[FFmpeg-cvslog] GSoC: Support fast guided filter.

Xuewei Meng git at videolan.org
Thu May 13 06:59:34 EEST 2021


ffmpeg | branch: master | Xuewei Meng <xwmeng96 at gmail.com> | Mon May 10 21:42:31 2021 +0800| [43d70feb788318b124418c5c666f2120ee5ca930] | committer: Steven Liu

GSoC: Support fast guided filter.

Two modes are supported in guided filter, basic mode and fast mode.
Basic mode is the initial pushed guided filter without optimization.
Fast mode is implemented based on the basic one by sub-sampling method.
The sub-sampling ratio which can be defined by users controls the
algorithm complexity. The larger the sub-sampling ratio, the lower
the algorithm complexity.

Signed-off-by: Xuewei Meng <xwmeng96 at gmail.com>
Reviewed-by: Steven Liu <liuqi05 at kuaishou.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=43d70feb788318b124418c5c666f2120ee5ca930
---

 doc/filters.texi        |  20 +++++++---
 libavfilter/vf_guided.c | 104 ++++++++++++++++++++++++++++++++----------------
 2 files changed, 85 insertions(+), 39 deletions(-)

diff --git a/doc/filters.texi b/doc/filters.texi
index 22d02c38f7..b574334bea 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -12963,12 +12963,22 @@ Apply guided filter for edge-preserving smoothing, dehazing and so on.
 The filter accepts the following options:
 @table @option
 @item radius
-Set the radius in pixels.
+Set the box radius in pixels.
 Allowed range is 1 to 20. Default is 3.
 
 @item eps
-Set regularization parameter.
-Allowed range is 0 to 1. Default is 0.1.
+Set regularization parameter (with square).
+Allowed range is 0 to 1. Default is 0.01.
+
+ at item mode
+Set filter mode. Can be @code{basic} or @code{fast}.
+Default is @code{basic}.
+
+ at item sub
+Set subsampling ratio.
+Allowed range is 1 to 64.
+Default is always 1 for @code{basic} value of @var{mode} option,
+and 4 for @code{fast} value of @var{mode} option.
 
 @item planes
 Set planes to filter. Default is first only.
@@ -12987,8 +12997,8 @@ ffmpeg -i in.png -i in.png -filter_complex guided out.png
 
 @item
 Dehazing, structure-transferring filtering, detail enhancement with guided filter.
-For the generation of guidance image,
-see @url{http://kaiminghe.com/publications/pami12guidedfilter.pdf}.
+For the generation of guidance image, refer to paper "Guided Image Filtering".
+See: @url{http://kaiminghe.com/publications/pami12guidedfilter.pdf}.
 @example
 ffmpeg -i in.png -i guidance.png -filter_complex guided out.png
 @end example
diff --git a/libavfilter/vf_guided.c b/libavfilter/vf_guided.c
index 20c142337a..e7c689e7be 100644
--- a/libavfilter/vf_guided.c
+++ b/libavfilter/vf_guided.c
@@ -27,12 +27,20 @@
 #include "internal.h"
 #include "video.h"
 
+enum FilterModes {
+    BASIC,
+    FAST,
+    NB_MODES,
+};
+
 typedef struct GuidedContext {
     const AVClass *class;
     FFFrameSync fs;
 
     int radius;
     float eps;
+    int mode;
+    int sub;
 
     int planes;
 
@@ -51,9 +59,13 @@ typedef struct GuidedContext {
 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_RUNTIME_PARAM
 
 static const AVOption guided_options[] = {
-    { "radius", "set the box radius",           OFFSET(radius), AV_OPT_TYPE_INT,   {.i64=3    },   1,  20, FLAGS },
-    { "eps",    "set the regularization parameter (with square)",              OFFSET(eps),    AV_OPT_TYPE_FLOAT, {.dbl=0.01  }, 0.0,   1, FLAGS },
-    { "planes", "set planes to filter", OFFSET(planes), AV_OPT_TYPE_INT,   {.i64=1    },   0, 0xF, FLAGS },
+    { "radius", "set the box radius",                               OFFSET(radius), AV_OPT_TYPE_INT,   {.i64 = 3    },   1,           20, FLAGS },
+    { "eps",    "set the regularization parameter (with square)",   OFFSET(eps),    AV_OPT_TYPE_FLOAT, {.dbl = 0.01 }, 0.0,            1, FLAGS },
+    { "mode",   "set filtering mode (0: basic mode; 1: fast mode)", OFFSET(mode),   AV_OPT_TYPE_INT,   {.i64 = BASIC},   0, NB_MODES - 1, FLAGS, "mode" },
+    { "basic",  "basic guided filter",                              0,              AV_OPT_TYPE_CONST, {.i64 = BASIC},   0,            0, FLAGS, "mode" },
+    { "fast",   "fast guided filter",                               0,              AV_OPT_TYPE_CONST, {.i64 = FAST },   0,            0, FLAGS, "mode" },
+    { "sub",    "subsampling ratio",                                OFFSET(sub),    AV_OPT_TYPE_INT,   {.i64 = 1    },   1,           64, FLAGS },
+    { "planes", "set planes to filter",                             OFFSET(planes), AV_OPT_TYPE_INT,   {.i64=1      },   0,          0xF, FLAGS },
     { NULL }
 };
 
