/*

  * Copyright (c) 2015 Stupeflix
  *

  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 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
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser 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
  * Generate one palette for a whole video stream.
  */
 
 #include "libavutil/avassert.h"

 #include "libavutil/internal.h"

 #include "libavutil/opt.h"

 #include "libavutil/qsort.h"

 #include "libavutil/intreadwrite.h"

 #include "avfilter.h"
 #include "internal.h"
 
 /* Reference a color and how much it's used */
 struct color_ref {
     uint32_t color;
     uint64_t count;
 };
 
 /* Store a range of colors */
 struct range_box {
     uint32_t color;     // average color
     int64_t variance;   // overall variance of the box (how much the colors are spread)
     int start;          // index in PaletteGenContext->refs
     int len;            // number of referenced colors
     int sorted_by;      // whether range of colors is sorted by red (0), green (1) or blue (2)
 };
 
 struct hist_node {
     struct color_ref *entries;
     int nb_entries;
 };
 
 enum {
     STATS_MODE_ALL_FRAMES,
     STATS_MODE_DIFF_FRAMES,

     STATS_MODE_SINGLE_FRAMES,

     NB_STATS_MODE
 };
 

 #define NBITS 5

 #define HIST_SIZE (1<<(3*NBITS))
 

 typedef struct PaletteGenContext {

     const AVClass *class;
 
     int max_colors;
     int reserve_transparent;
     int stats_mode;
 
     AVFrame *prev_frame;                    // previous frame used for the diff stats_mode
     struct hist_node histogram[HIST_SIZE];  // histogram/hashtable of the colors
     struct color_ref **refs;                // references of all the colors used in the stream
     int nb_refs;                            // number of color references (or number of different colors)
     struct range_box boxes[256];            // define the segmentation of the colorspace (the final palette)
     int nb_boxes;                           // number of boxes (increase will segmenting them)
     int palette_pushed;                     // if the palette frame is pushed into the outlink or not

     uint8_t transparency_color[4];          // background color for transparency

 } PaletteGenContext;
 
 #define OFFSET(x) offsetof(PaletteGenContext, x)
 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
 static const AVOption palettegen_options[] = {
     { "max_colors", "set the maximum number of colors to use in the palette", OFFSET(max_colors), AV_OPT_TYPE_INT, {.i64=256}, 4, 256, FLAGS },

     { "reserve_transparent", "reserve a palette entry for transparency", OFFSET(reserve_transparent), AV_OPT_TYPE_BOOL, {.i64=1}, 0, 1, FLAGS },

     { "transparency_color", "set a background color for transparency", OFFSET(transparency_color), AV_OPT_TYPE_COLOR, {.str="lime"}, CHAR_MIN, CHAR_MAX, FLAGS },

     { "stats_mode", "set statistics mode", OFFSET(stats_mode), AV_OPT_TYPE_INT, {.i64=STATS_MODE_ALL_FRAMES}, 0, NB_STATS_MODE-1, FLAGS, "mode" },

         { "full", "compute full frame histograms", 0, AV_OPT_TYPE_CONST, {.i64=STATS_MODE_ALL_FRAMES}, INT_MIN, INT_MAX, FLAGS, "mode" },
         { "diff", "compute histograms only for the part that differs from previous frame", 0, AV_OPT_TYPE_CONST, {.i64=STATS_MODE_DIFF_FRAMES}, INT_MIN, INT_MAX, FLAGS, "mode" },

         { "single", "compute new histogram for each frame", 0, AV_OPT_TYPE_CONST, {.i64=STATS_MODE_SINGLE_FRAMES}, INT_MIN, INT_MAX, FLAGS, "mode" },

     { NULL }
 };
 
 AVFILTER_DEFINE_CLASS(palettegen);
 
 static int query_formats(AVFilterContext *ctx)
 {
     static const enum AVPixelFormat in_fmts[]  = {AV_PIX_FMT_RGB32, AV_PIX_FMT_NONE};
     static const enum AVPixelFormat out_fmts[] = {AV_PIX_FMT_RGB32, AV_PIX_FMT_NONE};

     int ret;

 
     if ((ret = ff_formats_ref(ff_make_format_list(in_fmts) , &ctx->inputs[0]->out_formats)) < 0)
         return ret;
     if ((ret = ff_formats_ref(ff_make_format_list(out_fmts), &ctx->outputs[0]->in_formats)) < 0)

         return ret;

     return 0;
 }
 
 typedef int (*cmp_func)(const void *, const void *);
 
