Golang : Fix opencv.LoadHaarClassifierCascade The node does not represent a user object error

Problem:

You're trying load a Haarcascade file with opencv.LoadHaarClassifierCascade() function in Golang, but you get this error message instead :

OpenCV Error: Unspecified error (The node does not represent a user object (unknown type?)) in cvRead, file /tmp/opencv-20170224-77195-1rw28s/opencv-2.4.13.2/modules/core/src/persistence.cpp, line 5008

libc++abi.dylib: terminating with uncaught exception of type cv::Exception: /tmp/opencv-20170224-77195-1rw28s/opencv-2.4.13.2/modules/core/src/persistence.cpp:5008: error: (-2) The node does not represent a user object (unknown type?) in function cvRead

 package main

 import (
  "fmt"
  "github.com/lazywei/go-opencv/opencv"
 )

 var faceCascade = new(opencv.HaarCascade)
 var eyeCascade = new(opencv.HaarCascade)

 func main() {

  faceCascade = opencv.LoadHaarClassifierCascade("haarcascade_frontalface_alt.xml")
  defer faceCascade.Release()

  fmt.Println(faceCascade) // ---- ok

  eyeCascade = opencv.LoadHaarClassifierCascade("haarcascade_eye.xml") // --- will crash.
  defer eyeCascade.Release()

  fmt.Println(eyeCascade)

 }

What's going on and how to fix this issue?

Solution:

If you try to load the haarcascade_eye.xml file that you've downloaded from https://github.com/opencv/opencv/tree/master/data/haarcascades, you will still encounter the same error message. What you need to do is to download the Open CV 2.4.9 version from http://opencv.org/downloads.html and retrieve the haarcascade_eye.xml from /data/haarcascades folder.

Pretty sure it is a bug somewhere in OpenCV code.

References:

https://github.com/infusion/PHP-Facedetect/issues/19