OpenCV常用函数

分配与释放图像空间

 

• 分配图像空间:

  IplImage* cvCreateImage(CvSize size, int depth, int channels);
   
     size:   cvSize(width,height);
   
     depth: IPL_DEPTH_8U, IPL_DEPTH_8S, IPL_DEPTH_16U,
            IPL_DEPTH_16S, IPL_DEPTH_32S, IPL_DEPTH_32F, IPL_DEPTH_64F
   
     channels: 1, 2, 3 or 4. 
       注意数据为交叉存取.彩色图像的数据编排为b0 g0 r0 b1 g1 r1 ...
   

  举例:

  // 分配一个单通道字节图像
  IplImage* img1=cvCreateImage(cvSize(640,480),IPL_DEPTH_8U,1); 
   
  // 分配一个三通道浮点图像
  IplImage* img2=cvCreateImage(cvSize(640,480),IPL_DEPTH_32F,3);
   

   

• 释放图像空间:

  IplImage* img=cvCreateImage(cvSize(640,480),IPL_DEPTH_8U,1); 
  cvReleaseImage(&img);
   

   

• 复制图像:

  IplImage* img1=cvCreateImage(cvSize(640,480),IPL_DEPTH_8U,1); 
  IplImage* img2;
  img2=cvCloneImage(img1);
   

   

• 设定/获取兴趣区域:

  void   cvSetImageROI(IplImage* image, CvRect rect);
  void   cvResetImageROI(IplImage* image);
  vRect cvGetImageROI(const IplImage* image);
   
  大部分OpenCV函数都支持ROI.
   

   

• 设定/获取兴趣通道:

  void cvSetImageCOI(IplImage* image, int coi); // 0=all
  int cvGetImageCOI(const IplImage* image);
   
  大部分OpenCV函数暂不支持COI.
   

   

 

读取存储图像

 

• 从文件中载入图像:

     IplImage* img=0; 
     img=cvLoadImage(fileName);
     if(!img) printf("Could not load image file: %s/n",fileName);
   
     Supported image formats: BMP, DIB, JPEG, JPG, JPE, PNG, PBM, PGM, PPM,
                              SR, RAS, TIFF, TIF
   

  载入图像默认转为3通道彩色图像. 如果不是，则需加flag:

     img=cvLoadImage(fileName,flag);
   
     flag: >0 载入图像转为三通道彩色图像
           =0 载入图像转为单通道灰度图像
           <0 不转换载入图像(通道数与图像文件相同).
   

   

• 图像存储为图像文件:

     if(!cvSaveImage(outFileName,img)) printf("Could not save: %s/n",outFileName);
   

  输入文件格式由文件扩展名决定.

   

 

存取图像元素

 

• 假设需要读取在i行j列像点的第k通道. 其中, 行数i的范围为[0, height-1], 列数j的范围为[0, width-1], 通道k的范围为[0, nchannels-1].

   

• 间接存取: (比较通用, 但效率低, 可读取任一类型图像数据)

   

  • 对单通道字节图像:

    IplImage* img=cvCreateImage(cvSize(640,480),IPL_DEPTH_8U,1);
    CvScalar s;
    s=cvGet2D(img,i,j); // get the (i,j) pixel value
    printf("intensity=%f/n",s.val[0]);
    s.val[0]=111;
    cvSet2D(img,i,j,s); // set the (i,j) pixel value
     

     

  • 对多通道浮点或字节图像:

    IplImage* img=cvCreateImage(cvSize(640,480),IPL_DEPTH_32F,3);
    CvScalar s;
    s=cvGet2D(img,i,j); // get the (i,j) pixel value
    printf("B=%f, G=%f, R=%f/n",s.val[0],s.val[1],s.val[2]);
    s.val[0]=111;
    s.val[1]=111;
    s.val[2]=111;
    cvSet2D(img,i,j,s); // set the (i,j) pixel value
     

     

   

• 直接存取: (效率高, 但容易出错)

   

  • 对单通道字节图像:

    IplImage* img=cvCreateImage(cvSize(640,480),IPL_DEPTH_8U,1);
    ((uchar *)(img->imageData + i*img->widthStep))[j]=111;
     

     

  • 对多通道字节图像:

    IplImage* img=cvCreateImage(cvSize(640,480),IPL_DEPTH_8U,3);
    ((uchar *)(img->imageData + i*img->widthStep))[j*img->nChannels + 0]=111; // B
    ((uchar *)(img->imageData + i*img->widthStep))[j*img->nChannels + 1]=112; // G
    ((uchar *)(img->imageData + i*img->widthStep))[j*img->nChannels + 2]=113; // R
     

     

  • 对多通道浮点图像:

    IplImage* img=cvCreateImage(cvSize(640,480),IPL_DEPTH_32F,3);
    ((float *)(img->imageData + i*img->widthStep))[j*img->nChannels + 0]=111; // B
    ((float *)(img->imageData + i*img->widthStep))[j*img->nChannels + 1]=112; // G
    ((float *)(img->imageData + i*img->widthStep))[j*img->nChannels + 2]=113; // R
     

     

   

• 用指针直接存取 : (在某些情况下简单高效)

   

  • 对单通道字节图像:

    IplImage* img   = cvCreateImage(cvSize(640,480),IPL_DEPTH_8U,1);
    int height      = img->height;
    int width       = img->width;
    int step        = img->widthStep/sizeof(uchar);
    uchar* data     = (uchar *)img->imageData;
    data[i*step+j] = 111;
     

     

  • 对多通道字节图像:

    IplImage* img   = cvCreateImage(cvSize(640,480),IPL_DEPTH_8U,3);
    int height      = img->height;
    int width       = img->width;
    int step        = img->widthStep/sizeof(uchar);
    int channels    = img->nChannels;
    uchar* data     = (uchar *)img->imageData;
    data[i*step+j*channels+k] = 111;
     

