avfilter/vf_colorkey: Add colorkey video filter

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Changelog

@@ -2,6 +2,7 @@ Entries are sorted chronologically from oldest to youngest within each release,
 releases are sorted from youngest to oldest.
 
 version <next>:
+- colorkey video filter
 
 
 version 2.7:

MAINTAINERS

@@ -352,6 +352,7 @@ Filters:
   avf_showcqt.c                         Muhammad Faiz
   vf_blend.c                            Paul B Mahol
   vf_colorbalance.c                     Paul B Mahol
+  vf_colorkey.c                         Timo Rothenpieler
   vf_dejudder.c                         Nicholas Robbins
   vf_delogo.c                           Jean Delvare (CC <khali@linux-fr.org>)
   vf_drawbox.c/drawgrid                 Andrey Utkin

doc/filters.texi

@@ -3029,6 +3029,45 @@ colorbalance=rs=.3
 @end example
 @end itemize
 
+@section colorkey
+RGB colorspace color keying.
+
+The filter accepts the following options:
+
+@table @option
+@item color
+The color which will be replaced with transparency.
+
+@item similarity
+Similarity percentage with the key color.
+
+0.01 matches only the exact key color, while 1.0 matches everything.
+
+@item blend
+Blend percentage.
+
+0.0 makes pixels either fully transparent, or not transparent at all.
+
+Higher values result in semi-transparent pixels, with a higher transparency
+the more similar the pixels color is to the key color.
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Make every green pixel in the input image transparent:
+@example
+ffmpeg -i input.png -vf colorkey=green out.png
+@end example
+
+@item
+Overlay a greenscreen-video on top of a static background image.
+@example
+ffmpeg -i background.png -i video.mp4 -filter_complex "[1:v]colorkey=0x3BBD1E:0.3:0.2[ckout];[0:v][ckout]overlay[out]" -map "[out]" output.flv
+@end example
+@end itemize
+
 @section colorlevels
 
 Adjust video input frames using levels.

libavfilter/Makefile

@@ -102,6 +102,7 @@ OBJS-$(CONFIG_BOXBLUR_FILTER)                += vf_boxblur.o
 OBJS-$(CONFIG_CODECVIEW_FILTER)              += vf_codecview.o
 OBJS-$(CONFIG_COLORBALANCE_FILTER)           += vf_colorbalance.o
 OBJS-$(CONFIG_COLORCHANNELMIXER_FILTER)      += vf_colorchannelmixer.o
+OBJS-$(CONFIG_COLORKEY_FILTER)               += vf_colorkey.o
 OBJS-$(CONFIG_COLORLEVELS_FILTER)            += vf_colorlevels.o
 OBJS-$(CONFIG_COLORMATRIX_FILTER)            += vf_colormatrix.o
 OBJS-$(CONFIG_COPY_FILTER)                   += vf_copy.o

libavfilter/allfilters.c

@@ -118,6 +118,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(CODECVIEW,      codecview,      vf);
     REGISTER_FILTER(COLORBALANCE,   colorbalance,   vf);
     REGISTER_FILTER(COLORCHANNELMIXER, colorchannelmixer, vf);
+    REGISTER_FILTER(COLORKEY,       colorkey,       vf);
     REGISTER_FILTER(COLORLEVELS,    colorlevels,    vf);
     REGISTER_FILTER(COLORMATRIX,    colormatrix,    vf);
     REGISTER_FILTER(COPY,           copy,           vf);

libavfilter/vf_colorkey.c

@@ -0,0 +1,169 @@
+/*
+ * Copyright (c) 2015 Timo Rothenpieler <timo@rothenpieler.org>
+ *
+ * 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/imgutils.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+
+typedef struct ColorkeyContext {
+    const AVClass *class;
+
+    /* color offsets rgba */
+    int co[4];
+
+    uint8_t colorkey_rgba[4];
+    float similarity;
+    float blend;
+} ColorkeyContext;
+
+static uint8_t do_colorkey_pixel(ColorkeyContext *ctx, uint8_t r, uint8_t g, uint8_t b)
+{
+    int dr = (int)r - ctx->colorkey_rgba[0];
+    int dg = (int)g - ctx->colorkey_rgba[1];
+    int db = (int)b - ctx->colorkey_rgba[2];
+
+    double diff = sqrt((dr * dr + dg * dg + db * db) / (255.0 * 255.0));
+
+    if (ctx->blend > 0.0001) {
+        return av_clipd((diff - ctx->similarity) / ctx->blend, 0.0, 1.0) * 255.0;
+    } else {
+        return (diff > ctx->similarity) ? 255 : 0;
+    }
+}
+
+static int do_colorkey_slice(AVFilterContext *avctx, void *arg, int jobnr, int nb_jobs)
+{
+    AVFrame *frame = arg;
+
+    const int slice_start = (frame->height * jobnr) / nb_jobs;
+    const int slice_end = (frame->height * (jobnr + 1)) / nb_jobs;
+
+    ColorkeyContext *ctx = avctx->priv;
+
+    int o, x, y;
+
+    for (y = slice_start; y < slice_end; ++y) {
+        for (x = 0; x < frame->width; ++x) {
+            o = frame->linesize[0] * y + x * 4;
+
+            frame->data[0][o + ctx->co[3]] =
+                do_colorkey_pixel(ctx,
+                                  frame->data[0][o + ctx->co[0]],
+                                  frame->data[0][o + ctx->co[1]],
+                                  frame->data[0][o + ctx->co[2]]);
+        }
+    }
+
+    return 0;
+}
+
+static int filter_frame(AVFilterLink *link, AVFrame *frame)
+{
+    AVFilterContext *avctx = link->dst;
+    int res;
+
+    if (res = av_frame_make_writable(frame))
+        return res;
+
+    if (res = avctx->internal->execute(avctx, do_colorkey_slice, frame, NULL, FFMIN(frame->height, avctx->graph->nb_threads)))
+        return res;
+
+    return ff_filter_frame(avctx->outputs[0], frame);
+}
+
+static av_cold int config_output(AVFilterLink *outlink)
+{
+    AVFilterContext *avctx = outlink->src;
+    ColorkeyContext *ctx = avctx->priv;
+    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(outlink->format);
+    int i;
+
+    outlink->w = avctx->inputs[0]->w;
+    outlink->h = avctx->inputs[0]->h;
+    outlink->time_base = avctx->inputs[0]->time_base;
+
+    for (i = 0; i < 4; ++i)
+        ctx->co[i] = desc->comp[i].offset_plus1 - 1;
+
+    return 0;
+}
+
+static av_cold int query_formats(AVFilterContext *avctx)
+{
+    static const enum AVPixelFormat pixel_fmts[] = {
+        AV_PIX_FMT_ARGB,
+        AV_PIX_FMT_RGBA,
+        AV_PIX_FMT_ABGR,
+        AV_PIX_FMT_BGRA,
+        AV_PIX_FMT_NONE
+    };
+
+    AVFilterFormats *formats = NULL;
+
+    formats = ff_make_format_list(pixel_fmts);
+    if (!formats)
+        return AVERROR(ENOMEM);
+
+    return ff_set_common_formats(avctx, formats);
+}
+
+static const AVFilterPad colorkey_inputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = filter_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad colorkey_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+        .config_props  = config_output,
+    },
+    { NULL }
+};
+
+#define OFFSET(x) offsetof(ColorkeyContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+
+static const AVOption colorkey_options[] = {
+    { "color", "set the colorkey key color", OFFSET(colorkey_rgba), AV_OPT_TYPE_COLOR, { .str = "black" }, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "similarity", "set the colorkey similarity value", OFFSET(similarity), AV_OPT_TYPE_FLOAT, { .dbl = 0.01 }, 0.01, 1.0, FLAGS },
+    { "blend", "set the colorkey key blend value", OFFSET(blend), AV_OPT_TYPE_FLOAT, { .dbl = 0.0 }, 0.0, 1.0, FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(colorkey);
+
+AVFilter ff_vf_colorkey = {
+    .name          = "colorkey",
+    .description   = NULL_IF_CONFIG_SMALL("colorkey filter"),
+    .priv_size     = sizeof(ColorkeyContext),
+    .priv_class    = &colorkey_class,
+    .query_formats = query_formats,
+    .inputs        = colorkey_inputs,
+    .outputs       = colorkey_outputs,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC | AVFILTER_FLAG_SLICE_THREADS,
+};