Yalantis/uCrop · error · CImgArgumentException

load_camera(): Invalid request for camera #%u (no more than…

Error message

load_camera(): Invalid request for camera #%u (no more than 100 cameras can be managed simultaneously).

What it means

CImg manages a fixed static array of 64 cv::VideoCapture handles for load_camera(); requesting a camera_index >= 64 is rejected up-front with CImgArgumentException (note: the message text saying '100 cameras' is a stale comment — the real limit is 64).

Solutions

1. Keep camera_index within 0..63; map higher device numbers to a smaller logical index.
2. Release cameras (load_camera with release_camera=true, or stop captures) before opening more.
3. Use cv::VideoCapture directly for more than 64 concurrent cameras.

Example fix

// before
img.load_camera(70); // throws
// after
if (cameraIndex < 64) img.load_camera(cameraIndex);
else throw std::runtime_error("camera index must be < 64");

if (cameraIndex >= 64) throw std::invalid_argument("camera index must be < 64");

try { img.load_camera(cameraIndex); }
catch (CImgArgumentException& e) { /* clamp or remap index */ }

When it happens

Trigger: Calling load_camera(camera_index) with camera_index >= 64 (or any loop that enumerates cameras past index 63) when compiled with cimg_use_opencv.

Common situations: Probing /dev/video devices with a large range in a loop; passing a device ID from an external config that uses higher numbering; off-by-one assumptions about camera indexing.

Related errors

• load_camera(): Failed to initialize camera #%u.
• load_camera(): Failed to retrieve a %ux%u frame from camera…
• _cimg2cvmat() : Instance image is empty.
• _cimg2cvmat() : Invalid number of channels (should be '1'…
• _cvmat2cimg() : pixel type

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/53b1156a087967d8. Report an issue: GitHub.

Appendix: source

Thrown at ucrop/src/main/jni/CImg.h:60079

      return res;
    }

#endif

    //! Load image from a camera stream, using OpenCV.
    /**
       \param index Index of the camera to capture images from (from 0 to 63).
       \param capture_width Width of the desired image ('0' stands for default value).
       \param capture_height Height of the desired image ('0' stands for default value).
       \param skip_frames Number of frames to skip before the capture.
       \param release_camera Tells if the camera resource must be released at the end of the method.
    **/
    CImg<T>& load_camera(const unsigned int camera_index=0,
                         const unsigned int capture_width=0, const unsigned int capture_height=0,
                         const unsigned int skip_frames=0, const bool release_camera=true) {
#ifdef cimg_use_opencv
      if (camera_index>=64)
        throw CImgArgumentException(_cimg_instance
                                    "load_camera(): Invalid request for camera #%u "
                                    "(no more than 100 cameras can be managed simultaneously).",
                                    cimg_instance,
                                    camera_index);
      static cv::VideoCapture *captures[64] = {};
      static unsigned int captures_w[64], captures_h[64];
      if (release_camera) {
        cimg::mutex(9);
        if (captures[camera_index]) captures[camera_index]->release();
        delete captures[camera_index];
        captures[camera_index] = 0;
        captures_w[camera_index] = captures_h[camera_index] = 0;
        cimg::mutex(9,0);
        return *this;
      }
      if (!captures[camera_index]) {
        cimg::mutex(9);
        captures[camera_index] = new cv::VideoCapture(camera_index);

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