[FFmpeg-devel] [PATCH 2/2] lavfi/stackblur: add stackblur filter

Jun Zhao mypopydev at gmail.com
Wed Nov 13 16:17:05 EET 2019


From: Jun Zhao <barryjzhao at tencent.com>

add stackblur filter

Signed-off-by: Jun Zhao <barryjzhao at tencent.com>
---
 doc/filters.texi           |   22 +++
 libavfilter/Makefile       |    1 +
 libavfilter/allfilters.c   |    1 +
 libavfilter/vf_stackblur.c |  362 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 386 insertions(+), 0 deletions(-)
 create mode 100644 libavfilter/vf_stackblur.c

diff --git a/doc/filters.texi b/doc/filters.texi
index 23a3ded..0c450ff 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -17132,6 +17132,28 @@ ffmpeg -i main.mpg -i ref.mkv -lavfi  "[0:v]settb=1/AVTB,setpts=PTS-STARTPTS[mai
 @end example
 @end itemize
 
+ at section stackblur
+
+Blur the input image with stack blur algorithm, this is a compromise between Gaussian Blur
+and Box blur, It creates much better looking blurs than Box Blur, but is faster
+than the Gaussian Blur.
+
+Called it stack blur because this describes best how this filter works internally: it creates
+a kind of moving stack of colors whilst scanning through the image. Thereby it
+just has to add one new block of color to the right side of the stack and remove the
+leftmost color. The remaining colors on the topmost layer of the stack are either added on
+or reduced by one, depending on if they are on the right or on the left side of the stack.
+
+This filter accepts the following options:
+
+ at table @option
+ at item radius
+ at item r
+Set the blurring box radius. The option value must be a int number in
+the range [1, 179] that specifies the blur box size of the stack blur filter
+used to blur the image. Default value is @code{2}.
+ at end table
+
 @section stereo3d
 
