/*
  * Copyright (c) 2012 Jeremy Tran
  * Copyright (c) 2001 Donald A. Graft
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License along
  * with FFmpeg; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
 /**
  * @file
  * Histogram equalization filter, based on the VirtualDub filter by
  * Donald A. Graft  <neuron2 AT home DOT com>.
  * Implements global automatic contrast adjustment by means of
  * histogram equalization.
  */
 
 #include "libavutil/common.h"

 #include "libavutil/internal.h"

 #include "libavutil/opt.h"
 #include "libavutil/pixdesc.h"
 
 #include "avfilter.h"
 #include "drawutils.h"
 #include "formats.h"
 #include "internal.h"
 #include "video.h"
 
 // #define DEBUG
 
 // Linear Congruential Generator, see "Numerical Recipes"
 #define LCG_A 4096
 #define LCG_C 150889
 #define LCG_M 714025
 #define LCG(x) (((x) * LCG_A + LCG_C) % LCG_M)
 #define LCG_SEED 739187
 
 enum HisteqAntibanding {
     HISTEQ_ANTIBANDING_NONE   = 0,
     HISTEQ_ANTIBANDING_WEAK   = 1,
     HISTEQ_ANTIBANDING_STRONG = 2,
     HISTEQ_ANTIBANDING_NB,
 };
 

 typedef struct HisteqContext {

     const AVClass *class;
     float strength;
     float intensity;

     int antibanding;               ///< HisteqAntibanding

     int in_histogram [256];        ///< input histogram
     int out_histogram[256];        ///< output histogram
     int LUT[256];                  ///< lookup table derived from histogram[]
     uint8_t rgba_map[4];           ///< components position
     int bpp;                       ///< bytes per pixel
 } HisteqContext;
 
 #define OFFSET(x) offsetof(HisteqContext, x)
 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
 #define CONST(name, help, val, unit) { name, help, 0, AV_OPT_TYPE_CONST, {.i64=val}, INT_MIN, INT_MAX, FLAGS, unit }
 
 static const AVOption histeq_options[] = {
     { "strength",    "set the strength", OFFSET(strength), AV_OPT_TYPE_FLOAT, {.dbl=0.2}, 0, 1, FLAGS },
     { "intensity",   "set the intensity", OFFSET(intensity), AV_OPT_TYPE_FLOAT, {.dbl=0.21}, 0, 1, FLAGS },
     { "antibanding", "set the antibanding level", OFFSET(antibanding), AV_OPT_TYPE_INT, {.i64=HISTEQ_ANTIBANDING_NONE}, 0, HISTEQ_ANTIBANDING_NB-1, FLAGS, "antibanding" },
     CONST("none",    "apply no antibanding",     HISTEQ_ANTIBANDING_NONE,   "antibanding"),
     CONST("weak",    "apply weak antibanding",   HISTEQ_ANTIBANDING_WEAK,   "antibanding"),
     CONST("strong",  "apply strong antibanding", HISTEQ_ANTIBANDING_STRONG, "antibanding"),
     { NULL }
 };
 
 AVFILTER_DEFINE_CLASS(histeq);
 

 static av_cold int init(AVFilterContext *ctx)

 {
     HisteqContext *histeq = ctx->priv;
 
     av_log(ctx, AV_LOG_VERBOSE,
            "strength:%0.3f intensity:%0.3f antibanding:%d\n",
            histeq->strength, histeq->intensity, histeq->antibanding);
 
     return 0;
 }
 
 static int query_formats(AVFilterContext *ctx)
 {

     static const enum AVPixelFormat pix_fmts[] = {

         AV_PIX_FMT_ARGB, AV_PIX_FMT_RGBA, AV_PIX_FMT_ABGR, AV_PIX_FMT_BGRA,
         AV_PIX_FMT_RGB24, AV_PIX_FMT_BGR24,
         AV_PIX_FMT_NONE
     };

     AVFilterFormats *fmts_list = ff_make_format_list(pix_fmts);
     if (!fmts_list)
         return AVERROR(ENOMEM);
     return ff_set_common_formats(ctx, fmts_list);

 }
 
 static int config_input(AVFilterLink *inlink)
 {
     AVFilterContext *ctx = inlink->dst;
     HisteqContext *histeq = ctx->priv;
     const AVPixFmtDescriptor *pix_desc = av_pix_fmt_desc_get(inlink->format);
 
     histeq->bpp = av_get_bits_per_pixel(pix_desc) / 8;
     ff_fill_rgba_map(histeq->rgba_map, inlink->format);
 
     return 0;
 }
 
 #define R 0
 #define G 1
 #define B 2
 #define A 3
 
 #define GET_RGB_VALUES(r, g, b, src, map) do { \
     r = src[x + map[R]];                       \
     g = src[x + map[G]];                       \
     b = src[x + map[B]];                       \
 } while (0)
 

 static int filter_frame(AVFilterLink *inlink, AVFrame *inpic)

 {
     AVFilterContext   *ctx     = inlink->dst;
     HisteqContext     *histeq  = ctx->priv;
     AVFilterLink      *outlink = ctx->outputs[0];
     int strength  = histeq->strength  * 1000;
     int intensity = histeq->intensity * 1000;
     int x, y, i, luthi, lutlo, lut, luma, oluma, m;

