OpenCV访问像素点

OpenCV访问像素点 OpenCV访访访像像素, 数访元素等方法收集 访访访像像素的一些方法。 * Indirect access: (General, but inefficient, access to any type image)o For a single-channel byte image: 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 o For a multi-channel float (or byte) image: 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 * Direct access: (Efficient access, but error prone) o For a single-channel byte image: IplImage* img=cvCreateImage(cvSize(640,480),IPL_DEPTH_8U,1);((uchar *)(img->imageData + i*img->widthStep))[j]=111; o For a multi-channel byte image: 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; // Ro For a multi-channel float image: 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* Direct access using a pointer: (Simplified and efficient access under limiting assumptions) o For a single-channel byte image: 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; o For a multi-channel byte image: 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; o For a multi-channel float image (assuming a 4-byte alignment): 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; * Direct access using a c++ wrapper: (Simple and efficient access) o Define a c++ wrapper for single-channel byte images, multi-channel byte images, and multi- channel float images: template 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 RgbImage; typedef Image RgbImageFloat;typedef Image BwImage;typedef Image BwImageFloat; o For a single-channel byte image: IplImage* img=cvCreateImage(cvSize(640,480),IPL_DEPTH_8U,1); BwImage imgA(img); imgA[i][j] = 111; o For a multi-channel byte image: 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; o For a multi-channel float image: 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;