@@ -147,6 +159,26 @@ static int config_input(AVFilterLink *inlink)
         return AVERROR(EINVAL);
     }
 
+    if (s->mode == BASIC) {
+        if (s->sub != 1) {
+            av_log(ctx, AV_LOG_WARNING, "Subsampling ratio is 1 in basic mode.\n");
+            s->sub = 1;
+        }
+    }
+    else if (s->mode == FAST) {
+        if (s->sub == 1) {
+            av_log(ctx, AV_LOG_WARNING, "Subsampling ratio is larger than 1 in fast mode.\n");
+            s->sub = 4;
+        }
+        if (s->radius >= s->sub)
+            s->radius = s->radius / s->sub;
+        else {
+            s->radius = 1;
+        }
+    }
+    else {
+        return AVERROR_BUG;
+    }
 
     s->depth = desc->comp[0].depth;
     s->width = ctx->inputs[0]->w;
@@ -174,6 +206,10 @@ static int guided_##name(AVFilterContext *ctx, GuidedContext *s,
     const type *src = (const type *)ssrc;                                               \
     const type *srcRef = (const type *)ssrcRef;                                         \
                                                                                         \
+    int sub = s->sub;                                                                   \
+    int h = (height % sub) == 0 ? height / sub : height / sub + 1;                      \
+    int w = (width % sub) == 0 ? width / sub : width / sub + 1;                         \
+                                                                                        \
     ThreadData t;                                                                       \
     const int nb_threads = ff_filter_get_nb_threads(ctx);                               \
     float *I;                                                                           \
@@ -189,55 +225,55 @@ static int guided_##name(AVFilterContext *ctx, GuidedContext *s,
     float *meanA;                                                                       \
     float *meanB;                                                                       \
                                                                                         \
-    I      = av_calloc(width * height, sizeof(float));                                  \
-    II     = av_calloc(width * height, sizeof(float));                                  \
-    P      = av_calloc(width * height, sizeof(float));                                  \
-    IP     = av_calloc(width * height, sizeof(float));                                  \
-    meanI  = av_calloc(width * height, sizeof(float));                                  \
-    meanII = av_calloc(width * height, sizeof(float));                                  \
-    meanP  = av_calloc(width * height, sizeof(float));                                  \
-    meanIP = av_calloc(width * height, sizeof(float));                                  \
+    I      = av_calloc(w * h, sizeof(float));                                           \
+    II     = av_calloc(w * h, sizeof(float));                                           \
+    P      = av_calloc(w * h, sizeof(float));                                           \
+    IP     = av_calloc(w * h, sizeof(float));                                           \
+    meanI  = av_calloc(w * h, sizeof(float));                                           \
+    meanII = av_calloc(w * h, sizeof(float));                                           \
+    meanP  = av_calloc(w * h, sizeof(float));                                           \
+    meanIP = av_calloc(w * h, sizeof(float));                                           \
                                                                                         \
-    A      = av_calloc(width * height, sizeof(float));                                  \
-    B      = av_calloc(width * height, sizeof(float));                                  \
-    meanA  = av_calloc(width * height, sizeof(float));                                  \
-    meanB  = av_calloc(width * height, sizeof(float));                                  \
+    A      = av_calloc(w * h, sizeof(float));                                           \
+    B      = av_calloc(w * h, sizeof(float));                                           \
+    meanA  = av_calloc(w * h, sizeof(float));                                           \
+    meanB  = av_calloc(w * h, sizeof(float));                                           \
                                                                                         \
     if (!I || !II || !P || !IP || !meanI || !meanII || !meanP ||                        \
         !meanIP || !A || !B || !meanA || !meanB){                                       \
         ret = AVERROR(ENOMEM);                                                          \
         goto end;                                                                       \
     }                                                                                   \
-    for (int i = 0;i < height;i++) {                                                    \
-      for (int j = 0;j < width;j++) {                                                   \
-        int x = i * width + j;                                                          \
-        I[x]  = src[i * src_stride + j] / maxval;                                       \
+    for (int i = 0;i < h;i++) {                                                         \
+      for (int j = 0;j < w;j++) {                                                       \
+        int x = i * w + j;                                                              \
