/*
  * Copyright (c) 2013 Clément Bœsch
  *
  * 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
  */
 
 #include "libavutil/opt.h"

 #include "libavutil/bprint.h"

 #include "libavutil/eval.h"

 #include "libavutil/file.h"
 #include "libavutil/intreadwrite.h"

 #include "libavutil/avassert.h"

 #include "libavutil/pixdesc.h"

 #include "avfilter.h"

 #include "drawutils.h"

 #include "formats.h"
 #include "internal.h"
 #include "video.h"
 

 #define R 0
 #define G 1
 #define B 2
 #define A 3
 

 struct keypoint {
     double x, y;
     struct keypoint *next;
 };
 
 #define NB_COMP 3
 

 enum preset {
     PRESET_NONE,
     PRESET_COLOR_NEGATIVE,
     PRESET_CROSS_PROCESS,
     PRESET_DARKER,
     PRESET_INCREASE_CONTRAST,
     PRESET_LIGHTER,
     PRESET_LINEAR_CONTRAST,
     PRESET_MEDIUM_CONTRAST,
     PRESET_NEGATIVE,
     PRESET_STRONG_CONTRAST,
     PRESET_VINTAGE,
     NB_PRESETS,
 };
 

 typedef struct CurvesContext {

     const AVClass *class;

     int preset;

     char *comp_points_str[NB_COMP + 1];

     char *comp_points_str_all;

     uint16_t *graph[NB_COMP + 1];
     int lut_size;

     char *psfile;

     uint8_t rgba_map[4];
     int step;

     char *plot_filename;

     int is_16bit;

 } CurvesContext;
 

 typedef struct ThreadData {
     AVFrame *in, *out;
 } ThreadData;
 

 #define OFFSET(x) offsetof(CurvesContext, x)
 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
 static const AVOption curves_options[] = {

     { "preset", "select a color curves preset", OFFSET(preset), AV_OPT_TYPE_INT, {.i64=PRESET_NONE}, PRESET_NONE, NB_PRESETS-1, FLAGS, "preset_name" },

         { "none",               NULL, 0, AV_OPT_TYPE_CONST, {.i64=PRESET_NONE},                 INT_MIN, INT_MAX, FLAGS, "preset_name" },

         { "color_negative",     NULL, 0, AV_OPT_TYPE_CONST, {.i64=PRESET_COLOR_NEGATIVE},       INT_MIN, INT_MAX, FLAGS, "preset_name" },
         { "cross_process",      NULL, 0, AV_OPT_TYPE_CONST, {.i64=PRESET_CROSS_PROCESS},        INT_MIN, INT_MAX, FLAGS, "preset_name" },
         { "darker",             NULL, 0, AV_OPT_TYPE_CONST, {.i64=PRESET_DARKER},               INT_MIN, INT_MAX, FLAGS, "preset_name" },
         { "increase_contrast",  NULL, 0, AV_OPT_TYPE_CONST, {.i64=PRESET_INCREASE_CONTRAST},    INT_MIN, INT_MAX, FLAGS, "preset_name" },
         { "lighter",            NULL, 0, AV_OPT_TYPE_CONST, {.i64=PRESET_LIGHTER},              INT_MIN, INT_MAX, FLAGS, "preset_name" },
         { "linear_contrast",    NULL, 0, AV_OPT_TYPE_CONST, {.i64=PRESET_LINEAR_CONTRAST},      INT_MIN, INT_MAX, FLAGS, "preset_name" },
         { "medium_contrast",    NULL, 0, AV_OPT_TYPE_CONST, {.i64=PRESET_MEDIUM_CONTRAST},      INT_MIN, INT_MAX, FLAGS, "preset_name" },
         { "negative",           NULL, 0, AV_OPT_TYPE_CONST, {.i64=PRESET_NEGATIVE},             INT_MIN, INT_MAX, FLAGS, "preset_name" },
         { "strong_contrast",    NULL, 0, AV_OPT_TYPE_CONST, {.i64=PRESET_STRONG_CONTRAST},      INT_MIN, INT_MAX, FLAGS, "preset_name" },
         { "vintage",            NULL, 0, AV_OPT_TYPE_CONST, {.i64=PRESET_VINTAGE},              INT_MIN, INT_MAX, FLAGS, "preset_name" },

     { "master","set master points coordinates",OFFSET(comp_points_str[NB_COMP]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
     { "m",     "set master points coordinates",OFFSET(comp_points_str[NB_COMP]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },

