Yalantis/uCrop · error · CImgArgumentException

draw_triangle(): Invalid specified light texture (%u,%u,%u,%

Error message

draw_triangle(): Invalid specified light texture (%u,%u,%u,%u,%p).

What it means

draw_triangle() (2D variant) supports a `light` texture argument used for gouraud/textured shading. If the light image has depth > 1 (it is a volume, not a 2D texture) or fewer channels than the drawing image's spectrum, the texture cannot be sampled per-pixel, so CImg throws CImgArgumentException with the light image's dimensions for diagnosis.

Source

Thrown at ucrop/src/main/jni/CImg.h:51359

       \param opacity Drawing opacity.
    **/
    template<typename tc, typename tl>
    CImg<T>& draw_triangle(int x0, int y0,
                           int x1, int y1,
                           int x2, int y2,
                           const tc *const color,
                           const CImg<tl>& light,
                           int lx0, int ly0,
                           int lx1, int ly1,
                           int lx2, int ly2,
                           const float opacity=1) {
      if (is_empty()) return *this;
      if (!color)
        throw CImgArgumentException(_cimg_instance
                                    "draw_triangle(): Specified color is (null).",
                                    cimg_instance);
      if (light._depth>1 || light._spectrum<_spectrum)
        throw CImgArgumentException(_cimg_instance
                                    "draw_triangle(): Invalid specified light texture (%u,%u,%u,%u,%p).",
                                    cimg_instance,light._width,light._height,light._depth,light._spectrum,light._data);

      if (y0>y1) cimg::swap(x0,x1,y0,y1,lx0,lx1,ly0,ly1);
      if (y0>y2) cimg::swap(x0,x2,y0,y2,lx0,lx2,ly0,ly2);
      if (y1>y2) cimg::swap(x1,x2,y1,y2,lx1,lx2,ly1,ly2);
      if (y2<0 || y0>=height() || cimg::min(x0,x1,x2)>=width() || cimg::max(x0,x1,x2)<0 || !opacity) return *this;

      const int w1 = width() - 1, h1 = height() - 1, cy0 = cimg::cut(y0,0,h1), cy2 = cimg::cut(y2,0,h1);
      const longT
        dx01 = (longT)x1 - x0, dx02 = (longT)x2 - x0, dx12 = (longT)x2 - x1,
        dy01 = std::max((longT)1,(longT)y1 - y0),
        dy02 = std::max((longT)1,(longT)y2 - y0),
        dy12 = std::max((longT)1,(longT)y2 - y1),
        hdy01 = dy01/2, hdy02 = dy02/2, hdy12 = dy12/2,
        dlx01 = (longT)lx1 - lx0, dlx02 = (longT)lx2 - lx0, dlx12 = (longT)lx2 - lx1,
        dly01 = (longT)ly1 - ly0, dly02 = (longT)ly2 - ly0, dly12 = (longT)ly2 - ly1;
      const ulongT lwhd = (ulongT)light._width*light._height*light._depth;

View on GitHub (pinned to f788b534b4)

Solutions

Provide a 2D light image (depth == 1) whose spectrum() is >= the target image's spectrum()
Convert the light texture first: light.get_resize(w,h,1,spectrum()) or get_channel(0) expanded to the right channel count
If shading is not needed, omit the light texture (use the overload without light) instead of passing an unsuitable image
Log light._width/_height/_depth/_spectrum (as printed in the message) and fix the mismatch

Example fix

// before
draw_triangle(x0,y0,x1,y1,x2,y2,color,0,0,0,0,0,0,grayLight); // grayLight spectrum=1, image spectrum=3
// after
CImg<T> light = grayLight.get_resize(grayLight.width(),grayLight.height(),1,3);
draw_triangle(x0,y0,x1,y1,x2,y2,color,0,0,0,0,0,0,light);

Defensive patterns

Strategy: validation

Validate before calling

if (!light || light.depth() > 1 || light.spectrum() < image.spectrum())
  light.assign(light.width(),light.height(),1,image.spectrum()); // normalize
image.draw_triangle(x0,y0,x1,y1,x2,y2,color,lx0,ly0,lx1,ly1,lx2,ly2,light,opacity);

Type guard

bool validLight = (light.depth() == 1 && light.spectrum() >= image.spectrum());

Try / catch

try { image.draw_triangle(...,light); }
catch (cimg_library::CImgArgumentException &e) { log_error("light texture invalid: %s", e.what()); }

Prevention

Keep all light textures as single-channel or target-spectrum 2D images by convention
Normalize textures (resize to depth 1, matching spectrum) at load time, not at draw time
Print image.spectrum() and light.spectrum() in debug logs when wiring up textured draws
Avoid passing z-buffers or volumes as light textures

When it happens

Trigger: Calling draw_triangle(x0,y0,x1,y1,x2,y2,color,lx0..ly2,light,...) where `light` is a 3D (depth>1) image, or light.spectrum() < image.spectrum() (e.g. a grayscale light texture on an RGB image).

Common situations: Passing a volumetric image as the light map; reusing a light texture from a grayscale pipeline in a color (spectrum=3) draw; mixing images loaded with different channel counts.

Understand the failure class

Background: Tensor shape mismatch errors ("must have shape", "expected shape ... got ..."): when tensor dimensions disagree with what an op or layer was told to expect — this error's family across 6 libraries.

Related errors

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/a2654b2d3382b190. Report an issue: GitHub.