[FFmpeg-devel] [PATCH][WIP] lavfi: edgedetect filter

Clément Bœsch ubitux at gmail.com
Sun Aug 5 10:41:55 CEST 2012


---
Still a lot of things to do, fix and optimize, but results are good enough for
a first demonstration. I'm just sharing this to prevent SOCIS students (or
other people) to duplicate work.
---
 doc/filters.texi            |   4 +
 libavfilter/Makefile        |   1 +
 libavfilter/allfilters.c    |   1 +
 libavfilter/vf_edgedetect.c | 288 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 294 insertions(+)
 create mode 100644 libavfilter/vf_edgedetect.c

diff --git a/doc/filters.texi b/doc/filters.texi
index 2609065..cb54409 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -1929,6 +1929,10 @@ For more information about libfreetype, check:
 For more information about fontconfig, check:
 @url{http://freedesktop.org/software/fontconfig/fontconfig-user.html}.
 
+ at section edgedetect
+
+Detect and draw edges. No parameter available.
+
 @section fade
 
 Apply fade-in/out effect to input video.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 727ab4e..da657a2 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -89,6 +89,7 @@ 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
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 403383d..858b9e6 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -79,6 +79,7 @@ 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);
diff --git a/libavfilter/vf_edgedetect.c b/libavfilter/vf_edgedetect.c
new file mode 100644
index 0000000..baf0dc2
--- /dev/null
+++ b/libavfilter/vf_edgedetect.c
@@ -0,0 +1,288 @@
+/*
+ * 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
+ */
+
+#include <math.h>
+
+#include "libavutil/avstring.h"
+#include "libavutil/eval.h"
+#include "libavutil/pixdesc.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+
+typedef struct {
+    uint8_t *tmpbuf1;
+    uint8_t *tmpbuf2;
+    char *directions;
+} EdgeDetectContext;
+
+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->tmpbuf1    = av_malloc(inlink->w * inlink->h);
+    edgedetect->tmpbuf2    = av_malloc(inlink->w * inlink->h);
+    edgedetect->directions = av_malloc(inlink->w * inlink->h);
+    if (!edgedetect->tmpbuf1 || !edgedetect->tmpbuf2 || !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;
+
+    for (j = 0; j < h; j++) {
+        for (i = 0; i < w; i++) {
+            if (i < 2 || i >= w - 2 || j < 2 || j >= h - 2) {
+                // FIXME: necessary?
+                dst[j*dst_linesize + i] = src[j*src_linesize + i];
+            } else // TODO: optimize? (can be approximated)
+                dst[j*dst_linesize + i] =
+                 ((src[(j-2)*src_linesize + (i-2)] + src[(j+2)*src_linesize + (i-2)]) * 2
+                + (src[(j-2)*src_linesize + (i-1)] + src[(j+2)*src_linesize + (i-1)]) * 4
+                + (src[(j-2)*src_linesize +  i   ] + src[(j+2)*src_linesize +  i   ]) * 5
+                + (src[(j-2)*src_linesize + (i+1)] + src[(j+2)*src_linesize + (i+1)]) * 4
+                + (src[(j-2)*src_linesize + (i+2)] + src[(j+2)*src_linesize + (i+2)]) * 2
+
+                + (src[(j-1)*src_linesize + (i-2)] + src[(j-1)*src_linesize + (i-2)])*  4
+                + (src[(j-1)*src_linesize + (i-1)] + src[(j-1)*src_linesize + (i-1)])*  9
+                + (src[(j-1)*src_linesize +  i   ] + src[(j-1)*src_linesize +  i   ])* 12
+                + (src[(j-1)*src_linesize + (i+1)] + src[(j-1)*src_linesize + (i+1)])*  9
+                + (src[(j-1)*src_linesize + (i+2)] + src[(j-1)*src_linesize + (i+2)])*  4
+
+                + src[j*src_linesize + (i-2)] *  5
+                + src[j*src_linesize + (i-1)] * 12
+                + src[j*src_linesize +  i   ] * 15
+                + src[j*src_linesize + (i+1)] * 12
+                + src[j*src_linesize + (i+2)] *  5) / 159;
+        }
+    }
+}
+
+enum {
+    DIRECTION_45UP,
+    DIRECTION_45DOWN,
+    DIRECTION_HORIZONTAL,
+    DIRECTION_VERTICAL,
+};
+
+static int get_closer_direction(int gx, int gy)
+{
+    // TODO: avoid atan2() call by using the y/x tan
+    const double theta = atan2(FFABS(gy), FFABS(gx));
+
+    if (theta < 3*M_PI/8 && theta > M_PI/8) {
+        if ((gx > 0 && gy > 0) || (gx < 0 && gy < 0))
+            return DIRECTION_45DOWN;
+        else
+            return DIRECTION_45UP;
+    }
+    if (theta < M_PI/8)
+        return DIRECTION_HORIZONTAL;
+    return DIRECTION_VERTICAL;
+}
+
+static void sobel(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;
+
+    for (j = 0; j < h; j++) {
+        for (i = 0; i < w; i++) {
+            if (!i || i == w - 1 || !j || j == h - 1) {
+                // FIXME: necessary?
+                dst[j*dst_linesize + i] = src[j*src_linesize + i];