 Convert between different stereoscopic image formats.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index db4d5e6..b9a4ad0 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -392,6 +392,7 @@ OBJS-$(CONFIG_SPLIT_FILTER)                  += split.o
 OBJS-$(CONFIG_SPP_FILTER)                    += vf_spp.o
 OBJS-$(CONFIG_SR_FILTER)                     += vf_sr.o
 OBJS-$(CONFIG_SSIM_FILTER)                   += vf_ssim.o framesync.o
+OBJS-$(CONFIG_STACKBLUR_FILTER)              += vf_stackblur.o
 OBJS-$(CONFIG_STEREO3D_FILTER)               += vf_stereo3d.o
 OBJS-$(CONFIG_STREAMSELECT_FILTER)           += f_streamselect.o framesync.o
 OBJS-$(CONFIG_SUBTITLES_FILTER)              += vf_subtitles.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index d507bc5..4064ba0 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -373,6 +373,7 @@ extern AVFilter ff_vf_split;
 extern AVFilter ff_vf_spp;
 extern AVFilter ff_vf_sr;
 extern AVFilter ff_vf_ssim;
+extern AVFilter ff_vf_stackblur;
 extern AVFilter ff_vf_stereo3d;
 extern AVFilter ff_vf_streamselect;
 extern AVFilter ff_vf_subtitles;
diff --git a/libavfilter/vf_stackblur.c b/libavfilter/vf_stackblur.c
new file mode 100644
index 0000000..f1a6f20
--- /dev/null
+++ b/libavfilter/vf_stackblur.c
@@ -0,0 +1,362 @@
+/*
+ * Copyright (c) 2019 Jun Zhao
+ *
+ * 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
+ * Stack blur filter
+ *
+ * Stack Blur Algorithm by Mario Klingemann <mario at quasimondo.com>
+ *
+ * @see http://incubator.quasimondo.com/processing/stackblur.pde
+ */
+
+#include "libavutil/avassert.h"
+#include "libavutil/imgutils.h"
+#include "libavutil/opt.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+
+typedef struct SuperFastBlurContext {
+    const AVClass *class;
+
+    int radius;
+
+    uint32_t *vMIN;
+    uint8_t *rgb;
+    uint8_t *dv;
+
+    int *stack;
+} StackBlurContext;
+
+#define OFFSET(x) offsetof(StackBlurContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption stackblur_options[] = {
+    { "radius", "Radius of the stack blurring box", OFFSET(radius),  AV_OPT_TYPE_INT, {.i64 = 2}, 1, 179, FLAGS },
+    { "r",      "Radius of the stack blurring box", OFFSET(radius),  AV_OPT_TYPE_INT, {.i64 = 2}, 1, 179, FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(stackblur);
+
+static av_cold int init(AVFilterContext *ctx)
+{
+    StackBlurContext *s = ctx->priv;
+
+    // This line precalculates a lookup table for all the possible
+    // mean values that can occur. This is to avoid costly division
+    // in the inner loop. On some systems doing the division directly
+    // instead of a doing an array lookup might actually be faster
+    // nowadays.
+    uint32_t div = 2 * s->radius + 1;
+    int divsum = (div + 1) >> 1;
+    divsum *= divsum;
+    s->dv = av_malloc(256 * divsum * sizeof(*s->dv));
+    if (!s->dv)
+        return AVERROR(ENOMEM);
+    for (int i = 0; i < 256 * divsum; i++)
+        s->dv[i] = i / divsum;
+
+    return 0;
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum AVPixelFormat pix_fmts[] = {
+        AV_PIX_FMT_RGB24, AV_PIX_FMT_BGR24,
+        AV_PIX_FMT_NONE
+    };
+
+    AVFilterFormats *fmts_list = ff_make_format_list(pix_fmts);
+    if (!fmts_list)
+        return AVERROR(ENOMEM);
+    return ff_set_common_formats(ctx, fmts_list);
+}
+
+static int config_props(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    StackBlurContext *s = ctx->priv;
+
+    uint32_t div = 2 * s->radius + 1;
+    uint32_t wh = inlink->w * inlink->h;
+
+    s->rgb   = av_malloc(sizeof(*s->rgb) * wh * 3);
+    s->vMIN  = av_malloc(FFMAX(inlink->w, inlink->h) * sizeof(*s->vMIN));
+    s->stack = av_malloc(div * 3 * sizeof(*s->stack));
+    if (!s->vMIN || !s->rgb || !s->stack)
+        return AVERROR(ENOMEM);
+
+    return 0;
+}
+
+// Stack Blur v1.0
+//
+// Author: Mario Klingemann <mario at quasimondo.com>
+// http://incubator.quasimondo.com
+// created Feburary 29, 2004
+//
+// This is a compromise between Gaussian Blur and Box blur
+// It creates much better looking blurs than Box Blur, but is faster
+// than the Gaussian Blur implementation.
+//
+// Called it Stack Blur because this describes best how this
+// filter works internally: it creates a kind of moving stack
+// of colors whilst scanning through the image. Thereby it
+// just has to add one new block of color to the right side
+// of the stack and remove the leftmost color. The remaining
+// colors on the topmost layer of the stack are either added on
+// or reduced by one, depending on if they are on the right or
+// on the left side of the stack.
+//
+static void stack_blur(StackBlurContext *s, uint8_t *pix, int w, int h, int nb_comps)
+{
+    uint32_t wm = w - 1;
+    uint32_t hm = h - 1;
+    uint32_t wh = w * h;
+
+    int radius = s->radius;
+
+    uint8_t *rgb = s->rgb;
+    uint8_t *r = rgb;
+    uint8_t *g = rgb + wh;
+    uint8_t *b = rgb + wh * 2;
+    int rsum, gsum, bsum, x, y, i, p, yp, yi, yw;
+
+    uint32_t stackpointer;
+    uint32_t stackstart;
+    int *sir;
+    int rbs;
+    int r1 = radius + 1;
+    int routsum, goutsum, boutsum;
+    int rinsum, ginsum, binsum;
+
+    uint32_t div = 2 * radius + 1;
+
+    int(*stack)[3] = (int(*)[3])(s->stack);
+    uint32_t *vMIN = s->vMIN;
+    uint8_t *dv = s->dv;
+
+    yw = yi = 0;
+
+    for (y = 0; y < h; y++) {