     

  • 对单通道浮点图像(假设用4字节调整):

    IplImage* img   = cvCreateImage(cvSize(640,480),IPL_DEPTH_32F,3);
    int height      = img->height;
    int width       = img->width;
    int step        = img->widthStep/sizeof(float);
    int channels    = img->nChannels;
    float * data     = (float *)img->imageData;
    data[i*step+j*channels+k] = 111;
     

     

   

   

• 使用 c++ wrapper 进行直接存取: (简单高效)

   

  • 对单/多通道字节图像，多通道浮点图像定义一个 c++ wrapper:

    template<class T> class Image
    {
       private:
       IplImage* imgp;
       public:
       Image(IplImage* img=0) {imgp=img;}
       ~Image(){imgp=0;}
       void operator=(IplImage* img) {imgp=img;}
       inline T* operator[](const int rowIndx) {
         return ((T *)(imgp->imageData + rowIndx*imgp->widthStep));}
    };
     
    typedef struct{
       unsigned char b,g,r;
    } RgbPixel;
     
    typedef struct{
       float b,g,r;
    } RgbPixelFloat;
     
    typedef Image<RgbPixel>        RgbImage;
    typedef Image<RgbPixelFloat>   RgbImageFloat;
    typedef Image<unsigned char>   BwImage;
    typedef Image<float>           BwImageFloat;
     

     

  • 单通道字节图像:

    IplImage* img=cvCreateImage(cvSize(640,480),IPL_DEPTH_8U,1);
    BwImage imgA(img);
    imgA[i][j] = 111;
     

     

  • 多通道字节图像:

    IplImage* img=cvCreateImage(cvSize(640,480),IPL_DEPTH_8U,3);
    RgbImage   imgA(img);
    imgA[i][j].b = 111;
    imgA[i][j].g = 111;
    imgA[i][j].r = 111;
     

     

  • 多通道浮点图像:

    IplImage* img=cvCreateImage(cvSize(640,480),IPL_DEPTH_32F,3);
    RgbImageFloat imgA(img);
    imgA[i][j].b = 111;
    imgA[i][j].g = 111;
    imgA[i][j].r = 111;
     

     

   

 

图像转换

 

• 转为灰度或彩色字节图像:

  cvConvertImage(src, dst, flags=0);
   
     src = float/byte grayscale/color image
     dst = byte grayscale/color image
     flags = CV_CVTIMG_FLIP      (flip vertically)
             CV_CVTIMG_SWAP_RB   (swap the R and B channels)
   

   

• 转换彩色图像为灰度图像:

   

  
  使用OpenCV转换函数:

  cvCvtColor(cimg,gimg,CV_BGR2GRAY); // cimg -> gimg
   

   

  
  直接转换:

  for(i=0;i<cimg->height;i++) for(j=0;j<cimg->width;j++) 
     gimgA[i][j]= (uchar)(cimgA[i][j].b*0.114 + 
                          cimgA[i][j].g*0.587 + 
                          cimgA[i][j].r*0.299);
   

   

• 颜色空间转换:

   

  cvCvtColor(src,dst,code); // src -> dst
   
     code     = CV_<X>2<Y>
     <X>/<Y> = RGB, BGR, GRAY, HSV, YCrCb, XYZ, Lab, Luv, HLS
   
  e.g.: CV_BGR2GRAY, CV_BGR2HSV, CV_BGR2Lab
   

   

 

绘图命令

 

• 画长方体:

  // 用宽度为1的红线在(100,100)与(200,200)之间画一长方体
  cvRectangle(img, cvPoint(100,100), cvPoint(200,200), cvScalar(255,0,0), 1);
   

   

• 画圆:

  // 在(100,100)处画一半径为20的圆,使用宽度为1的绿线
  cvCircle(img, cvPoint(100,100), 20, cvScalar(0,255,0), 1);
   

   

• 画线段:

  // 在(100,100)与(200,200)之间画绿色线段，宽度为1
  cvLine(img, cvPoint(100,100), cvPoint(200,200), cvScalar(0,255,0), 1);
   

   

• 画一组线段:

  CvPoint   curve1[]={10,10,   10,100,   100,100,   100,10};
  CvPoint   curve2[]={30,30,   30,130,   130,130,   130,30,   150,10};
  CvPoint* curveArr[2]={curve1, curve2};
  int       nCurvePts[2]={4,5};
  int       nCurves=2;
  int       isCurveClosed=1;
  int       lineWidth=1;
   
  cvPolyLine(img,curveArr,nCurvePts,nCurves,isCurveClosed,cvScalar(0,255,255),lineWidth);
   

   

• 画内填充色的多边形:

  cvFillPoly(img,curveArr,nCurvePts,nCurves,cvScalar(0,255,255));
   

   

• 添加文本:

  CvFont font;
  double hScale=1.0;
  double vScale=1.0;
  int     lineWidth=1;
  cvInitFont(&font,CV_FONT_HERSHEY_SIMPLEX|CV_FONT_ITALIC, hScale,vScale,0,lineWidth);
   
  cvPutText (img,"My comment",cvPoint(200,400), &font, cvScalar(255,255,0));
   

  Other possible fonts:

  CV_FONT_HERSHEY_SIMPLEX, CV_FONT_HERSHEY_PLAIN,
  CV_FONT_HERSHEY_DUPLEX, CV_FONT_HERSHEY_COMPLEX,
  CV_FONT_HERSHEY_TRIPLEX, CV_FONT_HERSHEY_COMPLEX_SMALL,
  CV_FONT_HERSHEY_SCRIPT_SIMPLEX, CV_FONT_HERSHEY_SCRIPT_COMPLEX,