FFmpeg/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);
}