//YUV420P图片叠加算法
public static void mergeYUV420P(byte[] yuv420P_A, byte[] yuv420P_B, int offset_x, int offset_y,
                                int a_width, int a_height, int b_width, int b_height) {

    //y
    for (int i = 0; i < b_height; i++) {
        for (int j = 0; j < b_width; j++) {
            yuv420P_A[i * a_width + offset_y * a_width + j + offset_x] = yuv420P_B[i * b_width + j];
        }
    }

    //uv
    for (int i = 0; i < b_height / 4; i++) {
        for (int j = 0; j < b_width; j++) {
            if (j < b_width / 2) {
                yuv420P_A[i * a_width + offset_y / 4 * a_width + j + offset_x / 2 + a_width * a_height] = yuv420P_B[i * b_width + j + b_width * b_height];

                yuv420P_A[i * a_width + offset_y / 4 * a_width + j + offset_x / 2 + a_width * a_height + a_width * a_height / 4] =
                        yuv420P_B[i * b_width + j + b_width * b_height + b_width * b_height / 4];
            } else {
                yuv420P_A[i * a_width + offset_y / 4 * a_width + j + (a_width / 2 - b_width / 2) + offset_x / 2 + a_width * a_height] =
                        yuv420P_B[i * b_width + j + b_width * b_height];

                yuv420P_A[i * a_width + offset_y / 4 * a_width + j + (a_width / 2 - b_width / 2) + offset_x / 2 + a_width * a_height + a_width * a_height / 4] =
                        yuv420P_B[i * b_width + j + b_width * b_height + b_width * b_height / 4];
            }
        }
    }
}

//YUV420SP_NV12图片叠加算法
public static void mergeNV12(byte[] nv12_A, byte[] nv12_B, int offset_x, int offset_y, int a_width, int a_height, int b_width, int b_height) {

    //y
    for (int i = 0; i < b_height; i++) {
        for (int j = 0; j < b_width; j++) {
            nv12_A[i * a_width + offset_y * a_width + j + offset_x] = nv12_B[i * b_width + j];
        }
    }

    //uv
    for (int i = 0; i < b_height / 2; i++) {
        for (int j = 0; j < b_width; j++) {
            nv12_A[i * a_width + offset_y / 2 * a_width + j + offset_x + a_width * a_height] = nv12_B[i * b_width + j + b_width * b_height];
        }
    }
}