libyuv库的使用

libyuv是Google开源的实现各种YUV与RGB之间相互转换、旋转、缩放的库。它是跨平台的，可在Windows、Linux、Mac、Android等操作系统。x86、x64、arm架构上进行编译执行，支持SSE、AVX、NEON等SIMD指令加速。

以下说一下libyuv在Windows7VS2013 x64上的编译步骤及使用：

1.        从https://code.google.com/p/libyuv/source/checkout或者https://github.com/lemenkov/libyuv下载libyuv源代码；我是通过svn直接从google下载的，版本是1433，更新日期2015年6月13日。

2.        通过cmake gui生成vs2013 x64project，不须要额外的配置；

3.        打开Project.slnproject，又一次编译，就可以生成yuv.lib静态库。

4.    新加入一个test_libyuv控制台project。用于測试yuv.lib的正确性。測试代码例如以下：

#include 
#include 
#include "libyuv.h"
#include 
#include 

void test_BGRAToI420(const cv::Mat& matSrc, int width, int height, int size_frame, cv::Mat& matDst);
void test_BGRAToNV21(const cv::Mat& matSrc, int width, int height, int size_frame, cv::Mat& matDst);
void test_BGRAToNV12(const cv::Mat& matSrc, int width, int height, int size_frame, cv::Mat& matDst);

int main(int argc, char* argv[])
{
	cv::Mat matSrc = cv::imread("cat.jpg");
	if (!matSrc.data) {
		std::cout << "read src image error" << std::endl;
		return -1;
	}

	//cv::resize(matSrc, matSrc, cv::Size(500, 111));

	int width = matSrc.cols;
	int height = matSrc.rows;
	int size_frame = width * height;

	cv::Mat matI420, matNV21, matNV12;

	test_BGRAToI420(matSrc, width, height, size_frame, matI420);
	test_BGRAToNV21(matSrc, width, height, size_frame, matNV21);
	test_BGRAToNV12(matSrc, width, height, size_frame, matNV12);

	assert((matI420.depth() == matNV21.depth()) && (matI420.depth() == matNV12.depth()));
	assert((matI420.channels() == matNV21.channels()) && (matI420.channels() == matNV12.channels()));

	for (int i = 0; i < height; i++) {
		const unsigned char* pI420 = matI420.ptr(i);
		const unsigned char* pNV21 = matNV21.ptr(i);
		const unsigned char* pNV12 = matNV12.ptr(i);

		for (int j = 0, m = 0; j < width; j++, m+=4) {
			if ((pI420[m] != pNV21[m]) || (pI420[m] != pNV12[m]) ||
				(pI420[m + 1] != pNV21[m + 1]) || (pI420[m + 1] != pNV12[m + 1]) ||
				(pI420[m + 2] != pNV21[m + 2]) || (pI420[m + 2] != pNV12[m + 2]) ||
				(pI420[m + 3] != pNV21[m + 3]) || (pI420[m + 3] != pNV12[m + 3])) {
				std::cout << "convert error" << std::endl;
			}
		}
	}

	std::cout << "ok" << std::endl;
	return 0;
}

void test_BGRAToI420(const cv::Mat& matSrc, int width, int height, int size_frame, cv::Mat& matDst)
{
	// BGRA <--> I420(YUV420P)
	cv::Mat matBGRA, matI420, matARGB;
	cv::cvtColor(matSrc, matBGRA, cv::COLOR_BGR2BGRA);
	matARGB = cv::Mat(height, width, CV_8UC4, cv::Scalar::all(0));
	libyuv::BGRAToARGB(matBGRA.data, width * 4, matARGB.data, width * 4, width, height);

	uchar* pI420 = new uchar[width * height + (width + 1) / 2 * (height + 1) / 2 * 2];
	memset(pI420, 0, sizeof(uchar) * (width * height + (width + 1) / 2 * (height + 1) / 2 * 2));
	uchar* dst_y = pI420;
	int dst_y_stride = width;
	uchar* dst_u = pI420 + size_frame;
	int dst_u_stride = (width + 1) / 2;
	uchar* dst_v = pI420 + size_frame + dst_u_stride * (height + 1) / 2;
	int dst_v_stride = (width + 1) / 2;

	libyuv::BGRAToI420(matARGB.data, width * 4, dst_y, dst_y_stride, dst_u, dst_u_stride, dst_v, dst_v_stride, width, height);
	matI420 = cv::Mat(height, width, CV_8UC4, cv::Scalar::all(0));
	libyuv::I420ToBGRA(dst_y, dst_y_stride, dst_u, dst_u_stride, dst_v, dst_v_stride, matI420.data, width * 4, width, height);
	cv::Mat matBGRA_ = cv::Mat(height, width, CV_8UC4, cv::Scalar::all(0));
	libyuv::ARGBToBGRA(matI420.data, width * 4, matBGRA_.data, width * 4, width, height);
	cv::imwrite("I420_bgra.jpg", matBGRA_);
	matBGRA_.copyTo(matDst);

	int count_diff = 0;
	int max_diff = 0;
	int threshold = 20;//
	for (int i = 0; i < height; i++) {
		uchar* pSrc = matBGRA.ptr(i);
		uchar* pDst = matBGRA_.ptr(i);
		for (int j = 0, m = 0; j < width; j++, m += 4) {
			int tmp = std::max(abs(pSrc[m] - pDst[m]), abs(pSrc[m + 1] - pDst[m + 1]));
			tmp = std::max(tmp, abs(pSrc[m + 2] - pDst[m + 2]));
			if (tmp > max_diff)
				max_diff = tmp;

			if (abs(pSrc[m] - pDst[m]) > threshold ||
				abs(pSrc[m + 1] - pDst[m + 1]) > threshold ||
				abs(pSrc[m + 2] - pDst[m + 2]) > threshold) {
				count_diff++;
				//std::cout << i << "    " << j << std::endl;
			}