     { "red",   "set red points coordinates",   OFFSET(comp_points_str[0]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
     { "r",     "set red points coordinates",   OFFSET(comp_points_str[0]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
     { "green", "set green points coordinates", OFFSET(comp_points_str[1]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
     { "g",     "set green points coordinates", OFFSET(comp_points_str[1]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
     { "blue",  "set blue points coordinates",  OFFSET(comp_points_str[2]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },
     { "b",     "set blue points coordinates",  OFFSET(comp_points_str[2]), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },

     { "all",   "set points coordinates for all components", OFFSET(comp_points_str_all), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },

     { "psfile", "set Photoshop curves file name", OFFSET(psfile), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },

     { "plot", "save Gnuplot script of the curves in specified file", OFFSET(plot_filename), AV_OPT_TYPE_STRING, {.str=NULL}, .flags = FLAGS },

     { NULL }
 };
 
 AVFILTER_DEFINE_CLASS(curves);
 

 static const struct {
     const char *r;
     const char *g;
     const char *b;

     const char *master;

 } curves_presets[] = {
     [PRESET_COLOR_NEGATIVE] = {

         "0.129/1 0.466/0.498 0.725/0",
         "0.109/1 0.301/0.498 0.517/0",
         "0.098/1 0.235/0.498 0.423/0",

     },
     [PRESET_CROSS_PROCESS] = {

         "0/0 0.25/0.156 0.501/0.501 0.686/0.745 1/1",
         "0/0 0.25/0.188 0.38/0.501 0.745/0.815 1/0.815",
         "0/0 0.231/0.094 0.709/0.874 1/1",

     },

     [PRESET_DARKER]             = { .master = "0/0 0.5/0.4 1/1" },
     [PRESET_INCREASE_CONTRAST]  = { .master = "0/0 0.149/0.066 0.831/0.905 0.905/0.98 1/1" },
     [PRESET_LIGHTER]            = { .master = "0/0 0.4/0.5 1/1" },
     [PRESET_LINEAR_CONTRAST]    = { .master = "0/0 0.305/0.286 0.694/0.713 1/1" },
     [PRESET_MEDIUM_CONTRAST]    = { .master = "0/0 0.286/0.219 0.639/0.643 1/1" },

     [PRESET_NEGATIVE]           = { .master = "0/1 1/0" },

     [PRESET_STRONG_CONTRAST]    = { .master = "0/0 0.301/0.196 0.592/0.6 0.686/0.737 1/1" },

     [PRESET_VINTAGE] = {

         "0/0.11 0.42/0.51 1/0.95",

         "0/0 0.50/0.48 1/1",

         "0/0.22 0.49/0.44 1/0.8",
     }
 };
 

 static struct keypoint *make_point(double x, double y, struct keypoint *next)
 {
     struct keypoint *point = av_mallocz(sizeof(*point));
 
     if (!point)
         return NULL;
     point->x = x;
     point->y = y;
     point->next = next;
     return point;
 }
 

 static int parse_points_str(AVFilterContext *ctx, struct keypoint **points, const char *s,
                             int lut_size)

 {
     char *p = (char *)s; // strtod won't alter the string
     struct keypoint *last = NULL;

     const int scale = lut_size - 1;

 
     /* construct a linked list based on the key points string */
     while (p && *p) {
         struct keypoint *point = make_point(0, 0, NULL);
         if (!point)
             return AVERROR(ENOMEM);
         point->x = av_strtod(p, &p); if (p && *p) p++;
         point->y = av_strtod(p, &p); if (p && *p) p++;
         if (point->x < 0 || point->x > 1 || point->y < 0 || point->y > 1) {
             av_log(ctx, AV_LOG_ERROR, "Invalid key point coordinates (%f;%f), "
                    "x and y must be in the [0;1] range.\n", point->x, point->y);
             return AVERROR(EINVAL);
         }
         if (!*points)
             *points = point;
         if (last) {

             if ((int)(last->x * scale) >= (int)(point->x * scale)) {

                 av_log(ctx, AV_LOG_ERROR, "Key point coordinates (%f;%f) "
                        "and (%f;%f) are too close from each other or not "
                        "strictly increasing on the x-axis\n",
                        last->x, last->y, point->x, point->y);
                 return AVERROR(EINVAL);
             }
             last->next = point;
         }
         last = point;
     }
 

     if (*points && !(*points)->next) {
         av_log(ctx, AV_LOG_WARNING, "Only one point (at (%f;%f)) is defined, "
                "this is unlikely to behave as you expect. You probably want"
                "at least 2 points.",
                (*points)->x, (*points)->y);

