libavfilter: Add OpenCL convolution filter

Behaves like existing convolution filter.
Signed-off-by: Mark Thompson <sw@jkqxz.net>

configure

@@ -3235,6 +3235,7 @@ blackframe_filter_deps="gpl"
 boxblur_filter_deps="gpl"
 bs2b_filter_deps="libbs2b"
 colormatrix_filter_deps="gpl"
+convolution_opencl_filter_deps="opencl"
 convolve_filter_deps="avcodec"
 convolve_filter_select="fft"
 coreimage_filter_deps="coreimage appkit"

libavfilter/Makefile

@@ -159,6 +159,8 @@ OBJS-$(CONFIG_COLORLEVELS_FILTER)            += vf_colorlevels.o
 OBJS-$(CONFIG_COLORMATRIX_FILTER)            += vf_colormatrix.o
 OBJS-$(CONFIG_COLORSPACE_FILTER)             += vf_colorspace.o colorspacedsp.o
 OBJS-$(CONFIG_CONVOLUTION_FILTER)            += vf_convolution.o
+OBJS-$(CONFIG_CONVOLUTION_OPENCL_FILTER)     += vf_convolution_opencl.o opencl.o \
+	                                        opencl/convolution.o
 OBJS-$(CONFIG_CONVOLVE_FILTER)               += vf_convolve.o framesync.o
 OBJS-$(CONFIG_COPY_FILTER)                   += vf_copy.o
 OBJS-$(CONFIG_COREIMAGE_FILTER)              += vf_coreimage.o

libavfilter/allfilters.c

@@ -168,6 +168,7 @@ static void register_all(void)
     REGISTER_FILTER(COLORMATRIX,    colormatrix,    vf);
     REGISTER_FILTER(COLORSPACE,     colorspace,     vf);
     REGISTER_FILTER(CONVOLUTION,    convolution,    vf);
+    REGISTER_FILTER(CONVOLUTION_OPENCL, convolution_opencl, vf);
     REGISTER_FILTER(CONVOLVE,       convolve,       vf);
     REGISTER_FILTER(COPY,           copy,           vf);
     REGISTER_FILTER(COREIMAGE,      coreimage,      vf);

libavfilter/opencl/convolution.cl

+/*
+ * Copyright (c) 2018 Danil Iashchenko
+ *
+ * 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
+ */
+
+__kernel void convolution_global(__write_only image2d_t dst,
+                                 __read_only  image2d_t src,
+                                 int coef_matrix_dim,
+                                 __constant float *coef_matrix,
+                                 float div,
+                                 float bias)
+{
+    const sampler_t sampler = (CLK_NORMALIZED_COORDS_FALSE |
+                               CLK_ADDRESS_CLAMP_TO_EDGE   |
+                               CLK_FILTER_NEAREST);
+
+    const int half_matrix_dim = (coef_matrix_dim / 2);
+    int2 loc = (int2)(get_global_id(0), get_global_id(1));
+    float4 convPix = (float4)(0.0f, 0.0f, 0.0f, 0.0f);
+
+    for (int conv_i = -half_matrix_dim; conv_i <= half_matrix_dim; conv_i++) {
+        for (int conv_j = -half_matrix_dim; conv_j <= half_matrix_dim; conv_j++) {
+            float4 px = read_imagef(src, sampler, loc + (int2)(conv_j, conv_i));
+            convPix += px * coef_matrix[(conv_i + half_matrix_dim) * coef_matrix_dim +
+                                        (conv_j + half_matrix_dim)];
+        }
+     }
+     float4 dstPix = convPix * div + bias;
+     write_imagef(dst, loc, dstPix);
+}

libavfilter/opencl_source.h

@@ -20,6 +20,7 @@
 #define AVFILTER_OPENCL_SOURCE_H
 
 extern const char *ff_opencl_source_avgblur;
+extern const char *ff_opencl_source_convolution;
 extern const char *ff_opencl_source_overlay;
 extern const char *ff_opencl_source_unsharp;