Yalantis/uCrop · error · CImgArgumentException

draw_point(): Invalid specified point set (%u,%u,%u,%u,%p).

Error message

draw_point(): Invalid specified point set (%u,%u,%u,%u,%p).

What it means

CImg's draw_point(const CImg<t>& points, ...) overload draws multiple points from an image whose rows are point coordinates (2 or 3 values per point). The library requires points._height (the per-point coordinate count) to be at least 2; if the point-set image is empty (_height==0) or has only one row (_height==1), it cannot extract (x,y) per point and throws CImgArgumentException.

Source

Thrown at ucrop/src/main/jni/CImg.h:49881

    template<typename tc>
    CImg<T>& draw_point(const int x0, const int y0,
                        const tc *const color, const float opacity=1) {
      return draw_point(x0,y0,0,color,opacity);
    }

    // Draw a points cloud.
    /**
       \param points Image of vertices coordinates.
       \param color Pointer to \c spectrum() consecutive values, defining the drawing color.
       \param opacity Drawing opacity.
    **/
    template<typename t, typename tc>
    CImg<T>& draw_point(const CImg<t>& points,
                        const tc *const color, const float opacity=1) {
      if (is_empty() || !points) return *this;
      switch (points._height) {
      case 0 : case 1 :
        throw CImgArgumentException(_cimg_instance
                                    "draw_point(): Invalid specified point set (%u,%u,%u,%u,%p).",
                                    cimg_instance,
                                    points._width,points._height,points._depth,points._spectrum,points._data);
      case 2 : {
        cimg_forX(points,i) draw_point((int)points(i,0),(int)points(i,1),color,opacity);
      } break;
      default : {
        cimg_forX(points,i) draw_point((int)points(i,0),(int)points(i,1),(int)points(i,2),color,opacity);
      }
      }
      return *this;
    }

    //! Draw a 2D line.
    /**
       \param x0 X-coordinate of the starting line point.
       \param y0 Y-coordinate of the starting line point.
       \param x1 X-coordinate of the ending line point.

View on GitHub (pinned to f788b534b4)

Solutions

  1. Ensure the points image has _height>=2: use CImg<int> pts(nb_points,2) (or 3 with z) and fill pts(i,0)=x, pts(i,1)=y.
  2. Check the points image is non-empty before calling: if (points && points._height>=2) img.draw_point(...).
  3. If drawing a single point, use the scalar overload draw_point(x,y,color) instead of the point-set overload.
  4. For a point at a given index use the vector overload draw_point(x,y,z,color) rather than passing a 1-row image.

Example fix

// before
CImg<int> points(1,1); // height 1 -> throws
img.draw_point(points,color);

// after
CImg<int> points(1,2);
points(0,0)=10; points(0,1)=20;
img.draw_point(points,color);
Defensive patterns

Strategy: validation

Validate before calling

bool validPointSet(const CImg<int>& pts) {
  return pts && pts._height >= 2;
}
if (validPointSet(points)) img.draw_point(points, color);

Type guard

template<typename t>
bool is_valid_point_set(const CImg<t>& p) {
  return !p.is_empty() && p._height >= 2;
}

Try / catch

try {
  img.draw_point(points, color);
} catch (CImgArgumentException& e) {
  std::fprintf(stderr, "invalid point set: %s\n", e.what());
}

Prevention

When it happens

Trigger: Calling draw_point(CImg points, color) where the points image has _height==0 or _height==1, e.g. constructed with CImg<> pts(w,0) / (w,1), or a default-constructed empty CImg passed as the point set. Also fires on an unassigned points image (guard `!points` passes only when _data is non-null, but height can still be 0/1).

Common situations: Building the point list with wrong dimension order (CImg is column-major with x=point index, y=coordinates, so CImg<>(n,1) instead of CImg<>(1,n) style mistakes); an empty points image after failed population; copying API examples where points are (x,y) pairs but constructing with height 1.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/46a5f8b052a2163b. Report an issue: GitHub.