2 * Copyright (c) 2015 Stupeflix
4 * This file is part of FFmpeg.
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 * Generate one palette for a whole video stream.
26 #include "libavutil/avassert.h"
27 #include "libavutil/opt.h"
28 #include "libavutil/qsort.h"
32 /* Reference a color and how much it's used */
38 /* Store a range of colors */
40 uint32_t color; // average color
41 int64_t variance; // overall variance of the box (how much the colors are spread)
42 int start; // index in PaletteGenContext->refs
43 int len; // number of referenced colors
44 int sorted_by; // whether range of colors is sorted by red (0), green (1) or blue (2)
48 struct color_ref *entries;
53 STATS_MODE_ALL_FRAMES,
54 STATS_MODE_DIFF_FRAMES,
59 #define HIST_SIZE (1<<(3*NBITS))
65 int reserve_transparent;
68 AVFrame *prev_frame; // previous frame used for the diff stats_mode
69 struct hist_node histogram[HIST_SIZE]; // histogram/hashtable of the colors
70 struct color_ref **refs; // references of all the colors used in the stream
71 int nb_refs; // number of color references (or number of different colors)
72 struct range_box boxes[256]; // define the segmentation of the colorspace (the final palette)
73 int nb_boxes; // number of boxes (increase will segmenting them)
74 int palette_pushed; // if the palette frame is pushed into the outlink or not
77 #define OFFSET(x) offsetof(PaletteGenContext, x)
78 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
79 static const AVOption palettegen_options[] = {
80 { "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 },
81 { "reserve_transparent", "reserve a palette entry for transparency", OFFSET(reserve_transparent), AV_OPT_TYPE_INT, {.i64=1}, 0, 1, FLAGS },
82 { "stats_mode", "set statistics mode", OFFSET(stats_mode), AV_OPT_TYPE_INT, {.i64=STATS_MODE_ALL_FRAMES}, 0, NB_STATS_MODE, FLAGS, "mode" },
83 { "full", "compute full frame histograms", 0, AV_OPT_TYPE_CONST, {.i64=STATS_MODE_ALL_FRAMES}, INT_MIN, INT_MAX, FLAGS, "mode" },
84 { "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" },
88 AVFILTER_DEFINE_CLASS(palettegen);
90 static int query_formats(AVFilterContext *ctx)
92 static const enum AVPixelFormat in_fmts[] = {AV_PIX_FMT_RGB32, AV_PIX_FMT_NONE};
93 static const enum AVPixelFormat out_fmts[] = {AV_PIX_FMT_RGB32, AV_PIX_FMT_NONE};
94 AVFilterFormats *in = ff_make_format_list(in_fmts);
95 AVFilterFormats *out = ff_make_format_list(out_fmts);
99 return AVERROR(ENOMEM);
101 ff_formats_ref(in, &ctx->inputs[0]->out_formats);
102 ff_formats_ref(out, &ctx->outputs[0]->in_formats);
106 typedef int (*cmp_func)(const void *, const void *);
108 #define DECLARE_CMP_FUNC(name, pos) \
109 static int cmp_##name(const void *pa, const void *pb) \
111 const struct color_ref * const *a = pa; \
112 const struct color_ref * const *b = pb; \
113 return ((*a)->color >> (8 * (2 - (pos))) & 0xff) \
114 - ((*b)->color >> (8 * (2 - (pos))) & 0xff); \
117 DECLARE_CMP_FUNC(r, 0)
118 DECLARE_CMP_FUNC(g, 1)
119 DECLARE_CMP_FUNC(b, 2)
121 static const cmp_func cmp_funcs[] = {cmp_r, cmp_g, cmp_b};
124 * Simple color comparison for sorting the final palette
126 static int cmp_color(const void *a, const void *b)
128 const struct range_box *box1 = a;
129 const struct range_box *box2 = b;
130 return box1->color - box2->color;
133 static av_always_inline int diff(const uint32_t a, const uint32_t b)
135 const uint8_t c1[] = {a >> 16 & 0xff, a >> 8 & 0xff, a & 0xff};
136 const uint8_t c2[] = {b >> 16 & 0xff, b >> 8 & 0xff, b & 0xff};
137 const int dr = c1[0] - c2[0];
138 const int dg = c1[1] - c2[1];
139 const int db = c1[2] - c2[2];
140 return dr*dr + dg*dg + db*db;
144 * Find the next box to split: pick the one with the highest variance
146 static int get_next_box_id_to_split(PaletteGenContext *s)
148 int box_id, i, best_box_id = -1;
149 int64_t max_variance = -1;
151 if (s->nb_boxes == s->max_colors - s->reserve_transparent)
154 for (box_id = 0; box_id < s->nb_boxes; box_id++) {
155 struct range_box *box = &s->boxes[box_id];
157 if (s->boxes[box_id].len >= 2) {
159 if (box->variance == -1) {
160 int64_t variance = 0;
162 for (i = 0; i < box->len; i++) {
163 const struct color_ref *ref = s->refs[box->start + i];
164 variance += diff(ref->color, box->color) * ref->count;
166 box->variance = variance;
168 if (box->variance > max_variance) {
169 best_box_id = box_id;
170 max_variance = box->variance;
180 * Get the 32-bit average color for the range of RGB colors enclosed in the
181 * specified box. Takes into account the weight of each color.
