opencv: 基本知识（二）；

1、Mat与IplImage之间的相互转换；

//IplImage—>Mat  
//EXAMPLE：  
//浅拷贝：  
IplImage* pBinary=cvLoadImage("c://temp.jpg",0);  
Mat Img;  
Img=cvarrToMat(pBinary);  
//深拷贝只需要再在Mat里创建一个新的Mat对象，然后进行数据的复制，再用上述的函数进行数据头的复制（浅拷贝）：  
IplImage* pBinary=cvLoadImage("c://temp.jpg", 0);  
Mat ImgTemp;  
Img=cvarrToMat(pBinary);  
Mat Img = ImgTemp.clone();  
  
  
//Mat—>IplImage  
//EXAMPLE:  
//浅拷贝:  
Mat Img=imread("1.jpg");  
IplImage* pBinary = &IplImage(Img);  
//深拷贝只要再加一次复制数据：  
IplImage *input = cvCloneImage(pBinary);  

2、随机数；

标准库提供了随机函数std::srand,std::rand来生成随机数；

std::srand(unsigned(time(NULL));

std::rand();    //生成随机数；

3、矩阵缩放；

opencv的图像缩放函数为cv::resize();

Resizes an image.
C++: void resize(InputArray src, OutputArray dst, Size dsize, double fx=0, double fy=0, int interpolation=INTER_LINEAR )

Python: cv2.resize(src, dsize[, dst[, fx[, fy[, interpolation]]]]) → dst

C: void cvResize(const CvArr* src, CvArr* dst, int interpolation=CV_INTER_LINEAR )

Python: cv.Resize(src, dst, interpolation=CV_INTER_LINEAR) → None


Parameters:
src – Source image.
dst – Destination image. It has the size dsize (when it is non-zero) or the size computed from src.size() , fx , and fy . The type of dst is the same as of src .
dsize – 
Destination image size. If it is zero, it is computed as:

Either dsize or both fx and fy must be non-zero.
fx – 
Scale factor along the horizontal axis. When it is 0, it is computed as

fy – 
Scale factor along the vertical axis. When it is 0, it is computed as

interpolation – 
Interpolation method:
INTER_NEAREST - a nearest-neighbor interpolation
INTER_LINEAR - a bilinear interpolation (used by default)
INTER_AREA - resampling using pixel area relation. It may be a preferred method for image decimation, as it gives moire’-free results. But when the image is zoomed, it is similar to the INTER_NEAREST method.
INTER_CUBIC - a bicubic interpolation over 4x4 pixel neighborhood
INTER_LANCZOS4 - a Lanczos interpolation over 8x8 pixel neighborhood：

使用方法：

cv::Mat(srcIMg,dstImg,dstImg.Size,0,0,cv::INTER_CUBIC);   //fx,fy，将按照dstImg.size与srcImg的比值来进行设置

或者

cv::Mat(srcImg,dstImg,cv::Size(), 0.5,0.5,cv::INTER_CUBIC);