 #define DECLARE_CMP_FUNC(name, pos)                     \
 static int cmp_##name(const void *pa, const void *pb)   \
 {                                                       \
     const struct color_ref * const *a = pa;             \
     const struct color_ref * const *b = pb;             \
     return   ((*a)->color >> (8 * (2 - (pos))) & 0xff)  \
            - ((*b)->color >> (8 * (2 - (pos))) & 0xff); \
 }
 
 DECLARE_CMP_FUNC(r, 0)
 DECLARE_CMP_FUNC(g, 1)
 DECLARE_CMP_FUNC(b, 2)
 
 static const cmp_func cmp_funcs[] = {cmp_r, cmp_g, cmp_b};
 
 /**
  * Simple color comparison for sorting the final palette
  */
 static int cmp_color(const void *a, const void *b)
 {
     const struct range_box *box1 = a;
     const struct range_box *box2 = b;

     return FFDIFFSIGN(box1->color , box2->color);

 }
 
 static av_always_inline int diff(const uint32_t a, const uint32_t b)
 {
     const uint8_t c1[] = {a >> 16 & 0xff, a >> 8 & 0xff, a & 0xff};
     const uint8_t c2[] = {b >> 16 & 0xff, b >> 8 & 0xff, b & 0xff};
     const int dr = c1[0] - c2[0];
     const int dg = c1[1] - c2[1];
     const int db = c1[2] - c2[2];
     return dr*dr + dg*dg + db*db;
 }
 
 /**
  * Find the next box to split: pick the one with the highest variance
  */
 static int get_next_box_id_to_split(PaletteGenContext *s)
 {
     int box_id, i, best_box_id = -1;
     int64_t max_variance = -1;
 
     if (s->nb_boxes == s->max_colors - s->reserve_transparent)
         return -1;
 
     for (box_id = 0; box_id < s->nb_boxes; box_id++) {
         struct range_box *box = &s->boxes[box_id];
 
         if (s->boxes[box_id].len >= 2) {
 
             if (box->variance == -1) {
                 int64_t variance = 0;
 
                 for (i = 0; i < box->len; i++) {
                     const struct color_ref *ref = s->refs[box->start + i];
                     variance += diff(ref->color, box->color) * ref->count;
                 }
                 box->variance = variance;
             }
             if (box->variance > max_variance) {
                 best_box_id = box_id;
                 max_variance = box->variance;
             }
         } else {
             box->variance = -1;
         }
     }
     return best_box_id;
 }
 
 /**
  * Get the 32-bit average color for the range of RGB colors enclosed in the
  * specified box. Takes into account the weight of each color.
  */
 static uint32_t get_avg_color(struct color_ref * const *refs,
                               const struct range_box *box)
 {
     int i;
     const int n = box->len;
     uint64_t r = 0, g = 0, b = 0, div = 0;
 
     for (i = 0; i < n; i++) {
         const struct color_ref *ref = refs[box->start + i];
         r += (ref->color >> 16 & 0xff) * ref->count;
         g += (ref->color >>  8 & 0xff) * ref->count;
         b += (ref->color       & 0xff) * ref->count;
         div += ref->count;
     }
 
     r = r / div;
     g = g / div;
     b = b / div;
 
     return 0xffU<<24 | r<<16 | g<<8 | b;
 }
 
 /**
  * Split given box in two at position n. The original box becomes the left part
  * of the split, and the new index box is the right part.
  */
 static void split_box(PaletteGenContext *s, struct range_box *box, int n)
 {
     struct range_box *new_box = &s->boxes[s->nb_boxes++];
     new_box->start     = n + 1;
     new_box->len       = box->start + box->len - new_box->start;
     new_box->sorted_by = box->sorted_by;
     box->len -= new_box->len;
 
     av_assert0(box->len     >= 1);
     av_assert0(new_box->len >= 1);
 
     box->color     = get_avg_color(s->refs, box);
     new_box->color = get_avg_color(s->refs, new_box);
     box->variance     = -1;
     new_box->variance = -1;
 }
 
