lavfi: Port drawtext filter by Hemanth from the libavfilter soc repo

With the following additions:
* support to anti-aliased glyph rendering
* support to UTF-8 text and Unicode chars rendering
* support for RGB packed formats
* fix minor errors and typos in the filter description
* extend/clarify examples in the filter description
Signed-off-by: Anton Khirnov <anton@khirnov.net>

configure

@@ -169,6 +169,7 @@ External library support:
                            and libraw1394 [no]
   --enable-libdirac        enable Dirac support via libdirac [no]
   --enable-libfaac         enable FAAC support via libfaac [no]
+  --enable-libfreetype     enable libfreetype [no]
   --enable-libgsm          enable GSM support via libgsm [no]
   --enable-libmp3lame      enable MP3 encoding via libmp3lame [no]
   --enable-libnut          enable NUT (de)muxing via libnut,
@@ -928,6 +929,7 @@ CONFIG_LIST="
     libdc1394
     libdirac
     libfaac
+    libfreetype
     libgsm
     libmp3lame
     libnut
@@ -1077,6 +1079,7 @@ HAVE_LIST="
     llrintf
     local_aligned_16
     local_aligned_8
+    localtime_r
     log2
     log2f
     loongson
@@ -1462,6 +1465,7 @@ udp_protocol_deps="network"
 # filters
 blackframe_filter_deps="gpl"
 cropdetect_filter_deps="gpl"
+drawtext_filter_deps="libfreetype"
 frei0r_filter_deps="frei0r dlopen strtok_r"
 frei0r_src_filter_deps="frei0r dlopen strtok_r"
 hqdn3d_filter_deps="gpl"
@@ -2782,6 +2786,7 @@ check_func  getrusage
 check_struct "sys/time.h sys/resource.h" "struct rusage" ru_maxrss
 check_func  inet_aton $network_extralibs
 check_func  isatty
+check_func  localtime_r
 check_func  ${malloc_prefix}memalign            && enable memalign
 check_func  mkstemp
 check_func  mmap
@@ -2868,6 +2873,7 @@ enabled libdirac   && require_pkg_config dirac                          \
     "libdirac_decoder/dirac_parser.h libdirac_encoder/dirac_encoder.h"  \
     "dirac_decoder_init dirac_encoder_init"
 enabled libfaac    && require2 libfaac "stdint.h faac.h" faacEncGetVersion -lfaac
+enabled libfreetype && require_pkg_config freetype2 "ft2build.h freetype/freetype.h" FT_Init_FreeType
 enabled libgsm     && require  libgsm gsm/gsm.h gsm_create -lgsm
 enabled libmp3lame && require  "libmp3lame >= 3.98.3" lame/lame.h lame_set_VBR_quality -lmp3lame
 enabled libnut     && require  libnut libnut.h nut_demuxer_init -lnut

