/*

  * 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
  * Use a palette to downsample an input video stream.
  */
 
 #include "libavutil/bprint.h"

 #include "libavutil/internal.h"

 #include "libavutil/opt.h"

 #include "libavutil/qsort.h"

 #include "avfilter.h"

 #include "filters.h"

 #include "framesync.h"

 #include "internal.h"

 
 enum dithering_mode {
     DITHERING_NONE,
     DITHERING_BAYER,
     DITHERING_HECKBERT,
     DITHERING_FLOYD_STEINBERG,
     DITHERING_SIERRA2,
     DITHERING_SIERRA2_4A,
     NB_DITHERING
 };
 
 enum color_search_method {
     COLOR_SEARCH_NNS_ITERATIVE,
     COLOR_SEARCH_NNS_RECURSIVE,
     COLOR_SEARCH_BRUTEFORCE,
     NB_COLOR_SEARCHES
 };
 

 enum diff_mode {
     DIFF_MODE_NONE,
     DIFF_MODE_RECTANGLE,
     NB_DIFF_MODE
 };
 

 struct color_node {

     uint8_t val[4];

     uint8_t palette_id;
     int split;
     int left_id, right_id;
 };
 

 #define NBITS 5

 #define CACHE_SIZE (1<<(3*NBITS))
 
 struct cached_color {
     uint32_t color;
     uint8_t pal_entry;
 };
 
 struct cache_node {
     struct cached_color *entries;
     int nb_entries;
 };
 
 struct PaletteUseContext;
 

 typedef int (*set_frame_func)(struct PaletteUseContext *s, AVFrame *out, AVFrame *in,
                               int x_start, int y_start, int width, int height);

 
 typedef struct PaletteUseContext {
     const AVClass *class;

     FFFrameSync fs;

     struct cache_node cache[CACHE_SIZE];    /* lookup cache */
     struct color_node map[AVPALETTE_COUNT]; /* 3D-Tree (KD-Tree with K=3) for reverse colormap */
     uint32_t palette[AVPALETTE_COUNT];

     int transparency_index; /* index in the palette of transparency. -1 if there is no transparency in the palette. */
     int trans_thresh;

     int palette_loaded;
     int dither;

     int new;

     set_frame_func set_frame;
     int bayer_scale;
     int ordered_dither[8*8];

     int diff_mode;
     AVFrame *last_in;
     AVFrame *last_out;

 
     /* debug options */
     char *dot_filename;
     int color_search_method;
     int calc_mean_err;
     uint64_t total_mean_err;
     int debug_accuracy;
 } PaletteUseContext;
 
 #define OFFSET(x) offsetof(PaletteUseContext, x)
 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
 static const AVOption paletteuse_options[] = {
     { "dither", "select dithering mode", OFFSET(dither), AV_OPT_TYPE_INT, {.i64=DITHERING_SIERRA2_4A}, 0, NB_DITHERING-1, FLAGS, "dithering_mode" },
         { "bayer",           "ordered 8x8 bayer dithering (deterministic)",                            0, AV_OPT_TYPE_CONST, {.i64=DITHERING_BAYER},           INT_MIN, INT_MAX, FLAGS, "dithering_mode" },
         { "heckbert",        "dithering as defined by Paul Heckbert in 1982 (simple error diffusion)", 0, AV_OPT_TYPE_CONST, {.i64=DITHERING_HECKBERT},        INT_MIN, INT_MAX, FLAGS, "dithering_mode" },
         { "floyd_steinberg", "Floyd and Steingberg dithering (error diffusion)",                       0, AV_OPT_TYPE_CONST, {.i64=DITHERING_FLOYD_STEINBERG}, INT_MIN, INT_MAX, FLAGS, "dithering_mode" },
         { "sierra2",         "Frankie Sierra dithering v2 (error diffusion)",                          0, AV_OPT_TYPE_CONST, {.i64=DITHERING_SIERRA2},         INT_MIN, INT_MAX, FLAGS, "dithering_mode" },
         { "sierra2_4a",      "Frankie Sierra dithering v2 \"Lite\" (error diffusion)",                 0, AV_OPT_TYPE_CONST, {.i64=DITHERING_SIERRA2_4A},      INT_MIN, INT_MAX, FLAGS, "dithering_mode" },
     { "bayer_scale", "set scale for bayer dithering", OFFSET(bayer_scale), AV_OPT_TYPE_INT, {.i64=2}, 0, 5, FLAGS },

     { "diff_mode",   "set frame difference mode",     OFFSET(diff_mode),   AV_OPT_TYPE_INT, {.i64=DIFF_MODE_NONE}, 0, NB_DIFF_MODE-1, FLAGS, "diff_mode" },
         { "rectangle", "process smallest different rectangle", 0, AV_OPT_TYPE_CONST, {.i64=DIFF_MODE_RECTANGLE}, INT_MIN, INT_MAX, FLAGS, "diff_mode" },

     { "new", "take new palette for each output frame", OFFSET(new), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS },

     { "alpha_threshold", "set the alpha threshold for transparency", OFFSET(trans_thresh), AV_OPT_TYPE_INT, {.i64=128}, 0, 255 },

 
     /* following are the debug options, not part of the official API */
     { "debug_kdtree", "save Graphviz graph of the kdtree in specified file", OFFSET(dot_filename), AV_OPT_TYPE_STRING, {.str=NULL}, CHAR_MIN, CHAR_MAX, FLAGS },
     { "color_search", "set reverse colormap color search method", OFFSET(color_search_method), AV_OPT_TYPE_INT, {.i64=COLOR_SEARCH_NNS_ITERATIVE}, 0, NB_COLOR_SEARCHES-1, FLAGS, "search" },
         { "nns_iterative", "iterative search",             0, AV_OPT_TYPE_CONST, {.i64=COLOR_SEARCH_NNS_ITERATIVE}, INT_MIN, INT_MAX, FLAGS, "search" },
         { "nns_recursive", "recursive search",             0, AV_OPT_TYPE_CONST, {.i64=COLOR_SEARCH_NNS_RECURSIVE}, INT_MIN, INT_MAX, FLAGS, "search" },
         { "bruteforce",    "brute-force into the palette", 0, AV_OPT_TYPE_CONST, {.i64=COLOR_SEARCH_BRUTEFORCE},    INT_MIN, INT_MAX, FLAGS, "search" },