 /**
  * Write the palette into the output frame.
  */

 static void write_palette(AVFilterContext *ctx, AVFrame *out)

 {

     const PaletteGenContext *s = ctx->priv;

     int x, y, box_id = 0;
     uint32_t *pal = (uint32_t *)out->data[0];
     const int pal_linesize = out->linesize[0] >> 2;
     uint32_t last_color = 0;
 
     for (y = 0; y < out->height; y++) {
         for (x = 0; x < out->width; x++) {
             if (box_id < s->nb_boxes) {
                 pal[x] = s->boxes[box_id++].color;
                 if ((x || y) && pal[x] == last_color)

                     av_log(ctx, AV_LOG_WARNING, "Dupped color: %08"PRIX32"\n", pal[x]);

                 last_color = pal[x];
             } else {
                 pal[x] = 0xff000000; // pad with black
             }
         }
         pal += pal_linesize;
     }
 
     if (s->reserve_transparent) {
         av_assert0(s->nb_boxes < 256);

         pal[out->width - pal_linesize - 1] = AV_RB32(&s->transparency_color) >> 8;

     }
 }
 
 /**
  * Crawl the histogram to get all the defined colors, and create a linear list
  * of them (each color reference entry is a pointer to the value in the
  * histogram/hash table).
  */
 static struct color_ref **load_color_refs(const struct hist_node *hist, int nb_refs)
 {
     int i, j, k = 0;
     struct color_ref **refs = av_malloc_array(nb_refs, sizeof(*refs));
 
     if (!refs)
         return NULL;
 
     for (j = 0; j < HIST_SIZE; j++) {
         const struct hist_node *node = &hist[j];
 
         for (i = 0; i < node->nb_entries; i++)
             refs[k++] = &node->entries[i];
     }
 
     return refs;
 }
 

 static double set_colorquant_ratio_meta(AVFrame *out, int nb_out, int nb_in)
 {
     char buf[32];
     const double ratio = (double)nb_out / nb_in;
     snprintf(buf, sizeof(buf), "%f", ratio);
     av_dict_set(&out->metadata, "lavfi.color_quant_ratio", buf, 0);
     return ratio;
 }
 

 /**
  * Main function implementing the Median Cut Algorithm defined by Paul Heckbert
  * in Color Image Quantization for Frame Buffer Display (1982)
  */
 static AVFrame *get_palette_frame(AVFilterContext *ctx)
 {
     AVFrame *out;
     PaletteGenContext *s = ctx->priv;
     AVFilterLink *outlink = ctx->outputs[0];

     double ratio;

     int box_id = 0;
     struct range_box *box;
 
     /* reference only the used colors from histogram */
     s->refs = load_color_refs(s->histogram, s->nb_refs);
     if (!s->refs) {
         av_log(ctx, AV_LOG_ERROR, "Unable to allocate references for %d different colors\n", s->nb_refs);
         return NULL;
     }
 
     /* create the palette frame */
     out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
     if (!out)
         return NULL;
     out->pts = 0;
 
     /* set first box for 0..nb_refs */
     box = &s->boxes[box_id];
     box->len = s->nb_refs;
     box->sorted_by = -1;
     box->color = get_avg_color(s->refs, box);
     box->variance = -1;
     s->nb_boxes = 1;
 
     while (box && box->len > 1) {

         int i, rr, gr, br, longest;

         uint64_t median, box_weight = 0;
 
         /* compute the box weight (sum all the weights of the colors in the
          * range) and its boundings */
         uint8_t min[3] = {0xff, 0xff, 0xff};
         uint8_t max[3] = {0x00, 0x00, 0x00};
         for (i = box->start; i < box->start + box->len; i++) {
             const struct color_ref *ref = s->refs[i];
             const uint32_t rgb = ref->color;
             const uint8_t r = rgb >> 16 & 0xff, g = rgb >> 8 & 0xff, b = rgb & 0xff;
             min[0] = FFMIN(r, min[0]), max[0] = FFMAX(r, max[0]);
             min[1] = FFMIN(g, min[1]), max[1] = FFMAX(g, max[1]);
             min[2] = FFMIN(b, min[2]), max[2] = FFMAX(b, max[2]);
             box_weight += ref->count;
         }
 
