Subject: [PATCH] Added alpha layer support for smartblur
From: Andrea Mastroberti <[email-masked]>
To: [email-masked]
Date: Tue, 19 Mar 2024 17:44:04 +0100

Signed-off-by: Andrea Mastroberti <[email-masked]>
---
 doc/filters.texi           | 20 ++++++++++++++++-
 libavfilter/version.h      |  2 +-
 libavfilter/vf_smartblur.c | 44 ++++++++++++++++++++++++++++++--------
 3 files changed, 55 insertions(+), 11 deletions(-)

diff --git a/doc/filters.texi b/doc/filters.texi
index 913365671d..30b3627724 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -22688,9 +22688,27 @@ whether a pixel should be blurred or not. The option value must be an
 integer in the range [-30,30]. A value of 0 will filter all the image,
 a value included in [0,30] will filter flat areas and a value included
 in [-30,0] will filter edges. Default value is @option{luma_threshold}.
+
+@item alpha_radius, ar
+Set the alpha radius. The option value must be a float number in
+the range [0.1,5.0] that specifies the variance of the gaussian filter
+used to blur the image (slower if larger). Default value is 1.0.
+
+@item alpha_strength, as
+Set the alpha strength. The option value must be a float number
+in the range [-1.0,1.0] that configures the blurring. A value included
+in [0.0,1.0] will blur the image whereas a value included in
+[-1.0,0.0] will sharpen the image. Default value is 1.0.
+
+@item alpha_threshold, at
+Set the alpha threshold used as a coefficient to determine
+whether a pixel should be blurred or not. The option value must be an
+integer in the range [-30,30]. A value of 0 will filter all the image,
+a value included in [0,30] will filter flat areas and a value included
+in [-30,0] will filter edges. Default value is 0.
 @end table
 
-If a chroma option is not explicitly set, the corresponding luma value
+If a chroma or alpha option is not explicitly set, the corresponding luma value
 is set.
 
 @section sobel
diff --git a/libavfilter/version.h b/libavfilter/version.h
index d5a6bc143a..f01b3f8e91 100644
--- a/libavfilter/version.h
+++ b/libavfilter/version.h
@@ -32,7 +32,7 @@
 #include "version_major.h"
 
 #define LIBAVFILTER_VERSION_MINOR   0
-#define LIBAVFILTER_VERSION_MICRO 100
+#define LIBAVFILTER_VERSION_MICRO 101

 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
diff --git a/libavfilter/vf_smartblur.c b/libavfilter/vf_smartblur.c
index ae0ec05b2d..bc377d0b92 100644
--- a/libavfilter/vf_smartblur.c
+++ b/libavfilter/vf_smartblur.c
@@ -54,6 +54,7 @@ typedef struct SmartblurContext {
     const AVClass *class;
     FilterParam  luma;
     FilterParam  chroma;
+    FilterParam  alpha;
     int          hsub;
     int          vsub;
     unsigned int sws_flags;
@@ -77,6 +78,13 @@ static const AVOption smartblur_options[] = {
     { "chroma_threshold", "set chroma threshold", OFFSET(chroma.threshold), AV_OPT_TYPE_INT,   {.i64=THRESHOLD_MIN-1}, THRESHOLD_MIN-1, THRESHOLD_MAX, .flags=FLAGS },
     { "ct",               "set chroma threshold", OFFSET(chroma.threshold), AV_OPT_TYPE_INT,   {.i64=THRESHOLD_MIN-1}, THRESHOLD_MIN-1, THRESHOLD_MAX, .flags=FLAGS },
 
+    { "alpha_radius",    "set alpha radius",    OFFSET(alpha.radius),    AV_OPT_TYPE_FLOAT, {.dbl=1.0}, RADIUS_MIN, RADIUS_MAX, .flags=FLAGS },
+    { "ar"         ,    "set alpha radius",    OFFSET(alpha.radius),    AV_OPT_TYPE_FLOAT, {.dbl=1.0}, RADIUS_MIN, RADIUS_MAX, .flags=FLAGS },
+    { "alpha_strength",  "set alpha strength",  OFFSET(alpha.strength),  AV_OPT_TYPE_FLOAT, {.dbl=1.0}, STRENGTH_MIN, STRENGTH_MAX, .flags=FLAGS },
+    { "as",             "set alpha strength",  OFFSET(alpha.strength),  AV_OPT_TYPE_FLOAT, {.dbl=1.0}, STRENGTH_MIN, STRENGTH_MAX, .flags=FLAGS },
+    { "alpha_threshold", "set alpha threshold", OFFSET(alpha.threshold), AV_OPT_TYPE_INT,   {.i64=0}, THRESHOLD_MIN, THRESHOLD_MAX, .flags=FLAGS },
+    { "at",             "set alpha threshold", OFFSET(alpha.threshold), AV_OPT_TYPE_INT,   {.i64=0}, THRESHOLD_MIN, THRESHOLD_MAX, .flags=FLAGS },
+
     { NULL }
 };
 
