Question

I need to exchange data between FreeImage (FIBITMAP) and OpenCV format (IplImage and/or Mat). I’m fine with getting data from a FIBITMAP into an IplImage or Mat since FreeImage gives you a function FreeImage_GetScanLine which you can set the OPenCV imageData ptr equal to.

However, I’m stuck on how to do the reverse, i.e. once I have an OpenCV image, how do I get its data into a FreeImage image?

Answer 1

You have to be a little careful just copying the data pointer, a lot of image formats have padding to start each new line on eg a 4byte boundary.

If your image has a GetScanLine() function then it’s probably safer to make an empty plImage*/cv::Mat and memcopy each row with the pointer returned from GetScanLine() and the .ptr() member of cv::MAt

cv::Mat &src        
int srcRowBytes = width  * src.elemSize();

for (int ih=0;ih<height;ih++) {
    memcpy(dest.pointer_to_row(ih),src.ptr(ih),srcRowBytes);
}