         /* define the axis to sort by according to the widest range of colors */
         rr = max[0] - min[0];
         gr = max[1] - min[1];
         br = max[2] - min[2];
         longest = 1; // pick green by default (the color the eye is the most sensitive to)
         if (br >= rr && br >= gr) longest = 2;
         if (rr >= gr && rr >= br) longest = 0;
         if (gr >= rr && gr >= br) longest = 1; // prefer green again
 

         ff_dlog(ctx, "box #%02X [%6d..%-6d] (%6d) w:%-6"PRIu64" ranges:[%2x %2x %2x] sort by %c (already sorted:%c) ",

                 box_id, box->start, box->start + box->len - 1, box->len, box_weight,
                 rr, gr, br, "rgb"[longest], box->sorted_by == longest ? 'y':'n');
 
         /* sort the range by its longest axis if it's not already sorted */
         if (box->sorted_by != longest) {

             cmp_func cmpf = cmp_funcs[longest];
             AV_QSORT(&s->refs[box->start], box->len, const struct color_ref *, cmpf);

             box->sorted_by = longest;
         }
 
         /* locate the median where to split */
         median = (box_weight + 1) >> 1;
         box_weight = 0;
         /* if you have 2 boxes, the maximum is actually #0: you must have at
          * least 1 color on each side of the split, hence the -2 */
         for (i = box->start; i < box->start + box->len - 2; i++) {
             box_weight += s->refs[i]->count;
             if (box_weight > median)
                 break;
         }

         ff_dlog(ctx, "split @ i=%-6d with w=%-6"PRIu64" (target=%6"PRIu64")\n", i, box_weight, median);

         split_box(s, box, i);
 
         box_id = get_next_box_id_to_split(s);
         box = box_id >= 0 ? &s->boxes[box_id] : NULL;
     }
 

     ratio = set_colorquant_ratio_meta(out, s->nb_boxes, s->nb_refs);
     av_log(ctx, AV_LOG_INFO, "%d%s colors generated out of %d colors; ratio=%f\n",
            s->nb_boxes, s->reserve_transparent ? "(+1)" : "", s->nb_refs, ratio);

 
     qsort(s->boxes, s->nb_boxes, sizeof(*s->boxes), cmp_color);
 

     write_palette(ctx, out);

 
     return out;
 }
 
 /**
  * Hashing function for the color.
  * It keeps the NBITS least significant bit of each component to make it
  * "random" even if the scene doesn't have much different colors.
  */
 static inline unsigned color_hash(uint32_t color)
 {
     const uint8_t r = color >> 16 & ((1<<NBITS)-1);
     const uint8_t g = color >>  8 & ((1<<NBITS)-1);
     const uint8_t b = color       & ((1<<NBITS)-1);
     return r<<(NBITS*2) | g<<NBITS | b;
 }
 
 /**
  * Locate the color in the hash table and increment its counter.
  */
 static int color_inc(struct hist_node *hist, uint32_t color)
 {
     int i;
     const unsigned hash = color_hash(color);
     struct hist_node *node = &hist[hash];
     struct color_ref *e;
 
     for (i = 0; i < node->nb_entries; i++) {
         e = &node->entries[i];
         if (e->color == color) {
             e->count++;
             return 0;
         }
     }
 
     e = av_dynarray2_add((void**)&node->entries, &node->nb_entries,
                          sizeof(*node->entries), NULL);
     if (!e)
         return AVERROR(ENOMEM);
     e->color = color;
     e->count = 1;
     return 1;
 }
 
 /**
  * Update histogram when pixels differ from previous frame.
  */
 static int update_histogram_diff(struct hist_node *hist,
                                  const AVFrame *f1, const AVFrame *f2)
 {
     int x, y, ret, nb_diff_colors = 0;
 
     for (y = 0; y < f1->height; y++) {
         const uint32_t *p = (const uint32_t *)(f1->data[0] + y*f1->linesize[0]);
         const uint32_t *q = (const uint32_t *)(f2->data[0] + y*f2->linesize[0]);
 

         for (x = 0; x < f1->width; x++) {

             if (p[x] == q[x])
                 continue;
             ret = color_inc(hist, p[x]);
             if (ret < 0)
                 return ret;
             nb_diff_colors += ret;
         }
     }
     return nb_diff_colors;
 }
 
