how to create bgr file from jpg file?

[nqthai309]

how to create bgr file from jpg file?
Thanks in advance

[hongson23]

void savebgr(cv::Mat& img, const char* bgr_path)
{
if (bgr_path)
{
FILE* fp = fopen(bgr_path, "wb");
int step = img.step;
int h = img.rows;
int w = img.cols;
int c = img.channels();
for (int k = 0; k < c; k++)
for (int i = 0; i < h; i++)
for (int j = 0; j < w; j++)
{

				//fwrite(&img.data[i*step + j * c + k], sizeof(uint8_t), 1, fp);
				fwrite(&img.data[c*(i * w + j) + k], sizeof(uint8_t), 1, fp);
			}
	fclose(fp);
}

}

pls refer to https://zhuanlan.zhihu.com/p/107548509