     }
 
     return 0;
 }
 
 static int get_nb_points(const struct keypoint *d)
 {
     int n = 0;
     while (d) {
         n++;
         d = d->next;
     }
     return n;
 }
 
 /**
  * Natural cubic spline interpolation
  * Finding curves using Cubic Splines notes by Steven Rauch and John Stockie.
  * @see http://people.math.sfu.ca/~stockie/teaching/macm316/notes/splines.pdf
  */

 
 #define CLIP(v) (nbits == 8 ? av_clip_uint8(v) : av_clip_uint16(v))
 

 static inline int interpolate(void *log_ctx, uint16_t *y,

                               const struct keypoint *points, int nbits)

 {
     int i, ret = 0;

     const struct keypoint *point = points;

     double xprev = 0;

     const int lut_size = 1<<nbits;
     const int scale = lut_size - 1;

     double (*matrix)[3];
     double *h, *r;

     const int n = get_nb_points(points); // number of splines

     if (n == 0) {

         for (i = 0; i < lut_size; i++)

             y[i] = i;
         return 0;
     }
 
     if (n == 1) {

         for (i = 0; i < lut_size; i++)
             y[i] = CLIP(point->y * scale);

         return 0;
     }
 
     matrix = av_calloc(n, sizeof(*matrix));
     h = av_malloc((n - 1) * sizeof(*h));
     r = av_calloc(n, sizeof(*r));

 
     if (!matrix || !h || !r) {
         ret = AVERROR(ENOMEM);
         goto end;
     }
 
     /* h(i) = x(i+1) - x(i) */
     i = -1;
     for (point = points; point; point = point->next) {
         if (i != -1)
             h[i] = point->x - xprev;
         xprev = point->x;
         i++;
     }
 
     /* right-side of the polynomials, will be modified to contains the solution */
     point = points;
     for (i = 1; i < n - 1; i++) {

         const double yp = point->y;
         const double yc = point->next->y;
         const double yn = point->next->next->y;

         r[i] = 6 * ((yn-yc)/h[i] - (yc-yp)/h[i-1]);
         point = point->next;
     }
 

 #define BD 0 /* sub  diagonal (below main) */
 #define MD 1 /* main diagonal (center) */
 #define AD 2 /* sup  diagonal (above main) */

 
     /* left side of the polynomials into a tridiagonal matrix. */

     matrix[0][MD] = matrix[n - 1][MD] = 1;

     for (i = 1; i < n - 1; i++) {

         matrix[i][BD] = h[i-1];
         matrix[i][MD] = 2 * (h[i-1] + h[i]);
         matrix[i][AD] = h[i];

     }
 
     /* tridiagonal solving of the linear system */
     for (i = 1; i < n; i++) {

         const double den = matrix[i][MD] - matrix[i][BD] * matrix[i-1][AD];
         const double k = den ? 1./den : 1.;

         matrix[i][AD] *= k;
         r[i] = (r[i] - matrix[i][BD] * r[i - 1]) * k;

     }
     for (i = n - 2; i >= 0; i--)

         r[i] = r[i] - matrix[i][AD] * r[i + 1];

 
     point = points;

 
     /* left padding */

     for (i = 0; i < (int)(point->x * scale); i++)
         y[i] = CLIP(point->y * scale);

 
     /* compute the graph with x=[x0..xN] */
     i = 0;

     av_assert0(point->next); // always at least 2 key points
     while (point->next) {

         const double yc = point->y;
         const double yn = point->next->y;

         const double a = yc;
         const double b = (yn-yc)/h[i] - h[i]*r[i]/2. - h[i]*(r[i+1]-r[i])/6.;
         const double c = r[i] / 2.;
         const double d = (r[i+1] - r[i]) / (6.*h[i]);

 
         int x;

         const int x_start = point->x       * scale;
         const int x_end   = point->next->x * scale;

         av_assert0(x_start >= 0 && x_start < lut_size &&
                    x_end   >= 0 && x_end   < lut_size);

 
         for (x = x_start; x <= x_end; x++) {

             const double xx = (x - x_start) * 1./scale;

             const double yy = a + b*xx + c*xx*xx + d*xx*xx*xx;

             y[x] = CLIP(yy * scale);

             av_log(log_ctx, AV_LOG_DEBUG, "f(%f)=%f -> y[%d]=%d\n", xx, yy, x, y[x]);