		}
	}

	std::cout << "convert I420 to BGRA diff max: " << max_diff << std::endl;
	if (count_diff > width + height) {//
		std::cout << "convert I420 to BGRA error." << std::endl;
		std::cout << "diff num: " << count_diff << std::endl;
	}

	delete[] pI420;
}

void test_BGRAToNV12(const cv::Mat& matSrc, int width, int height, int size_frame, cv::Mat& matDst)
{
	// BGRA <--> NV12
	cv::Mat matBGRA, matNV12;
	cv::cvtColor(matSrc, matBGRA, cv::COLOR_BGR2BGRA);

	uchar* pNV12 = new uchar[width * height + ((width + 1) / 2) * ((height + 1) / 2) * 2];
	memset(pNV12, 0, sizeof(uchar) * (width * height + ((width + 1) / 2) * ((height + 1) / 2) * 2));
	uchar* dst_y = pNV12;
	int dst_y_stride = width;
	uchar* dst_vu = pNV12 + size_frame;
	int dst_vu_stride = (width + 1) / 2 * 2;

	libyuv::ARGBToNV12(matBGRA.data, width * 4, dst_y, dst_y_stride, dst_vu, dst_vu_stride, width, height);
	matNV12 = cv::Mat(height, width, CV_8UC4, cv::Scalar::all(0));
	libyuv::NV12ToARGB(dst_y, dst_y_stride, dst_vu, dst_vu_stride, matNV12.data, width * 4, width, height);
	cv::imwrite("NV12_bgra.jpg", matNV12);
	matNV12.copyTo(matDst);

	int count_diff = 0;
	int max_diff = 0;
	int threshold = 20;//
	for (int i = 0; i < height; i++) {
		uchar* pSrc = matBGRA.ptr(i);
		uchar* pDst = matNV12.ptr(i);
		for (int j = 0, m = 0; j < width; j++, m += 4) {
			int tmp = std::max(abs(pSrc[m] - pDst[m]), abs(pSrc[m + 1] - pDst[m + 1]));
			tmp = std::max(tmp, abs(pSrc[m + 2] - pDst[m + 2]));
			if (tmp > max_diff)
				max_diff = tmp;

			if (abs(pSrc[m] - pDst[m]) > threshold ||
				abs(pSrc[m + 1] - pDst[m + 1]) > threshold ||
				abs(pSrc[m + 2] - pDst[m + 2]) > threshold) {
				count_diff++;
				//std::cout << i << "    " << j << std::endl;
			}
		}
	}

	std::cout << "convert NV12 to BGRA diff max: " << max_diff << std::endl;
	if (count_diff > width + height) {//
		std::cout << "convert NV12 to BGRA error." << std::endl;
		std::cout << "diff num: " << count_diff << std::endl;
	}

	delete[] pNV12;
}

void test_BGRAToNV21(const cv::Mat& matSrc, int width, int height, int size_frame, cv::Mat& matDst)
{
	// BGRA <--> NV21
	cv::Mat matBGRA, matNV21;
	cv::cvtColor(matSrc, matBGRA, cv::COLOR_BGR2BGRA);

	uchar* pNV21 = new uchar[width * height + ((width + 1) / 2) * ((height + 1) / 2) * 2];
	memset(pNV21, 0, sizeof(uchar) * (width * height + ((width + 1) / 2) * ((height + 1) / 2) * 2));
	uchar* dst_y = pNV21;
	int dst_y_stride = width;
	uchar* dst_vu = pNV21 + size_frame;
	int dst_vu_stride = (width + 1) / 2 * 2;

	libyuv::ARGBToNV21(matBGRA.data, width * 4, dst_y, dst_y_stride, dst_vu, dst_vu_stride, width, height);
	matNV21 = cv::Mat(height, width, CV_8UC4, cv::Scalar::all(0));
	libyuv::NV21ToARGB(dst_y, dst_y_stride, dst_vu, dst_vu_stride, matNV21.data, width * 4, width, height);
	cv::imwrite("NV21_bgra.jpg", matNV21);
	matNV21.copyTo(matDst);

	int count_diff = 0;
	int max_diff = 0;
	int threshold = 20;//
	for (int i = 0; i < height; i++) {
		uchar* pSrc = matBGRA.ptr(i);
		uchar* pDst = matNV21.ptr(i);
		for (int j = 0, m = 0; j < width; j++, m += 4) {
			int tmp = std::max(abs(pSrc[m] - pDst[m]), abs(pSrc[m + 1] - pDst[m + 1]));
			tmp = std::max(tmp, abs(pSrc[m + 2] - pDst[m + 2]));
			if (tmp > max_diff)
				max_diff = tmp;

			if (abs(pSrc[m] - pDst[m]) > threshold ||
				abs(pSrc[m + 1] - pDst[m + 1]) > threshold ||
				abs(pSrc[m + 2] - pDst[m + 2]) > threshold) {
				count_diff++;
				//std::cout << i << "    " << j << std::endl;
			}
		}
	}

	std::cout << "convert NV21 to BGRA diff max: " << max_diff << std::endl;
	if (count_diff > width + height) {//
		std::cout << "convert NV21 to BGRA error." << std::endl;
		std::cout << "diff num: " << count_diff << std::endl;
	}

	delete[] pNV21;
}

GitHub： https://github.com/fengbingchun/Libyuv_Test