OpenCV的几个小技巧

申明：以下的小技巧，均为 OpenCV2.4.2 下验证过的，但并不保证其它版本依然奏效 （1）利用数组来构建 cv::Mat 示例代码如下所示： void ArrayToMat(){double m[3][3];for (int i=0; i3; i++){for (int j=0; j3; j++){m[i][j] = i+j;coutm[i][j] ;}coutendl;

申明：以下的小技巧，均为OpenCV2.4.2下验证过的，但并不保证其它版本依然奏效

（1）利用数组来构建cv::Mat

   示例代码如下所示：

void ArrayToMat()
{
	double m[3][3];
	for (int i=0; i(i,j);
			cout
<p>不出意外的话，执行结果应该如下所示：</p>
<p><img  src="/inc/test.jsp?url=http%3A%2F%2Fimg.my.csdn.net%2Fuploads%2F201212%2F15%2F1355541146_2315.png&refer=http%3A%2F%2Fblog.csdn.net%2Fcarson2005%2Farticle%2Fdetails%2F8298453" alt="OpenCV的几个小技巧" ><br>
</p>
<p>（2） IplImage*<span>跟</span><span>cv::Mat</span><span>之间的互相转换</span></p>
<p>示例代码：</p>
<pre class="brush:php;toolbar:false">void IplImageToMat()
{
	IplImage* pImg = cvLoadImage("c:/test.jpg");
	if (!pImg)
	{
		cout
<p>笔者任意加载了电脑上一副图片，结果如下所示：</p>
<img  src="/inc/test.jsp?url=http%3A%2F%2Fimg.my.csdn.net%2Fuploads%2F201212%2F15%2F1355541209_9786.png&refer=http%3A%2F%2Fblog.csdn.net%2Fcarson2005%2Farticle%2Fdetails%2F8298453" alt="OpenCV的几个小技巧" ><br>
<p>提醒，这里的格式转换并不申请新的内存，而仅仅是改变数据结构而已</p>

<p>（3）Mat<span>转换为</span><span>IplImge</span></p>
<p>示例代码：</p>
<pre class="brush:php;toolbar:false">void MatToIplImage()
{
	Mat m = imread("c:/test.jpg");
	if (m.empty())
	{
		cout
<p>笔者任意加载一张图片，上述代码的执行结果为：</p>
<img  src="/inc/test.jsp?url=http%3A%2F%2Fimg.my.csdn.net%2Fuploads%2F201212%2F15%2F1355541209_9786.png&refer=http%3A%2F%2Fblog.csdn.net%2Fcarson2005%2Farticle%2Fdetails%2F8298453" alt="OpenCV的几个小技巧" ><br>
<p>（4）访问二维数据（<span>cv::Mat</span><span>）最高效的方式是先得到该二维数据的每一行的指针，然后利用下标运算符逐列访问</span></p>
<p>示例代码：</p>
<pre class="brush:php;toolbar:false">void MatAccess()
{
	double m[3][3];
	for (int i=0; i(i);
		for (int j=0; j<cols j sum mi cout>
<p>上面的代码执行结果为：</p>
<img  src="/inc/test.jsp?url=http%3A%2F%2Fimg.my.csdn.net%2Fuploads%2F201212%2F15%2F1355541319_9708.png&refer=http%3A%2F%2Fblog.csdn.net%2Fcarson2005%2Farticle%2Fdetails%2F8298453" alt="OpenCV的几个小技巧" ><br>
<p>（5）cv::Mat<span>支持</span><span>STL</span><span>中的迭代器功能</span></p>
<p>示例代码：</p>
<pre class="brush:php;toolbar:false">void MatAccess()
{
	double m[3][3];
	for (int i=0; i(i);
		for (int j=0; j<cols j sum mi cout matconstiterator_> it = M.begin<double>();
	MatConstIterator_<double> itEnd = M.end<double>();
	for (;it!=itEnd; it++)
	{
		sum += *it;
	}
	cout
<p>运行结果：</p>
<img  src="/inc/test.jsp?url=http%3A%2F%2Fimg.my.csdn.net%2Fuploads%2F201212%2F15%2F1355541377_4184.png&refer=http%3A%2F%2Fblog.csdn.net%2Fcarson2005%2Farticle%2Fdetails%2F8298453" alt="OpenCV的几个小技巧" ><br>
<p>（6） satureat_cast : openCV<span>中用于数据“饱和”判断</span></p>
<p>示例：</p>
<pre class="brush:php;toolbar:false">void Saturate_castTest()
{
	int r = 300;
	uchar t = saturate_cast<uchar>(r);
	cout
<p>结果：</p>
<img  src="/inc/test.jsp?url=http%3A%2F%2Fimg.my.csdn.net%2Fuploads%2F201212%2F15%2F1355541432_7328.png&refer=http%3A%2F%2Fblog.csdn.net%2Fcarson2005%2Farticle%2Fdetails%2F8298453" alt="OpenCV的几个小技巧" ><br>
<p>（7）获取函数执行时间</p>
<p><span>getTickCount</span>()和<span>getTickFrequency</span>()结合起来可以用来计算函数执行时间，尤其是很小的代码片段的执行时间</p>
<p>举例：</p>
<pre class="brush:php;toolbar:false">void GetFuncTime()
{
	double exec_time = (double)getTickCount();
	for (int i=0; i
<p>上面的代码，重点在于for<span>循环，且，该循环中什么也不处理；用一般的时间函数很难计算出该代码片段的执行时间，但利用</span><span>getTickCount</span><span>（）和</span><span>getTickFrequency</span><span>（）就很容易。笔者电脑上的结果是：</span></p>
<img  src="/inc/test.jsp?url=http%3A%2F%2Fimg.my.csdn.net%2Fuploads%2F201212%2F15%2F1355541488_8158.png&refer=http%3A%2F%2Fblog.csdn.net%2Fcarson2005%2Farticle%2Fdetails%2F8298453" alt="OpenCV的几个小技巧" ><br>
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