Opencv-python: AttributeError: module 'cv2.cv2' has no attribute 'MultiTracker_create' with latest build

[brendanind]

Expected behaviour

Expected this code to return a multi tracker object:

import cv2
cv2.MultiTracker_create()

Actual behaviour

Throws the error:
AttributeError: module 'cv2.cv2' has no attribute 'MultiTracker_create'

Steps to reproduce

I installed the latest wheel of cv2 on a win10 x64 machine using pip in a venv (pip install opencv-contrib-python)

cv2.getVersionString() returns '4.5.1'

I can then import cv2 successfully in the python console, however cv2.MultiTracker_create() throws an error.

I completely uninstalled cv2 and installed again except with different version: pip install opencv-contrib-python~= 3.4.4.19
Since the function reportedly works in this version in a StackOverflow answer here

Once installed, the code runs successfully. So I assume it's a problem with this specific build of cv2 (i.e. version 4.5.1)

In the toolchain you have created, how do you select or deselect the modules that are installed form the C files? Is there a way that I can manually reinclude MultiTracker_create() back into my build, since don't have the expertise to build my own wheel. No worries if not, I'm just wondering why MultiTracker_create() was in an earlier build and not the most recent.

Thanks.

Issue submission checklist

• [X] This is not a generic OpenCV usage question (looking for help for coding, other usage questions, homework etc.)
  

• [X] I have read the README of this repository and understand that this repository provides only an automated build toolchain for OpenCV Python packages (there is no actual OpenCV code here)
  



• [X] The issue is related to the build scripts in this repository, to the pre-built binaries or is a feature request (such as "please enable this additional dependency")


• [x] I'm using the latest version of opencv-python

[skvark]

It's missing from OpenCV documentation also on 4.5.1: https://docs.opencv.org/4.5.1/d8/d77/classcv_1_1MultiTracker.html

But found in 4.5.0 and earlier: https://docs.opencv.org/4.5.0/d8/d77/classcv_1_1MultiTracker.html

This commit reveals that OpenCV developers changed the API between those versions: https://github.com/opencv/opencv_contrib/commit/80c197590ccfbd1dd9b4f54b250d26e06e840683

OpenCV contrib modules are known to be "unstable" which means that they can break or change. In this case the whole tacker API is being rewritten / modified, see: https://github.com/opencv/opencv_contrib/pull/2737 and https://github.com/opencv/opencv/issues/18481.

You can find the legacy multitracker API now from here, it has been preserved to maintain backward compatibility: https://docs.opencv.org/4.5.1/df/d4a/classcv_1_1legacy_1_1MultiTracker.html

Example:

Python 3.9.0 (tags/v3.9.0:9cf6752, Oct  5 2020, 15:34:40) [MSC v.1927 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import cv2
>>> cv2.legacy.MultiTracker_create()
<legacy_MultiTracker 00000203D312A9B0>

Please refer to the official OpenCV documentation in the future - make sure you have selected the correct version from dropdown menu. All the available OpenCV functions are clearly documented there: https://docs.opencv.org/4.5.1/df/d4a/classcv_1_1legacy_1_1MultiTracker.html

Note: Please do not refer to that Stack Overflow answer, it's completely wrong.

[brendanind]

Thank you very much of giving up your time to answer my question so well.