opencv 相关函数集合

/* 合并多图像矩阵到一个大矩阵上 */
Mat mergeImgMats(vector<Mat> img_mats, int per_width, int per_height, int cols, int split_w) {
	int count = img_mats.size();
	CV_Assert(count > 0);
	// 定义 行
	int rows = count % cols == 0 ? count / cols : count / cols + 1;

	//准备一个大矩阵
	Mat bigMat(per_height * rows + split_w * (rows - 1), per_width*cols + split_w * (cols - 1), img_mats[0].type());
	bigMat.setTo(Scalar::all(0));
	Mat tmp;
	for (size_t i = 0; i < count; i++)
	{
		resize(img_mats[i], tmp, Size(per_width, per_height));

		int location_x = 0, location_y = 0;;
		//copy to location
		if (i < cols) { //第一行
			location_x = i * (per_width + split_w);
			location_y = 0;
		}
		else
		{ // 第二行开始
			location_x = i % cols * (per_width + split_w);
			location_y = i / cols * (per_height + split_w);
		}
		Mat roi = bigMat(Rect(location_x, location_y, per_width, per_height));
		tmp.copyTo(roi);
	}

	tmp.release();
	return bigMat;
}


int BGR2YUV420P(Mat img, uint8_t *yuv_data, int w, int h) {
	assert(w % 2 == 0 && h % 2 == 0);
	Mat yuv;
	cvtColor(img, yuv, CV_BGR2YUV_I420);  //CV_BGR2YUV_I420

	Mat Y = yuv(Rect(0, 0, w, h));
	Mat U = yuv(Rect(0, h, w / 2, h / 2));
	Mat V = yuv(Rect(w / 2, h, w / 2, h / 2));

	memcpy_s(yuv_data, w * h, Y.data, h * w);
	for (size_t i = 0; i < h / 2; i++)
	{
		for (size_t j = 0; j < w; j++)
		{
			int index = i * w + j;
			if (j < 2 / w) yuv_data[w*h + index] = U.data[index];
			else yuv_data[w*h + index] = V.data[index - w / 2];
		}
	}
	yuv.release();

	return 0;
}

# YUV --> AVI 
# 只适用于YUV格式数据直接存储的视频文件
int YuvFile_to_AviFile(string &yuv_filename, int src_img_w, int src_img_h, string &avi_filenanme, int dst_img_w, int dst_img_h) {
	int img_w = src_img_w, img_h = src_img_h;
	int scale_w = dst_img_w, scale_h = dst_img_h;

	int yuv_size = img_w * img_h * 3 / 2;
	FILE *f = NULL;
	uint8_t *yuv_data = new uint8_t[yuv_size];
	auto code = fopen_s(&f, yuv_filename.c_str(), "rb");
	assert(code == 0);
	Mat img(img_h, img_w, CV_8UC3);
	Mat yuvFrame(img_h * 3 / 2, img_w, CV_8UC1, yuv_data);

	VideoWriter newcw;
	auto flag = newcw.open(avi_filenanme, CV_FOURCC('M', 'P', '4', '2'), 25.0, Size(scale_w, scale_h));
	assert(true == flag);

	while (1)
	{
		auto _size = fread_s(yuv_data, yuv_size, 1, yuv_size, f);
		if (_size < yuv_size) {
			break;
		}

		cvtColor(yuvFrame, img, CV_YUV420p2RGB);
		assert(img.empty() == false && img.cols > 0);

		if (scale_w != img_w || scale_h != img_h) {
			resize(img, img, Size(scale_w, scale_h));
		}
		newcw.write(img);
	}

	yuvFrame.release();
	img.release();
	delete[] yuv_data;
	fclose(f);
	newcw.release();

	return 0;
}



# 编码
static	unsigned char* img2Encode(Mat src, int& dataLength) {
	vector<unsigned char> inImage;
	imencode(".jpg", src, inImage);
	size_t datalen = inImage.size();
	unsigned char *outImage = new unsigned char[datalen];
	for (int i = 0; i < datalen; i++)
	{
		outImage[i] = inImage[i];
	}
	inImage.clear();
	dataLength = datalen;

	return outImage;
}

# 解码
static Mat img2Decode(unsigned char *inImage, int dataLength) {
	vector<unsigned char> buff;
	for (int i = 0; i < dataLength; i++)
	{
		buff.push_back(inImage[i]);
	}
	Mat mat = imdecode(buff, CV_LOAD_IMAGE_COLOR);
	buff.clear();

	return mat;
}