Cascade detectMultiScale shows error while running

1

Hi

I am trying to run the code below but it always fails as described. I am not sure what I am doing incorrectly there, but the code is very simple.

std::vector<Rect> detectFacesInImage(Mat& img)
{
    std::vector<Rect> faces;
    CascadeClassifier cascade;
    std::string f = "haarcascades//haarcascade_frontalface_default.xml";
    if (cascade.load(f) == true)
    {
        cascade.detectMultiScale(img, faces);
        return faces;
    }
    return faces;
}

At this point, the image is already converted to grayscale. While running

cascade.detectMultiScale(img, faces);

an error is thrown.

This used to work so I have a suspicion that it is due to

Windows 11
or because of my graphic card
or both

I used to run this without problems before using Windows 10 and a different hardware set.
Is there anything I am missing here?

Thanks for the help
Daniel

2

which is ? you probably want to tell us ! …

1 Like
4

Hi
I apologize, I forgot to add this information.

Exceção gerada em 0x00007FFA9543567C em diImage.exe: Exceção do Microsoft C++: cv::Exception no local de memória 0x000000C373DAD130.
"diImage.exe" (Win32): Carregado "C:\Windows\System32\opencl.dll". 
"diImage.exe" (Win32): Carregado "C:\Windows\System32\DXCore.dll". 
"diImage.exe" (Win32): Carregado "C:\Windows\System32\AppXDeploymentClient.dll". 
"diImage.exe" (Win32): Carregado "C:\Windows\System32\dxgi.dll". 
"diImage.exe" (Win32): Carregado "C:\Windows\System32\ResourcePolicyClient.dll". 
"diImage.exe" (Win32): Não carregado "C:\Windows\System32\ResourcePolicyClient.dll"
"diImage.exe" (Win32): Carregado "C:\Windows\System32\directxdatabasehelper.dll". 
"diImage.exe" (Win32): Não carregado "C:\Windows\System32\directxdatabasehelper.dll"
"diImage.exe" (Win32): Não carregado "C:\Windows\System32\dxgi.dll"
"diImage.exe" (Win32): Carregado "C:\Windows\System32\nvopencl.dll". 
"diImage.exe" (Win32): Carregado "C:\Windows\System32\nvapi64.dll". 
Exceção gerada em 0x0000000000000000 em diImage.exe: 0xC0000005: violação de acesso ao executar o local 0x0000000000000

It is an access violation exception.

5

that’s an invalid path.

learn about the “working directory”, and in which working dir your process actually executes. this is how relative paths are resolved.

also: load the cascade XML once at the start of the program, not every time you want to detect.

1 Like
6

Hi Crackwitz,

Yes, I have the working folder running under that relative path.

However, the standard C++ way of using paths is using a double “\”, but as you said, I made a mistake. I used the wrong escape sequence “//” ( You may forgive me because I work with both windows and Linux ), usually, compilers would write this warning.

>C:\Users\Administrador\Documents\GitHub\ImageProcessing\opcvwrapper.cpp(823,21): warning C4129: 'h': sequência de escape de caractere não reconhecida

Also:
cascade.load(f) returned true before, meaning that it was properly loaded, which does not happen if I use a single “/”

Edit: I had also checked the existence of the path using c++17

#include <filesystem>
namespace fs = std::filesystem;
bool file_exists(const std::string& file)
{
	return fs::exists(file);
}

Edit 2:
it does not work with a single /
std::string f = “haarcascades\haarcascade_frontalface_default.xml”;

I even copied it to the working directory

image
image824×361 36.1 KB

Same error.

regards
Daniel

7

I can’t read this language but I can see the cv::Exception.

catch the exception and print it. put a try-catch around the entire program.

1 Like
8

that exception is thrown when I run this code:

        auto axes = CvPlot::plotImage(clone);
        cv::Mat mat = axes.render(clone.size().width, clone.size().height);
        CvPlot::show(title, axes);
        waitKey(0);

This is a graph library wrapper written for openCV , but this exception does not stop the program execution.

But thanks for your help. It looks like something at my hardware causes the error probably. Because I used to run this code on another computer.

Thanks
Daniel

9

well what does the cv::exception say? it’s got a message text attached to it. you have not shared this piece of information yet.

10

That exception cannot be captured. At least I cannot use a try catch to grab it. However, it does not work if I remove the code from the library and use imshow instead. There is a try catch that already does it. I have appreciated your help in this case, but it does look like something on my graphic board.

11

why? it’s a cv::Exception. it’s made to be caught.

1 Like
12

The exception is thrown internally inside CvPlot::show(title, axes). I think the code in the library simply ignores the exception so that is why I cannot capture it. Visual Studio shows us in the debug mode.

13 
try {
    auto axes = CvPlot::plotImage(clone);
    cv::Mat mat = axes.render(clone.size().width, clone.size().height);
    CvPlot::show(title, axes);
    waitKey(0);
}
catch (cv::Exception& e)
{
    std::cerr << e.msg << std::endl;
}