Yalantis/uCrop · error · CImgArgumentException

[cimg_appname_math_parser] CImg<%s>::%s: %s: Colormap size (

Error message

[cimg_appname_math_parser] CImg<%s>::%s: %s: Colormap size (%lu values) and specified dimension of colormap entries (%u) do not match.

What it means

Math-parser palette/colormap application functions take a colormap vector and the per-entry dimension (number of values per color entry, e.g. 3 for RGB). The colormap size must be an exact multiple of that dimension; p2 (colormap size) must satisfy p2 == (p2/arg3)*arg3. Otherwise CImg throws this error reporting the actual size and requested dimension.

Source

Thrown at ucrop/src/main/jni/CImg.h:22124

              arg4 = arg5 = 0;
              if (s1<se1) {
                s2 = ++s1; while (s2<se1 && (*s2!=',' || level[s2 - expr._data]!=clevel1)) ++s2;
                arg4 = compile(s1,s2,depth1,0,block_flags);
                arg5 = s2<se1?compile(++s2,se1,depth1,0,block_flags):0;
              }
              _cimg_mp_check_type(arg1,1,2,0);
              _cimg_mp_check_type(arg2,2,2,0);
              _cimg_mp_check_const_scalar(arg3,3,3);
              _cimg_mp_check_type(arg4,4,1,0);
              _cimg_mp_check_const_scalar(arg5,5,2);
              p1 = size(arg1);
              p2 = size(arg2);
              arg3 = (unsigned int)mem[arg3];
              arg5 = (unsigned int)mem[arg5];
              p3 = p2/arg3; // Number of color entries
              if (p2!=p3*arg3) {
                _cimg_mp_strerr;
                throw CImgArgumentException("[" cimg_appname "_math_parser] "
                                            "CImg<%s>::%s: %s: Colormap size (%lu values) and specified "
                                            "dimension of colormap entries (%u) do not match.",
                                            pixel_type(),_cimg_mp_calling_function,s_op,
                                            std::max(p2,1U),arg3);
              }
              if (p1%arg3) {
                _cimg_mp_strerr;
                throw CImgArgumentException("[" cimg_appname "_math_parser] "
                                            "CImg<%s>::%s: %s: Input vector size (%lu values) and specified "
                                            "dimension of colormap entries (%u) do not match.",
                                            pixel_type(),_cimg_mp_calling_function,s_op,
                                            std::max(p1,1U),arg3);
              }
              pos = vector(arg5?p1:p1/arg3);
              CImg<ulongT>::vector((ulongT)mp_index,pos,arg1,p1,arg2,p2,arg3,arg4,arg5).move_to(code);
              return_comp = true;
              _cimg_mp_return(pos);
            }

View on GitHub (pinned to f788b534b4)

Solutions

  1. Make the colormap length an exact multiple of the entries dimension (pad or truncate values)
  2. Pass the correct dimension argument (3 for RGB, 4 for RGBA) matching the colormap layout
  3. Validate `colormap.size() % dim == 0` in code before invoking the expression
  4. Build colormaps via CImg API helpers that enforce the layout instead of manual vectors

Example fix

// before
img.fill("apply([0,0,0, 255,255,255, 128,128], 3, ...)"); // 9 not divisible by 3? actually 10 values
// after
img.fill("apply([0,0,0, 255,255,255, 128,128,128], 3, ...)"); // 9 values / dim 3
Defensive patterns

Strategy: validation

Validate before calling

void checkColormap(double[] cmap, int dim) {
  if (cmap.length % dim != 0)
    throw new IllegalArgumentException("Colormap size " + cmap.length + " not a multiple of dim " + dim);
}

Try / catch

try { img.fill(expr); } catch (CImgArgumentException e) { if (e.getMessage().contains("Colormap size") && e.getMessage().contains("do not match")) { /* fix cmap layout or dim and retry */ } throw e; }

Prevention

When it happens

Trigger: Calling a colormap-based expression function (e.g. palette lookup / `apply_palette` style ops) with a colormap vector whose length is not divisible by the given nb_entries/dimension argument, e.g. a 10-value colormap with dimension 3.

Common situations: Hand-built colormaps with a trailing or missing channel value; mixing RGBA colormaps (dim 4) with RGB code expecting dim 3; passing image pixel buffers instead of packed colormap vectors.

Related errors

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/7b867f016831400f. Report an issue: GitHub.