Yalantis/uCrop · error · CImgIOException

load_magick(): Unable to load file '%s' unless libMagick++ i

Error message

load_magick(): Unable to load file '%s' unless libMagick++ is enabled.

What it means

load_magick() only functions when CImg was compiled with cimg_use_magick, enabling the libMagick++ code path. In the #else branch it unconditionally throws CImgIOException, since ImageMagick-dependent decoding is unavailable. The file may be perfectly valid; the library build simply cannot handle it.

Source

Thrown at ucrop/src/main/jni/CImg.h:57322

        for (ulongT off = (ulongT)W*H; off; --off) {
          *(ptr_r++) = (T)(pixels->red);
          *(ptr_a++) = (T)(pixels->opacity);
          ++pixels;
        }
      } break;
      default : {
        assign(W,H,1,1);
        T *ptr_r = data(0,0,0,0);
        Magick::PixelPacket *pixels = image.getPixels(0,0,W,H);
        for (ulongT off = (ulongT)W*H; off; --off) {
          *(ptr_r++) = (T)(pixels->red);
          ++pixels;
        }
      }
      }
      return *this;
#else
      throw CImgIOException(_cimg_instance
                            "load_magick(): Unable to load file '%s' unless libMagick++ is enabled.",
                            cimg_instance,
                            filename);
#endif
    }

    //! Load image from a file, using Magick++ library \newinstance.
    static CImg<T> get_load_magick(const char *const filename) {
      return CImg<T>().load_magick(filename);
    }

    //! Load image from a PNG file.
    /**
       \param filename Filename, as a C-string.
       \param[out] bits_per_value Number of bits used to store a scalar value in the image file.
    **/
    CImg<T>& load_png(const char *const filename, unsigned int *const bits_per_value=0) {
      return _load_png(0,filename,bits_per_value);

View on GitHub (pinned to f788b534b4)

Solutions

Install ImageMagick development headers, define cimg_use_magick, and link Magick++/MagickCore, then rebuild.
Or avoid load_magick entirely and use a format-specific loader (load_png, load_jpeg) or load() which auto-detects based on available codecs.
On Android, convert the image outside the app or bundle a supported codec instead of shipping Magick++.

Example fix

// before
img.load_magick("photo.tiff"); // throws: no libMagick++
// after
img.load("photo.tiff"); // routes to available codec
// or build with: -Dcimg_use_magick and LOCAL_LDLIBS += -lMagick++-7.Q16HDRI

Defensive patterns

Strategy: fallback

Validate before calling

#ifndef cimg_use_magick
  // compile-time signal: load_magick is unusable in this build
  constexpr bool kMagickAvailable = false;
#else
  constexpr bool kMagickAvailable = true;
#endif

Try / catch

try { img.load_magick(path); } catch (CImgIOException& e) { img.load(path); // fallback to auto-detected supported codec }

Prevention

Gate Magick-dependent calls behind #ifdef cimg_use_magick in your own code
Use CImg::load() with format auto-detection instead of load_magick when possible
Document build requirements (ImageMagick dev + cimg_use_magick) for Magick paths

When it happens

Trigger: Calling load_magick(filename) in a build where cimg_use_magick was not defined (no #define cimg_use_magick before including CImg.h and no Magick++ link).

Common situations: Default CImg builds (no ImageMagick dev package installed), Android NDK builds (like this ucrop JNI) where Magick++ was never added to the makefile, or defining cimg_use_magick but not linking Magick++ (link error precedes this).

Understand the failure class

Background: "X is not installed. Please install it with pip install Y": missing optional dependency errors — ImportError/ValueError raised when a library's optional extra was never installed — this error's family across 22 libraries.

Related errors

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/9e85779747d97d2f. Report an issue: GitHub.