YUV数据的裁剪与重叠

1. YUV 数据的裁剪

/**
 * 裁剪YUV数据 : 宽高左右起点均为偶数
 * @param src_i420_data   源数据
 * @param src_width       源宽
 * @param src_height      源高
 * @param dst_i420_data   裁剪的数据
 * @param width           裁剪宽
 * @param height          裁剪高
 * @param left            开始左起点
 * @param top             开始右起点
 */
void CropI420p(uint8_t *src_i420_data, int src_width, jint src_height, uint8_t *dst_i420_data,
               int clip_width, int clip_height, int left, int top) {
    uint8_t *src_yplane = src_i420_data;
    uint8_t *src_uplane = src_i420_data + src_width * src_height;
    uint8_t *src_vplane = src_uplane + (src_width * src_height / 4);

    uint8_t *dst_yplane = dst_i420_data;
    uint8_t *dst_uplane = dst_i420_data + clip_width * clip_height;
    uint8_t *dst_vplane = dst_uplane + (clip_width * clip_height / 4);

    //uv 参数
    int uv_total_width = src_width / 2;
    int y_clip_width = sizeof(uint8_t) * clip_width;
    int uv_clip_width = sizeof(uint8_t) * clip_width / 2;

    //uv 参数
    int total_clip_width = sizeof(uint8_t) * clip_width / 2;
    for (int i = 0; i < clip_height; i++) {
        int y_h = top + i;
        int src_pos = left + src_width * y_h;
        memcpy(dst_yplane + (i * clip_width), src_yplane + src_pos, y_clip_width); //Y
        if (i < clip_height / 2) {
            //获取 UV分量
            int uv_h = top / 2 + i;
            int src_pos_u = left / 2 + uv_total_width * uv_h;
            int src_pos_v = left / 2 + uv_total_width * uv_h;
            int des_pos = total_clip_width * i;
            memcpy(dst_uplane + des_pos, src_uplane + src_pos_u, uv_clip_width);//U
            memcpy(dst_vplane + des_pos, src_vplane + src_pos_v, uv_clip_width);//V
        }
    }
}

2. YUV 数据的重叠

/**
 * 重叠YUV数据 : 宽高左右起点均为偶数
 * @param src_i420_data    重叠部分数据
 * @param src_width        重叠宽
 * @param src_height       重叠高
 * @param dst_i420_data    源数据
 * @param width            源宽
 * @param height           源高
 * @param left             源开始左起点
 * @param top              源开始上起点
 */
void I420CopyI420(uint8_t *src_i420_data, int src_width, jint src_height, uint8_t *dst_i420_data,
                  int width, int height, int left, int top) {

    uint8_t *src_yplane = src_i420_data;
    uint8_t *src_uplane = src_i420_data + src_width * src_height;
    uint8_t *src_vplane = src_uplane + (src_width * src_height / 4);

    uint8_t *dst_yplane = dst_i420_data;
    uint8_t *dst_uplane = dst_i420_data + width * height;
    uint8_t *dst_vplane = dst_uplane + (width * height / 4);

    //uv 参数
    int total_clip_width = src_width / 2;
    int uv_total_width = width / 2;
    int y_src_width = sizeof(uint8_t) * src_width;
    int uv_src_width = sizeof(uint8_t) * src_width / 2;

    for (int i = 0; i < src_height; i++) {
        int y_h = top + i;
        int src_pos = left + width * y_h;
        memcpy(dst_yplane + src_pos, src_yplane + (i * src_width), y_src_width); //Y
        if (i < src_height / 2) {
            //获取 UV分量
            int uv_h = top / 2 + i;
            int src_pos_u = left / 2 + uv_total_width * uv_h;
            int src_pos_v = left / 2 + uv_total_width * uv_h;
            int des_pos = total_clip_width * i;
            memcpy(dst_uplane + src_pos_u, src_uplane + des_pos, uv_src_width);//U
            memcpy(dst_vplane + src_pos_v, src_vplane + des_pos, uv_src_width);//V
        }
    }
}

3.参考裁剪数据

//裁剪 YUV 420p 数据
void DemoCropI420p(uint8_t *src_i420_data, int dec_width, jint dec_height, uint8_t *dst_i420_data,
                   int clip_width, int clip_height, int x_start, int y_start) {
    //y 参数
    int total_clip_w = clip_width;
    int total_width = dec_width;
    int src_size = dec_width * dec_height;
    //uv 参数
    int total_clip_width = clip_width / 2;
    int uv_total_width = dec_width / 2;
    for (int x = 0; x < clip_height; x++) {
        int y_h = y_start + x;
        int src_pos = x_start + total_width * y_h;
        memcpy(dst_i420_data + (total_clip_w * x), src_i420_data + src_pos,
               sizeof(char) * total_clip_w); //Y
        if (x < clip_height / 2) {
            //获取 UV分量
            int uv_h = y_start / 2 + x;
            int src_pos_u = src_size + x_start / 2 + uv_total_width * uv_h;
            int src_pos_v = src_size + src_size / 4 + x_start / 2 + uv_total_width * uv_h;
            int des_pos = total_clip_width * x;
            memcpy(dst_i420_data + des_pos, src_i420_data + src_pos_u,
                   sizeof(char) * total_clip_width);//U
            memcpy(dst_i420_data + des_pos, src_i420_data + src_pos_v,
                   sizeof(char) * total_clip_width);//V
        }
    }
}