     { "mean_err", "compute and print mean error", OFFSET(calc_mean_err), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS },
     { "debug_accuracy", "test color search accuracy", OFFSET(debug_accuracy), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS },

     { NULL }
 };
 
 AVFILTER_DEFINE_CLASS(paletteuse);
 

 static int load_apply_palette(FFFrameSync *fs);
 

 static int query_formats(AVFilterContext *ctx)
 {
     static const enum AVPixelFormat in_fmts[]    = {AV_PIX_FMT_RGB32, AV_PIX_FMT_NONE};
     static const enum AVPixelFormat inpal_fmts[] = {AV_PIX_FMT_RGB32, AV_PIX_FMT_NONE};
     static const enum AVPixelFormat out_fmts[]   = {AV_PIX_FMT_PAL8,  AV_PIX_FMT_NONE};

     int ret;

     AVFilterFormats *in    = ff_make_format_list(in_fmts);
     AVFilterFormats *inpal = ff_make_format_list(inpal_fmts);
     AVFilterFormats *out   = ff_make_format_list(out_fmts);

     if (!in || !inpal || !out) {
         av_freep(&in);
         av_freep(&inpal);
         av_freep(&out);

         return AVERROR(ENOMEM);

     }

     if ((ret = ff_formats_ref(in   , &ctx->inputs[0]->out_formats)) < 0 ||
         (ret = ff_formats_ref(inpal, &ctx->inputs[1]->out_formats)) < 0 ||
         (ret = ff_formats_ref(out  , &ctx->outputs[0]->in_formats)) < 0)
         return ret;

     return 0;
 }
 
 static av_always_inline int dither_color(uint32_t px, int er, int eg, int eb, int scale, int shift)
 {

     return av_clip_uint8( px >> 24                                      ) << 24
          | av_clip_uint8((px >> 16 & 0xff) + ((er * scale) / (1<<shift))) << 16

          | av_clip_uint8((px >>  8 & 0xff) + ((eg * scale) / (1<<shift))) <<  8
          | av_clip_uint8((px       & 0xff) + ((eb * scale) / (1<<shift)));

 }
 

 static av_always_inline int diff(const uint8_t *c1, const uint8_t *c2, const int trans_thresh)

 {
     // XXX: try L*a*b with CIE76 (dL*dL + da*da + db*db)

     const int dr = c1[1] - c2[1];
     const int dg = c1[2] - c2[2];
     const int db = c1[3] - c2[3];
 
     if (c1[0] < trans_thresh && c2[0] < trans_thresh) {
         return 0;
     } else if (c1[0] >= trans_thresh && c2[0] >= trans_thresh) {
         return dr*dr + dg*dg + db*db;
     } else {
         return 255*255 + 255*255 + 255*255;
     }

 }
 

 static av_always_inline uint8_t colormap_nearest_bruteforce(const uint32_t *palette, const uint8_t *argb, const int trans_thresh)

 {
     int i, pal_id = -1, min_dist = INT_MAX;
 
     for (i = 0; i < AVPALETTE_COUNT; i++) {
         const uint32_t c = palette[i];
 

         if (c >> 24 >= trans_thresh) { // ignore transparent entry
             const uint8_t palargb[] = {
                 palette[i]>>24 & 0xff,

                 palette[i]>>16 & 0xff,
                 palette[i]>> 8 & 0xff,
                 palette[i]     & 0xff,
             };

             const int d = diff(palargb, argb, trans_thresh);

             if (d < min_dist) {
                 pal_id = i;
                 min_dist = d;
             }
         }
     }
     return pal_id;
 }
 
 /* Recursive form, simpler but a bit slower. Kept for reference. */
 struct nearest_color {
     int node_pos;
     int dist_sqd;
 };
 
 static void colormap_nearest_node(const struct color_node *map,
                                   const int node_pos,
                                   const uint8_t *target,

                                   const int trans_thresh,

                                   struct nearest_color *nearest)
 {
     const struct color_node *kd = map + node_pos;
     const int s = kd->split;
     int dx, nearer_kd_id, further_kd_id;
     const uint8_t *current = kd->val;

     const int current_to_target = diff(target, current, trans_thresh);

 
     if (current_to_target < nearest->dist_sqd) {
         nearest->node_pos = node_pos;
         nearest->dist_sqd = current_to_target;
     }
 
     if (kd->left_id != -1 || kd->right_id != -1) {
         dx = target[s] - current[s];
 
         if (dx <= 0) nearer_kd_id = kd->left_id,  further_kd_id = kd->right_id;
         else         nearer_kd_id = kd->right_id, further_kd_id = kd->left_id;
 
         if (nearer_kd_id != -1)

             colormap_nearest_node(map, nearer_kd_id, target, trans_thresh, nearest);

 
         if (further_kd_id != -1 && dx*dx < nearest->dist_sqd)

             colormap_nearest_node(map, further_kd_id, target, trans_thresh, nearest);

     }
 }
 

 static av_always_inline uint8_t colormap_nearest_recursive(const struct color_node *node, const uint8_t *rgb, const int trans_thresh)

 {
     struct nearest_color res = {.dist_sqd = INT_MAX, .node_pos = -1};

     colormap_nearest_node(node, 0, rgb, trans_thresh, &res);

     return node[res.node_pos].palette_id;
 }
 
 struct stack_node {
     int color_id;
     int dx2;
 };
 

 static av_always_inline uint8_t colormap_nearest_iterative(const struct color_node *root, const uint8_t *target, const int trans_thresh)

