixer_blend_y41b;
+      mixer->overlay = mixer->blend;
       mixer->fill_checker = gst_video_mixer_fill_checker_y41b;
       mixer->fill_color = gst_video_mixer_fill_color_y41b;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_RGB:
       mixer->blend = gst_video_mixer_blend_rgb;
+      mixer->overlay = mixer->blend;
       mixer->fill_checker = gst_video_mixer_fill_checker_rgb;
       mixer->fill_color = gst_video_mixer_fill_color_rgb;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_BGR:
       mixer->blend = gst_video_mixer_blend_bgr;
+      mixer->overlay = mixer->blend;
       mixer->fill_checker = gst_video_mixer_fill_checker_bgr;
       mixer->fill_color = gst_video_mixer_fill_color_bgr;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_xRGB:
       mixer->blend = gst_video_mixer_blend_xrgb;
+      mixer->overlay = mixer->blend;
       mixer->fill_checker = gst_video_mixer_fill_checker_xrgb;
       mixer->fill_color = gst_video_mixer_fill_color_xrgb;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_xBGR:
       mixer->blend = gst_video_mixer_blend_xbgr;
+      mixer->overlay = mixer->blend;
       mixer->fill_checker = gst_video_mixer_fill_checker_xbgr;
       mixer->fill_color = gst_video_mixer_fill_color_xbgr;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_RGBx:
       mixer->blend = gst_video_mixer_blend_rgbx;
+      mixer->overlay = mixer->blend;
       mixer->fill_checker = gst_video_mixer_fill_checker_rgbx;
       mixer->fill_color = gst_video_mixer_fill_color_rgbx;
       ret = TRUE;
       break;
     case GST_VIDEO_FORMAT_BGRx:
       mixer->blend = gst_video_mixer_blend_bgrx;
+      mixer->overlay = mixer->blend;
       mixer->fill_checker = gst_video_mixer_fill_checker_bgrx;
       mixer->fill_color = gst_video_mixer_fill_color_bgrx;
       ret = TRUE;
@@ -1387,6 +1409,13 @@ static void
 gst_videomixer_blend_buffers (GstVideoMixer * mix, GstBuffer * outbuf)
 {
   GSList *walk;
+  BlendFunction blend;
+  if (mix->background == VIDEO_MIXER_BACKGROUND_TRANSPARENT) {
+    blend = mix->overlay;
+  } else {
+    blend = mix->blend;
+  }
+
 
   walk = mix->sinkpads;
   while (walk) {                /* We walk with this list because it's ordered */
@@ -1411,7 +1440,7 @@ gst_videomixer_blend_buffers (GstVideoMixer * mix, GstBuffer * outbuf)
       if (GST_CLOCK_TIME_IS_VALID (stream_time))
         gst_object_sync_values (G_OBJECT (pad), stream_time);
 
-      mix->blend (GST_BUFFER_DATA (mixcol->buffer),
+      blend (GST_BUFFER_DATA (mixcol->buffer),
           pad->xpos, pad->ypos, pad->in_width, pad->in_height, pad->alpha,
           GST_BUFFER_DATA (outbuf), mix->out_width, mix->out_height);
     }
@@ -1580,6 +1609,11 @@ gst_videomixer_collected (GstCollectPads * pads, GstVideoMixer * mix)
       mix->fill_color (GST_BUFFER_DATA (outbuf), mix->out_width,
           mix->out_height, 240, 128, 128);
       break;
+    case VIDEO_MIXER_BACKGROUND_TRANSPARENT:
+      memset (GST_BUFFER_DATA (outbuf), 0,
+          gst_video_format_get_row_stride (mix->fmt, 0,
+              mix->out_width) * mix->out_height);
+      break;
   }
 
   gst_videomixer_blend_buffers (mix, outbuf);

diff --git a/gst/videomixer/videomixer.h b/gst/videomixer/videomixer.h
index 830f2885330784c6834bee14916331a2908967e4..fe55a5e20ef3085b35df83449865eb9a89f6cf7b 100644 (file)
--- a/gst/videomixer/videomixer.h
+++ b/gst/videomixer/videomixer.h
@@ -45,6 +45,7 @@ typedef struct _GstVideoMixerClass GstVideoMixerClass;
  * @VIDEO_MIXER_BACKGROUND_CHECKER: checker pattern background
  * @VIDEO_MIXER_BACKGROUND_BLACK: solid color black background
  * @VIDEO_MIXER_BACKGROUND_WHITE: solid color white background
+ * @VIDEO_MIXER_BACKGROUND_TRANSPARENT: background is left transparent and layers are composited using "A OVER B" composition rules. This is only applicable to AYUV and ARGB (and variants) as it preserves the alpha channel and allows for further mixing.
  *
  * The different backgrounds videomixer can blend over.
  */
@@ -52,7 +53,8 @@ typedef enum
 {
   VIDEO_MIXER_BACKGROUND_CHECKER,
   VIDEO_MIXER_BACKGROUND_BLACK,
-  VIDEO_MIXER_BACKGROUND_WHITE
+  VIDEO_MIXER_BACKGROUND_WHITE,
+  VIDEO_MIXER_BACKGROUND_TRANSPARENT,
 }
 GstVideoMixerBackground;
 
@@ -112,7 +114,7 @@ struct _GstVideoMixer
   gdouble proportion;
   GstClockTime earliest_time;
 
-  BlendFunction blend;
+  BlendFunction blend, overlay;
   FillCheckerFunction fill_checker;
   FillColorFunction fill_color;