avfilter/vf_convolution: add scharr operator

Changelog

@@ -18,6 +18,7 @@ version <next>:
 - AV1 Low overhead bitstream format muxer
 - swscale slice threading
 - MSN Siren decoder
+- scharr video filter
 
 
 version 4.4:

doc/filters.texi

@@ -18349,6 +18349,27 @@ If the specified expression is not valid, it is kept at its current
 value.
 @end table
 
+@section scharr
+Apply scharr operator to input video stream.
+
+The filter accepts the following option:
+
+@table @option
+@item planes
+Set which planes will be processed, unprocessed planes will be copied.
+By default value 0xf, all planes will be processed.
+
+@item scale
+Set value which will be multiplied with filtered result.
+
+@item delta
+Set value which will be added to filtered result.
+@end table
+
+@subsection Commands
+
+This filter supports the all above options as @ref{commands}.
+
 @section scroll
 Scroll input video horizontally and/or vertically by constant speed.
 

libavfilter/Makefile

@@ -409,6 +409,7 @@ OBJS-$(CONFIG_SCALE_VAAPI_FILTER)            += vf_scale_vaapi.o scale_eval.o va
 OBJS-$(CONFIG_SCALE_VULKAN_FILTER)           += vf_scale_vulkan.o vulkan.o
 OBJS-$(CONFIG_SCALE2REF_FILTER)              += vf_scale.o scale_eval.o
 OBJS-$(CONFIG_SCDET_FILTER)                  += vf_scdet.o
+OBJS-$(CONFIG_SCHARR_FILTER)                 += vf_convolution.o
 OBJS-$(CONFIG_SCROLL_FILTER)                 += vf_scroll.o
 OBJS-$(CONFIG_SEGMENT_FILTER)                += f_segment.o
 OBJS-$(CONFIG_SELECT_FILTER)                 += f_select.o

libavfilter/allfilters.c

@@ -390,6 +390,7 @@ extern const AVFilter ff_vf_scale_vaapi;
 extern const AVFilter ff_vf_scale_vulkan;
 extern const AVFilter ff_vf_scale2ref;
 extern const AVFilter ff_vf_scdet;
+extern const AVFilter ff_vf_scharr;
 extern const AVFilter ff_vf_scroll;
 extern const AVFilter ff_vf_segment;
 extern const AVFilter ff_vf_select;

libavfilter/version.h

@@ -30,8 +30,8 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   8
-#define LIBAVFILTER_VERSION_MINOR   7
+#define LIBAVFILTER_VERSION_MINOR   8
-#define LIBAVFILTER_VERSION_MICRO 101
+#define LIBAVFILTER_VERSION_MICRO 100
 
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \

libavfilter/vf_convolution.c

@@ -160,6 +160,26 @@ static void filter16_sobel(uint8_t *dstp, int width,
     }
 }
 
+static void filter16_scharr(uint8_t *dstp, int width,
+                            float scale, float delta, const int *const matrix,
+                            const uint8_t *c[], int peak, int radius,
+                            int dstride, int stride, int size)
+{
+    uint16_t *dst = (uint16_t *)dstp;
+    int x;
+
+    for (x = 0; x < width; x++) {
+        float suma = AV_RN16A(&c[0][2 * x]) * -47 + AV_RN16A(&c[1][2 * x]) * -162 + AV_RN16A(&c[2][2 * x]) *  -47 +
+                     AV_RN16A(&c[6][2 * x]) *  47 + AV_RN16A(&c[7][2 * x]) *  162 + AV_RN16A(&c[8][2 * x]) *   47;
+        float sumb = AV_RN16A(&c[0][2 * x]) * -47 + AV_RN16A(&c[2][2 * x]) *   47 + AV_RN16A(&c[3][2 * x]) * -162 +
+                     AV_RN16A(&c[5][2 * x]) * 162 + AV_RN16A(&c[6][2 * x]) *  -47 + AV_RN16A(&c[8][2 * x]) *   47;
+
+        suma /= 256.f;
+        sumb /= 256.f;
+        dst[x] = av_clip(sqrtf(suma*suma + sumb*sumb) * scale + delta, 0, peak);
+    }
+}
+
 static void filter16_kirsch(uint8_t *dstp, int width,
                             float scale, float delta, const int *const matrix,
                             const uint8_t *c[], int peak, int radius,
@@ -264,6 +284,28 @@ static void filter_sobel(uint8_t *dst, int width,
     }
 }
 
