avfilter: add gradients source video filter

Changelog

@@ -68,6 +68,7 @@ version <next>:
 - pcm_rechunk bitstream filter
 - scdet filter
 - NotchLC decoder
+- gradients source video filter
 
 
 version 4.2:

doc/filters.texi

@@ -22281,6 +22281,33 @@ need for a nullsrc video source.
 @end itemize
 
 
+@section gradients
+Generate several gradients.
+
+@table @option
+@item size, s
+Set frame size. For the syntax of this option, check the @ref{video size syntax,,"Video
+size" section in the ffmpeg-utils manual,ffmpeg-utils}. Default value is "640x480".
+
+@item rate, r
+Set frame rate, expressed as number of frames per second. Default
+value is "25".
+
+@item c0, c1, c2, c3, c4, c5, c6, c7
+Set 8 colors. Default values for colors is to pick random one.
+
+@item x0, y0, y0, y1
+Set gradient line source and destination points. If negative or out of range, random ones
+are picked.
+
+@item nb_colors, n
+Set number of colors to use at once. Allowed range is from 2 to 8. Default value is 2.
+
+@item seed
+Set seed for picking gradient line points.
+@end table
+
+
 @section mandelbrot
 
 Generate a Mandelbrot set fractal, and progressively zoom towards the

libavfilter/Makefile

@@ -471,6 +471,7 @@ OBJS-$(CONFIG_CELLAUTO_FILTER)               += vsrc_cellauto.o
 OBJS-$(CONFIG_COLOR_FILTER)                  += vsrc_testsrc.o
 OBJS-$(CONFIG_COREIMAGESRC_FILTER)           += vf_coreimage.o
 OBJS-$(CONFIG_FREI0R_SRC_FILTER)             += vf_frei0r.o
+OBJS-$(CONFIG_GRADIENTS_FILTER)              += vsrc_gradients.o
 OBJS-$(CONFIG_HALDCLUTSRC_FILTER)            += vsrc_testsrc.o
 OBJS-$(CONFIG_LIFE_FILTER)                   += vsrc_life.o
 OBJS-$(CONFIG_MANDELBROT_FILTER)             += vsrc_mandelbrot.o

libavfilter/allfilters.c

@@ -449,6 +449,7 @@ extern AVFilter ff_vsrc_cellauto;
 extern AVFilter ff_vsrc_color;
 extern AVFilter ff_vsrc_coreimagesrc;
 extern AVFilter ff_vsrc_frei0r_src;
+extern AVFilter ff_vsrc_gradients;
 extern AVFilter ff_vsrc_haldclutsrc;
 extern AVFilter ff_vsrc_life;
 extern AVFilter ff_vsrc_mandelbrot;

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   7
-#define LIBAVFILTER_VERSION_MINOR  81
+#define LIBAVFILTER_VERSION_MINOR  82
 #define LIBAVFILTER_VERSION_MICRO 100