         }
 
         point = point->next;
         i++;
     }
 

     /* right padding */

     for (i = (int)(point->x * scale); i < lut_size; i++)
         y[i] = CLIP(point->y * scale);

 end:
     av_free(matrix);
     av_free(h);
     av_free(r);
     return ret;
 }
 

 #define DECLARE_INTERPOLATE_FUNC(nbits)                                     \

 static int interpolate##nbits(void *log_ctx, uint16_t *y,                   \
                               const struct keypoint *points)                \

 {                                                                           \

     return interpolate(log_ctx, y, points, nbits);                          \

 }
 
 DECLARE_INTERPOLATE_FUNC(8)
 DECLARE_INTERPOLATE_FUNC(16)
 

 static int parse_psfile(AVFilterContext *ctx, const char *fname)
 {
     CurvesContext *curves = ctx->priv;
     uint8_t *buf;
     size_t size;
     int i, ret, av_unused(version), nb_curves;
     AVBPrint ptstr;
     static const int comp_ids[] = {3, 0, 1, 2};
 
     av_bprint_init(&ptstr, 0, AV_BPRINT_SIZE_AUTOMATIC);
 
     ret = av_file_map(fname, &buf, &size, 0, NULL);
     if (ret < 0)
         return ret;
 
 #define READ16(dst) do {                \

     if (size < 2) {                     \
         ret = AVERROR_INVALIDDATA;      \
         goto end;                       \
     }                                   \

     dst = AV_RB16(buf);                 \
     buf  += 2;                          \
     size -= 2;                          \
 } while (0)
 
     READ16(version);
     READ16(nb_curves);
     for (i = 0; i < FFMIN(nb_curves, FF_ARRAY_ELEMS(comp_ids)); i++) {
         int nb_points, n;
         av_bprint_clear(&ptstr);
         READ16(nb_points);
         for (n = 0; n < nb_points; n++) {
             int y, x;
             READ16(y);
             READ16(x);
             av_bprintf(&ptstr, "%f/%f ", x / 255., y / 255.);
         }
         if (*ptstr.str) {
             char **pts = &curves->comp_points_str[comp_ids[i]];
             if (!*pts) {
                 *pts = av_strdup(ptstr.str);
                 av_log(ctx, AV_LOG_DEBUG, "curves %d (intid=%d) [%d points]: [%s]\n",
                        i, comp_ids[i], nb_points, *pts);
                 if (!*pts) {
                     ret = AVERROR(ENOMEM);
                     goto end;
                 }
             }
         }
     }
 end:
     av_bprint_finalize(&ptstr, NULL);
     av_file_unmap(buf, size);
     return ret;
 }
 

 static int dump_curves(const char *fname, uint16_t *graph[NB_COMP + 1],
                        struct keypoint *comp_points[NB_COMP + 1],
                        int lut_size)

 {
     int i;
     AVBPrint buf;

     const double scale = 1. / (lut_size - 1);

     static const char * const colors[] = { "red", "green", "blue", "#404040", };
     FILE *f = av_fopen_utf8(fname, "w");
 
     av_assert0(FF_ARRAY_ELEMS(colors) == NB_COMP + 1);
 
     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, "set xtics 0.1\n");
     av_bprintf(&buf, "set ytics 0.1\n");
     av_bprintf(&buf, "set size square\n");
     av_bprintf(&buf, "set grid\n");
 
     for (i = 0; i < FF_ARRAY_ELEMS(colors); i++) {
         av_bprintf(&buf, "%s'-' using 1:2 with lines lc '%s' title ''",
                    i ? ", " : "plot ", colors[i]);
         if (comp_points[i])
             av_bprintf(&buf, ", '-' using 1:2 with points pointtype 3 lc '%s' title ''",
                     colors[i]);
     }
     av_bprintf(&buf, "\n");
 
     for (i = 0; i < FF_ARRAY_ELEMS(colors); i++) {
         int x;
 
         /* plot generated values */

         for (x = 0; x < lut_size; x++)
             av_bprintf(&buf, "%f %f\n", x * scale, graph[i][x] * scale);

         av_bprintf(&buf, "e\n");
 