+static void filter_scharr(uint8_t *dst, int width,
+                          float scale, float delta, const int *const matrix,
+                          const uint8_t *c[], int peak, int radius,
+                          int dstride, int stride, int size)
+{
+    const uint8_t *c0 = c[0], *c1 = c[1], *c2 = c[2];
+    const uint8_t *c3 = c[3], *c5 = c[5];
+    const uint8_t *c6 = c[6], *c7 = c[7], *c8 = c[8];
+    int x;
+
+    for (x = 0; x < width; x++) {
+        float suma = c0[x] * -47 + c1[x] * -162 + c2[x] *  -47 +
+                     c6[x] *  47 + c7[x] *  162 + c8[x] *   47;
+        float sumb = c0[x] * -47 + c2[x] *   47 + c3[x] * -162 +
+                     c5[x] * 162 + c6[x] *  -47 + c8[x] *   47;
+
+        suma /= 256.f;
+        sumb /= 256.f;
+        dst[x] = av_clip_uint8(sqrtf(suma*suma + sumb*sumb) * scale + delta);
+    }
+}
+
 static void filter_kirsch(uint8_t *dst, int width,
                           float scale, float delta, const int *const matrix,
                           const uint8_t *c[], int peak, int radius,
@@ -715,6 +757,10 @@ static int config_input(AVFilterLink *inlink)
         if (s->depth > 8)
             for (p = 0; p < s->nb_planes; p++)
                 s->filter[p] = filter16_kirsch;
+    } else if (!strcmp(ctx->filter->name, "scharr")) {
+        if (s->depth > 8)
+            for (p = 0; p < s->nb_planes; p++)
+                s->filter[p] = filter16_scharr;
     }
 
     return 0;
@@ -867,6 +913,17 @@ static av_cold int init(AVFilterContext *ctx)
             s->rdiv[i] = s->scale;
             s->bias[i] = s->delta;
         }
+    } else if (!strcmp(ctx->filter->name, "scharr")) {
+        for (i = 0; i < 4; i++) {
+            if ((1 << i) & s->planes)
+                s->filter[i] = filter_scharr;
+            else
+                s->copy[i] = 1;
+            s->size[i] = 3;
+            s->setup[i] = setup_3x3;
+            s->rdiv[i] = s->scale;
+            s->bias[i] = s->delta;
+        }
     }
 
     return 0;
@@ -1006,4 +1063,24 @@ const AVFilter ff_vf_kirsch = {
 
 #endif /* CONFIG_KIRSCH_FILTER */
 
-#endif /* CONFIG_PREWITT_FILTER || CONFIG_ROBERTS_FILTER || CONFIG_SOBEL_FILTER */
+#if CONFIG_SCHARR_FILTER
+
+#define scharr_options prewitt_roberts_sobel_options
+AVFILTER_DEFINE_CLASS(scharr);
+
+const AVFilter ff_vf_scharr = {
+    .name          = "scharr",
+    .description   = NULL_IF_CONFIG_SMALL("Apply scharr operator."),
+    .priv_size     = sizeof(ConvolutionContext),
+    .priv_class    = &scharr_class,
+    .init          = init,
+    .query_formats = query_formats,
+    FILTER_INPUTS(convolution_inputs),
+    FILTER_OUTPUTS(convolution_outputs),
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC | AVFILTER_FLAG_SLICE_THREADS,
+    .process_command = process_command,
+};
+
+#endif /* CONFIG_SCHARR_FILTER */
+
+#endif /* CONFIG_PREWITT_FILTER || CONFIG_ROBERTS_FILTER || CONFIG_SOBEL_FILTER || CONFIG_SCHARR_FILTER */