325 lines
11 KiB
C
325 lines
11 KiB
C
/*
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* Copyright (c) 2012 Clément Bœsch
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* Edge detection filter
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*
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* @see https://en.wikipedia.org/wiki/Canny_edge_detector
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*/
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#include "libavutil/opt.h"
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#include "avfilter.h"
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#include "formats.h"
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#include "internal.h"
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#include "video.h"
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typedef struct {
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const AVClass *class;
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uint8_t *tmpbuf;
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uint16_t *gradients;
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char *directions;
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double low, high;
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uint8_t low_u8, high_u8;
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} EdgeDetectContext;
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#define OFFSET(x) offsetof(EdgeDetectContext, x)
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#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
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static const AVOption edgedetect_options[] = {
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{ "high", "set high threshold", OFFSET(high), AV_OPT_TYPE_DOUBLE, {.dbl=50/255.}, 0, 1, FLAGS },
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{ "low", "set low threshold", OFFSET(low), AV_OPT_TYPE_DOUBLE, {.dbl=20/255.}, 0, 1, FLAGS },
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{ NULL },
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};
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AVFILTER_DEFINE_CLASS(edgedetect);
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static av_cold int init(AVFilterContext *ctx, const char *args)
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{
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int ret;
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EdgeDetectContext *edgedetect = ctx->priv;
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edgedetect->class = &edgedetect_class;
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av_opt_set_defaults(edgedetect);
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if ((ret = av_set_options_string(edgedetect, args, "=", ":")) < 0)
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return ret;
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edgedetect->low_u8 = edgedetect->low * 255. + .5;
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edgedetect->high_u8 = edgedetect->high * 255. + .5;
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return 0;
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}
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static int query_formats(AVFilterContext *ctx)
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{
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static const enum PixelFormat pix_fmts[] = {PIX_FMT_GRAY8, PIX_FMT_NONE};
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ff_set_common_formats(ctx, ff_make_format_list(pix_fmts));
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return 0;
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}
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static int config_props(AVFilterLink *inlink)
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{
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AVFilterContext *ctx = inlink->dst;
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EdgeDetectContext *edgedetect = ctx->priv;
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edgedetect->tmpbuf = av_malloc(inlink->w * inlink->h);
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edgedetect->gradients = av_calloc(inlink->w * inlink->h, sizeof(*edgedetect->gradients));
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edgedetect->directions = av_malloc(inlink->w * inlink->h);
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if (!edgedetect->tmpbuf || !edgedetect->gradients || !edgedetect->directions)
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return AVERROR(ENOMEM);
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return 0;
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}
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static void gaussian_blur(AVFilterContext *ctx, int w, int h,
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uint8_t *dst, int dst_linesize,
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const uint8_t *src, int src_linesize)
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{
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int i, j;
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memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
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memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
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for (j = 2; j < h - 2; j++) {
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dst[0] = src[0];
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dst[1] = src[1];
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for (i = 2; i < w - 2; i++) {
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/* Gaussian mask of size 5x5 with sigma = 1.4 */
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dst[i] = ((src[-2*src_linesize + i-2] + src[2*src_linesize + i-2]) * 2
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+ (src[-2*src_linesize + i-1] + src[2*src_linesize + i-1]) * 4
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+ (src[-2*src_linesize + i ] + src[2*src_linesize + i ]) * 5
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+ (src[-2*src_linesize + i+1] + src[2*src_linesize + i+1]) * 4
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+ (src[-2*src_linesize + i+2] + src[2*src_linesize + i+2]) * 2
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+ (src[ -src_linesize + i-2] + src[ src_linesize + i-2]) * 4
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+ (src[ -src_linesize + i-1] + src[ src_linesize + i-1]) * 9
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+ (src[ -src_linesize + i ] + src[ src_linesize + i ]) * 12
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+ (src[ -src_linesize + i+1] + src[ src_linesize + i+1]) * 9
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+ (src[ -src_linesize + i+2] + src[ src_linesize + i+2]) * 4
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+ src[i-2] * 5
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+ src[i-1] * 12
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+ src[i ] * 15
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+ src[i+1] * 12
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+ src[i+2] * 5) / 159;
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}
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dst[i ] = src[i ];