 {
     int pos = 0, best_node_id = -1, best_dist = INT_MAX, cur_color_id = 0;
     struct stack_node nodes[16];
     struct stack_node *node = &nodes[0];
 
     for (;;) {
 
         const struct color_node *kd = &root[cur_color_id];
         const uint8_t *current = kd->val;

         const int current_to_target = diff(target, current, trans_thresh);

 
         /* Compare current color node to the target and update our best node if
          * it's actually better. */
         if (current_to_target < best_dist) {
             best_node_id = cur_color_id;
             if (!current_to_target)
                 goto end; // exact match, we can return immediately
             best_dist = current_to_target;
         }
 
         /* Check if it's not a leaf */
         if (kd->left_id != -1 || kd->right_id != -1) {
             const int split = kd->split;
             const int dx = target[split] - current[split];
             int nearer_kd_id, further_kd_id;
 
             /* Define which side is the most interesting. */
             if (dx <= 0) nearer_kd_id = kd->left_id,  further_kd_id = kd->right_id;
             else         nearer_kd_id = kd->right_id, further_kd_id = kd->left_id;
 
             if (nearer_kd_id != -1) {
                 if (further_kd_id != -1) {
                     /* Here, both paths are defined, so we push a state for
                      * when we are going back. */
                     node->color_id = further_kd_id;
                     node->dx2 = dx*dx;
                     pos++;
                     node++;
                 }
                 /* We can now update current color with the most probable path
                  * (no need to create a state since there is nothing to save
                  * anymore). */
                 cur_color_id = nearer_kd_id;
                 continue;
             } else if (dx*dx < best_dist) {
                 /* The nearest path isn't available, so there is only one path
                  * possible and it's the least probable. We enter it only if the
                  * distance from the current point to the hyper rectangle is
                  * less than our best distance. */
                 cur_color_id = further_kd_id;
                 continue;
             }
         }
 
         /* Unstack as much as we can, typically as long as the least probable
          * branch aren't actually probable. */
         do {
             if (--pos < 0)
                 goto end;
             node--;
         } while (node->dx2 >= best_dist);
 
         /* We got a node where the least probable branch might actually contain
          * a relevant color. */
         cur_color_id = node->color_id;
     }
 
 end:
     return root[best_node_id].palette_id;
 }
 

 #define COLORMAP_NEAREST(search, palette, root, target, trans_thresh)                                    \
     search == COLOR_SEARCH_NNS_ITERATIVE ? colormap_nearest_iterative(root, target, trans_thresh) :      \
     search == COLOR_SEARCH_NNS_RECURSIVE ? colormap_nearest_recursive(root, target, trans_thresh) :      \
                                            colormap_nearest_bruteforce(palette, target, trans_thresh)

 
 /**
  * Check if the requested color is in the cache already. If not, find it in the
  * color tree and cache it.

  * Note: a, r, g, and b are the components of color, but are passed as well to avoid

  * recomputing them (they are generally computed by the caller for other uses).
  */

 static av_always_inline int color_get(PaletteUseContext *s, uint32_t color,

                                       uint8_t a, uint8_t r, uint8_t g, uint8_t b,

                                       const enum color_search_method search_method)

 {
     int i;

     const uint8_t argb_elts[] = {a, r, g, b};

     const uint8_t rhash = r & ((1<<NBITS)-1);
     const uint8_t ghash = g & ((1<<NBITS)-1);
     const uint8_t bhash = b & ((1<<NBITS)-1);
     const unsigned hash = rhash<<(NBITS*2) | ghash<<NBITS | bhash;

     struct cache_node *node = &s->cache[hash];

     struct cached_color *e;
 

     // first, check for transparency

     if (a < s->trans_thresh && s->transparency_index >= 0) {
         return s->transparency_index;

     }
 

     for (i = 0; i < node->nb_entries; i++) {
         e = &node->entries[i];
         if (e->color == color)
             return e->pal_entry;
     }
 
     e = av_dynarray2_add((void**)&node->entries, &node->nb_entries,
                          sizeof(*node->entries), NULL);
     if (!e)
         return AVERROR(ENOMEM);
     e->color = color;

     e->pal_entry = COLORMAP_NEAREST(search_method, s->palette, s->map, argb_elts, s->trans_thresh);

     return e->pal_entry;
 }
 

 static av_always_inline int get_dst_color_err(PaletteUseContext *s,
                                               uint32_t c, int *er, int *eg, int *eb,

                                               const enum color_search_method search_method)

 {

     const uint8_t a = c >> 24 & 0xff;

     const uint8_t r = c >> 16 & 0xff;
     const uint8_t g = c >>  8 & 0xff;
     const uint8_t b = c       & 0xff;

     uint32_t dstc;

     const int dstx = color_get(s, c, a, r, g, b, search_method);

     if (dstx < 0)
         return dstx;
     dstc = s->palette[dstx];

     *er = r - (dstc >> 16 & 0xff);
     *eg = g - (dstc >>  8 & 0xff);
     *eb = b - (dstc       & 0xff);
     return dstx;
 }
 
 static av_always_inline int set_frame(PaletteUseContext *s, AVFrame *out, AVFrame *in,

