c+m+b mmvi opencv 编程入门.htm

When I use opencv, I use this very useful paper to begin the study. This is all I searched from the

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      <H1><A>矩阵操作</A> </H1>
      <P></P>
      <H2><A>分配释放矩阵空间</A> </H2>
      <P></P>
      <UL>
        <LI>综述: 
        <UL>
          <LI>OpenCV有针对矩阵操作的C语言函数. 许多其他方法提供了更加方便的C++接口，其效率与OpenCV一样. 
          <LI>OpenCV将向量作为1维矩阵处理. 
          <LI>矩阵按行存储，每行有4字节的校整. </LI></UL>
        <P></P>
        <LI>分配矩阵空间: <PRE>CvMat* cvCreateMat(int rows, int cols, int type);<BR><BR>  type: 矩阵元素类型. 格式为CV_&lt;bit_depth&gt;(S|U|F)C&lt;number_of_channels&gt;.  <BR>  例如: CV_8UC1 表示8位无符号单通道矩阵, CV_32SC2表示32位有符号双通道矩阵.<BR><BR>  例程:<BR>  CvMat* M = cvCreateMat(4,4,CV_32FC1);<BR></PRE>
        <P></P>
        <LI>释放矩阵空间: <PRE>CvMat* M = cvCreateMat(4,4,CV_32FC1);<BR>cvReleaseMat(&amp;M);<BR></PRE>
        <P></P>
        <LI>复制矩阵: <PRE>CvMat* M1 = cvCreateMat(4,4,CV_32FC1);<BR>CvMat* M2;<BR>M2=cvCloneMat(M1);<BR></PRE>
        <P></P>
        <LI>初始化矩阵: <PRE>double a[] = { 1,  2,  3,  4,<BR>               5,  6,  7,  8,<BR>               9, 10, 11, 12 };<BR><BR>CvMat Ma=cvMat(3, 4, CV_64FC1, a);<BR></PRE>
        <P>另一种方法: </P><PRE>CvMat Ma;<BR>cvInitMatHeader(&amp;Ma, 3, 4, CV_64FC1, a);<BR></PRE>
        <P></P>
        <LI>初始化矩阵为单位阵: <PRE>CvMat* M = cvCreateMat(4,4,CV_32FC1);<BR>cvSetIdentity(M); // 这里似乎有问题，不成功<BR></PRE>
        <P></P></LI></UL>
      <P></P>
      <H2><A>存取矩阵元素</A> </H2>
      <P></P>
      <UL>
        <LI>假设需要存取一个2维浮点矩阵的第(i,j)个元素. 
        <P></P>
        <LI>间接存取矩阵元素: <PRE>cvmSet(M,i,j,2.0); // Set M(i,j)<BR>t = cvmGet(M,i,j); // Get M(i,j)<BR></PRE>
        <P></P>
        <LI>直接存取，假设使用4-字节校正: <PRE>CvMat* M    = cvCreateMat(4,4,CV_32FC1);<BR>int n       = M-&gt;cols;<BR>float *data = M-&gt;data.fl;<BR><BR>data[i*n+j] = 3.0;<BR></PRE>
        <P></P>
        <LI>直接存取，校正字节任意: <PRE>CvMat* M    = cvCreateMat(4,4,CV_32FC1);<BR>int   step  = M-&gt;step/sizeof(float);<BR>float *data = M-&gt;data.fl;<BR><BR>(data+i*step)[j] = 3.0;<BR></PRE>
        <P></P>
        <LI>直接存取一个初始化的矩阵元素: <PRE>double a[16];<BR>CvMat Ma = cvMat(3, 4, CV_64FC1, a);<BR>a[i*4+j] = 2.0; // Ma(i,j)=2.0;<BR></PRE>
        <P></P></LI></UL>
      <P></P>
      <H2><A>矩阵/向量操作</A> </H2>
      <P></P>
      <UL>
        <LI>矩阵-矩阵操作: <PRE>CvMat *Ma, *Mb, *Mc;<BR>cvAdd(Ma, Mb, Mc);      // Ma+Mb   -&gt; Mc<BR>cvSub(Ma, Mb, Mc);      // Ma-Mb   -&gt; Mc<BR>cvMatMul(Ma, Mb, Mc);   // Ma*Mb   -&gt; Mc<BR></PRE>
        <P></P>
        <LI>按元素的矩阵操作: <PRE>CvMat *Ma, *Mb, *Mc;<BR>cvMul(Ma, Mb, Mc);      // Ma.*Mb  -&gt; Mc<BR>cvDiv(Ma, Mb, Mc);      // Ma./Mb  -&gt; Mc<BR>cvAddS(Ma, cvScalar(-10.0), Mc); // Ma.-10 -&gt; Mc<BR></PRE>
        <P></P>
        <P></P>
        <LI>向量乘积: <PRE>double va[] = {1, 2, 3};<BR>double vb[] = {0, 0, 1};<BR>double vc[3];<BR><BR>CvMat Va=cvMat(3, 1, CV_64FC1, va);<BR>CvMat Vb=cvMat(3, 1, CV_64FC1, vb);<BR>CvMat Vc=cvMat(3, 1, CV_64FC1, vc);<BR><BR>double res=cvDotProduct(&amp;Va,&amp;Vb); // 点乘:   Va . Vb -&gt; res<BR>cvCrossProduct(&amp;Va, &amp;Vb, &amp;Vc);    // 向量积: Va x Vb -&gt; Vc<BR>end{verbatim}<BR></PRE>