@@ -86,7 +94,7 @@ static av_cold int init(AVFilterContext *ctx)
 {
     SmartblurContext *s = ctx->priv;
 
-    /* make chroma default to luma values, if not explicitly set */
+    /* make chroma and alpha default to luma values, if not explicitly set */
     if (s->chroma.radius < RADIUS_MIN)
         s->chroma.radius = s->luma.radius;
     if (s->chroma.strength < STRENGTH_MIN)
@@ -94,15 +102,23 @@ static av_cold int init(AVFilterContext *ctx)
     if (s->chroma.threshold < THRESHOLD_MIN)
         s->chroma.threshold = s->luma.threshold;
 
-    s->luma.quality = s->chroma.quality = 3.0;
+    if (s->alpha.radius < RADIUS_MIN)
+        s->alpha.radius = s->alpha.radius;
+    if (s->alpha.strength < STRENGTH_MIN)
+        s->alpha.strength  = s->alpha.strength;
+    if (s->alpha.threshold < THRESHOLD_MIN)
+        s->alpha.threshold = s->alpha.threshold;
+
+    s->luma.quality = s->chroma.quality = s->alpha.quality = 3.0;
     s->sws_flags = SWS_BICUBIC;
 
     av_log(ctx, AV_LOG_VERBOSE,
            "luma_radius:%f luma_strength:%f luma_threshold:%d "
-           "chroma_radius:%f chroma_strength:%f chroma_threshold:%d\n",
+           "chroma_radius:%f chroma_strength:%f chroma_threshold:%d\n"
+           "alpha_radius:%f alpha_strength:%f alpha_threshold:%d ",
            s->luma.radius, s->luma.strength, s->luma.threshold,
-           s->chroma.radius, s->chroma.strength, s->chroma.threshold);
-
+           s->chroma.radius, s->chroma.strength, s->chroma.threshold,
+           s->alpha.radius, s->alpha.strength, s->alpha.threshold);
     return 0;
 }
 
@@ -112,13 +128,15 @@ static av_cold void uninit(AVFilterContext *ctx)
 
     sws_freeContext(s->luma.filter_context);
     sws_freeContext(s->chroma.filter_context);
+    sws_freeContext(s->alpha.filter_context);
 }
 
 static const enum AVPixelFormat pix_fmts[] = {
-    AV_PIX_FMT_YUV444P,      AV_PIX_FMT_YUV422P,
-    AV_PIX_FMT_YUV420P,      AV_PIX_FMT_YUV411P,
-    AV_PIX_FMT_YUV410P,      AV_PIX_FMT_YUV440P,
-    AV_PIX_FMT_GRAY8,
+    AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUVA444P,
+    AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUVA422P,
+    AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUVA420P,
+    AV_PIX_FMT_YUV411P, AV_PIX_FMT_YUV410P,
+    AV_PIX_FMT_YUV440P, AV_PIX_FMT_GRAY8,
     AV_PIX_FMT_NONE
 };
 
@@ -162,6 +180,7 @@ static int config_props(AVFilterLink *inlink)
                       AV_CEIL_RSHIFT(inlink->w, s->hsub),
                       AV_CEIL_RSHIFT(inlink->h, s->vsub),
                       s->sws_flags);
+    alloc_sws_context(&s->alpha, inlink->w, inlink->h, s->sws_flags);
 
     return 0;
 }
@@ -261,6 +280,13 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *inpic)
              s->chroma.filter_context);
     }
 
+    if (inpic->data[3]) {
+        blur(outpic->data[3], outpic->linesize[3],
+             inpic->data[3],  inpic->linesize[3],
+             inlink->w, inlink->h, s->alpha.threshold,
+             s->alpha.filter_context);
+    }
+
     av_frame_free(&inpic);
     return ff_filter_frame(outlink, outpic);
 }
-- 
2.44.0