183 static uint32_t get_avg_color(struct color_ref * const *refs,
184 const struct range_box *box)
187 const int n = box->len;
188 uint64_t r = 0, g = 0, b = 0, div = 0;
190 for (i = 0; i < n; i++) {
191 const struct color_ref *ref = refs[box->start + i];
192 r += (ref->color >> 16 & 0xff) * ref->count;
193 g += (ref->color >> 8 & 0xff) * ref->count;
194 b += (ref->color & 0xff) * ref->count;
202 return 0xffU<<24 | r<<16 | g<<8 | b;
206 * Split given box in two at position n. The original box becomes the left part
207 * of the split, and the new index box is the right part.
209 static void split_box(PaletteGenContext *s, struct range_box *box, int n)
211 struct range_box *new_box = &s->boxes[s->nb_boxes++];
212 new_box->start = n + 1;
213 new_box->len = box->start + box->len - new_box->start;
214 new_box->sorted_by = box->sorted_by;
215 box->len -= new_box->len;
217 av_assert0(box->len >= 1);
218 av_assert0(new_box->len >= 1);
220 box->color = get_avg_color(s->refs, box);
221 new_box->color = get_avg_color(s->refs, new_box);
223 new_box->variance = -1;
227 * Write the palette into the output frame.
229 static void write_palette(AVFilterContext *ctx, AVFrame *out)
231 const PaletteGenContext *s = ctx->priv;
232 int x, y, box_id = 0;
233 uint32_t *pal = (uint32_t *)out->data[0];
234 const int pal_linesize = out->linesize[0] >> 2;
235 uint32_t last_color = 0;
237 for (y = 0; y < out->height; y++) {
238 for (x = 0; x < out->width; x++) {
239 if (box_id < s->nb_boxes) {
240 pal[x] = s->boxes[box_id++].color;
241 if ((x || y) && pal[x] == last_color)
242 av_log(ctx, AV_LOG_WARNING, "Dupped color: %08X\n", pal[x]);
245 pal[x] = 0xff000000; // pad with black
251 if (s->reserve_transparent) {
252 av_assert0(s->nb_boxes < 256);
253 pal[out->width - pal_linesize - 1] = 0x0000ff00; // add a green transparent color
258 * Crawl the histogram to get all the defined colors, and create a linear list
259 * of them (each color reference entry is a pointer to the value in the
260 * histogram/hash table).
262 static struct color_ref **load_color_refs(const struct hist_node *hist, int nb_refs)
265 struct color_ref **refs = av_malloc_array(nb_refs, sizeof(*refs));
270 for (j = 0; j < HIST_SIZE; j++) {
271 const struct hist_node *node = &hist[j];
273 for (i = 0; i < node->nb_entries; i++)
274 refs[k++] = &node->entries[i];
280 static double set_colorquant_ratio_meta(AVFrame *out, int nb_out, int nb_in)
283 const double ratio = (double)nb_out / nb_in;
284 snprintf(buf, sizeof(buf), "%f", ratio);
285 av_dict_set(&out->metadata, "lavfi.color_quant_ratio", buf, 0);
290 * Main function implementing the Median Cut Algorithm defined by Paul Heckbert
291 * in Color Image Quantization for Frame Buffer Display (1982)
293 static AVFrame *get_palette_frame(AVFilterContext *ctx)
296 PaletteGenContext *s = ctx->priv;
297 AVFilterLink *outlink = ctx->outputs[0];
300 struct range_box *box;
302 /* reference only the used colors from histogram */
303 s->refs = load_color_refs(s->histogram, s->nb_refs);
305 av_log(ctx, AV_LOG_ERROR, "Unable to allocate references for %d different colors\n", s->nb_refs);
309 /* create the palette frame */
310 out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
315 /* set first box for 0..nb_refs */
316 box = &s->boxes[box_id];
317 box->len = s->nb_refs;
319 box->color = get_avg_color(s->refs, box);
323 while (box && box->len > 1) {
324 int i, rr, gr, br, longest;
325 uint64_t median, box_weight = 0;
327 /* compute the box weight (sum all the weights of the colors in the
328 * range) and its boundings */
329 uint8_t min[3] = {0xff, 0xff, 0xff};
330 uint8_t max[3] = {0x00, 0x00, 0x00};
331 for (i = box->start; i < box->start + box->len; i++) {
332 const struct color_ref *ref = s->refs[i];
333 const uint32_t rgb = ref->color;
334 const uint8_t r = rgb >> 16 & 0xff, g = rgb >> 8 & 0xff, b = rgb & 0xff;
335 min[0] = FFMIN(r, min[0]), max[0] = FFMAX(r, max[0]);
336 min[1] = FFMIN(g, min[1]), max[1] = FFMAX(g, max[1]);
337 min[2] = FFMIN(b, min[2]), max[2] = FFMAX(b, max[2]);
338 box_weight += ref->count;
341 /* define the axis to sort by according to the widest range of colors */
342 rr = max[0] - min[0];
343 gr = max[1] - min[1];
344 br = max[2] - min[2];
345 longest = 1; // pick green by default (the color the eye is the most sensitive to)
346 if (br >= rr && br >= gr) longest = 2;
347 if (rr >= gr && rr >= br) longest = 0;
348 if (gr >= rr && gr >= br) longest = 1; // prefer green again
350 av_dlog(ctx, "box #%02X [%6d..%-6d] (%6d) w:%-6"PRIu64" ranges:[%2x %2x %2x] sort by %c (already sorted:%c) ",
351 box_id, box->start, box->start + box->len - 1, box->len, box_weight,
352 rr, gr, br, "rgb"[longest], box->sorted_by == longest ? 'y':'n');
354 /* sort the range by its longest axis if it's not already sorted */
355 if (box->sorted_by != longest) {
356 cmp_func cmpf = cmp_funcs[longest];
357 AV_QSORT(&s->refs[box->start], box->len, const struct color_ref *, cmpf);
358 box->sorted_by = longest;
361 /* locate the median where to split */
362 median = (box_weight + 1) >> 1;
364 /* if you have 2 boxes, the maximum is actually #0: you must have at
365 * least 1 color on each side of the split, hence the -2 */
366 for (i = box->start; i < box->start + box->len - 2; i++) {
367 box_weight += s->refs[i]->count;
368 if (box_weight > median)
371 av_dlog(ctx, "split @ i=%-6d with w=%-6"PRIu64" (target=%6"PRIu64")\n", i, box_weight, median);
372 split_box(s, box, i);
374 box_id = get_next_box_id_to_split(s);
375 box = box_id >= 0 ? &s->boxes[box_id] : NULL;
378 ratio = set_colorquant_ratio_meta(out, s->nb_boxes, s->nb_refs);
379 av_log(ctx, AV_LOG_INFO, "%d%s colors generated out of %d colors; ratio=%f\n",
380 s->nb_boxes, s->reserve_transparent ? "(+1)" : "", s->nb_refs, ratio);
382 qsort(s->boxes, s->nb_boxes, sizeof(*s->boxes), cmp_color);
384 write_palette(ctx, out);
390 * Hashing function for the color.
391 * It keeps the NBITS least significant bit of each component to make it
392 * "random" even if the scene doesn't have much different colors.
394 static inline unsigned color_hash(uint32_t color)
396 const uint8_t r = color >> 16 & ((1<<NBITS)-1);
397 const uint8_t g = color >> 8 & ((1<<NBITS)-1);
398 const uint8_t b = color & ((1<<NBITS)-1);
399 return r<<(NBITS*2) | g<<NBITS | b;
403 * Locate the color in the hash table and increment its counter.
405 static int color_inc(struct hist_node *hist, uint32_t color)
408 const unsigned hash = color_hash(color);
409 struct hist_node *node = &hist[hash];
412 for (i = 0; i < node->nb_entries; i++) {
413 e = &node->entries[i];
414 if (e->color == color) {
420 e = av_dynarray2_add((void**)&node->entries, &node->nb_entries,
421 sizeof(*node->entries), NULL);
423 return AVERROR(ENOMEM);
430 * Update histogram when pixels differ from previous frame.
432 static int update_histogram_diff(struct hist_node *hist,
433 const AVFrame *f1, const AVFrame *f2)
435 int x, y, ret, nb_diff_colors = 0;
437 for (y = 0; y < f1->height; y++) {
438 const uint32_t *p = (const uint32_t *)(f1->data[0] + y*f1->linesize[0]);
439 const uint32_t *q = (const uint32_t *)(f2->data[0] + y*f2->linesize[0]);
441 for (x = 0; x < f1->width; x++) {
444 ret = color_inc(hist, p[x]);
447 nb_diff_colors += ret;
450 return nb_diff_colors;
454 * Simple histogram of the frame.
456 static int update_histogram_frame(struct hist_node *hist, const AVFrame *f)
458 int x, y, ret, nb_diff_colors = 0;
460 for (y = 0; y < f->height; y++) {
461 const uint32_t *p = (const uint32_t *)(f->data[0] + y*f->linesize[0]);
463 for (x = 0; x < f->width; x++) {
464 ret = color_inc(hist, p[x]);
467 nb_diff_colors += ret;
470 return nb_diff_colors;
474 * Update the histogram for each passing frame. No frame will be pushed here.
476 static int filter_frame(AVFilterLink *inlink, AVFrame *in)
478 AVFilterContext *ctx = inlink->dst;
479 PaletteGenContext *s = ctx->priv;
480 const int ret = s->prev_frame ? update_histogram_diff(s->histogram, s->prev_frame, in)
481 : update_histogram_frame(s->histogram, in);
486 if (s->stats_mode == STATS_MODE_DIFF_FRAMES) {
487 av_frame_free(&s->prev_frame);
497 * Returns only one frame at the end containing the full palette.
499 static int request_frame(AVFilterLink *outlink)
501 AVFilterContext *ctx = outlink->src;
502 AVFilterLink *inlink = ctx->inputs[0];
503 PaletteGenContext *s = ctx->priv;
506 r = ff_request_frame(inlink);
507 if (r == AVERROR_EOF && !s->palette_pushed && s->nb_refs) {
508 r = ff_filter_frame(outlink, get_palette_frame(ctx));
509 s->palette_pushed = 1;
516 * The output is one simple 16x16 squared-pixels palette.
518 static int config_output(AVFilterLink *outlink)
520 outlink->w = outlink->h = 16;
521 outlink->sample_aspect_ratio = av_make_q(1, 1);
522 outlink->flags |= FF_LINK_FLAG_REQUEST_LOOP;
526 static av_cold void uninit(AVFilterContext *ctx)
529 PaletteGenContext *s = ctx->priv;
531 for (i = 0; i < HIST_SIZE; i++)
532 av_freep(&s->histogram[i].entries);
534 av_frame_free(&s->prev_frame);
537 static const AVFilterPad palettegen_inputs[] = {
540 .type = AVMEDIA_TYPE_VIDEO,
541 .filter_frame = filter_frame,
546 static const AVFilterPad palettegen_outputs[] = {
549 .type = AVMEDIA_TYPE_VIDEO,
550 .config_props = config_output,
551 .request_frame = request_frame,
556 AVFilter ff_vf_palettegen = {
557 .name = "palettegen",
558 .description = NULL_IF_CONFIG_SMALL("Find the optimal palette for a given stream."),
559 .priv_size = sizeof(PaletteGenContext),
561 .query_formats = query_formats,
562 .inputs = palettegen_inputs,
563 .outputs = palettegen_outputs,
564 .priv_class = &palettegen_class,