Yalantis/uCrop · warning

load_ascii(): Only %lu/%lu values read from file

Error message

load_ascii(): Only %lu/%lu values read from file '%s'.

What it means

CImg::load_ascii() parses whitespace-separated numeric values from a .cimg/.ascii file using fscanf("%lf..."); when fscanf stops returning 1 before the expected number of values is read, CImg warns with the count actually read (off-1 of siz) and returns the partially filled image. The image is truncated, not the correct size/content.

Solutions

1. Verify the file contains exactly width*height*depth*spectrum numeric values matching its header
2. Check the file size/completeness (re-transfer or re-export the file if truncated)
3. Open the file and inspect the area around value off-1 for non-numeric garbage
4. Check the fscanf return value path: treat the partially filled image as invalid instead of using it
5. Regenerate the file programmatically (e.g. save in binary .cimg format) to avoid ASCII parsing issues

Example fix

// before
CImg<float> img;
img.load_ascii("data.txt"); // truncated file -> partial data
// after
std::FILE* f = std::fopen("data.txt", "r");
CImg<unsigned long> dims;
dims.load_cimg_header(f); // or validate value count beforehand
cimg::fclose(f);
CImg<float> img;
img.load_ascii("data.txt");

bool asciiDataComplete(const char* path, unsigned long expected) {
  std::ifstream in(path);
  double v; unsigned long n = 0;
  while (in >> v) ++n;
  return n == expected;
}

When it happens

Trigger: Loading an ASCII CImg file whose text contains fewer parseable numbers than the header-declared size, or non-numeric garbage where a value was expected; also a mid-file I/O error.

Common situations: Hand-edited data files with missing values; files truncated by a failed transfer or interrupted save; locale/text issues introducing unexpected characters; wrong file passed to load_ascii.

Related errors

• cimg::fclose(): Error code
• cimg::fclose(): Specified file is (null).
• cimg::fempty(): Specified filename is (null).
• cimg::fopen(): Failed to open file
• cimg::fopen(): File ' ', specified mode is (null).

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/c3d1029c9e6d9b8a. Report an issue: GitHub.

Appendix: source

Thrown at ucrop/src/main/jni/CImg.h:56682

      if (!dx || !dy || !dz || !dc) {
        if (!file) cimg::fclose(nfile);
        throw CImgIOException(_cimg_instance
                              "load_ascii(): Invalid ascii header in file '%s', image dimensions are set "
                              "to (%u,%u,%u,%u).",
                              cimg_instance,
                              filename?filename:"(FILE*)",dx,dy,dz,dc);
      }
      assign(dx,dy,dz,dc);
      const ulongT siz = size();
      ulongT off = 0;
      double val;
      T *ptr = _data;
      for (err = 1, off = 0; off<siz && err==1; ++off) {
        err = std::fscanf(nfile,"%lf%*[^0-9.eEinfa+-]",&val);
        *(ptr++) = (T)val;
      }
      if (err!=1)
        cimg::warn(_cimg_instance
                   "load_ascii(): Only %lu/%lu values read from file '%s'.",
                   cimg_instance,
                   off - 1,siz,filename?filename:"(FILE*)");

      if (!file) cimg::fclose(nfile);
      return *this;
    }

    //! Load image from a DLM file.
    /**
      \param filename Filename, as a C-string.
    **/
    CImg<T>& load_dlm(const char *const filename) {
      return _load_dlm(0,filename);
    }

    //! Load image from a DLM file \newinstance.
    static CImg<T> get_load_dlm(const char *const filename) {

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