        <P>注意 Va, Vb, Vc 在向量积中向量元素个数须相同. </P>
        <P><BR></P>
        <P></P>
        <LI>单矩阵操作: <PRE>CvMat *Ma, *Mb;<BR>cvTranspose(Ma, Mb);      // transpose(Ma) -&gt; Mb (不能对自身进行转置)<BR>CvScalar t = cvTrace(Ma); // trace(Ma) -&gt; t.val[0] <BR>double d = cvDet(Ma);     // det(Ma) -&gt; d<BR>cvInvert(Ma, Mb);         // inv(Ma) -&gt; Mb<BR></PRE>
        <P></P>
        <LI>非齐次线性系统求解: <PRE>CvMat* A  = cvCreateMat(3,3,CV_32FC1);<BR>CvMat* x  = cvCreateMat(3,1,CV_32FC1);<BR>CvMat* b  = cvCreateMat(3,1,CV_32FC1);<BR>cvSolve(&amp;A, &amp;b, &amp;x);    // solve (Ax=b) for x<BR></PRE>
        <P></P>
        <LI>特征值分析(针对对称矩阵): <PRE>CvMat* A  = cvCreateMat(3,3,CV_32FC1);<BR>CvMat* E  = cvCreateMat(3,3,CV_32FC1);<BR>CvMat* l  = cvCreateMat(3,1,CV_32FC1);<BR>cvEigenVV(&amp;A, &amp;E, &amp;l);  // l = A的特征值 (降序排列)<BR>                        // E = 对应的特征向量 (每行)<BR></PRE>
        <P></P>
        <LI>奇异值分解SVD: <PRE>CvMat* A  = cvCreateMat(3,3,CV_32FC1);<BR>CvMat* U  = cvCreateMat(3,3,CV_32FC1);<BR>CvMat* D  = cvCreateMat(3,3,CV_32FC1);<BR>CvMat* V  = cvCreateMat(3,3,CV_32FC1);<BR>cvSVD(A, D, U, V, CV_SVD_U_T|CV_SVD_V_T); // A = U D V^T<BR></PRE>
        <P>标号使得 U&nbsp;和 V 返回时被转置(若没有转置标号，则有问题不成功!!!). </P>
        <P></P></LI></UL>
      <P></P>
      <H1><A>视频序列操作</A> </H1>
      <P></P>
      <H2><A>从视频序列中抓取一帧</A> </H2>
      <P></P>
      <UL>
        <LI>OpenCV支持从摄像头或视频文件(AVI)中抓取图像. 
        <P></P>
        <LI>从摄像头获取初始化: <PRE>CvCapture* capture = cvCaptureFromCAM(0); // capture from video device #0<BR></PRE>
        <P></P>
        <LI>从视频文件获取初始化: <PRE>CvCapture* capture = cvCaptureFromAVI("infile.avi");<BR></PRE>
        <P></P>
        <LI>抓取帧: <PRE>IplImage* img = 0; <BR>if(!cvGrabFrame(capture)){              // 抓取一帧 <BR>  printf("Could not grab a frame\n\7");<BR>  exit(0);<BR>}<BR>img=cvRetrieveFrame(capture);           // 恢复获取的帧图像<BR></PRE>
        <P>要从多个摄像头同时获取图像, 首先从每个摄像头抓取一帧. 在抓取动作都结束后再恢复帧图像.&nbsp; </P>
        <P></P>
        <LI>释放抓取源: <PRE>cvReleaseCapture(&amp;capture);<BR></PRE>
        <P>注意由设备抓取的图像是由capture函数自动分配和释放的. 不要试图自己释放它. </P>
        <P></P></LI></UL>
      <P></P>
      <H2><A>获取/设定帧信息</A> </H2>
      <P></P>
      <UL>
        <LI>获取设备特性: <PRE>cvQueryFrame(capture); // this call is necessary to get correct <BR>                       // capture properties<BR>int frameH    = (int) cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_HEIGHT);<BR>int frameW    = (int) cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_WIDTH);<BR>int fps       = (int) cvGetCaptureProperty(capture, CV_CAP_PROP_FPS);<BR>int numFrames = (int) cvGetCaptureProperty(capture,  CV_CAP_PROP_FRAME_COUNT);<BR></PRE>
        <P>所有帧数似乎只与视频文件有关. 用摄像头时不对，奇怪!!!. </P>
        <P></P>
        <P></P>
        <LI>获取帧信息: <PRE>float posMsec   =       cvGetCaptureProperty(capture, CV_CAP_PROP_POS_MSEC);<BR>int posFrames   = (int) cvGetCaptureProperty(capture, CV_CAP_PROP_POS_FRAMES);<BR>float posRatio  =       cvGetCaptureProperty(capture, CV_CAP_PROP_POS_AVI_RATIO);<BR></PRE>
        <P>获取所抓取帧在视频序列中的位置, 从首帧开始按[毫秒]算. 或者从首帧开始从0标号, 获取所抓取帧的标号. 