+            } else {
+                const int gx =
+                    -1*src[(j-1)*src_linesize + i-1] + 1*src[(j-1)*src_linesize + i+1]
+                    -2*src[ j   *src_linesize + i-1] + 2*src[ j   *src_linesize + i+1]
+                    -1*src[(j+1)*src_linesize + i-1] + 1*src[(j+1)*src_linesize + i+1];
+                const int gy =
+                    -1*src[(j-1)*src_linesize + i-1] + 1*src[(j+1)*src_linesize + i-1]
+                    -2*src[(j-1)*src_linesize + i  ] + 2*src[(j+1)*src_linesize + i  ]
+                    -1*src[(j-1)*src_linesize + i+1] + 1*src[(j+1)*src_linesize + i+1];
+
+                dst[j*dst_linesize + i] = av_clip_uint8(FFABS(gx) + FFABS(gy));
+                edgedetect->directions[j*w + i] = get_closer_direction(gx, gy);
+            }
+        }
+    }
+}
+
+static void non_maximum_suppression(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;
+
+#define RESET_NON_MAXIMA(ay, ax, by, bx) do {                               \
+    if (src[j*src_linesize + i] > src[(j+(ay))*src_linesize + i+(ax)] &&    \
+        src[j*src_linesize + i] > src[(j+(by))*src_linesize + i+(bx)])      \
+        dst[j*dst_linesize + i] = src[j*src_linesize + i];                  \
+    else                                                                    \
+        dst[j*dst_linesize + i] = 0;                                        \
+} while (0)
+
+    for (j = 0; j < h; j++) {
+        for (i = 0; i < w; i++) {
+
+            if (!i || i == w - 1 || !j || j == h - 1) {
+                // FIXME: sth better?
+                dst[j*dst_linesize + i] = 0;
+                continue;
+            }
+
+#if 0
+            /* skip double threshold step when using this */
+            switch (edgedetect->directions[j*w + i]) {
+            case DIRECTION_45UP:        dst[j*dst_linesize + i] = 0x00; break;
+            case DIRECTION_45DOWN:      dst[j*dst_linesize + i] = 0x55; break;
+            case DIRECTION_HORIZONTAL:  dst[j*dst_linesize + i] = 0xaa; break;
+            case DIRECTION_VERTICAL:    dst[j*dst_linesize + i] = 0xff; break;
+            }
+#else
+            switch (edgedetect->directions[j*w + i]) {
+            case DIRECTION_45UP:        RESET_NON_MAXIMA( 1, -1, -1,  1); break;
+            case DIRECTION_45DOWN:      RESET_NON_MAXIMA(-1, -1,  1,  1); break;
+            case DIRECTION_HORIZONTAL:  RESET_NON_MAXIMA( 0, -1,  0,  1); break;
+            case DIRECTION_VERTICAL:    RESET_NON_MAXIMA(-1,  0,  1,  0); break;
+            }
+#endif
+        }
+    }
+}
+
+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;
+
+#define THRES_HIGH 80
+#define THRES_LOW  20
+
+    for (j = 0; j < h; j++) {
+        for (i = 0; i < w; i++) {
+            if (src[j*src_linesize + i] > THRES_HIGH) {
+                dst[j*dst_linesize + i] = src[j*src_linesize + i];
+                continue;
+            }
+
+            if ((!i || i == w - 1 || !j || j == h - 1) &&
+                src[j*src_linesize + i] > THRES_LOW &&
+                (src[(j-1)*src_linesize + i-1] > THRES_HIGH ||
+                 src[(j-1)*src_linesize + i  ] > THRES_HIGH ||
+                 src[(j-1)*src_linesize + i+1] > THRES_HIGH ||
+                 src[ j   *src_linesize + i-1] > THRES_HIGH ||
+                 src[ j   *src_linesize + i+1] > THRES_HIGH ||
+                 src[(j+1)*src_linesize + i-1] > THRES_HIGH ||
+                 src[(j+1)*src_linesize + i  ] > THRES_HIGH ||
+                 src[(j+1)*src_linesize + i+1] > THRES_HIGH))
+                dst[j*dst_linesize + i] = src[j*src_linesize + i];
+            else
+                dst[j*dst_linesize + i] = 0;
+        }
+    }
+}
+
+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 *tmpbuf1 = edgedetect->tmpbuf1;
+    uint8_t *tmpbuf2 = edgedetect->tmpbuf2;
+
+    /* canny edge detection */
+
+    gaussian_blur(ctx, inlink->w, inlink->h,
+                  tmpbuf1, inlink->w,
+                  inpicref->data[0], inpicref->linesize[0]);
+
+    sobel(ctx, inlink->w, inlink->h,
+          tmpbuf2, inlink->w,
+          tmpbuf1, inlink->w);
+
+    non_maximum_suppression(ctx, inlink->w, inlink->h,
+                            tmpbuf1, inlink->w,
+                            tmpbuf2, inlink->w);
+
+    double_threshold(ctx, inlink->w, inlink->h,
+                     outpicref->data[0], outpicref->linesize[0],
+                     tmpbuf1, 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->tmpbuf1);
+    av_freep(&edgedetect->tmpbuf2);
+    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),
+    .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 }
+    },
+};
-- 
1.7.11.4



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