         /* plot user knots */
         if (comp_points[i]) {
             const struct keypoint *point = comp_points[i];
 
             while (point) {
                 av_bprintf(&buf, "%f %f\n", point->x, point->y);
                 point = point->next;
             }
             av_bprintf(&buf, "e\n");
         }
     }
 
     fwrite(buf.str, 1, buf.len, f);
     fclose(f);
     av_bprint_finalize(&buf, NULL);
     return 0;
 }
 

 static av_cold int curves_init(AVFilterContext *ctx)

 {

     int i, ret;

     CurvesContext *curves = ctx->priv;

     char **pts = curves->comp_points_str;

     const char *allp = curves->comp_points_str_all;
 

     //if (!allp && curves->preset != PRESET_NONE && curves_presets[curves->preset].all)
     //    allp = curves_presets[curves->preset].all;

     if (allp) {

         for (i = 0; i < NB_COMP; i++) {
             if (!pts[i])

                 pts[i] = av_strdup(allp);

             if (!pts[i])
                 return AVERROR(ENOMEM);
         }
     }

     if (curves->psfile) {
         ret = parse_psfile(ctx, curves->psfile);
         if (ret < 0)
             return ret;
     }
 

     if (curves->preset != PRESET_NONE) {

 #define SET_COMP_IF_NOT_SET(n, name) do {                           \
     if (!pts[n] && curves_presets[curves->preset].name) {           \
         pts[n] = av_strdup(curves_presets[curves->preset].name);    \
         if (!pts[n])                                                \
             return AVERROR(ENOMEM);                                 \
     }                                                               \
 } while (0)
         SET_COMP_IF_NOT_SET(0, r);
         SET_COMP_IF_NOT_SET(1, g);
         SET_COMP_IF_NOT_SET(2, b);
         SET_COMP_IF_NOT_SET(3, master);

     }
 

     return 0;
 }
 
 static int query_formats(AVFilterContext *ctx)
 {
     static const enum AVPixelFormat pix_fmts[] = {
         AV_PIX_FMT_RGB24,  AV_PIX_FMT_BGR24,
         AV_PIX_FMT_RGBA,   AV_PIX_FMT_BGRA,
         AV_PIX_FMT_ARGB,   AV_PIX_FMT_ABGR,
         AV_PIX_FMT_0RGB,   AV_PIX_FMT_0BGR,
         AV_PIX_FMT_RGB0,   AV_PIX_FMT_BGR0,

         AV_PIX_FMT_RGB48,  AV_PIX_FMT_BGR48,
         AV_PIX_FMT_RGBA64, AV_PIX_FMT_BGRA64,

         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)
 {
     int i, j, ret;
     AVFilterContext *ctx = inlink->dst;
     CurvesContext *curves = ctx->priv;
     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
     char **pts = curves->comp_points_str;
     struct keypoint *comp_points[NB_COMP + 1] = {0};
 
     ff_fill_rgba_map(curves->rgba_map, inlink->format);

     curves->is_16bit = desc->comp[0].depth > 8;
     curves->lut_size = curves->is_16bit ? 1<<16 : 1<<8;
     curves->step = av_get_padded_bits_per_pixel(desc) >> (3 + curves->is_16bit);

     for (i = 0; i < NB_COMP + 1; i++) {

         curves->graph[i] = av_mallocz_array(curves->lut_size, sizeof(*curves->graph[0]));

         if (!curves->graph[i])
             return AVERROR(ENOMEM);

         ret = parse_points_str(ctx, comp_points + i, curves->comp_points_str[i], curves->lut_size);

         if (ret < 0)
             return ret;

         if (curves->is_16bit) ret = interpolate16(ctx, curves->graph[i], comp_points[i]);
         else                  ret = interpolate8(ctx, curves->graph[i], comp_points[i]);

         if (ret < 0)
             return ret;
     }
 

     if (pts[NB_COMP]) {
         for (i = 0; i < NB_COMP; i++)

             for (j = 0; j < curves->lut_size; j++)

                 curves->graph[i][j] = curves->graph[NB_COMP][curves->graph[i][j]];
     }
 

     if (av_log_get_level() >= AV_LOG_VERBOSE) {
         for (i = 0; i < NB_COMP; i++) {

             const struct keypoint *point = comp_points[i];

             av_log(ctx, AV_LOG_VERBOSE, "#%d points:", i);
             while (point) {
                 av_log(ctx, AV_LOG_VERBOSE, " (%f;%f)", point->x, point->y);
                 point = point->next;
             }
         }
     }
 

     if (curves->plot_filename)

         dump_curves(curves->plot_filename, curves->graph, comp_points, curves->lut_size);

     for (i = 0; i < NB_COMP + 1; i++) {

         struct keypoint *point = comp_points[i];
         while (point) {
             struct keypoint *next = point->next;
             av_free(point);
             point = next;
         }
     }
 
     return 0;
 }
 

 static int filter_slice(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)