+        I[x]  = src[(i * src_stride + j) * sub] / maxval;                               \
         II[x] = I[x] * I[x];                                                            \
-        P[x]  = srcRef[i * src_ref_stride + j] / maxval;                                \
+        P[x]  = srcRef[(i * src_ref_stride + j) * sub] / maxval;                        \
         IP[x] = I[x] * P[x];                                                            \
       }                                                                                 \
     }                                                                                   \
                                                                                         \
-    t.width  = width;                                                                   \
-    t.height = height;                                                                  \
-    t.srcStride = width;                                                                \
-    t.dstStride = width;                                                                \
+    t.width  = w;                                                                       \
+    t.height = h;                                                                       \
+    t.srcStride = w;                                                                    \
+    t.dstStride = w;                                                                    \
     t.src = I;                                                                          \
     t.dst = meanI;                                                                      \
-    ctx->internal->execute(ctx, s->box_slice, &t, NULL, FFMIN(height, nb_threads));     \
+    ctx->internal->execute(ctx, s->box_slice, &t, NULL, FFMIN(h, nb_threads));          \
     t.src = II;                                                                         \
     t.dst = meanII;                                                                     \
-    ctx->internal->execute(ctx, s->box_slice, &t, NULL, FFMIN(height, nb_threads));     \
+    ctx->internal->execute(ctx, s->box_slice, &t, NULL, FFMIN(h, nb_threads));          \
     t.src = P;                                                                          \
     t.dst = meanP;                                                                      \
-    ctx->internal->execute(ctx, s->box_slice, &t, NULL, FFMIN(height, nb_threads));     \
+    ctx->internal->execute(ctx, s->box_slice, &t, NULL, FFMIN(h, nb_threads));          \
     t.src = IP;                                                                         \
     t.dst = meanIP;                                                                     \
-    ctx->internal->execute(ctx, s->box_slice, &t, NULL, FFMIN(height, nb_threads));     \
+    ctx->internal->execute(ctx, s->box_slice, &t, NULL, FFMIN(h, nb_threads));          \
                                                                                         \
-    for (int i = 0;i < height;i++) {                                                    \
-      for (int j = 0;j < width;j++) {                                                   \
-        int x = i * width + j;                                                          \
+    for (int i = 0;i < h;i++) {                                                         \
+      for (int j = 0;j < w;j++) {                                                       \
+        int x = i * w + j;                                                              \
         float varI = meanII[x] - (meanI[x] * meanI[x]);                                 \
         float covIP = meanIP[x] - (meanI[x] * meanP[x]);                                \
         A[x] = covIP / (varI + eps);                                                    \
@@ -247,14 +283,14 @@ static int guided_##name(AVFilterContext *ctx, GuidedContext *s,
                                                                                         \
     t.src = A;                                                                          \
     t.dst = meanA;                                                                      \
-    ctx->internal->execute(ctx, s->box_slice, &t, NULL, FFMIN(height, nb_threads));     \
+    ctx->internal->execute(ctx, s->box_slice, &t, NULL, FFMIN(h, nb_threads));          \
     t.src = B;                                                                          \
     t.dst = meanB;                                                                      \
-    ctx->internal->execute(ctx, s->box_slice, &t, NULL, FFMIN(height, nb_threads));     \
+    ctx->internal->execute(ctx, s->box_slice, &t, NULL, FFMIN(h, nb_threads));          \
                                                                                         \
     for (int i = 0;i < height;i++) {                                                    \
       for (int j = 0;j < width;j++) {                                                   \
-        int x = i * width + j;                                                          \
+        int x = i / sub * w + j / sub;                                                  \
         dst[i * dst_stride + j] = meanA[x] * src[i * src_stride + j] +                  \
                                   meanB[x] * maxval;                                    \
       }                                                                                 \



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