doc/filters.texi

@@ -353,6 +353,129 @@ drawbox
 drawbox=10:20:200:60:red@@0.5"
 @end example
 
+@section drawtext
+
+Draw text string or text from specified file on top of video using the
+libfreetype library.
+
+To enable compilation of this filter you need to configure FFmpeg with
+@code{--enable-libfreetype}.
+
+The filter also recognizes strftime() sequences in the provided text
+and expands them accordingly. Check the documentation of strftime().
+
+The filter accepts parameters as a list of @var{key}=@var{value} pairs,
+separated by ":".
+
+The description of the accepted parameters follows.
+
+@table @option
+
+@item fontfile
+The font file to be used for drawing text. Path must be included.
+This parameter is mandatory.
+
+@item text
+The text string to be drawn. The text must be a sequence of UTF-8
+encoded characters.
+This parameter is mandatory if no file is specified with the parameter
+@var{textfile}.
+
+@item textfile
+A text file containing text to be drawn. The text must be a sequence
+of UTF-8 encoded characters.
+
+This parameter is mandatory if no text string is specified with the
+parameter @var{text}.
+
+If both text and textfile are specified, an error is thrown.
+
+@item x, y
+The offsets where text will be drawn within the video frame.
+Relative to the top/left border of the output image.
+
+The default value of @var{x} and @var{y} is 0.
+
+@item fontsize
+The font size to be used for drawing text.
+The default value of @var{fontsize} is 16.
+
+@item fontcolor
+The color to be used for drawing fonts.
+Either a string (e.g. "red") or in 0xRRGGBB[AA] format
+(e.g. "0xff000033"), possibly followed by an alpha specifier.
+The default value of @var{fontcolor} is "black".
+
+@item boxcolor
+The color to be used for drawing box around text.
+Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
+(e.g. "0xff00ff"), possibly followed by an alpha specifier.
+The default value of @var{boxcolor} is "white".
+
+@item box
+Used to draw a box around text using background color.
+Value should be either 1 (enable) or 0 (disable).
+The default value of @var{box} is 0.
+
+@item ft_load_flags
+Flags to be used for loading the fonts.
+
+The flags map the corresponding flags supported by libfreetype, and are
+a combination of the following values:
+@table @var
+@item default
+@item no_scale
+@item no_hinting
+@item render
+@item no_bitmap
+@item vertical_layout
+@item force_autohint
+@item crop_bitmap
+@item pedantic
+@item ignore_global_advance_width
+@item no_recurse
+@item ignore_transform
+@item monochrome
+@item linear_design
+@item no_autohint
+@item end table
+@end table
+
+Default value is "render".
+
+For more information consult the documentation for the FT_LOAD_*
+libfreetype flags.
+
+@item tabsize
+The size in number of spaces to use for rendering the tab.
+Default value is 4.
+@end table
+
+For example the command:
+@example
+drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
+@end example
+
+will draw "Test Text" with font FreeSerif, using the default values
+for the optional parameters.
+
+The command:
+@example
+drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
+          x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2"
+@end example
+
+will draw 'Test Text' with font FreeSerif of size 24 at position x=100
+and y=50 (counting from the top-left corner of the screen), text is
+yellow with a red box around it. Both the text and the box have an
+opacity of 20%.
+
+Note that the double quotes are not necessary if spaces are not used
+within the parameter list.
+
+For more information about libfreetype, check:
+@url{http://www.freetype.org/}.
+
 @section fade
 
 Apply fade-in/out effect to input video.

libavfilter/Makefile

@@ -26,6 +26,7 @@ OBJS-$(CONFIG_COPY_FILTER)                   += vf_copy.o
 OBJS-$(CONFIG_CROP_FILTER)                   += vf_crop.o
 OBJS-$(CONFIG_CROPDETECT_FILTER)             += vf_cropdetect.o
 OBJS-$(CONFIG_DRAWBOX_FILTER)                += vf_drawbox.o
+OBJS-$(CONFIG_DRAWTEXT_FILTER)               += vf_drawtext.o
 OBJS-$(CONFIG_FADE_FILTER)                   += vf_fade.o
 OBJS-$(CONFIG_FIELDORDER_FILTER)             += vf_fieldorder.o
 OBJS-$(CONFIG_FIFO_FILTER)                   += vf_fifo.o

libavfilter/allfilters.c

@@ -45,6 +45,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER (CROP,        crop,        vf);
     REGISTER_FILTER (CROPDETECT,  cropdetect,  vf);
     REGISTER_FILTER (DRAWBOX,     drawbox,     vf);
+    REGISTER_FILTER (DRAWTEXT,    drawtext,    vf);
     REGISTER_FILTER (FADE,        fade,        vf);
     REGISTER_FILTER (FIELDORDER,  fieldorder,  vf);
     REGISTER_FILTER (FIFO,        fifo,        vf);

libavfilter/avfilter.h

@@ -26,8 +26,8 @@
 #include "libavutil/samplefmt.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  2
-#define LIBAVFILTER_VERSION_MINOR  3
-#define LIBAVFILTER_VERSION_MICRO  1
+#define LIBAVFILTER_VERSION_MINOR  4
+#define LIBAVFILTER_VERSION_MICRO  0
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \