How to convert this c code to c++ in opencv

Question

I'm a starter in opencv, and Learning Opencv has is code written in C. I need to convert to C++.

IplImage *imgY = cvCreateImage(imageSize, IPL_DEPTH_8U, 1);  
IplImage *imgCr = cvCreateImage(imageSize, IPL_DEPTH_8U, 1);  
IplImage *imgCb = cvCreateImage(imageSize, IPL_DEPTH_8U, 1);  
IplImage *imgYCrCb = cvCreateImage(imageSize, img->depth, img->nChannels); 

cvCvtColor(img,imgYCrCb,CV_BGR2YCrCb);  
cvSplit(imgYCrCb, imgY, imgCr, imgCb, 0);  

unsigned char *pY, *pCr, *pCb, *pMask;
pY = (unsigned char *)imgY->imageData;  
pCr = (unsigned char *)imgCr->imageData;  
pCb = (unsigned char *)imgCb->imageData;
pMask = (unsigned char *)mask->imageData;

Almost all C code is valid C++. You'll need to be more specific than that. — Oliver Charlesworth
– Oliver Charlesworth, Commented Jun 22, 2012 at 0:43

Pascal T. · Accepted Answer · 2012-06-23 08:41:03Z

8

Refer to:

For example,

IplImage *imgY = cvCreateImage(imageSize, IPL_DEPTH_8U, 1);

becomes

cv::Mat imgY = cv::Mat(imageSize, CV_8UC1);

and

cvCvtColor(img,imgYCrCb,CV_BGR2YCrCb);

becomes

cv::cvtColor(img, imgYCrCb, CV_BGR2YCrCb);

and so on ...

Edit :

Answer to your comment : OpenCV 2 removes the need to manage manually the memory.

So, the code can be rewritten as :

cv::Mat imgYCrCb;
std::vector<cv::mat> yCrCb_channels;

cv::cvtColor(img,imgYCrCb,CV_BGR2YCrCb);   
cv::split(imgYCrCb, yCrCb_channels);
unsigned char * pY = (uchar *) yCrCn_channels[1].data;

Advice : read http://www.amazon.com/dp/1849513244/?tag=stackoverfl08-20 , it covers the C++ opencv interface.

edited Jun 23, 2012 at 8:41

answered Jun 22, 2012 at 0:43

Pascal T.

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3 Comments

RIK Over a year ago

My 1st problem is with split function. In c++ only accepts a vector. The 2nd problem is that i don't know how to make pY = (unsigned char *)imgY->imageData; in C++. Thanks.

Mona Jalal Over a year ago

Hi Pascal, are these also equal?

//frame = cvCreateImage(cvSize(depth_width, depth_height), 8, 3); // Create the frame 	cv::Mat frame = cv::Mat(cvSize(depth_width, depth_height), CV_8UC3);

Pascal T. Over a year ago

Hi Mona, better use cv::Mat frame = cv::Mat(cv::Size(width, height), CV_8UC3) . In summary, replace cvSize by cv::Size. Also, the name depth_width makes me wonders you might be confusing image depth vs image size.

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