Yalantis/uCrop · error · CImgArgumentException

load_cimg(): Specified filename is (null).

Error message

load_cimg(): Specified filename is (null).

What it means

CImgList::load_cimg() requires either a filename or an open FILE*; if both are null it throws CImgArgumentException before doing any I/O (CImg.h:66782). It is a programming/API-misuse guard, not a file problem.

Solutions

1. Check the path string is non-empty and pass it only when non-null.
2. If reading from memory, open the stream yourself: load_cimg("file.cimg") or pass an std::FILE* from fopen.
3. Fix the upstream code that produced the null/empty path (missing env var, failed config lookup).

Example fix

// before
const char* path = getenv("CIMG_DATA"); // may be NULL
imgs.load_cimg(path);

// after
const char* path = getenv("CIMG_DATA");
if (path && *path) imgs.load_cimg(path);
else throw std::invalid_argument("CIMG_DATA path not set");

bool canLoadCimg(const char* path) { return path != nullptr && *path != '\0'; }

if (!canLoadCimg(path))
  throw std::invalid_argument("load_cimg: filename must be non-empty");
try {
  imgs.load_cimg(path);
} catch (cimg_library::CImgArgumentException& e) {
  logError("null path: %s", e.what());
}

When it happens

Trigger: Calling list.load_cimg(NULL) or load_cimg(std::string().c_str()) where the string is empty, or passing filename=NULL with file=NULL because an earlier path-lookup returned null.

Common situations: A config/env variable holding the dataset path is empty; a JNI layer passing a null jstring converted to nullptr; a failed path join producing an empty string.

Related errors

• atN(): Empty instance.
• atNX(): Empty instance.
• atNXY(): Empty instance.
• atNXYZ(): Empty instance.
• atNXYZC(): Empty instance.

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/2ad8b947e4b219a9. Report an issue: GitHub.

Appendix: source

Thrown at ucrop/src/main/jni/CImg.h:66782

              } else { \
                CImg<Tss> raw; \
                for (ulongT to_read = img.size(); to_read; ) { \
                  raw.assign((unsigned int)std::min(to_read,cimg_iobuffer)); \
                  cimg::fread(raw._data,raw._width,nfile); \
                  if (endian!=cimg::endianness()) cimg::invert_endianness(raw._data,raw.size()); \
                  const Tss *ptrs = raw._data; \
                  for (ulongT off = (ulongT)raw._width; off; --off) *(ptrd++) = (T)*(ptrs++); \
                  to_read-=raw._width; \
                } \
              } \
            } \
          } \
        } \
        loaded = true; \
      }

      if (!filename && !file)
        throw CImgArgumentException(_cimglist_instance
                                    "load_cimg(): Specified filename is (null).",
                                    cimglist_instance);

      const ulongT cimg_iobuffer = (ulongT)24*1024*1024;
      std::FILE *const nfile = file?file:cimg::fopen(filename,"rb");
      bool loaded = false, endian = cimg::endianness();
      CImg<charT> tmp(256), str_pixeltype(256), str_endian(256);
      *tmp = *str_pixeltype = *str_endian = 0;
      unsigned int j, N = 0, W, H, D, C;
      cimg_uint64 csiz;
      int i, err;
      do {
        j = 0; while ((i=std::fgetc(nfile))!='\n' && i>=0 && j<255) tmp[j++] = (char)i; tmp[j] = 0;
      } while (*tmp=='#' && i>=0);
      err = cimg_sscanf(tmp,"%u%*c%255[A-Za-z123468_]%*c%255[sA-Za-z_ ]",
                        &N,str_pixeltype._data,str_endian._data);
      if (err<2) {
        if (!file) cimg::fclose(nfile);

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