     AVFrame *outpic;

     unsigned int r, g, b, jran;
     uint8_t *src, *dst;
 

     outpic = ff_get_video_buffer(outlink, outlink->w, outlink->h);

     if (!outpic) {

         av_frame_free(&inpic);

         return AVERROR(ENOMEM);
     }

     av_frame_copy_props(outpic, inpic);

 
     /* Seed random generator for antibanding. */
     jran = LCG_SEED;
 
     /* Calculate and store the luminance and calculate the global histogram
        based on the luminance. */
     memset(histeq->in_histogram, 0, sizeof(histeq->in_histogram));
     src = inpic->data[0];
     dst = outpic->data[0];
     for (y = 0; y < inlink->h; y++) {
         for (x = 0; x < inlink->w * histeq->bpp; x += histeq->bpp) {
             GET_RGB_VALUES(r, g, b, src, histeq->rgba_map);
             luma = (55 * r + 182 * g + 19 * b) >> 8;
             dst[x + histeq->rgba_map[A]] = luma;
             histeq->in_histogram[luma]++;
         }
         src += inpic->linesize[0];
         dst += outpic->linesize[0];
     }
 
 #ifdef DEBUG
     for (x = 0; x < 256; x++)

         ff_dlog(ctx, "in[%d]: %u\n", x, histeq->in_histogram[x]);

 #endif
 
     /* Calculate the lookup table. */
     histeq->LUT[0] = histeq->in_histogram[0];
     /* Accumulate */
     for (x = 1; x < 256; x++)
         histeq->LUT[x] = histeq->LUT[x-1] + histeq->in_histogram[x];
 
     /* Normalize */
     for (x = 0; x < 256; x++)
         histeq->LUT[x] = (histeq->LUT[x] * intensity) / (inlink->h * inlink->w);
 
     /* Adjust the LUT based on the selected strength. This is an alpha
        mix of the calculated LUT and a linear LUT with gain 1. */
     for (x = 0; x < 256; x++)
         histeq->LUT[x] = (strength * histeq->LUT[x]) / 255 +
                          ((255 - strength) * x)      / 255;
 
     /* Output the equalized frame. */
     memset(histeq->out_histogram, 0, sizeof(histeq->out_histogram));
 
     src = inpic->data[0];
     dst = outpic->data[0];
     for (y = 0; y < inlink->h; y++) {
         for (x = 0; x < inlink->w * histeq->bpp; x += histeq->bpp) {
             luma = dst[x + histeq->rgba_map[A]];
             if (luma == 0) {
                 for (i = 0; i < histeq->bpp; ++i)
                     dst[x + i] = 0;
                 histeq->out_histogram[0]++;
             } else {
                 lut = histeq->LUT[luma];
                 if (histeq->antibanding != HISTEQ_ANTIBANDING_NONE) {
                     if (luma > 0) {
                         lutlo = histeq->antibanding == HISTEQ_ANTIBANDING_WEAK ?
                                 (histeq->LUT[luma] + histeq->LUT[luma - 1]) / 2 :
                                  histeq->LUT[luma - 1];
                     } else
                         lutlo = lut;
 
                     if (luma < 255) {
                         luthi = (histeq->antibanding == HISTEQ_ANTIBANDING_WEAK) ?
                             (histeq->LUT[luma] + histeq->LUT[luma + 1]) / 2 :
                              histeq->LUT[luma + 1];
                     } else
                         luthi = lut;
 
                     if (lutlo != luthi) {
                         jran = LCG(jran);
                         lut = lutlo + ((luthi - lutlo + 1) * jran) / LCG_M;
                     }
                 }
 
                 GET_RGB_VALUES(r, g, b, src, histeq->rgba_map);
                 if (((m = FFMAX3(r, g, b)) * lut) / luma > 255) {
                     r = (r * 255) / m;
                     g = (g * 255) / m;
                     b = (b * 255) / m;
                 } else {
                     r = (r * lut) / luma;
                     g = (g * lut) / luma;
                     b = (b * lut) / luma;
                 }
                 dst[x + histeq->rgba_map[R]] = r;
                 dst[x + histeq->rgba_map[G]] = g;
                 dst[x + histeq->rgba_map[B]] = b;

                 oluma = av_clip_uint8((55 * r + 182 * g + 19 * b) >> 8);

                 histeq->out_histogram[oluma]++;
             }
         }
         src += inpic->linesize[0];
         dst += outpic->linesize[0];
     }
 #ifdef DEBUG
     for (x = 0; x < 256; x++)

         ff_dlog(ctx, "out[%d]: %u\n", x, histeq->out_histogram[x]);

 #endif
 

     av_frame_free(&inpic);

     return ff_filter_frame(outlink, outpic);
 }
 
 static const AVFilterPad histeq_inputs[] = {
     {

         .name         = "default",
         .type         = AVMEDIA_TYPE_VIDEO,
         .config_props = config_input,
         .filter_frame = filter_frame,

     },
     { NULL }
 };
 
 static const AVFilterPad histeq_outputs[] = {
     {

         .name = "default",
         .type = AVMEDIA_TYPE_VIDEO,

     },
     { NULL }
 };
 

 AVFilter ff_vf_histeq = {

     .name          = "histeq",
     .description   = NULL_IF_CONFIG_SMALL("Apply global color histogram equalization."),
     .priv_size     = sizeof(HisteqContext),
     .init          = init,
     .query_formats = query_formats,
     .inputs        = histeq_inputs,
     .outputs       = histeq_outputs,
     .priv_class    = &histeq_class,

     .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,

 };