'A OVER B' compositing is explained at
http://en.wikipedia.org/wiki/Alpha_compositing.
Previously, overlaying text on a transparent background image left the
text overlay also transparent. This pipeline shows such an example:
gst-launch videotestsrc pattern=white ! video/x-raw-yuv,format=\(fourcc\)AYUV ! alpha alpha=0.0 ! textoverlay text=Testing auto-resize=False font-desc=60px ! videomixer ! ffmpegcolorspace ! autovideosink
With this patch, text is composited "OVER" the background image and
thus is visible regardless of the alpha of the background image. The
overlay in the above pipeline works after applying this patch.
Pango is not reentrant. Use a class wide mutex to protect pange use in
gst_text_overlay_render_pangocairo(). This works reliable in contrast to the
hack in my previous commit.
Fixes Bug #412678
In case of odd values for xpos or ypos, the division by two in CbCr
plane would result in an off-by-one error, which in the case of NV12,
NV21, or UYVY would cause inversion of blue and red colors. (And
would be not so easily noticed for I420 as it would just cause the
chroma to be offset slightly from the luma.)
This patch also fixes a silly typo from the earlier patch which
added NV12 support that broke UYVY support.
The textoverlay element will rerender the text string whenever
overlay sets the 'need_render' flag to TRUE. Previously, we
lazily set the flag to TRUE every time the time string was requested.
Now, we save a copy of the previously given string, and only set
'need_render' to TRUE if the string has changed.
In my tests with a 30fps video stream, and a time string including
a seconds field, this change reduced the CPU usage of the clockoverlay
element from 60% to 5%.
Fixes bug #627780.
Rather than only left, right, top, etc, allow for horizontal and vertical
positioning on a scale from 0 to 1.
Also cater for configuring rendered text color.
Fixes#624920.
API: GstTextOverlay:xpos
API: GstTextOverlay:ypos
API: GstTextOverlay:color
And fix the resulting compile failures.
I'm sorry about the patch necessary to gstclockoverlay.h but after
talking to Tim we decided we can live with it.
This reverts commit 60aa09d28c.
First drawing the real text and then the outline produces ugly
text in lower resolutions. The outline line width needs to be somehow
changed relative to the resolution. Fixes bug #602924.
