[FFmpeg-devel] [PATCH 4/6] avfilter: add palettegen filter
Clément Bœsch
u at pkh.me
Mon Feb 9 18:35:12 CET 2015
---
doc/filters.texi | 45 ++++
libavfilter/Makefile | 1 +
libavfilter/allfilters.c | 1 +
libavfilter/vf_palettegen.c | 523 ++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 570 insertions(+)
create mode 100644 libavfilter/vf_palettegen.c
diff --git a/doc/filters.texi b/doc/filters.texi
index a90825a..2b4e0bc 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -6890,6 +6890,51 @@ pad="2*iw:2*ih:ow-iw:oh-ih"
@end example
@end itemize
+ at section palettegen
+
+Generate one palette for a whole video stream.
+
+It accepts the following options:
+
+ at table @option
+ at item max_colors
+Set the maximum number of colors to quantize in the palette.
+Note: the palette will still contain 256 colors; the unused palette entries
+will be black.
+
+ at item reserve_transparent
+Create a palette of 255 colors maximum and reserve the last one for
+transparency. Reserving the transparency color is useful for GIF optimization.
+If not set, the maximum of colors in the palette will be 256. You probably want
+to disable this option for a standalone image.
+Set by default.
+
+ at item stats_mode
+Set statistics mode.
+
+It accepts the following values:
+ at table @samp
+ at item full
+Compute full frame histograms.
+ at item diff
+Compute histograms only for the part that differs from previous frame. This
+might be relevant to give more importance to the moving part of your input if
+the background is static.
+ at end table
+
+Default value is @var{full}.
+ at end table
+
+ at subsection Examples
+
+ at itemize
+ at item
+Generate a representative palette of a given video using @command{ffmpeg}:
+ at example
+ffmpeg -i input.mkv -vf palettegen palette.png
+ at end example
+ at end itemize
+
@section perspective
Correct perspective of video not recorded perpendicular to the screen.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 3434d5b..0128641 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -159,6 +159,7 @@ OBJS-$(CONFIG_OPENCL) += deshake_opencl.o unsharp_opencl.
OBJS-$(CONFIG_OVERLAY_FILTER) += vf_overlay.o dualinput.o framesync.o
OBJS-$(CONFIG_OWDENOISE_FILTER) += vf_owdenoise.o
OBJS-$(CONFIG_PAD_FILTER) += vf_pad.o
+OBJS-$(CONFIG_PALETTEGEN_FILTER) += vf_palettegen.o
OBJS-$(CONFIG_PERMS_FILTER) += f_perms.o
OBJS-$(CONFIG_PERSPECTIVE_FILTER) += vf_perspective.o
OBJS-$(CONFIG_PHASE_FILTER) += vf_phase.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 3b13ed7..7f3d94f 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -174,6 +174,7 @@ void avfilter_register_all(void)
REGISTER_FILTER(OVERLAY, overlay, vf);
REGISTER_FILTER(OWDENOISE, owdenoise, vf);
REGISTER_FILTER(PAD, pad, vf);
+ REGISTER_FILTER(PALETTEGEN, palettegen, vf);
REGISTER_FILTER(PERMS, perms, vf);
REGISTER_FILTER(PERSPECTIVE, perspective, vf);
REGISTER_FILTER(PHASE, phase, vf);
diff --git a/libavfilter/vf_palettegen.c b/libavfilter/vf_palettegen.c
new file mode 100644
index 0000000..39ca224
--- /dev/null
+++ b/libavfilter/vf_palettegen.c
@@ -0,0 +1,523 @@
+/*
+ * 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.
+ *
+ * TODO: experiment with the variance. "An Improved Median-cut Algorithm of
+ * Color Image Quantization" from CHEN Wei-dong and DING Wei (2008) might
+ * eventually be relevant.
+ */
+
+#include "libavutil/avassert.h"
+#include "libavutil/opt.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
+ 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,
+ NB_STATS_MODE
+};
+
+#define NBITS 4
+#define HIST_SIZE (1<<(3*NBITS))
+
+typedef struct {
+ 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
+} 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_INT, {.i64=1}, 0, 1, FLAGS },
+ { "stats_mode", "set statistics mode", OFFSET(stats_mode), AV_OPT_TYPE_INT, {.i64=STATS_MODE_ALL_FRAMES}, 0, NB_STATS_MODE, 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" },
+ { 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};
+ AVFilterFormats *in = ff_make_format_list(in_fmts);
+ AVFilterFormats *out = ff_make_format_list(out_fmts);
+ if (!in || !out)
+ return AVERROR(ENOMEM);
+ ff_formats_ref(in, &ctx->inputs[0]->out_formats);
+ ff_formats_ref(out, &ctx->outputs[0]->in_formats);
+ 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 box1->color - box2->color;
+}
+
+/**
+ * Find the next box to split. Current heuristic is to try to split the box
+ * with the most different indexed colors.
+ * TODO: we might want to involve the variance or the weight of the color to
+ * find a better box to split.
+ */
+static int get_next_box_id_to_split(PaletteGenContext *s)
+{
+ int i, max_len = -1, box_id;
+
+ if (s->nb_boxes == s->max_colors - s->reserve_transparent)
+ return -1;
+
+ for (i = 0; i < s->nb_boxes; i++) {
+ if (s->boxes[i].len > max_len) {
+ max_len = s->boxes[i].len;
+ box_id = i;
+ }
+ }
+ return max_len > 1 ? box_id : -1;
+}
+
+/**
+ * Get the 32-bit average color for the range of RGB colors enclosed in the
+ * specified box.
+ * XXX: should we take into account the weight of the color?
+ */
+static uint32_t get_avg_color(struct color_ref * const *refs,
+ const struct range_box *box)
+{
+ const int n = box->len;
+ int i, r = 0, g = 0, b = 0;
+
+ for (i = 0; i < n; i++) {
+ const struct color_ref *ref = refs[box->start + i];
+ r += ref->color >> 16 & 0xff;
+ g += ref->color >> 8 & 0xff;
+ b += ref->color & 0xff;
+ }
+
+ r = r / n;
+ g = g / n;
+ b = b / n;
+
+ 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);
+}
+
+/**
+ * Write the palette into the output frame.
+ */
+static void write_palette(const PaletteGenContext *s, AVFrame *out)
+{
+ 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(NULL, AV_LOG_WARNING, "Dupped color: %08X\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] = 0x0000ff00; // add a green transparent color
+ }
+}
+
+/**
+ * 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;
+}
+
+/**
+ * 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];
+ int box_id = 0;
+ int longest = 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;
+ s->nb_boxes = 1;
+
+ while (box && box->len > 1) {
+ int i, rr, gr, br;
+ 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
+
+ av_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) {
+ qsort(&s->refs[box->start], box->len, sizeof(*s->refs), cmp_funcs[longest]);
+ box->sorted_by = longest;
+ }
+
+ /* locate the median where to split. XXX: paper mention a split
+ * according to the variance which might be more efficient */
+ median = box_weight >> 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;
+ }
+ av_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;
+ }
+
+ av_log(ctx, AV_LOG_DEBUG, "%d%s boxes generated out of %d colors\n",
+ s->nb_boxes, s->reserve_transparent ? "(+1)" : "", s->nb_refs);
+
+ for (box_id = 0; box_id < s->nb_boxes; box_id++)
+ s->boxes[box_id].color = get_avg_color(s->refs, &s->boxes[box_id]);
+ qsort(s->boxes, s->nb_boxes, sizeof(*s->boxes), cmp_color);
+
+ write_palette(s, 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;
+
+ if (node->nb_entries) {
+ 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 < f2->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;
+ const 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 {
+ 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) {
+ 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);
+ outlink->flags |= FF_LINK_FLAG_REQUEST_LOOP;
+ 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_freep(&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,
+};
--
2.3.0
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