Dlib: cv_image issue with OpenCV 4.0 +

[mipko]

This is the same issue as #1492

Expected Behavior

To be able to pass cv::Mat in cv_image constructor

Current Behavior

Compilation error with OpenCV version 4.0.0 and above.

/dlib/opencv/cv_image.h:37:22: **error**: conversion from ‘const cv::Mat’ to non-scalar type ‘IplImage’ {aka ‘_IplImage’} requested IplImage temp = img;

Steps to Reproduce

try to construct cv_image from cv::Mat

FIX

the same as in #1492

• Version: 19.19
• Where did you get dlib: official site
• Platform: Ubuntu 19.04
• Compiler: gcc 8.3.0

[davisking]

You need to post more detailed instructions because I am not able to reproduce this. See also this recent thread: https://github.com/davisking/dlib/pull/1494#issuecomment-565770272 where someone asked the same question, only later to report that this isn't an issue.

[mipko]

Thank you very much for the reply.

I will try to explain it a bit detailed.

This is code snippet from my C++ project:

 dlib::array2d<unsigned char> dlib_img;
 dlib::assign_image(dlib_img, dlib::cv_image<unsigned char>(_mat));

within the dlib::cv_image constructor there is a statement

IplImage temp = img;

The above statement causes compilation error with OpenCV 4.x.y.

To fix the problem I have changed the above line from cv_image constructor to this:

temp = cvIplImage(img);

I have just cloned the master branch from the OpenCV github.
I have installed dlib 19.19.

[davisking]

Thanks for the report. I just pushed a change to github that should fix this for all versions of OpenCV.

[mipko]

Thank you very much for the fix. Everything is OK now.

[amir-saniyan]

For resolve compilation error, the following code could be used:

IplImage ipl_img = cvIplImage(image);
dlib::cv_image<dlib::bgr_pixel> cimg(&ipl_img);

[nwrkbiz]

@amir-saniyan

or simply:
` dlib::assign_image(dlib_img, dlib::cv_image<unsigned char>(cvIplImage(ocv_mat)));