                                       int x_start, int y_start, int w, int h,

                                       enum dithering_mode dither,
                                       const enum color_search_method search_method)
 {
     int x, y;
     const int src_linesize = in ->linesize[0] >> 2;
     const int dst_linesize = out->linesize[0];

     uint32_t *src = ((uint32_t *)in ->data[0]) + y_start*src_linesize;
     uint8_t  *dst =              out->data[0]  + y_start*dst_linesize;

     w += x_start;
     h += y_start;
 
     for (y = y_start; y < h; y++) {
         for (x = x_start; x < w; x++) {

             int er, eg, eb;
 
             if (dither == DITHERING_BAYER) {
                 const int d = s->ordered_dither[(y & 7)<<3 | (x & 7)];

                 const uint8_t a8 = src[x] >> 24 & 0xff;

                 const uint8_t r8 = src[x] >> 16 & 0xff;
                 const uint8_t g8 = src[x] >>  8 & 0xff;
                 const uint8_t b8 = src[x]       & 0xff;
                 const uint8_t r = av_clip_uint8(r8 + d);
                 const uint8_t g = av_clip_uint8(g8 + d);
                 const uint8_t b = av_clip_uint8(b8 + d);

                 const int color = color_get(s, src[x], a8, r, g, b, search_method);

 
                 if (color < 0)
                     return color;
                 dst[x] = color;
 
             } else if (dither == DITHERING_HECKBERT) {

                 const int right = x < w - 1, down = y < h - 1;

                 const int color = get_dst_color_err(s, src[x], &er, &eg, &eb, search_method);

 
                 if (color < 0)
                     return color;
                 dst[x] = color;
 
                 if (right)         src[               x + 1] = dither_color(src[               x + 1], er, eg, eb, 3, 3);
                 if (         down) src[src_linesize + x    ] = dither_color(src[src_linesize + x    ], er, eg, eb, 3, 3);
                 if (right && down) src[src_linesize + x + 1] = dither_color(src[src_linesize + x + 1], er, eg, eb, 2, 3);
 
             } else if (dither == DITHERING_FLOYD_STEINBERG) {

                 const int right = x < w - 1, down = y < h - 1, left = x > x_start;

                 const int color = get_dst_color_err(s, src[x], &er, &eg, &eb, search_method);

 
                 if (color < 0)
                     return color;
                 dst[x] = color;
 
                 if (right)         src[               x + 1] = dither_color(src[               x + 1], er, eg, eb, 7, 4);
                 if (left  && down) src[src_linesize + x - 1] = dither_color(src[src_linesize + x - 1], er, eg, eb, 3, 4);
                 if (         down) src[src_linesize + x    ] = dither_color(src[src_linesize + x    ], er, eg, eb, 5, 4);
                 if (right && down) src[src_linesize + x + 1] = dither_color(src[src_linesize + x + 1], er, eg, eb, 1, 4);
 
             } else if (dither == DITHERING_SIERRA2) {

                 const int right  = x < w - 1, down  = y < h - 1, left  = x > x_start;
                 const int right2 = x < w - 2,                    left2 = x > x_start + 1;

                 const int color = get_dst_color_err(s, src[x], &er, &eg, &eb, search_method);

 
                 if (color < 0)
                     return color;
                 dst[x] = color;
 
                 if (right)          src[                 x + 1] = dither_color(src[                 x + 1], er, eg, eb, 4, 4);
                 if (right2)         src[                 x + 2] = dither_color(src[                 x + 2], er, eg, eb, 3, 4);
 
                 if (down) {
                     if (left2)      src[  src_linesize + x - 2] = dither_color(src[  src_linesize + x - 2], er, eg, eb, 1, 4);
                     if (left)       src[  src_linesize + x - 1] = dither_color(src[  src_linesize + x - 1], er, eg, eb, 2, 4);

                     if (1)          src[  src_linesize + x    ] = dither_color(src[  src_linesize + x    ], er, eg, eb, 3, 4);

                     if (right)      src[  src_linesize + x + 1] = dither_color(src[  src_linesize + x + 1], er, eg, eb, 2, 4);
                     if (right2)     src[  src_linesize + x + 2] = dither_color(src[  src_linesize + x + 2], er, eg, eb, 1, 4);
                 }
 
             } else if (dither == DITHERING_SIERRA2_4A) {

                 const int right = x < w - 1, down = y < h - 1, left = x > x_start;

                 const int color = get_dst_color_err(s, src[x], &er, &eg, &eb, search_method);

 
                 if (color < 0)
                     return color;
                 dst[x] = color;
 
                 if (right)         src[               x + 1] = dither_color(src[               x + 1], er, eg, eb, 2, 2);
                 if (left  && down) src[src_linesize + x - 1] = dither_color(src[src_linesize + x - 1], er, eg, eb, 1, 2);
                 if (         down) src[src_linesize + x    ] = dither_color(src[src_linesize + x    ], er, eg, eb, 1, 2);
 
             } else {

                 const uint8_t a = src[x] >> 24 & 0xff;

                 const uint8_t r = src[x] >> 16 & 0xff;
                 const uint8_t g = src[x] >>  8 & 0xff;
                 const uint8_t b = src[x]       & 0xff;

                 const int color = color_get(s, src[x], a, r, g, b, search_method);

 
                 if (color < 0)
                     return color;
                 dst[x] = color;
             }
         }
         src += src_linesize;
         dst += dst_linesize;
     }
     return 0;
 }
 
 #define INDENT 4
 static void disp_node(AVBPrint *buf,
                       const struct color_node *map,
                       int parent_id, int node_id,
                       int depth)
 {
     const struct color_node *node = &map[node_id];

     const uint32_t fontcolor = node->val[1] > 0x50 &&
                                node->val[2] > 0x50 &&
                                node->val[3] > 0x50 ? 0 : 0xffffff;

     const int rgb_comp = node->split - 1;

     av_bprintf(buf, "%*cnode%d ["
                "label=\"%c%02X%c%02X%c%02X%c\" "
                "fillcolor=\"#%02x%02x%02x\" "

                "fontcolor=\"#%06"PRIX32"\"]\n",

                depth*INDENT, ' ', node->palette_id,

                "[  "[rgb_comp], node->val[1],
                "][ "[rgb_comp], node->val[2],
                " ]["[rgb_comp], node->val[3],
                "  ]"[rgb_comp],

                node->val[1], node->val[2], node->val[3],

                fontcolor);
     if (parent_id != -1)
         av_bprintf(buf, "%*cnode%d -> node%d\n", depth*INDENT, ' ',
                    map[parent_id].palette_id, node->palette_id);
     if (node->left_id  != -1) disp_node(buf, map, node_id, node->left_id,  depth + 1);
     if (node->right_id != -1) disp_node(buf, map, node_id, node->right_id, depth + 1);
 }
 