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dst[i + 1] = src[i + 1];
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dst += dst_linesize;
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src += src_linesize;
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}
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memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
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memcpy(dst, src, w);
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}
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enum {
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DIRECTION_45UP,
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DIRECTION_45DOWN,
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DIRECTION_HORIZONTAL,
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DIRECTION_VERTICAL,
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};
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static int get_rounded_direction(int gx, int gy)
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{
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/* reference angles:
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* tan( pi/8) = sqrt(2)-1
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* tan(3pi/8) = sqrt(2)+1
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* Gy/Gx is the tangent of the angle (theta), so Gy/Gx is compared against
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* <ref-angle>, or more simply Gy against <ref-angle>*Gx
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*
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* Gx and Gy bounds = [1020;1020], using 16-bit arithmetic:
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* round((sqrt(2)-1) * (1<<16)) = 27146
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* round((sqrt(2)+1) * (1<<16)) = 158218
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*/
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if (gx) {
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int tanpi8gx, tan3pi8gx;
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if (gx < 0)
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gx = -gx, gy = -gy;
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gy <<= 16;
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tanpi8gx = 27146 * gx;
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tan3pi8gx = 158218 * gx;
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if (gy > -tan3pi8gx && gy < -tanpi8gx) return DIRECTION_45UP;
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if (gy > -tanpi8gx && gy < tanpi8gx) return DIRECTION_HORIZONTAL;
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if (gy > tanpi8gx && gy < tan3pi8gx) return DIRECTION_45DOWN;
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}
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return DIRECTION_VERTICAL;
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}
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static void sobel(AVFilterContext *ctx, int w, int h,
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uint16_t *dst, int dst_linesize,
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const uint8_t *src, int src_linesize)
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{
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int i, j;
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EdgeDetectContext *edgedetect = ctx->priv;
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for (j = 1; j < h - 1; j++) {
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dst += dst_linesize;
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src += src_linesize;
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for (i = 1; i < w - 1; i++) {
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const int gx =
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-1*src[-src_linesize + i-1] + 1*src[-src_linesize + i+1]
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-2*src[ i-1] + 2*src[ i+1]
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-1*src[ src_linesize + i-1] + 1*src[ src_linesize + i+1];
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const int gy =
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-1*src[-src_linesize + i-1] + 1*src[ src_linesize + i-1]
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-2*src[-src_linesize + i ] + 2*src[ src_linesize + i ]
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-1*src[-src_linesize + i+1] + 1*src[ src_linesize + i+1];
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dst[i] = FFABS(gx) + FFABS(gy);
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edgedetect->directions[j*w + i] = get_rounded_direction(gx, gy);
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}
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}
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}
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static void non_maximum_suppression(AVFilterContext *ctx, int w, int h,
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uint8_t *dst, int dst_linesize,
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const uint16_t *src, int src_linesize)
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{
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int i, j;
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EdgeDetectContext *edgedetect = ctx->priv;
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#define COPY_MAXIMA(ay, ax, by, bx) do { \
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if (src[i] > src[(ay)*src_linesize + i+(ax)] && \
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src[i] > src[(by)*src_linesize + i+(bx)]) \
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dst[i] = av_clip_uint8(src[i]); \
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} while (0)
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for (j = 1; j < h - 1; j++) {
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dst += dst_linesize;
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src += src_linesize;
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for (i = 1; i < w - 1; i++) {
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switch (edgedetect->directions[j*w + i]) {
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case DIRECTION_45UP: COPY_MAXIMA( 1, -1, -1, 1); break;
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case DIRECTION_45DOWN: COPY_MAXIMA(-1, -1, 1, 1); break;
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case DIRECTION_HORIZONTAL: COPY_MAXIMA( 0, -1, 0, 1); break;
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case DIRECTION_VERTICAL: COPY_MAXIMA(-1, 0, 1, 0); break;
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}
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}
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}
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}
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static void double_threshold(AVFilterContext *ctx, int w, int h,
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uint8_t *dst, int dst_linesize,
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const uint8_t *src, int src_linesize)
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{
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int i, j;
