Yalantis/uCrop · error · CImgIOException

load_gzip_external(): Failed to load file '%s' with external

Error message

load_gzip_external(): Failed to load file '%s' with external command 'gunzip'.

What it means

load_gzip_external() runs `"gunzip" -c "<file>" > <tmpfile>` via cimg::system(); a non-zero exit status throws this CImgIOException. The gunzip tool was found and launched, but the decompression command failed.

Source

Thrown at ucrop/src/main/jni/CImg.h:59741

      do {
        if (!cimg::strcasecmp(ext,"gz")) {
          if (*ext2) cimg_snprintf(filename_tmp,filename_tmp._width,"%s%c%s.%s",
                                   cimg::temporary_path(),cimg_file_separator,cimg::filenamerand(),ext2);
          else cimg_snprintf(filename_tmp,filename_tmp._width,"%s%c%s",
                             cimg::temporary_path(),cimg_file_separator,cimg::filenamerand());
        } else {
          if (*ext) cimg_snprintf(filename_tmp,filename_tmp._width,"%s%c%s.%s",
                                  cimg::temporary_path(),cimg_file_separator,cimg::filenamerand(),ext);
          else cimg_snprintf(filename_tmp,filename_tmp._width,"%s%c%s",
                             cimg::temporary_path(),cimg_file_separator,cimg::filenamerand());
        }
      } while (cimg::path_exists(filename_tmp));
      cimg_snprintf(command,command._width,"\"%s\" -c \"%s\" > \"%s\"",
                    cimg::gunzip_path(),
                    CImg<charT>::string(filename)._system_strescape().data(),
                    CImg<charT>::string(filename_tmp)._system_strescape().data());
      if (cimg::system(command)!=0)
        throw CImgIOException(_cimg_instance
                              "load_gzip_external(): Failed to load file '%s' with external command 'gunzip'.",
                              cimg_instance,
                              filename);
      if (!cimg::path_exists(filename_tmp)) {
        cimg::fclose(cimg::fopen(filename,"r"));
        throw CImgIOException(_cimg_instance
                              "load_gzip_external(): Failed to load file '%s' with external command 'gunzip'.",
                              cimg_instance,
                              filename);

      }
      load(filename_tmp);
      std::remove(filename_tmp);
      return *this;
    }

    //! Load gzipped image file, using external tool 'gunzip' \newinstance.
    static CImg<T> get_load_gzip_external(const char *const filename) {

View on GitHub (pinned to f788b534b4)

Solutions

1. Run the same gunzip command manually to see the real failure
2. Verify gzip integrity with `gzip -t file.gz` before loading
3. Ensure the temp output directory is writable and gunzip exists (cimg::gunzip_path())
4. Decompress in-process with zlib (gzread) into memory and load via CImg from a temp plain file, avoiding external tools

Example fix

// before
img.load_gzip_external("data.cimg.gz"); // gunzip exit != 0
// after
if (cimg::system("gzip -t data.cimg.gz") == 0) {
  img.load_gzip_external("data.cimg.gz");
} else {
  // decompress with zlib in-process and load the plain file
  decompress_zlib_to("data.cimg.gz", "/tmp/data.cimg");
  img.load_cimg("/tmp/data.cimg");
}

// test archive integrity and tool availability first
bool gz_ok = cimg::system("gzip -t data.cimg.gz") == 0;
bool tool_ok = cimg::gunzip_path()[0] != '\0';

try {
  img.load_gzip_external(path);
} catch (CImgIOException& e) {
  // decompress in-process with zlib, then load plain file
  gunzip_to_temp(path, "/tmp/out.cimg");
  img.load_cimg("/tmp/out.cimg");
}

When it happens

Trigger: Corrupt or truncated .gz payload (gunzip exits non-zero), gunzip not actually on PATH in a way cimg::gunzip_path() resolves oddly, or shell redirection failing (unwritable temp directory).

Common situations: Partially uploaded .gz files; files compressed with unsupported variants; restricted Android/app environments where exec of external binaries is blocked or PATH is empty; full temp filesystem.

Related errors

• load_gzip_external(): Specified filename is (null) or does n
• save_gzip_external(): Specified filename is (null).
• save_gzip_external(): Failed to save file '%s' with external
• load_graphicsmagick_external(): Failed to load file '%s' wit
• load_imagemagick_external(): Failed to load file '%s' with e

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/e798c2ab9210b501. Report an issue: GitHub.