OpenCV's iplimage and Mat are exchanging with each other.

OpenCV the two methods are shared with memory, because the memory is shared, so any change of one side will change the original numerical value.

(1) Iplimage to Mat

Ex.
iplimage* pImg = cvloadimage ("lena.jpg");
Cv::mat img (pimg,0); 0 is not a duplicate image, that is, Pimg and IMG data share the same memory location, header each has

(2) Mat to Iplimage

Ex.
iplimage* pImg = cvloadimage ("lena.jpg");
Cv::mat img (pimg,0); IMG gets pimg's data.
Iplimage qimg;
qimg = Iplimage (IMG); The file is not copied, so Qimg.imagedata is pointing to Pimg->imagedata.