Read image on iPhone from C-CodePudding

I am working on a C library that shall do image processing. My approach now is to pass two strings to C from swift. One string is the path to the image and the second is the output directory.

All the time I get that the file does not exist. How can I get the correct path the asset? The image lies in a directory I have created on my own and is called "test.jpg". I also have a "test2.jpg" in Assets. Have not managed to find that either.

Swift Code:

func getGrayImage() -> Image {
    if var resourcePath = Bundle.main.url(forResource: "test", withExtension: "jpg") {
        let dir = resourcePath.deletingLastPathComponent()
        VideoProcessingWrapper().rgb2gray(resourcePath.absoluteString, dir.absoluteString)
    }
    return Image("test2")
}

C Code:

void VideoProcessing::rgb2gray(const std::string& image_path, const std::string& dir) {
  std::cout << "C  : " << std::endl;
  std::cout << image_path << std::endl;
  std::cout << std::endl;
  std::cout << dir << std::endl;
  std::cout << "In directory: " <<std::endl;
  for (const auto& entry : std::filesystem::directory_iterator(dir)) {
        std::cout << entry.path() << std::endl;
  }
  if (std::filesystem::exists(image_path)) {
    std::cout << "File exists" << std::endl;
  } else {
    std::cout << "File does NOT exist" << std::endl;
    return;
  }
  cv::imread(image_path, cv::IMREAD_COLOR);
}

It even crashes when trying to display all files in the directory, stating that the directory does not exist. But what have I then been given from Bundle.main.url-call?

This is the printout from the C function using a simulator:

C  : 
file:///Users/name/Library/Developer/CoreSimulator/Devices/7F438661-8BF5-4A60-B41F-1D4B7FEC6A8E/data/Containers/Bundle/Application/AB3EFF3E-79A4-469C-A3BF-ABDD31A09E61/TestVideoProcess.app/test.jpg

file:///Users/name/Library/Developer/CoreSimulator/Devices/7F438661-8BF5-4A60-B41F-1D4B7FEC6A8E/data/Containers/Bundle/Application/AB3EFF3E-79A4-469C-A3BF-ABDD31A09E61/TestVideoProcess.app/

I get the same behaviour when running on a real iPhone.

CodePudding user response：

No matter what you do, the bundle directory is inside your application and you have no write access to it.

CodePudding user response：

The problem here is that Foundation framework represents paths with

In this case you need the path part only. One trick you can employ here is to build the path from pathComponents of the URL instance:

if let resourcePath = Bundle.main.url(forResource: "test", withExtension: "jpg") {
    let dir = resourcePath.deletingLastPathComponent()
    VideoProcessingWrapper().rgb2gray(resourcePath.pathComponents.joined(separator: "/"),
                                      dir.pathComponents.joined(separator: "/"))

}

Alternatively, as suggested by mani in the comments to your question, you can use the path property of the same class, however the documentation says that it also may include parameter string and for some reason it's now deprecated.