/*
 * Copyright (c) 2020 Yaroslav Pogrebnyak <yyyaroslav@gmail.com>
 *
 * 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
 */

extern "C" {

__global__ void Overlay_Cuda(
    int x_position, int y_position,
    unsigned char* main, int main_linesize,
    unsigned char* overlay, int overlay_linesize,
    int overlay_w, int overlay_h,
    unsigned char* overlay_alpha, int alpha_linesize,
    int alpha_adj_x, int alpha_adj_y)
{
    int x = blockIdx.x * blockDim.x + threadIdx.x;
    int y = blockIdx.y * blockDim.y + threadIdx.y;

    if (x >= overlay_w + x_position ||
        y >= overlay_h + y_position ||
        x < x_position ||
        y < y_position ) {

        return;
    }

    int overlay_x = x - x_position;
    int overlay_y = y - y_position;

    float alpha = 1.0;
    if (alpha_linesize) {
        alpha = overlay_alpha[alpha_adj_x * overlay_x  + alpha_adj_y * overlay_y * alpha_linesize] / 255.0f;
    }

    main[x + y*main_linesize] = alpha * overlay[overlay_x + overlay_y * overlay_linesize] + (1.0f - alpha) * main[x + y*main_linesize];
}

}