 /**
  * Simple histogram of the frame.
  */
 static int update_histogram_frame(struct hist_node *hist, const AVFrame *f)
 {
     int x, y, ret, nb_diff_colors = 0;
 
     for (y = 0; y < f->height; y++) {
         const uint32_t *p = (const uint32_t *)(f->data[0] + y*f->linesize[0]);
 
         for (x = 0; x < f->width; x++) {
             ret = color_inc(hist, p[x]);
             if (ret < 0)
                 return ret;
             nb_diff_colors += ret;
         }
     }
     return nb_diff_colors;
 }
 
 /**
  * Update the histogram for each passing frame. No frame will be pushed here.
  */
 static int filter_frame(AVFilterLink *inlink, AVFrame *in)
 {
     AVFilterContext *ctx = inlink->dst;
     PaletteGenContext *s = ctx->priv;

     int ret = s->prev_frame ? update_histogram_diff(s->histogram, s->prev_frame, in)
                             : update_histogram_frame(s->histogram, in);

 
     if (ret > 0)
         s->nb_refs += ret;
 
     if (s->stats_mode == STATS_MODE_DIFF_FRAMES) {
         av_frame_free(&s->prev_frame);
         s->prev_frame = in;

     } else if (s->stats_mode == STATS_MODE_SINGLE_FRAMES) {
         AVFrame *out;
         int i;
 
         out = get_palette_frame(ctx);
         out->pts = in->pts;
         av_frame_free(&in);
         ret = ff_filter_frame(ctx->outputs[0], out);
         for (i = 0; i < HIST_SIZE; i++)
             av_freep(&s->histogram[i].entries);
         av_freep(&s->refs);
         s->nb_refs = 0;
         s->nb_boxes = 0;
         memset(s->boxes, 0, sizeof(s->boxes));
         memset(s->histogram, 0, sizeof(s->histogram));

     } else {
         av_frame_free(&in);
     }
 
     return ret;
 }
 
 /**
  * Returns only one frame at the end containing the full palette.
  */
 static int request_frame(AVFilterLink *outlink)
 {
     AVFilterContext *ctx = outlink->src;
     AVFilterLink *inlink = ctx->inputs[0];
     PaletteGenContext *s = ctx->priv;
     int r;
 
     r = ff_request_frame(inlink);

     if (r == AVERROR_EOF && !s->palette_pushed && s->nb_refs && s->stats_mode != STATS_MODE_SINGLE_FRAMES) {

         r = ff_filter_frame(outlink, get_palette_frame(ctx));
         s->palette_pushed = 1;
         return r;
     }
     return r;
 }
 
 /**
  * The output is one simple 16x16 squared-pixels palette.
  */
 static int config_output(AVFilterLink *outlink)
 {
     outlink->w = outlink->h = 16;
     outlink->sample_aspect_ratio = av_make_q(1, 1);
     return 0;
 }
 
 static av_cold void uninit(AVFilterContext *ctx)
 {
     int i;
     PaletteGenContext *s = ctx->priv;
 
     for (i = 0; i < HIST_SIZE; i++)
         av_freep(&s->histogram[i].entries);
     av_freep(&s->refs);

     av_frame_free(&s->prev_frame);

 }
 
 static const AVFilterPad palettegen_inputs[] = {
     {
         .name         = "default",
         .type         = AVMEDIA_TYPE_VIDEO,
         .filter_frame = filter_frame,
     },
     { NULL }
 };
 
 static const AVFilterPad palettegen_outputs[] = {
     {
         .name          = "default",
         .type          = AVMEDIA_TYPE_VIDEO,
         .config_props  = config_output,
         .request_frame = request_frame,
     },
     { NULL }
 };
 
 AVFilter ff_vf_palettegen = {
     .name          = "palettegen",
     .description   = NULL_IF_CONFIG_SMALL("Find the optimal palette for a given stream."),
     .priv_size     = sizeof(PaletteGenContext),
     .uninit        = uninit,
     .query_formats = query_formats,
     .inputs        = palettegen_inputs,
     .outputs       = palettegen_outputs,
     .priv_class    = &palettegen_class,
 };