OpenCV : convert the pointer in memory to image

2
votes

I have a grabber which can get the images and show them on the screen with the following code

while((lastPicNr = Fg_getLastPicNumberBlockingEx(fg,lastPicNr+1,0,10,_memoryAllc))<200) {                                                           
                iPtr=(unsigned char*)Fg_getImagePtrEx(fg,lastPicNr,0,_memoryAllc);                  
                ::DrawBuffer(nId,iPtr,lastPicNr,"testing");                                         }

but I want to use the pointer to the image data and display them with OpenCV, cause I need to do the processing on the pixels. my camera is a CCD mono camera and the depth of the pixels is 8bits. I am new to OpenCV, is there any option in opencv that can get the return of the (unsigned char*)Fg_getImagePtrEx(fg,lastPicNr,0,_memoryAllc); and disply it on the screen? or get the data from the iPtr pointer an allow me to use the image data?

2
c++cimagepointersopencv
Is your Camera not supported or why are you trying to mess with pointers? – Stephan Dollberg
hi bamboon, im not sure about this, does it mean that if it supports my camera then I dont need to use the framegrabber interface, and I can use the OpenCV directly to get the images? – user261002
Thank you so much. Im going to try it now. – user261002
im trying to use the sample from this link : opencv.willowgarage.com/wiki/CameraCapture but it keep giving me this message : Error:capture is NULL, do you know how can I find out if the opencv is supporting my camera. ?? – user261002
there is a list here which I assume is probably not complete though. opencv.willowgarage.com/wiki/… – Stephan Dollberg

2 Answers

5
votes

Creating an IplImage from unsigned char* raw_data takes 2 important instructions: cvCreateImageHeader() and cvSetData():

// 1 channel for mono camera, and for RGB would be 3
int channels = 1; 
IplImage* cv_image = cvCreateImageHeader(cvSize(width,height), IPL_DEPTH_8U, channels);
if (!cv_image)
{
    // print error, failed to allocate image!
}

cvSetData(cv_image, raw_data, cv_image->widthStep);

cvNamedWindow("win1", CV_WINDOW_AUTOSIZE);
cvShowImage("win1", cv_image);
cvWaitKey(10);

// release resources
cvReleaseImageHeader(&cv_image);
cvDestroyWindow("win1");

I haven't tested the code, but the roadmap for the code you are looking for is there.

2
votes

If you are using C++, I don't understand why your are not doing it the simple way like this:

If your camera is supported, I would do it this way:

   cv::VideoCapture capture(0);

   if(!capture.isOpened()) {
     // print error
     return -1;
   }

   cv::namedWindow("viewer");

   cv::Mat frame;

   while( true )
   {
     capture >> frame;

     // ... processing here

     cv::imshow("viewer", frame);
     int c = cv::waitKey(10);
     if( (char)c == 'c' ) { break; } // press c to quit
   }

I would recommend starting to read the docs and tutorials which you can find here.