Yalantis/uCrop · error · CImgArgumentException

load_medcon_external(): Specified filename is (null) or does

Error message

load_medcon_external(): Specified filename is (null) or does not exist.

What it means

load_medcon_external() loads a DICOM image by delegating to the external 'medcon' tool. Before doing anything, it validates the argument: if filename is null or cimg::is_file() says no such regular file exists, it throws this CImgArgumentException immediately.

Source

Thrown at ucrop/src/main/jni/CImg.h:59863

#else
      load_pnm(filename_tmp);
#endif
      std::remove(filename_tmp);
      return *this;
    }

    //! Load image using ImageMagick's external tool 'convert' \newinstance.
    static CImg<T> get_load_imagemagick_external(const char *const filename) {
      return CImg<T>().load_imagemagick_external(filename);
    }

    //! Load image from a DICOM file, using Medcon's external tool 'medcon'.
    /**
       \param filename Filename, as a C-string.
    **/
    CImg<T>& load_medcon_external(const char *const filename) {
      if (!filename || !cimg::is_file(filename))
        throw CImgArgumentException(_cimg_instance
                                    "load_medcon_external(): Specified filename is (null) or does not exist.",
                                    cimg_instance);
      CImg<charT> command(1024), filename_tmp(256), body(256);
      do {
        cimg_snprintf(filename_tmp,filename_tmp._width,"%s.hdr",cimg::filenamerand());
      } while (cimg::path_exists(filename_tmp));
      cimg_snprintf(command,command._width,"\"%s\" -w -c anlz -o \"%s\" -f \"%s\"",
                    cimg::medcon_path(),
                    CImg<charT>::string(filename_tmp)._system_strescape().data(),
                    CImg<charT>::string(filename)._system_strescape().data());
      cimg::system(command,cimg::medcon_path());
      cimg::split_filename(filename_tmp,body);

      cimg_snprintf(command,command._width,"%s.hdr",body._data);
      if (!cimg::path_exists(command)) {
        cimg_snprintf(command,command._width,"m000-%s.hdr",body._data);
        if (!cimg::path_exists(command)) {
          throw CImgIOException(_cimg_instance

View on GitHub (pinned to f788b534b4)

Solutions

Check the path with stat/access before calling: ensure the file exists and is a regular file.
Print/log the exact absolute path being passed (realpath()) and fix the construction of the path.
Verify the process working directory if using relative paths; switch to absolute paths.
Fix the source of the path (config field, database record, user argument) so it is never null/empty.
If DICOM loading is optional, guard the call and skip with a clear message instead of passing a bad path.

Example fix

// before
img.load_medcon_external(cfg.dicomPath); // may be null/missing
// after
if (!cfg.dicomPath || !cimg::is_file(cfg.dicomPath))
  throw std::invalid_argument("DICOM file missing: " + std::string(cfg.dicomPath?cfg.dicomPath:"(null)"));
img.load_medcon_external(cfg.dicomPath);

Defensive patterns

Strategy: validation

Validate before calling

if (!path || !cimg::is_file(path))
  throw std::invalid_argument("DICOM path null or does not exist");

Type guard

bool isExistingFile(const char* p){ return p && cimg::is_file(p); }

Try / catch

try { img.load_medcon_external(path); }
catch (CImgArgumentException& e) { log("bad DICOM path"); }

Prevention

Always resolve and validate paths before external loaders
Use absolute paths
Check case-sensitive extensions on Linux
Validate config/DB fields that supply file paths

When it happens

Trigger: Calling CImg<T>::load_medcon_external(nullptr), or passing a path that does not exist, is a directory, or is a dangling symlink. Also reached when callers pass a path relative to a different working directory than the one the process runs in.

Common situations: Config or user input supplying an empty/missing DICOM path; filename built by string concatenation where an optional directory part was empty; working-directory mismatch between dev and deployment; typo in extension or case-sensitive filesystem differences.

Understand the failure class

Background: "File not found" and ENOENT errors: why libraries can't find a file that should exist — this error's family across 50 libraries.

Related errors

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/887f0f9047050031. Report an issue: GitHub.