        或者取相对位置，首帧为0，末帧为1, 只对视频文件有效. </P>
        <P></P>
        <LI>设定所抓取的第一帧标号: <PRE>// 从视频文件相对位置0.9处开始抓取<BR>cvSetCaptureProperty(capture, CV_CAP_PROP_POS_AVI_RATIO, (double)0.9);<BR></PRE>
        <P>只对从视频文件抓取有效. 不过似乎也不成功!!!</P>
        <P></P></LI></UL>
      <P></P>
      <H2><A>存储视频文件</A> </H2>
      <P></P>
      <UL>
        <LI>初始化视频存储器: <PRE>CvVideoWriter *writer = 0;<BR>int isColor = 1;<BR>int fps     = 25;  // or 30<BR>int frameW  = 640; // 744 for firewire cameras<BR>int frameH  = 480; // 480 for firewire cameras<BR>writer=cvCreateVideoWriter("out.avi",CV_FOURCC('P','I','M','1'),<BR>                           fps,cvSize(frameW,frameH),isColor);<BR></PRE>
        <P>其他有效编码: </P><PRE>CV_FOURCC('P','I','M','1')    = MPEG-1 codec<BR>CV_FOURCC('M','J','P','G')    = motion-jpeg codec (does not work well)<BR>CV_FOURCC('M', 'P', '4', '2') = MPEG-4.2 codec<BR>CV_FOURCC('D', 'I', 'V', '3') = MPEG-4.3 codec<BR>CV_FOURCC('D', 'I', 'V', 'X') = MPEG-4 codec<BR>CV_FOURCC('U', '2', '6', '3') = H263 codec<BR>CV_FOURCC('I', '2', '6', '3') = H263I codec<BR>CV_FOURCC('F', 'L', 'V', '1') = FLV1 codec<BR></PRE>
        <P>若把视频编码设为-1则将打开一个编码选择窗口(windows系统下). </P>
        <P></P>
        <P></P>
        <LI>存储视频文件: <PRE>IplImage* img = 0; <BR>int nFrames = 50;<BR>for(i=0;i&lt;nFrames;i++){<BR>  cvGrabFrame(capture);          // 抓取帧<BR>  img=cvRetrieveFrame(capture);  // 恢复图像<BR>  cvWriteFrame(writer,img);      // 将帧添加入视频文件<BR>}<BR></PRE>
        <P>若想在抓取中查看抓取图像, 可在循环中加入下列代码: </P><PRE>cvShowImage("mainWin", img); <BR>key=cvWaitKey(20);           // wait 20 ms<BR></PRE>
        <P>若没有20[毫秒]延迟，将无法正确显示视频序列. </P>
        <P></P>
        <LI>释放视频存储器: <PRE>cvReleaseVideoWriter(&amp;writer);<BR></PRE>
        <P></P></LI></UL></DIV></DIV>
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              <DIV class="bvCommentText bvwordwrap"><SPAN 
              class=TextBold>h.qiu</SPAN>
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              <DIV>鼓励在贴一篇opev CV,directX,open GL的相关比较</DIV>
              <DIV>这三个功能感觉差不多么</DIV>
              <DIV>真的要去学我都不知道该学哪个了</DIV></DIV>11月23日 11:09<BR><A 
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              <DIV class="bvCommentText bvwordwrap"><SPAN 
              class=TextBold>Linan</SPAN>
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              <DIV>实在是无语了。。。。只能向Mensch同学好好学习了！！！</D