doc: add libswscale.texi and ffmpeg-scaler.texi files

doc/Makefile

 DOCLIBS-$(CONFIG_AVUTIL)  += libavutil
+DOCLIBS-$(CONFIG_SWSCALE) += libswscale
 DOCLIBS-$(CONFIG_SWRESAMPLE) += libswresample
 DOCLIBS-$(CONFIG_AVCODEC) += libavcodec
 DOCLIBS-$(CONFIG_AVFILTER) += libavfilter
 
-COMPONENTS=$(PROGS-yes) ffmpeg-codecs ffmpeg-filters ffmpeg-resampler
+COMPONENTS=$(PROGS-yes) ffmpeg-codecs ffmpeg-filters ffmpeg-resampler ffmpeg-scaler
 
 MANPAGES    = $(COMPONENTS:%=doc/%.1)    $(DOCLIBS-yes:%=doc/%.3)
 PODPAGES    = $(COMPONENTS:%=doc/%.pod)  $(DOCLIBS-yes:%=doc/%.pod)

doc/ffmpeg-scaler.texi

+\input texinfo @c -*- texinfo -*-
+
+@settitle FFmpeg Scaler Documentation
+@titlepage
+@center @titlefont{FFmpeg Scaler Documentation}
+@end titlepage
+
+@top
+
+@contents
+
+@chapter Description
+@c man begin DESCRIPTION
+
+The FFmpeg rescaler provides an high-level interface to the libswscale
+library image conversion utilities. In particular it allows to perform
+image rescaling and pixel format conversion.
+
+@c man end DESCRIPTION
+
+@chapter Scaler Options
+@c man begin SCALER OPTIONS
+
+The video scaler supports the following named options.
+
+Options may be set by specifying -@var{option} @var{value} in the
+FFmpeg tools. For programmatic use, they can be set explicitly in the
+@code{SwsContext} options or through the @file{libavutil/opt.h} API.
+
+@table @option
+
+@item sws_flags
+Set the scaler flags. This is also used to set the scaling
+algorithm. Only a single algorithm should be selected.
+
+It accepts the following values:
+@table @samp
+@item fast_bilinear
+Select fast bilinear scaling algorithm.
+
+@item bilinear
+Select bilinear scaling algorithm.
+
+@item bicubic
+Select bicubic scaling algorithm.
+
+@item experimental
+Select experimental scaling algorithm.
+
+@item neighbor
+Select nearest neighbor rescaling algorithm.
+
+@item area
+Select averaging area rescaling algorithm.
+
+@item bicubiclin
+Select bicubic scaling algorithm for the luma component, bilinear for
+chroma components.
+
+@item gauss
+Select Gaussian rescaling algorithm.
+
+@item sinc
+Select sinc rescaling algorithm.
+
+@item lanczos
+Select lanczos rescaling algorithm.
+
+@item spline
+Select natural bicubic spline rescaling algorithm.
+
+@item print_info
+Enable printing/debug logging.
+
+@item accurate_rnd
+Enable accurate rounding.
+
+@item full_chroma_int
+Enable full chroma interpolation.
+
+@item full_chroma_inp
+Select full chroma input.
+
+@item bitexact
+Enable bitexact output.
+@end table
+
+@item srcw
+Set source width.
+
+@item srch
+Set source height.
+
+@item dstw
+Set destination width.
+
+@item dsth
+Set destination height.
+
+@item src_format
+Set source pixel format (must be expressed as an integer).
+
+@item dst_format
+Set destination pixel format (must be expressed as an integer).
+
+@item src_range
+Select source range.
+
+@item dst_range
+Select destination range.
+
+@item param0, param1
+Set scaling algorithm parameters. The specified values are specific of
+some scaling algorithms and ignored by others. The specified values
+are floating point number values.
+
+@end table
+
+@c man end SCALER OPTIONS
+
+@ignore
+
+@setfilename ffmpeg-scaler
+@settitle FFmpeg video scaling and pixel format converter
+
+@c man begin SEEALSO
+ffmpeg(1), ffplay(1), ffprobe(1), ffserver(1), libswscale(3)
+@c man end
+
+@c man begin AUTHORS
+See Git history (git://source.ffmpeg.org/ffmpeg)
+@c man end
+
+@end ignore
+
+@bye

doc/libswscale.texi

+\input texinfo @c -*- texinfo -*-
+
+@settitle Libswscale Documentation
+@titlepage
+@center @titlefont{Libswscale Documentation}
+@end titlepage
+
+@top
+
+@contents
+
+@chapter Description
+@c man begin DESCRIPTION
+
+The libswscale library performs highly optimized image scaling and
+colorspace and pixel format conversion operations.
+
+Specifically, this library performs the following conversions:
+
+@itemize
+@item
+@emph{Rescaling}: is the process of changing the video size. Several
+rescaling options and algorithms are available. This is usually a
+lossy process.
+
+@item
+@emph{Pixel format conversion}: is the process of converting the image
+format and colorspace of the image, for example from planar YUV420P to
+RGB24 packed. It also handles packing conversion, that is converts
+from packed layout (all pixels belonging to distinct planes
+interleaved in the same buffer), to planar layout (all samples
+belonging to the same plane stored in a dedicated buffer or "plane").
+
+This is usually a lossy process in case the source and destination
+colorspaces differ.
+@end itemize
+
+@c man end DESCRIPTION
+
+@ignore
+
+@setfilename libswscale
+@settitle video scaling and pixel format conversion library
+
+@c man begin SEEALSO
+ffmpeg(1), ffplay(1), ffprobe(1), ffserver(1), ffmpeg-scaler(1), libavutil(3)
+@c man end
+
+@c man begin AUTHORS
+See Git history (git://source.ffmpeg.org/ffmpeg)
+@c man end
+
+@end ignore
+
+@bye