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cairooverlay: Add property for drawing on a transparent surface and then blending

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This allows us to use the GstVideoOverlayComposition API and correctly
handle pre-multiplied alpha, while also only doing the alpha conversion
once instead of twice for the whole frame.

At a later point we can attach the meta to the buffer instead of
blending ourselves if downstream supports that.

https://bugzilla.gnome.org/show_bug.cgi?id=797091
This commit is contained in:
Sebastian Dröge 2018-09-25 15:31:20 +03:00
parent defae35035
commit 9844bdbf7a
2 changed files with 118 additions and 5 deletions
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114
ext/cairo/gstcairooverlay.c
View file

@ -119,6 +119,14 @@ GST_STATIC_PAD_TEMPLATE ("sink",
G_DEFINE_TYPE (GstCairoOverlay, gst_cairo_overlay, GST_TYPE_VIDEO_FILTER);
enum
{
PROP_0,
PROP_DRAW_ON_TRANSPARENT_SURFACE,
};
#define DEFAULT_DRAW_ON_TRANSPARENT_SURFACE (FALSE)
enum
{
SIGNAL_DRAW,
@ -128,6 +136,46 @@ enum
static guint gst_cairo_overlay_signals[N_SIGNALS];
static void
gst_cairo_overlay_set_property (GObject * object, guint property_id,
const GValue * value, GParamSpec * pspec)
{
GstCairoOverlay *overlay = GST_CAIRO_OVERLAY (object);
GST_OBJECT_LOCK (overlay);
switch (property_id) {
case PROP_DRAW_ON_TRANSPARENT_SURFACE:
overlay->draw_on_transparent_surface = g_value_get_boolean (value);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
break;
}
GST_OBJECT_UNLOCK (overlay);
}
static void
gst_cairo_overlay_get_property (GObject * object, guint property_id,
GValue * value, GParamSpec * pspec)
{
GstCairoOverlay *overlay = GST_CAIRO_OVERLAY (object);
GST_OBJECT_LOCK (overlay);
switch (property_id) {
case PROP_DRAW_ON_TRANSPARENT_SURFACE:
g_value_set_boolean (value, overlay->draw_on_transparent_surface);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
break;
}
GST_OBJECT_UNLOCK (overlay);
}
static gboolean
gst_cairo_overlay_set_info (GstVideoFilter * vfilter, GstCaps * in_caps,
GstVideoInfo * in_info, GstCaps * out_caps, GstVideoInfo * out_info)
@ -148,6 +196,7 @@ gst_cairo_overlay_transform_frame_ip (GstVideoFilter * vfilter,
cairo_surface_t *surface;
cairo_t *cr;
cairo_format_t format;
gboolean draw_on_transparent_surface = overlay->draw_on_transparent_surface;
switch (GST_VIDEO_FRAME_FORMAT (frame)) {
case GST_VIDEO_FORMAT_ARGB:
@ -169,10 +218,18 @@ gst_cairo_overlay_transform_frame_ip (GstVideoFilter * vfilter,
}
}
if (draw_on_transparent_surface) {
surface =
cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
GST_VIDEO_FRAME_WIDTH (frame), GST_VIDEO_FRAME_HEIGHT (frame));
} else {
/* FIXME: Need to pre-multiply the alpha in case of ARGB32 */
surface =
cairo_image_surface_create_for_data (GST_VIDEO_FRAME_PLANE_DATA (frame,
0), format, GST_VIDEO_FRAME_WIDTH (frame),
GST_VIDEO_FRAME_HEIGHT (frame), GST_VIDEO_FRAME_PLANE_STRIDE (frame, 0));
GST_VIDEO_FRAME_HEIGHT (frame), GST_VIDEO_FRAME_PLANE_STRIDE (frame,
0));
}
if (G_UNLIKELY (!surface))
return GST_FLOW_ERROR;
@ -188,7 +245,47 @@ gst_cairo_overlay_transform_frame_ip (GstVideoFilter * vfilter,
NULL);
cairo_destroy (cr);
if (draw_on_transparent_surface) {
guint size;
GstBuffer *surface_buffer;
GstVideoOverlayRectangle *rect;
GstVideoOverlayComposition *composition;
gsize offset[GST_VIDEO_MAX_PLANES] = { 0, };
gint stride[GST_VIDEO_MAX_PLANES] = { 0, };
size =
cairo_image_surface_get_height (surface) *
cairo_image_surface_get_stride (surface);
stride[0] = cairo_image_surface_get_stride (surface);
/* Create a GstVideoOverlayComposition for blending, this handles
* pre-multiplied alpha correctly */
surface_buffer =
gst_buffer_new_wrapped_full (0, cairo_image_surface_get_data (surface),
size, 0, size, surface, (GDestroyNotify) cairo_surface_destroy);
gst_buffer_add_video_meta_full (surface_buffer, GST_VIDEO_FRAME_FLAG_NONE,
(G_BYTE_ORDER ==
G_LITTLE_ENDIAN ? GST_VIDEO_FORMAT_BGRA : GST_VIDEO_FORMAT_ARGB),
GST_VIDEO_FRAME_WIDTH (frame), GST_VIDEO_FRAME_HEIGHT (frame), 1,
offset, stride);
rect =
gst_video_overlay_rectangle_new_raw (surface_buffer, 0, 0,
GST_VIDEO_FRAME_WIDTH (frame), GST_VIDEO_FRAME_HEIGHT (frame),
GST_VIDEO_OVERLAY_FORMAT_FLAG_PREMULTIPLIED_ALPHA);
gst_buffer_unref (surface_buffer);
composition = gst_video_overlay_composition_new (rect);
gst_video_overlay_rectangle_unref (rect);
g_assert (gst_video_overlay_composition_blend (composition, frame));
gst_video_overlay_composition_unref (composition);
/* TODO: Put as meta on the buffer */
} else {
cairo_surface_destroy (surface);
/* FIXME: Need to un-premultiply the alpha in case of ARGB32 */
}
return GST_FLOW_OK;
}
@ -198,13 +295,28 @@ gst_cairo_overlay_class_init (GstCairoOverlayClass * klass)
{
GstVideoFilterClass *vfilter_class;
GstElementClass *element_class;
GObjectClass *gobject_class;
vfilter_class = (GstVideoFilterClass *) klass;
element_class = (GstElementClass *) klass;
gobject_class = (GObjectClass *) klass;
vfilter_class->set_info = gst_cairo_overlay_set_info;
vfilter_class->transform_frame_ip = gst_cairo_overlay_transform_frame_ip;
gobject_class->set_property = gst_cairo_overlay_set_property;
gobject_class->get_property = gst_cairo_overlay_get_property;
g_object_class_install_property (gobject_class,
PROP_DRAW_ON_TRANSPARENT_SURFACE,
g_param_spec_boolean ("draw-on-transparent-surface",
"Draw on transparent surface",
"Let the draw signal work on a transparent surface "
"and blend the results with the video at a later time",
DEFAULT_DRAW_ON_TRANSPARENT_SURFACE,
GST_PARAM_CONTROLLABLE | GST_PARAM_MUTABLE_PLAYING | G_PARAM_READWRITE
| G_PARAM_STATIC_STRINGS));
/**
* GstCairoOverlay::draw:
* @overlay: Overlay element emitting the signal.

1
ext/cairo/gstcairooverlay.h
View file

@ -45,6 +45,7 @@ typedef struct _GstCairoOverlayClass GstCairoOverlayClass;
struct _GstCairoOverlay {
GstVideoFilter video_filter;
gboolean draw_on_transparent_surface;
};
struct _GstCairoOverlayClass {