Missing binding in python : rescaleCV

Question

Hi

I just played with new jevois-inventor and it's just amazing !! Great stuff indeed

Obviously, it becomes incredibly natural to add new python modules with that tool and I think I have discovered a missing binding in python that would be useful (at least in my app) : rescaleCv

when I do a pyhton jevois.rescaleCv(...) I get an error 'module libjevois' has no attribute rescaleCv

In think in file PythonSupport.C there is a missing

JEVOIS_PYTHON_RAWIMAGE_FUNC(rescaleCV);

Or maybe I am making another mistake ?

If you confirm the function is not exported in python, glurk ... 

Adding the missing binding (supposing I have the proper fix) and then recompiling all jevois-sdk is a task out of my league ...

If the issue is confirmed, any trick , any workaround ?

Thx

Answer 1

oh, thanks, we will check and add the binding, but 1.8.1 is frozen now (compiling the debs rihght now...) so that will be for 1.8.2.

Now do not despair, jevois::rescaleCv() is only a trivial wrapper over cv::resize(), which just chooses a different interpolation method depending on whether we are upscaling or downscaling:

cv::Mat jevois::rescaleCv(cv::Mat const & img, cv::Size const & newdims)
{
  cv::Mat scaled;

  if (newdims.width == img.cols && newdims.height == img.rows)
    scaled = img;
  else if (newdims.width > img.cols || newdims.height > img.rows)
    cv::resize(img, scaled, newdims, 0, 0, cv::INTER_LINEAR);
  else
    cv::resize(img, scaled, newdims, 0, 0, cv::INTER_AREA);

  return scaled;
}

so, in Python, you should be able to just do something along the lines of:

res = cv2.resize(img, (2*width, 2*height), interpolation = cv.INTER_CUBIC)

(I got that example from https://docs.opencv.org/3.4.0/da/d6e/tutorial_py_geometric_transformations.html )

Comments

Great ! I did not understand it was a wrapper so tiny !!
Thx for the fast and accurate answer !!