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EdgeDetectContext *edgedetect = ctx->priv;
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const int low = edgedetect->low_u8;
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const int high = edgedetect->high_u8;
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for (j = 0; j < h; j++) {
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for (i = 0; i < w; i++) {
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if (src[i] > high) {
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dst[i] = src[i];
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continue;
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}
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if ((!i || i == w - 1 || !j || j == h - 1) &&
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src[i] > low &&
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(src[-src_linesize + i-1] > high ||
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src[-src_linesize + i ] > high ||
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src[-src_linesize + i+1] > high ||
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src[ i-1] > high ||
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src[ i+1] > high ||
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src[ src_linesize + i-1] > high ||
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src[ src_linesize + i ] > high ||
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src[ src_linesize + i+1] > high))
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dst[i] = src[i];
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else
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dst[i] = 0;
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}
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dst += dst_linesize;
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src += src_linesize;
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}
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}
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static int end_frame(AVFilterLink *inlink)
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{
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AVFilterContext *ctx = inlink->dst;
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EdgeDetectContext *edgedetect = ctx->priv;
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AVFilterLink *outlink = inlink->dst->outputs[0];
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AVFilterBufferRef *inpicref = inlink->cur_buf;
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AVFilterBufferRef *outpicref = outlink->out_buf;
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uint8_t *tmpbuf = edgedetect->tmpbuf;
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uint16_t *gradients = edgedetect->gradients;
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/* gaussian filter to reduce noise */
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gaussian_blur(ctx, inlink->w, inlink->h,
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tmpbuf, inlink->w,
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inpicref->data[0], inpicref->linesize[0]);
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/* compute the 16-bits gradients and directions for the next step */
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sobel(ctx, inlink->w, inlink->h,
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gradients, inlink->w,
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tmpbuf, inlink->w);
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/* non_maximum_suppression() will actually keep & clip what's necessary and
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* ignore the rest, so we need a clean output buffer */
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memset(tmpbuf, 0, inlink->w * inlink->h);
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non_maximum_suppression(ctx, inlink->w, inlink->h,
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tmpbuf, inlink->w,
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gradients, inlink->w);
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/* keep high values, or low values surrounded by high values */
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double_threshold(ctx, inlink->w, inlink->h,
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outpicref->data[0], outpicref->linesize[0],
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tmpbuf, inlink->w);
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ff_draw_slice(outlink, 0, outlink->h, 1);
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return ff_end_frame(outlink);
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}
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static av_cold void uninit(AVFilterContext *ctx)
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{
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EdgeDetectContext *edgedetect = ctx->priv;
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av_freep(&edgedetect->tmpbuf);
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av_freep(&edgedetect->gradients);
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av_freep(&edgedetect->directions);
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}
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static int null_draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir) { return 0; }
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AVFilter avfilter_vf_edgedetect = {
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.name = "edgedetect",
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.description = NULL_IF_CONFIG_SMALL("Detect and draw edge."),
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.priv_size = sizeof(EdgeDetectContext),
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.init = init,
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.uninit = uninit,
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.query_formats = query_formats,
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.inputs = (const AVFilterPad[]) {
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{
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.name = "default",
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.type = AVMEDIA_TYPE_VIDEO,
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.draw_slice = null_draw_slice,
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.config_props = config_props,
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.end_frame = end_frame,
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.min_perms = AV_PERM_READ
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},
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{ .name = NULL }
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},
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.outputs = (const AVFilterPad[]) {
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{
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.name = "default",
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.type = AVMEDIA_TYPE_VIDEO,
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},
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{ .name = NULL }
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},
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};
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