lavfi: port perspective filter from libmpcodecs

Signed-off-by: Paul B Mahol <onemda@gmail.com>

Changelog

@@ -4,6 +4,7 @@ releases are sorted from youngest to oldest.
 version <next>
 
 - aecho filter
+- perspective filter ported from libmpcodecs
 
 
 version 2.0:

LICENSE

@@ -39,6 +39,7 @@ Specifically, the GPL parts of FFmpeg are
     - vf_mp.c
     - vf_noise.c
     - vf_owdenoise.c
+    - vf_perspective.c
     - vf_pp.c
     - vf_sab.c
     - vf_smartblur.c

configure

@@ -2175,6 +2175,7 @@ mpdecimate_filter_deps="gpl avcodec"
 mptestsrc_filter_deps="gpl"
 negate_filter_deps="lut_filter"
 noise_filter_deps="gpl"
+perspective_filter_deps="gpl"
 resample_filter_deps="avresample"
 ocv_filter_deps="libopencv"
 owdenoise_filter_deps="gpl"

doc/filters.texi

@@ -5722,6 +5722,44 @@ pad="2*iw:2*ih:ow-iw:oh-ih"
 @end example
 @end itemize
 
+@section perspective
+
+Correct perspective of video not recorded perpendicular to the screen.
+
+A description of the accepted parameters follows.
+
+@table @option
+@item x0
+@item y0
+@item x1
+@item y1
+@item x2
+@item y2
+@item x3
+@item y3
+Set coordinates expression for top left, top right, bottom left and bottom right corners.
+Default values are @code{0:0:W:0:0:H:W:H} with which perspective will remain unchanged.
+
+The expressions can use the following variables:
+
+@table @option
+@item W
+@item H
+the width and height of video frame.
+@end table
+
+@item interpolation
+Set interpolation for perspective correction.
+
+It accepts the following values:
+@table @samp
+@item linear
+@item cubic
+@end table
+
+Default value is @samp{linear}.
+@end table
+
 @section pixdesctest
 
 Pixel format descriptor test filter, mainly useful for internal

libavfilter/Makefile

@@ -166,6 +166,7 @@ OBJS-$(CONFIG_OVERLAY_FILTER)                += vf_overlay.o dualinput.o
 OBJS-$(CONFIG_OWDENOISE_FILTER)              += vf_owdenoise.o
 OBJS-$(CONFIG_PAD_FILTER)                    += vf_pad.o
 OBJS-$(CONFIG_PERMS_FILTER)                  += f_perms.o
+OBJS-$(CONFIG_PERSPECTIVE_FILTER)            += vf_perspective.o
 OBJS-$(CONFIG_PIXDESCTEST_FILTER)            += vf_pixdesctest.o
 OBJS-$(CONFIG_PP_FILTER)                     += vf_pp.o
 OBJS-$(CONFIG_PSNR_FILTER)                   += vf_psnr.o dualinput.o

libavfilter/allfilters.c

@@ -161,6 +161,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(OWDENOISE,      owdenoise,      vf);
     REGISTER_FILTER(PAD,            pad,            vf);
     REGISTER_FILTER(PERMS,          perms,          vf);
+    REGISTER_FILTER(PERSPECTIVE,    perspective,    vf);
     REGISTER_FILTER(PIXDESCTEST,    pixdesctest,    vf);
     REGISTER_FILTER(PP,             pp,             vf);
     REGISTER_FILTER(PSNR,           psnr,           vf);

libavfilter/version.h

@@ -30,8 +30,8 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  3
-#define LIBAVFILTER_VERSION_MINOR  80
-#define LIBAVFILTER_VERSION_MICRO 101
+#define LIBAVFILTER_VERSION_MINOR  81
+#define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \