avfilter: add maskfun filter

Changelog

@@ -14,6 +14,7 @@ version <next>:
 - vividas demuxer
 - hymt decoder
 - anlmdn filter
+- maskfun filter
 
 
 version 4.1:

doc/filters.texi

@@ -11914,6 +11914,33 @@ copied from first stream.
 By default value 0xf, all planes will be processed.
 @end table
 
+@section maskfun
+Create mask from input video.
+
+For example it is useful to create motion masks after @code{tblend} filter.
+
+This filter accepts the following options:
+
+@table @option
+@item low
+Set low threshold. Any pixel component lower or exact than this value will be set to 0.
+
+@item high
+Set high threshold. Any pixel component higher than this value will be set to max value
+allowed for current pixel format.
+
+@item planes
+Set planes to filter, by default all available planes are filtered.
+
+@item fill
+Fill all frame pixels with this value.
+
+@item sum
+Set max average pixel value for frame. If sum of all pixel components is higher that this
+average, output frame will be completely filled with value set by @var{fill} option.
+Typically useful for scene changes when used in combination with @code{tblend} filter.
+@end table
+
 @section mcdeint
 
 Apply motion-compensation deinterlacing.

libavfilter/Makefile

@@ -280,6 +280,7 @@ OBJS-$(CONFIG_LUTRGB_FILTER)                 += vf_lut.o
 OBJS-$(CONFIG_LUTYUV_FILTER)                 += vf_lut.o
 OBJS-$(CONFIG_MASKEDCLAMP_FILTER)            += vf_maskedclamp.o framesync.o
 OBJS-$(CONFIG_MASKEDMERGE_FILTER)            += vf_maskedmerge.o framesync.o
+OBJS-$(CONFIG_MASKFUN_FILTER)                += vf_maskfun.o
 OBJS-$(CONFIG_MCDEINT_FILTER)                += vf_mcdeint.o
 OBJS-$(CONFIG_MERGEPLANES_FILTER)            += vf_mergeplanes.o framesync.o
 OBJS-$(CONFIG_MESTIMATE_FILTER)              += vf_mestimate.o motion_estimation.o

libavfilter/allfilters.c

@@ -266,6 +266,7 @@ extern AVFilter ff_vf_lutrgb;
 extern AVFilter ff_vf_lutyuv;
 extern AVFilter ff_vf_maskedclamp;
 extern AVFilter ff_vf_maskedmerge;
+extern AVFilter ff_vf_maskfun;
 extern AVFilter ff_vf_mcdeint;
 extern AVFilter ff_vf_mergeplanes;
 extern AVFilter ff_vf_mestimate;

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   7
-#define LIBAVFILTER_VERSION_MINOR  47
+#define LIBAVFILTER_VERSION_MINOR  48
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \