lavfi: add edgedetect filter.

Changelog

@@ -47,6 +47,7 @@ version next:
 - hue filter
 - ICO muxer
 - SubRip encoder and decoder without embedded timing
+- edge detection filter
 
 
 version 0.11:

doc/filters.texi

@@ -1929,6 +1929,33 @@ For more information about libfreetype, check:
 For more information about fontconfig, check:
 @url{http://freedesktop.org/software/fontconfig/fontconfig-user.html}.
 
+@section edgedetect
+
+Detect and draw edges. The filter uses the Canny Edge Detection algorithm.
+
+This filter accepts the following optional named parameters:
+
+@table @option
+@item low, high
+Set low and high threshold values used by the Canny thresholding
+algorithm.
+
+The high threshold selects the "strong" edge pixels, which are then
+connected through 8-connectivity with the "weak" edge pixels selected
+by the low threshold.
+
+@var{low} and @var{high} threshold values must be choosen in the range
+[0,1], and @var{low} should be lesser or equal to @var{high}.
+
+Default value for @var{low} is @code{20/255}, and default value for @var{high}
+is @code{50/255}.
+@end table
+
+Example:
+@example
+edgedetect=low=0.1:high=0.4
+@end example
+
 @section fade
 
 Apply fade-in/out effect to input video.

libavfilter/Makefile

@@ -90,6 +90,7 @@ OBJS-$(CONFIG_DELOGO_FILTER)                 += vf_delogo.o
 OBJS-$(CONFIG_DESHAKE_FILTER)                += vf_deshake.o
 OBJS-$(CONFIG_DRAWBOX_FILTER)                += vf_drawbox.o
 OBJS-$(CONFIG_DRAWTEXT_FILTER)               += vf_drawtext.o
+OBJS-$(CONFIG_EDGEDETECT_FILTER)             += vf_edgedetect.o
 OBJS-$(CONFIG_FADE_FILTER)                   += vf_fade.o
 OBJS-$(CONFIG_FIELDORDER_FILTER)             += vf_fieldorder.o
 OBJS-$(CONFIG_FIFO_FILTER)                   += fifo.o

libavfilter/allfilters.c

@@ -81,6 +81,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER (DESHAKE,     deshake,     vf);
     REGISTER_FILTER (DRAWBOX,     drawbox,     vf);
     REGISTER_FILTER (DRAWTEXT,    drawtext,    vf);
+    REGISTER_FILTER (EDGEDETECT,  edgedetect,  vf);
     REGISTER_FILTER (FADE,        fade,        vf);
     REGISTER_FILTER (FIELDORDER,  fieldorder,  vf);
     REGISTER_FILTER (FIFO,        fifo,        vf);

libavfilter/version.h

@@ -29,8 +29,8 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  3
-#define LIBAVFILTER_VERSION_MINOR  9
-#define LIBAVFILTER_VERSION_MICRO 102
+#define LIBAVFILTER_VERSION_MINOR  10
+#define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \

libavfilter/vf_edgedetect.c

+/*
+ * Copyright (c) 2012 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
+ */
+
+/**
+ * @file
+ * Edge detection filter
+ *
+ * @url https://en.wikipedia.org/wiki/Canny_edge_detector
+ */
+
+#include "libavutil/opt.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+
+typedef struct {
+    const AVClass *class;
+    uint8_t  *tmpbuf;
+    uint16_t *gradients;
+    char     *directions;
+    double   low, high;
+    uint8_t  low_u8, high_u8;
+} EdgeDetectContext;
+
+#define OFFSET(x) offsetof(EdgeDetectContext, x)
+static const AVOption edgedetect_options[] = {
+    { "high", "set high threshold", OFFSET(high), AV_OPT_TYPE_DOUBLE, {.dbl=50/255.}, 0, 1 },
+    { "low",  "set low threshold",  OFFSET(low),  AV_OPT_TYPE_DOUBLE, {.dbl=20/255.}, 0, 1 },
+    { NULL },
+};
+
+AVFILTER_DEFINE_CLASS(edgedetect);
+
+static av_cold int init(AVFilterContext *ctx, const char *args)
+{
+    int ret;
+    EdgeDetectContext *edgedetect = ctx->priv;
+
+    edgedetect->class = &edgedetect_class;
+    av_opt_set_defaults(edgedetect);
+
+    if ((ret = av_set_options_string(edgedetect, args, "=", ":")) < 0)
+        return ret;
+
+    edgedetect->low_u8  = edgedetect->low  * 255.;
+    edgedetect->high_u8 = edgedetect->high * 255.;
+    return 0;
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum PixelFormat pix_fmts[] = {PIX_FMT_GRAY8, PIX_FMT_NONE};
+    ff_set_common_formats(ctx, ff_make_format_list(pix_fmts));
+    return 0;
+}
+
+static int config_props(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    EdgeDetectContext *edgedetect = ctx->priv;
+
+    edgedetect->tmpbuf     = av_malloc(inlink->w * inlink->h);
+    edgedetect->gradients  = av_calloc(inlink->w * inlink->h, sizeof(*edgedetect->gradients));
+    edgedetect->directions = av_malloc(inlink->w * inlink->h);
+    if (!edgedetect->tmpbuf || !edgedetect->gradients || !edgedetect->directions)
+        return AVERROR(ENOMEM);
+    return 0;
+}
+
+static void gaussian_blur(AVFilterContext *ctx, int w, int h,
+                                uint8_t *dst, int dst_linesize,
+                          const uint8_t *src, int src_linesize)
+{
+    int i, j;
+
+    memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
+    memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
+    for (j = 2; j < h - 2; j++) {
+        dst[0] = src[0];
+        dst[1] = src[1];
+        for (i = 2; i < w - 2; i++) {
+            /* Gaussian mask of size 5x5 with sigma = 1.4 */
+            dst[i] = ((src[-2*src_linesize + i-2] + src[2*src_linesize + i-2]) * 2
+                    + (src[-2*src_linesize + i-1] + src[2*src_linesize + i-1]) * 4
+                    + (src[-2*src_linesize + i  ] + src[2*src_linesize + i  ]) * 5
+                    + (src[-2*src_linesize + i+1] + src[2*src_linesize + i+1]) * 4
+                    + (src[-2*src_linesize + i+2] + src[2*src_linesize + i+2]) * 2
+
+                    + (src[  -src_linesize + i-2] + src[  src_linesize + i-2]) *  4
+                    + (src[  -src_linesize + i-1] + src[  src_linesize + i-1]) *  9
+                    + (src[  -src_linesize + i  ] + src[  src_linesize + i  ]) * 12
+                    + (src[  -src_linesize + i+1] + src[  src_linesize + i+1]) *  9
+                    + (src[  -src_linesize + i+2] + src[  src_linesize + i+2]) *  4
+
+                    + src[i-2] *  5
+                    + src[i-1] * 12
+                    + src[i  ] * 15
+                    + src[i+1] * 12
+                    + src[i+2] *  5) / 159;
+        }
+        dst[i    ] = src[i    ];
+        dst[i + 1] = src[i + 1];
+
+        dst += dst_linesize;
+        src += src_linesize;
+    }
+    memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
+    memcpy(dst, src, w);
+}
+
+enum {
+    DIRECTION_45UP,
+    DIRECTION_45DOWN,
+    DIRECTION_HORIZONTAL,
+    DIRECTION_VERTICAL,
+};
+
+static int get_rounded_direction(int gx, int gy)
+{
+    /* reference angles:
+     *   tan( pi/8) = sqrt(2)-1
+     *   tan(3pi/8) = sqrt(2)+1
+     * Gy/Gx is the tangent of the angle (theta), so Gy/Gx is compared against
+     * <ref-angle>, or more simply Gy against <ref-angle>*Gx
+     *
+     * Gx and Gy bounds = [1020;1020], using 16-bit arithmetic:
+     *   round((sqrt(2)-1) * (1<<16)) =  27146
+     *   round((sqrt(2)+1) * (1<<16)) = 158218
+     */
+    if (gx) {
+        int tanpi8gx, tan3pi8gx;
+
+        if (gx < 0)
+            gx = -gx, gy = -gy;
+        gy <<= 16;
+        tanpi8gx  =  27146 * gx;
+        tan3pi8gx = 158218 * gx;
+        if (gy > -tan3pi8gx && gy < -tanpi8gx)  return DIRECTION_45UP;
+        if (gy > -tanpi8gx  && gy <  tanpi8gx)  return DIRECTION_HORIZONTAL;
+        if (gy >  tanpi8gx  && gy <  tan3pi8gx) return DIRECTION_45DOWN;
+    }
+    return DIRECTION_VERTICAL;
+}
+
+static void sobel(AVFilterContext *ctx, int w, int h,
+                        uint16_t *dst, int dst_linesize,
+                  const uint8_t  *src, int src_linesize)
+{
+    int i, j;
+    EdgeDetectContext *edgedetect = ctx->priv;
+
+    for (j = 1; j < h - 1; j++) {
+        dst += dst_linesize;
+        src += src_linesize;
+        for (i = 1; i < w - 1; i++) {
+            const int gx =
+                -1*src[-src_linesize + i-1] + 1*src[-src_linesize + i+1]
+                -2*src[                i-1] + 2*src[                i+1]
+                -1*src[ src_linesize + i-1] + 1*src[ src_linesize + i+1];
+            const int gy =
+                -1*src[-src_linesize + i-1] + 1*src[ src_linesize + i-1]
+                -2*src[-src_linesize + i  ] + 2*src[ src_linesize + i  ]
+                -1*src[-src_linesize + i+1] + 1*src[ src_linesize + i+1];
+
+            dst[i] = FFABS(gx) + FFABS(gy);
+            edgedetect->directions[j*w + i] = get_rounded_direction(gx, gy);
+        }
+    }
+}
+
+static void non_maximum_suppression(AVFilterContext *ctx, int w, int h,
+                                          uint8_t  *dst, int dst_linesize,
+                                    const uint16_t *src, int src_linesize)
+{
+    int i, j;
+    EdgeDetectContext *edgedetect = ctx->priv;
+
+#define COPY_MAXIMA(ay, ax, by, bx) do {                \
+    if (src[i] > src[(ay)*src_linesize + i+(ax)] &&     \
+        src[i] > src[(by)*src_linesize + i+(bx)])       \
+        dst[i] = av_clip_uint8(src[i]);                 \
+} while (0)
+
+    for (j = 1; j < h - 1; j++) {
+        dst += dst_linesize;
+        src += src_linesize;
+        for (i = 1; i < w - 1; i++) {
+            switch (edgedetect->directions[j*w + i]) {
+            case DIRECTION_45UP:        COPY_MAXIMA( 1, -1, -1,  1); break;
+            case DIRECTION_45DOWN:      COPY_MAXIMA(-1, -1,  1,  1); break;
+            case DIRECTION_HORIZONTAL:  COPY_MAXIMA( 0, -1,  0,  1); break;
+            case DIRECTION_VERTICAL:    COPY_MAXIMA(-1,  0,  1,  0); break;
+            }
+        }
+    }
+}
+
+static void double_threshold(AVFilterContext *ctx, int w, int h,
+                                   uint8_t *dst, int dst_linesize,
+                             const uint8_t *src, int src_linesize)
+{
+    int i, j;
+    EdgeDetectContext *edgedetect = ctx->priv;
+    const int low  = edgedetect->low_u8;
+    const int high = edgedetect->high_u8;
+
+    for (j = 0; j < h; j++) {
+        for (i = 0; i < w; i++) {
+            if (src[i] > high) {
+                dst[i] = src[i];
+                continue;
+            }
+
+            if ((!i || i == w - 1 || !j || j == h - 1) &&
+                src[i] > low &&
+                (src[-src_linesize + i-1] > high ||
+                 src[-src_linesize + i  ] > high ||
+                 src[-src_linesize + i+1] > high ||
+                 src[                i-1] > high ||
+                 src[                i+1] > high ||
+                 src[ src_linesize + i-1] > high ||
+                 src[ src_linesize + i  ] > high ||
+                 src[ src_linesize + i+1] > high))
+                dst[i] = src[i];
+            else
+                dst[i] = 0;
+        }
+        dst += dst_linesize;
+        src += src_linesize;
+    }
+}
+
+static int end_frame(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    EdgeDetectContext *edgedetect = ctx->priv;
+    AVFilterLink *outlink = inlink->dst->outputs[0];
+    AVFilterBufferRef  *inpicref = inlink->cur_buf;
+    AVFilterBufferRef *outpicref = outlink->out_buf;
+    uint8_t  *tmpbuf    = edgedetect->tmpbuf;
+    uint16_t *gradients = edgedetect->gradients;
+
+    /* gaussian filter to reduce noise  */
+    gaussian_blur(ctx, inlink->w, inlink->h,
+                  tmpbuf,            inlink->w,
+                  inpicref->data[0], inpicref->linesize[0]);
+
+    /* compute the 16-bits gradients and directions for the next step */
+    sobel(ctx, inlink->w, inlink->h,
+          gradients, inlink->w,
+          tmpbuf,    inlink->w);
+
+    /* non_maximum_suppression() will actually keep & clip what's necessary and
+     * ignore the rest, so we need a clean output buffer */
+    memset(tmpbuf, 0, inlink->w * inlink->h);
+    non_maximum_suppression(ctx, inlink->w, inlink->h,
+                            tmpbuf,    inlink->w,
+                            gradients, inlink->w);
+
+    /* keep high values, or low values surrounded by high values */
+    double_threshold(ctx, inlink->w, inlink->h,
+                     outpicref->data[0], outpicref->linesize[0],
+                     tmpbuf,             inlink->w);
+
+    ff_draw_slice(outlink, 0, outlink->h, 1);
+    return ff_end_frame(outlink);
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    EdgeDetectContext *edgedetect = ctx->priv;
+    av_freep(&edgedetect->tmpbuf);
+    av_freep(&edgedetect->gradients);
+    av_freep(&edgedetect->directions);
+}
+
+static int null_draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir) { return 0; }
+
+AVFilter avfilter_vf_edgedetect = {
+    .name          = "edgedetect",
+    .description   = NULL_IF_CONFIG_SMALL("Detect and draw edge."),
+    .priv_size     = sizeof(EdgeDetectContext),
+    .init          = init,
+    .uninit        = uninit,
+    .query_formats = query_formats,
+
+    .inputs    = (const AVFilterPad[]) {
+       {
+           .name             = "default",
+           .type             = AVMEDIA_TYPE_VIDEO,
+           .draw_slice       = null_draw_slice,
+           .config_props     = config_props,
+           .end_frame        = end_frame,
+           .min_perms        = AV_PERM_READ
+        },
+        { .name = NULL }
+    },
+    .outputs   = (const AVFilterPad[]) {
+        {
+            .name            = "default",
+            .type            = AVMEDIA_TYPE_VIDEO,
+        },
+        { .name = NULL }
+    },
+};

tests/lavfi-regression.sh

@@ -42,6 +42,7 @@ do_lavfi "crop_scale"         "crop=iw-100:ih-100:100:100,scale=400:-1"
 do_lavfi "crop_scale_vflip"   "null,null,crop=iw-200:ih-200:200:200,crop=iw-20:ih-20:20:20,scale=200:200,scale=250:250,vflip,vflip,null,scale=200:200,crop=iw-100:ih-100:100:100,vflip,scale=200:200,null,vflip,crop=iw-100:ih-100:100:100,null"
 do_lavfi "crop_vflip"         "crop=iw-100:ih-100:100:100,vflip"
 do_lavfi "drawbox"            "drawbox=224:24:88:72:#FF8010@0.5"
+do_lavfi "edgedetect"         "edgedetect"
 do_lavfi "fade"               "fade=in:5:15,fade=out:30:15"
 do_lavfi "null"               "null"
 do_lavfi "overlay"            "split[m],scale=88:72,pad=96:80:4:4[o2];[m]fifo[o1],[o1][o2]overlay=240:16"

tests/ref/lavfi/edgedetect

+edgedetect          16bce636eef1a82e18837d176f4187c1