 // debug_kdtree=kdtree.dot -> dot -Tpng kdtree.dot > kdtree.png
 static int disp_tree(const struct color_node *node, const char *fname)
 {
     AVBPrint buf;
     FILE *f = av_fopen_utf8(fname, "w");
 
     if (!f) {
         int ret = AVERROR(errno);
         av_log(NULL, AV_LOG_ERROR, "Cannot open file '%s' for writing: %s\n",
                fname, av_err2str(ret));
         return ret;
     }
 
     av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
 
     av_bprintf(&buf, "digraph {\n");
     av_bprintf(&buf, "    node [style=filled fontsize=10 shape=box]\n");
     disp_node(&buf, node, -1, 0, 0);
     av_bprintf(&buf, "}\n");
 
     fwrite(buf.str, 1, buf.len, f);
     fclose(f);
     av_bprint_finalize(&buf, NULL);
     return 0;
 }
 

 static int debug_accuracy(const struct color_node *node, const uint32_t *palette, const int trans_thresh,

                           const enum color_search_method search_method)
 {
     int r, g, b, ret = 0;
 
     for (r = 0; r < 256; r++) {
         for (g = 0; g < 256; g++) {
             for (b = 0; b < 256; b++) {

                 const uint8_t argb[] = {0xff, r, g, b};
                 const int r1 = COLORMAP_NEAREST(search_method, palette, node, argb, trans_thresh);
                 const int r2 = colormap_nearest_bruteforce(palette, argb, trans_thresh);

                 if (r1 != r2) {
                     const uint32_t c1 = palette[r1];
                     const uint32_t c2 = palette[r2];

                     const uint8_t palargb1[] = { 0xff, c1>>16 & 0xff, c1>> 8 & 0xff, c1 & 0xff };
                     const uint8_t palargb2[] = { 0xff, c2>>16 & 0xff, c2>> 8 & 0xff, c2 & 0xff };
                     const int d1 = diff(palargb1, argb, trans_thresh);
                     const int d2 = diff(palargb2, argb, trans_thresh);

                     if (d1 != d2) {
                         av_log(NULL, AV_LOG_ERROR,

                                "/!\\ %02X%02X%02X: %d ! %d (%06"PRIX32" ! %06"PRIX32") / dist: %d ! %d\n",

                                r, g, b, r1, r2, c1 & 0xffffff, c2 & 0xffffff, d1, d2);
                         ret = 1;
                     }
                 }
             }
         }
     }
     return ret;
 }
 
 struct color {
     uint32_t value;
     uint8_t pal_id;
 };
 
 struct color_rect {
     uint8_t min[3];
     uint8_t max[3];
 };
 
 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 *a = pa;                         \
     const struct color *b = pb;                         \

     return   (a->value >> (8 * (3 - (pos))) & 0xff)     \
            - (b->value >> (8 * (3 - (pos))) & 0xff);    \

 }
 

 DECLARE_CMP_FUNC(a, 0)
 DECLARE_CMP_FUNC(r, 1)
 DECLARE_CMP_FUNC(g, 2)
 DECLARE_CMP_FUNC(b, 3)

 static const cmp_func cmp_funcs[] = {cmp_a, cmp_r, cmp_g, cmp_b};

 
 static int get_next_color(const uint8_t *color_used, const uint32_t *palette,

                           const int trans_thresh,

                           int *component, const struct color_rect *box)
 {
     int wr, wg, wb;
     int i, longest = 0;
     unsigned nb_color = 0;
     struct color_rect ranges;
     struct color tmp_pal[256];

     cmp_func cmpf;

 
     ranges.min[0] = ranges.min[1] = ranges.min[2] = 0xff;
     ranges.max[0] = ranges.max[1] = ranges.max[2] = 0x00;
 
     for (i = 0; i < AVPALETTE_COUNT; i++) {
         const uint32_t c = palette[i];

         const uint8_t a = c >> 24 & 0xff;

         const uint8_t r = c >> 16 & 0xff;
         const uint8_t g = c >>  8 & 0xff;
         const uint8_t b = c       & 0xff;
 

         if (a < trans_thresh) {
             continue;
         }
 
         if (color_used[i] || (a != 0xff) ||

             r < box->min[0] || g < box->min[1] || b < box->min[2] ||
             r > box->max[0] || g > box->max[1] || b > box->max[2])
             continue;
 
         if (r < ranges.min[0]) ranges.min[0] = r;
         if (g < ranges.min[1]) ranges.min[1] = g;
         if (b < ranges.min[2]) ranges.min[2] = b;
 
         if (r > ranges.max[0]) ranges.max[0] = r;
         if (g > ranges.max[1]) ranges.max[1] = g;
         if (b > ranges.max[2]) ranges.max[2] = b;
 
         tmp_pal[nb_color].value  = c;
         tmp_pal[nb_color].pal_id = i;
 
         nb_color++;
     }
 
     if (!nb_color)
         return -1;
 
     /* define longest axis that will be the split component */
     wr = ranges.max[0] - ranges.min[0];
     wg = ranges.max[1] - ranges.min[1];
     wb = ranges.max[2] - ranges.min[2];

     if (wr >= wg && wr >= wb) longest = 1;
     if (wg >= wr && wg >= wb) longest = 2;
     if (wb >= wr && wb >= wg) longest = 3;

     cmpf = cmp_funcs[longest];

     *component = longest;
 
     /* sort along this axis to get median */

     AV_QSORT(tmp_pal, nb_color, struct color, cmpf);

 
     return tmp_pal[nb_color >> 1].pal_id;
 }
 
 static int colormap_insert(struct color_node *map,
                            uint8_t *color_used,
                            int *nb_used,
                            const uint32_t *palette,

                            const int trans_thresh,

                            const struct color_rect *box)
 {
     uint32_t c;
     int component, cur_id;
     int node_left_id = -1, node_right_id = -1;
     struct color_node *node;
     struct color_rect box1, box2;

     const int pal_id = get_next_color(color_used, palette, trans_thresh, &component, box);

 
     if (pal_id < 0)
         return -1;
 
     /* create new node with that color */
     cur_id = (*nb_used)++;
     c = palette[pal_id];
     node = &map[cur_id];
     node->split = component;
     node->palette_id = pal_id;

     node->val[0] = c>>24 & 0xff;
     node->val[1] = c>>16 & 0xff;
     node->val[2] = c>> 8 & 0xff;
     node->val[3] = c     & 0xff;

 
     color_used[pal_id] = 1;
 
     /* get the two boxes this node creates */
     box1 = box2 = *box;

     box1.max[component-1] = node->val[component];
     box2.min[component-1] = node->val[component] + 1;

     node_left_id = colormap_insert(map, color_used, nb_used, palette, trans_thresh, &box1);

     if (box2.min[component-1] <= box2.max[component-1])
         node_right_id = colormap_insert(map, color_used, nb_used, palette, trans_thresh, &box2);

 
     node->left_id  = node_left_id;
     node->right_id = node_right_id;
 
     return cur_id;
 }
 
 static int cmp_pal_entry(const void *a, const void *b)
 {
     const int c1 = *(const uint32_t *)a & 0xffffff;
     const int c2 = *(const uint32_t *)b & 0xffffff;
     return c1 - c2;
 }
 
 static void load_colormap(PaletteUseContext *s)
 {
     int i, nb_used = 0;
     uint8_t color_used[AVPALETTE_COUNT] = {0};
     uint32_t last_color = 0;
     struct color_rect box;
 
     /* disable transparent colors and dups */
     qsort(s->palette, AVPALETTE_COUNT, sizeof(*s->palette), cmp_pal_entry);

     // update transparency index:
     if (s->transparency_index >= 0) {
         for (i = 0; i < AVPALETTE_COUNT; i++) {
             if ((s->palette[i]>>24 & 0xff) == 0) {
                 s->transparency_index = i; // we are assuming at most one transparent color in palette
                 break;
             }
         }
     }
 

     for (i = 0; i < AVPALETTE_COUNT; i++) {
         const uint32_t c = s->palette[i];
         if (i != 0 && c == last_color) {
             color_used[i] = 1;
             continue;
         }
         last_color = c;

         if (c >> 24 < s->trans_thresh) {

             color_used[i] = 1; // ignore transparent color(s)
             continue;
         }
     }
 
     box.min[0] = box.min[1] = box.min[2] = 0x00;
     box.max[0] = box.max[1] = box.max[2] = 0xff;
 

     colormap_insert(s->map, color_used, &nb_used, s->palette, s->trans_thresh, &box);

 
     if (s->dot_filename)
         disp_tree(s->map, s->dot_filename);
 
     if (s->debug_accuracy) {

         if (!debug_accuracy(s->map, s->palette, s->trans_thresh, s->color_search_method))

             av_log(NULL, AV_LOG_INFO, "Accuracy check passed\n");
     }
 }
 
 static void debug_mean_error(PaletteUseContext *s, const AVFrame *in1,
                              const AVFrame *in2, int frame_count)
 {
     int x, y;
     const uint32_t *palette = s->palette;
     uint32_t *src1 = (uint32_t *)in1->data[0];
     uint8_t  *src2 =             in2->data[0];
     const int src1_linesize = in1->linesize[0] >> 2;
     const int src2_linesize = in2->linesize[0];
     const float div = in1->width * in1->height * 3;
     unsigned mean_err = 0;
 
     for (y = 0; y < in1->height; y++) {
         for (x = 0; x < in1->width; x++) {
             const uint32_t c1 = src1[x];
             const uint32_t c2 = palette[src2[x]];

             const uint8_t argb1[] = {0xff, c1 >> 16 & 0xff, c1 >> 8 & 0xff, c1 & 0xff};
             const uint8_t argb2[] = {0xff, c2 >> 16 & 0xff, c2 >> 8 & 0xff, c2 & 0xff};
             mean_err += diff(argb1, argb2, s->trans_thresh);

         }
         src1 += src1_linesize;
         src2 += src2_linesize;
     }
 
     s->total_mean_err += mean_err;
 
     av_log(NULL, AV_LOG_INFO, "MEP:%.3f TotalMEP:%.3f\n",
            mean_err / div, s->total_mean_err / (div * frame_count));
 }
 

 static void set_processing_window(enum diff_mode diff_mode,
                                   const AVFrame *prv_src, const AVFrame *cur_src,
                                   const AVFrame *prv_dst,       AVFrame *cur_dst,
                                   int *xp, int *yp, int *wp, int *hp)
 {
     int x_start = 0, y_start = 0;
     int width  = cur_src->width;
     int height = cur_src->height;
 
     if (prv_src && diff_mode == DIFF_MODE_RECTANGLE) {
         int y;
         int x_end = cur_src->width  - 1,
             y_end = cur_src->height - 1;
         const uint32_t *prv_srcp = (const uint32_t *)prv_src->data[0];
         const uint32_t *cur_srcp = (const uint32_t *)cur_src->data[0];
         const uint8_t  *prv_dstp = prv_dst->data[0];
         uint8_t        *cur_dstp = cur_dst->data[0];
 
         const int prv_src_linesize = prv_src->linesize[0] >> 2;
         const int cur_src_linesize = cur_src->linesize[0] >> 2;
         const int prv_dst_linesize = prv_dst->linesize[0];
         const int cur_dst_linesize = cur_dst->linesize[0];
 
         /* skip common lines */
         while (y_start < y_end && !memcmp(prv_srcp + y_start*prv_src_linesize,
                                           cur_srcp + y_start*cur_src_linesize,
                                           cur_src->width * 4)) {
             memcpy(cur_dstp + y_start*cur_dst_linesize,
                    prv_dstp + y_start*prv_dst_linesize,
                    cur_dst->width);
             y_start++;
         }
         while (y_end > y_start && !memcmp(prv_srcp + y_end*prv_src_linesize,
                                           cur_srcp + y_end*cur_src_linesize,
                                           cur_src->width * 4)) {
             memcpy(cur_dstp + y_end*cur_dst_linesize,
                    prv_dstp + y_end*prv_dst_linesize,
                    cur_dst->width);
             y_end--;
         }
 
         height = y_end + 1 - y_start;
 
         /* skip common columns */
         while (x_start < x_end) {
             int same_column = 1;
             for (y = y_start; y <= y_end; y++) {
                 if (prv_srcp[y*prv_src_linesize + x_start] != cur_srcp[y*cur_src_linesize + x_start]) {
                     same_column = 0;
                     break;
                 }
             }
             if (!same_column)
                 break;
             x_start++;
         }
         while (x_end > x_start) {
             int same_column = 1;
             for (y = y_start; y <= y_end; y++) {
                 if (prv_srcp[y*prv_src_linesize + x_end] != cur_srcp[y*cur_src_linesize + x_end]) {
                     same_column = 0;
                     break;
                 }
             }
             if (!same_column)
                 break;
             x_end--;
         }
         width = x_end + 1 - x_start;
 
         if (x_start) {
             for (y = y_start; y <= y_end; y++)
                 memcpy(cur_dstp + y*cur_dst_linesize,
                        prv_dstp + y*prv_dst_linesize, x_start);
         }
         if (x_end != cur_src->width - 1) {
             const int copy_len = cur_src->width - 1 - x_end;
             for (y = y_start; y <= y_end; y++)
                 memcpy(cur_dstp + y*cur_dst_linesize + x_end + 1,
                        prv_dstp + y*prv_dst_linesize + x_end + 1,
                        copy_len);
         }
     }
     *xp = x_start;
     *yp = y_start;
     *wp = width;
     *hp = height;
 }
 

 static AVFrame *apply_palette(AVFilterLink *inlink, AVFrame *in)
 {

     int x, y, w, h;

     AVFilterContext *ctx = inlink->dst;
     PaletteUseContext *s = ctx->priv;
     AVFilterLink *outlink = inlink->dst->outputs[0];
 
     AVFrame *out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
     if (!out) {
         av_frame_free(&in);
         return NULL;
     }
     av_frame_copy_props(out, in);

 
     set_processing_window(s->diff_mode, s->last_in, in,
                           s->last_out, out, &x, &y, &w, &h);
     av_frame_free(&s->last_in);
     av_frame_free(&s->last_out);
     s->last_in  = av_frame_clone(in);
     s->last_out = av_frame_clone(out);
     if (!s->last_in || !s->last_out ||
         av_frame_make_writable(s->last_in) < 0) {

         av_frame_free(&in);
         av_frame_free(&out);
         return NULL;
     }

     ff_dlog(ctx, "%dx%d rect: (%d;%d) -> (%d,%d) [area:%dx%d]\n",

             w, h, x, y, x+w, y+h, in->width, in->height);
 
     if (s->set_frame(s, out, in, x, y, w, h) < 0) {
         av_frame_free(&out);
         return NULL;
     }

     memcpy(out->data[1], s->palette, AVPALETTE_SIZE);
     if (s->calc_mean_err)

         debug_mean_error(s, in, out, inlink->frame_count_out);

     av_frame_free(&in);
     return out;
 }
 
 static int config_output(AVFilterLink *outlink)
 {
     int ret;
     AVFilterContext *ctx = outlink->src;
     PaletteUseContext *s = ctx->priv;
 

     ret = ff_framesync_init_dualinput(&s->fs, ctx);

     if (ret < 0)
         return ret;
     s->fs.opt_repeatlast = 1; // only 1 frame in the palette
     s->fs.in[1].before = s->fs.in[1].after = EXT_INFINITY;
     s->fs.on_event = load_apply_palette;
 

     outlink->w = ctx->inputs[0]->w;
     outlink->h = ctx->inputs[0]->h;
 
     outlink->time_base = ctx->inputs[0]->time_base;

     if ((ret = ff_framesync_configure(&s->fs)) < 0)

         return ret;
     return 0;
 }
 
 static int config_input_palette(AVFilterLink *inlink)
 {
     AVFilterContext *ctx = inlink->dst;
 
     if (inlink->w * inlink->h != AVPALETTE_COUNT) {
         av_log(ctx, AV_LOG_ERROR,
                "Palette input must contain exactly %d pixels. "
                "Specified input has %dx%d=%d pixels\n",
                AVPALETTE_COUNT, inlink->w, inlink->h,
                inlink->w * inlink->h);
         return AVERROR(EINVAL);
     }
     return 0;
 }
 
 static void load_palette(PaletteUseContext *s, const AVFrame *palette_frame)
 {
     int i, x, y;
     const uint32_t *p = (const uint32_t *)palette_frame->data[0];
     const int p_linesize = palette_frame->linesize[0] >> 2;
 

     s->transparency_index = -1;
 

     if (s->new) {
         memset(s->palette, 0, sizeof(s->palette));
         memset(s->map, 0, sizeof(s->map));
         for (i = 0; i < CACHE_SIZE; i++)
             av_freep(&s->cache[i].entries);
         memset(s->cache, 0, sizeof(s->cache));
     }
 

     i = 0;
     for (y = 0; y < palette_frame->height; y++) {

         for (x = 0; x < palette_frame->width; x++) {
             s->palette[i] = p[x];
             if (p[x]>>24 < s->trans_thresh) {
                 s->transparency_index = i; // we are assuming at most one transparent color in palette
             }
             i++;
         }

         p += p_linesize;
     }
 
     load_colormap(s);
 

     if (!s->new)
         s->palette_loaded = 1;

 }
 

 static int load_apply_palette(FFFrameSync *fs)

 {

     AVFilterContext *ctx = fs->parent;

     AVFilterLink *inlink = ctx->inputs[0];
     PaletteUseContext *s = ctx->priv;

     AVFrame *master, *second, *out;

     int ret;
 
     // writable for error diffusal dithering

     ret = ff_framesync_dualinput_get_writable(fs, &master, &second);

     if (ret < 0)
         return ret;

     if (!master || !second) {

         ret = AVERROR_BUG;
         goto error;
     }

     if (!s->palette_loaded) {
         load_palette(s, second);
     }

     out = apply_palette(inlink, master);

     return ff_filter_frame(ctx->outputs[0], out);

 error:

     av_frame_free(&master);

     av_frame_free(&second);
     return ret;

 }
 
 #define DEFINE_SET_FRAME(color_search, name, value)                             \

 static int set_frame_##name(PaletteUseContext *s, AVFrame *out, AVFrame *in,    \
                             int x_start, int y_start, int w, int h)             \

 {                                                                               \

     return set_frame(s, out, in, x_start, y_start, w, h, value, color_search);  \

 }
 
 #define DEFINE_SET_FRAME_COLOR_SEARCH(color_search, color_search_macro)                                 \
     DEFINE_SET_FRAME(color_search_macro, color_search##_##none,            DITHERING_NONE)              \
     DEFINE_SET_FRAME(color_search_macro, color_search##_##bayer,           DITHERING_BAYER)             \
     DEFINE_SET_FRAME(color_search_macro, color_search##_##heckbert,        DITHERING_HECKBERT)          \
     DEFINE_SET_FRAME(color_search_macro, color_search##_##floyd_steinberg, DITHERING_FLOYD_STEINBERG)   \
     DEFINE_SET_FRAME(color_search_macro, color_search##_##sierra2,         DITHERING_SIERRA2)           \
     DEFINE_SET_FRAME(color_search_macro, color_search##_##sierra2_4a,      DITHERING_SIERRA2_4A)        \
 
 DEFINE_SET_FRAME_COLOR_SEARCH(nns_iterative, COLOR_SEARCH_NNS_ITERATIVE)
 DEFINE_SET_FRAME_COLOR_SEARCH(nns_recursive, COLOR_SEARCH_NNS_RECURSIVE)
 DEFINE_SET_FRAME_COLOR_SEARCH(bruteforce,    COLOR_SEARCH_BRUTEFORCE)
 
 #define DITHERING_ENTRIES(color_search) {       \
     set_frame_##color_search##_none,            \
     set_frame_##color_search##_bayer,           \
     set_frame_##color_search##_heckbert,        \
     set_frame_##color_search##_floyd_steinberg, \
     set_frame_##color_search##_sierra2,         \
     set_frame_##color_search##_sierra2_4a,      \
 }
 
 static const set_frame_func set_frame_lut[NB_COLOR_SEARCHES][NB_DITHERING] = {
     DITHERING_ENTRIES(nns_iterative),
     DITHERING_ENTRIES(nns_recursive),
     DITHERING_ENTRIES(bruteforce),
 };
 
 static int dither_value(int p)
 {
     const int q = p ^ (p >> 3);
     return   (p & 4) >> 2 | (q & 4) >> 1 \
            | (p & 2) << 1 | (q & 2) << 2 \
            | (p & 1) << 4 | (q & 1) << 5;
 }
 
 static av_cold int init(AVFilterContext *ctx)
 {
     PaletteUseContext *s = ctx->priv;
 
     s->set_frame = set_frame_lut[s->color_search_method][s->dither];
 
     if (s->dither == DITHERING_BAYER) {
         int i;
         const int delta = 1 << (5 - s->bayer_scale); // to avoid too much luma
 
         for (i = 0; i < FF_ARRAY_ELEMS(s->ordered_dither); i++)
             s->ordered_dither[i] = (dither_value(i) >> s->bayer_scale) - delta;
     }
 
     return 0;
 }
 

 static int activate(AVFilterContext *ctx)

 {

     PaletteUseContext *s = ctx->priv;

     return ff_framesync_activate(&s->fs);

 }
 
 static av_cold void uninit(AVFilterContext *ctx)
 {
     int i;
     PaletteUseContext *s = ctx->priv;
 

     ff_framesync_uninit(&s->fs);

     for (i = 0; i < CACHE_SIZE; i++)
         av_freep(&s->cache[i].entries);

     av_frame_free(&s->last_in);
     av_frame_free(&s->last_out);

 }
 
 static const AVFilterPad paletteuse_inputs[] = {
     {
         .name           = "default",
         .type           = AVMEDIA_TYPE_VIDEO,
     },{
         .name           = "palette",
         .type           = AVMEDIA_TYPE_VIDEO,
         .config_props   = config_input_palette,
     },
     { NULL }
 };
 
 static const AVFilterPad paletteuse_outputs[] = {
     {
         .name          = "default",
         .type          = AVMEDIA_TYPE_VIDEO,
         .config_props  = config_output,
     },
     { NULL }
 };
 
 AVFilter ff_vf_paletteuse = {
     .name          = "paletteuse",
     .description   = NULL_IF_CONFIG_SMALL("Use a palette to downsample an input video stream."),
     .priv_size     = sizeof(PaletteUseContext),
     .query_formats = query_formats,
     .init          = init,
     .uninit        = uninit,

     .activate      = activate,

     .inputs        = paletteuse_inputs,
     .outputs       = paletteuse_outputs,
     .priv_class    = &paletteuse_class,
 };