 {

     int x, y;
     const CurvesContext *curves = ctx->priv;
     const ThreadData *td = arg;
     const AVFrame *in  = td->in;
     const AVFrame *out = td->out;
     const int direct = out == in;

     const int step = curves->step;
     const uint8_t r = curves->rgba_map[R];
     const uint8_t g = curves->rgba_map[G];
     const uint8_t b = curves->rgba_map[B];
     const uint8_t a = curves->rgba_map[A];

     const int slice_start = (in->height *  jobnr   ) / nb_jobs;
     const int slice_end   = (in->height * (jobnr+1)) / nb_jobs;

 
     if (curves->is_16bit) {
         for (y = slice_start; y < slice_end; y++) {
             uint16_t       *dstp = (      uint16_t *)(out->data[0] + y * out->linesize[0]);
             const uint16_t *srcp = (const uint16_t *)(in ->data[0] + y *  in->linesize[0]);
 
             for (x = 0; x < in->width * step; x += step) {
                 dstp[x + r] = curves->graph[R][srcp[x + r]];
                 dstp[x + g] = curves->graph[G][srcp[x + g]];
                 dstp[x + b] = curves->graph[B][srcp[x + b]];
                 if (!direct && step == 4)
                     dstp[x + a] = srcp[x + a];
             }
         }
     } else {

         uint8_t       *dst = out->data[0] + slice_start * out->linesize[0];
         const uint8_t *src =  in->data[0] + slice_start *  in->linesize[0];
 
         for (y = slice_start; y < slice_end; y++) {
             for (x = 0; x < in->width * step; x += step) {
                 dst[x + r] = curves->graph[R][src[x + r]];
                 dst[x + g] = curves->graph[G][src[x + g]];
                 dst[x + b] = curves->graph[B][src[x + b]];
                 if (!direct && step == 4)
                     dst[x + a] = src[x + a];
             }
             dst += out->linesize[0];
             src += in ->linesize[0];

         }

     }

     return 0;
 }
 
 static int filter_frame(AVFilterLink *inlink, AVFrame *in)
 {
     AVFilterContext *ctx = inlink->dst;
     AVFilterLink *outlink = ctx->outputs[0];
     AVFrame *out;
     ThreadData td;

 
     if (av_frame_is_writable(in)) {
         out = in;
     } else {
         out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
         if (!out) {
             av_frame_free(&in);
             return AVERROR(ENOMEM);
         }
         av_frame_copy_props(out, in);
     }
 

     td.in  = in;
     td.out = out;

     ctx->internal->execute(ctx, filter_slice, &td, NULL, FFMIN(outlink->h, ff_filter_get_nb_threads(ctx)));

     if (out != in)

         av_frame_free(&in);
 
     return ff_filter_frame(outlink, out);
 }
 

 static av_cold void curves_uninit(AVFilterContext *ctx)

 {
     int i;
     CurvesContext *curves = ctx->priv;
 
     for (i = 0; i < NB_COMP + 1; i++)
         av_freep(&curves->graph[i]);
 }
 

 static const AVFilterPad curves_inputs[] = {
     {
         .name         = "default",
         .type         = AVMEDIA_TYPE_VIDEO,
         .filter_frame = filter_frame,

         .config_props = config_input,

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

     {
         .name = "default",
         .type = AVMEDIA_TYPE_VIDEO,
     },
     { NULL }

 };
 

 AVFilter ff_vf_curves = {

     .name          = "curves",
     .description   = NULL_IF_CONFIG_SMALL("Adjust components curves."),
     .priv_size     = sizeof(CurvesContext),

     .init          = curves_init,
     .uninit        = curves_uninit,

     .query_formats = query_formats,
     .inputs        = curves_inputs,
     .outputs       = curves_outputs,
     .priv_class    = &curves_class,

     .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC | AVFILTER_FLAG_SLICE_THREADS,

 };