+        rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;
+        for (i = -radius; i <= radius; i++) {
+            p = yi + (FFMIN(wm, FFMAX(i, 0)));
+            sir = stack[i + radius];
+            sir[0] = pix[(p*nb_comps)];
+            sir[1] = pix[(p*nb_comps) + 1];
+            sir[2] = pix[(p*nb_comps) + 2];
+
+            rbs = r1 - FFABS(i);
+            rsum += sir[0] * rbs;
+            gsum += sir[1] * rbs;
+            bsum += sir[2] * rbs;
+            if (i > 0) {
+                rinsum += sir[0];
+                ginsum += sir[1];
+                binsum += sir[2];
+            } else {
+                routsum += sir[0];
+                goutsum += sir[1];
+                boutsum += sir[2];
+            }
+        }
+        stackpointer = radius;
+
+        for (x = 0; x < w; x++) {
+            r[yi] = dv[rsum];
+            g[yi] = dv[gsum];
+            b[yi] = dv[bsum];
+
+            rsum -= routsum;
+            gsum -= goutsum;
+            bsum -= boutsum;
+
+            stackstart = stackpointer - radius + div;
+            sir = stack[stackstart % div];
+
+            routsum -= sir[0];
+            goutsum -= sir[1];
+            boutsum -= sir[2];
+
+            if (y == 0)
+                vMIN[x] = FFMIN(x + radius + 1, wm);
+            p = yw + vMIN[x];
+
+            sir[0] = pix[(p*nb_comps)];
+            sir[1] = pix[(p*nb_comps) + 1];
+            sir[2] = pix[(p*nb_comps) + 2];
+            rinsum += sir[0];
+            ginsum += sir[1];
+            binsum += sir[2];
+
+            rsum += rinsum;
+            gsum += ginsum;
+            bsum += binsum;
+
+            stackpointer = (stackpointer + 1) % div;
+            sir = stack[(stackpointer) % div];
+
+            routsum += sir[0];
+            goutsum += sir[1];
+            boutsum += sir[2];
+
+            rinsum -= sir[0];
+            ginsum -= sir[1];
+            binsum -= sir[2];
+
+            yi++;
+        }
+        yw += w;
+    }
+    for (x = 0; x < w; x++) {
+        rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;
+        yp = -radius * w;
+        for (i = -radius; i <= radius; i++) {
+            yi = FFMAX(0, yp) + x;
+
+            sir = stack[i + radius];
+
+            sir[0] = r[yi];
+            sir[1] = g[yi];
+            sir[2] = b[yi];
+
+            rbs = r1 - FFABS(i);
+
+            rsum += r[yi] * rbs;
+            gsum += g[yi] * rbs;
+            bsum += b[yi] * rbs;
+
+            if (i > 0) {
+                rinsum += sir[0];
+                ginsum += sir[1];
+                binsum += sir[2];
+            } else {
+                routsum += sir[0];
+                goutsum += sir[1];
+                boutsum += sir[2];
+            }
+
+            if (i < hm)
+                yp += w;
+        }
+        yi = x;
+        stackpointer = radius;
+        for (y = 0; y < h; y++) {
+            pix[(yi*nb_comps)]     = dv[rsum];
+            pix[(yi*nb_comps) + 1] = dv[gsum];
+            pix[(yi*nb_comps) + 2] = dv[bsum];
+            rsum -= routsum;
+            gsum -= goutsum;
+            bsum -= boutsum;
+
+            stackstart = stackpointer - radius + div;
+            sir = stack[stackstart % div];
+
+            routsum -= sir[0];
+            goutsum -= sir[1];
+            boutsum -= sir[2];
+
+            if (x == 0)
+                vMIN[y] = FFMIN(y + r1, hm) * w;
+            p = x + vMIN[y];
+
+            sir[0] = r[p];
+            sir[1] = g[p];
+            sir[2] = b[p];
+
+            rinsum += sir[0];
+            ginsum += sir[1];
+            binsum += sir[2];
+
+            rsum += rinsum;
+            gsum += ginsum;
+            bsum += binsum;
+
+            stackpointer = (stackpointer + 1) % div;
+            sir = stack[stackpointer];
+
+            routsum += sir[0];
+            goutsum += sir[1];
+            boutsum += sir[2];
+
+            rinsum -= sir[0];
+            ginsum -= sir[1];
+            binsum -= sir[2];
+
+            yi += w;
+        }
+    }
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVFilterContext *ctx = inlink->dst;
+    StackBlurContext *s = ctx->priv;
+    AVFilterLink *outlink = ctx->outputs[0];
+    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
+
+    stack_blur(s, in->data[0], inlink->w, inlink->h, desc->nb_components);
+
+    return ff_filter_frame(outlink, in);
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    StackBlurContext *s = ctx->priv;
+
+    av_freep(&s->rgb);
+    av_freep(&s->vMIN);
+    av_freep(&s->dv);
+    av_freep(&s->stack);
+}
+
+static const AVFilterPad stackblur_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .config_props = config_props,
+        .filter_frame = filter_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad stackblur_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_stackblur = {
+    .name          = "stackblur",
+    .description   = NULL_IF_CONFIG_SMALL("Blur the input with stack algorithm."),
+    .priv_size     = sizeof(StackBlurContext),
+    .init          = init,
+    .uninit        = uninit,
+    .query_formats = query_formats,
+    .inputs        = stackblur_inputs,
+    .outputs       = stackblur_outputs,
+    .priv_class    = &stackblur_class,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
+};
-- 
1.7.1



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