histogram filter

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

Changelog

@@ -13,6 +13,7 @@ version <next>:
 - allpass, bass, bandpass, bandreject, biquad, equalizer, highpass, lowpass
   and treble audio filter
 - improved showspectrum filter, with multichannel support and sox-like colors
+- histogram filter
 
 
 version 1.1:

doc/filters.texi

@@ -3098,6 +3098,89 @@ the histogram. Possible values are @code{none}, @code{weak} or
 @code{strong}. It defaults to @code{none}.
 @end table
 
+@section histogram
+
+Compute and draw a color distribution histogram for the input video.
+
+The computed histogram is a representation of distribution of color components
+in an image.
+
+The filter accepts the following named parameters:
+
+@table @option
+@item mode
+Set histogram mode.
+
+It accepts the following values:
+@table @samp
+@item levels
+standard histogram that display color components distribution in an image.
+Displays color graph for each color component. Shows distribution
+of the Y, U, V, A or G, B, R components, depending on input format,
+in current frame. Bellow each graph is color component scale meter.
+
+@item color
+chroma values in vectorscope, if brighter more such chroma values are
+distributed in an image.
+Displays chroma values (U/V color placement) in two dimensional graph
+(which is called a vectorscope). It can be used to read of the hue and
+saturation of the current frame. At a same time it is a histogram.
+The whiter a pixel in the vectorscope, the more pixels of the input frame
+correspond to that pixel (that is the more pixels have this chroma value).
+The V component is displayed on the horizontal (X) axis, with the leftmost
+side being V = 0 and the rightmost side being V = 255.
+The U component is displayed on the vertical (Y) axis, with the top
+representing U = 0 and the bottom representing U = 255.
+
+The position of a white pixel in the graph corresponds to the chroma value
+of a pixel of the input clip. So the graph can be used to read of the
+hue (color flavor) and the saturation (the dominance of the hue in the color).
+As the hue of a color changes, it moves around the square. At the center of
+the square, the saturation is zero, which means that the corresponding pixel
+has no color. If you increase the amount of a specific color, while leaving
+the other colors unchanged, the saturation increases, and you move towards
+the edge of the square.
+
+@item color2
+chroma values in vectorscope, similar as @code{color} but actual chroma values
+are displayed.
+
+@item waveform
+per row/column luminance graph. In row mode the left side represents luma = 0
+and right side represents luma = 255. In column mode top side represends
+luma = 0 and bottom side represents luma = 255.
+@end table
+Default value is @code{levels}.
+
+@item level_height
+Set height of level in @code{levels}. Default value is @code{200}.
+Allowed range is [50, 2048].
+
+@item scale_height
+Set height of color scale in @code{levels}. Default value is @code{12}.
+Allowed range is [0, 40].
+
+@item step
+Set step for @code{waveform} mode. Smaller values are useful to find out how much
+of same luminance values across input rows/columns are distributed.
+Default value is @code{10}. Allowed range is [1, 255].
+
+@item waveform_mode
+Set mode for @code{waveform}. Can be either @code{row}, or @code{column}.
+Default is @code{row}.
+
+@subsection Examples
+
+@itemize
+
+@item
+Calculate and draw histogram:
+@example
+ffplay -i input -vf histogram
+@end example
+
+@end itemize
+
 @section hqdn3d
 
 High precision/quality 3d denoise filter. This filter aims to reduce

libavfilter/Makefile

@@ -122,6 +122,7 @@ OBJS-$(CONFIG_GEQ_FILTER)                    += vf_geq.o
 OBJS-$(CONFIG_GRADFUN_FILTER)                += vf_gradfun.o
 OBJS-$(CONFIG_HFLIP_FILTER)                  += vf_hflip.o
 OBJS-$(CONFIG_HISTEQ_FILTER)                 += vf_histeq.o
+OBJS-$(CONFIG_HISTOGRAM_FILTER)              += vf_histogram.o
 OBJS-$(CONFIG_HQDN3D_FILTER)                 += vf_hqdn3d.o
 OBJS-$(CONFIG_HUE_FILTER)                    += vf_hue.o
 OBJS-$(CONFIG_IDET_FILTER)                   += vf_idet.o

libavfilter/allfilters.c

@@ -116,6 +116,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(GRADFUN,        gradfun,        vf);
     REGISTER_FILTER(HFLIP,          hflip,          vf);
     REGISTER_FILTER(HISTEQ,         histeq,         vf);
+    REGISTER_FILTER(HISTOGRAM,      histogram,      vf);
     REGISTER_FILTER(HQDN3D,         hqdn3d,         vf);
     REGISTER_FILTER(HUE,            hue,            vf);
     REGISTER_FILTER(IDET,           idet,           vf);

libavfilter/version.h

@@ -29,8 +29,8 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  3
-#define LIBAVFILTER_VERSION_MINOR  35
-#define LIBAVFILTER_VERSION_MICRO 101
+#define LIBAVFILTER_VERSION_MINOR  36
+#define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \