{"record":{"id":"ebd9adc7849b9ae2","repo":"Yalantis/uCrop","slug":"save-webp-failed-to-encode-image-to-file-s","errorCode":null,"errorMessage":"save_webp(): Failed to encode image to file '%s'.","messagePattern":"save_webp\\(\\): Failed to encode image to file '(.+?)'\\.","errorType":"exception","errorClass":"CImgIOException","httpStatus":null,"severity":"error","filePath":"ucrop/src/main/jni/CImg.h","lineNumber":61627,"sourceCode":"      uint8_t *ptr = rgbaBuffer._data;\n      cimg_forY(*this,y) {\n        cimg_forX(*this,x) {\n          *(ptr++) = (T)*(ptr_r++);\n          *(ptr++) = (T)*(ptr_g++);\n          *(ptr++) = (T)*(ptr_b++);\n          if (ptr_a) *(ptr++) = (T)*(ptr_a++);\n        }\n      }\n      uint8_t *imgData = NULL;\n      const int stride = _width*_spectrum*sizeof(uint8_t);\n      size_t size = 0;\n      if (_spectrum==3) {\n        size = WebPEncodeRGB(rgbaBuffer._data, _width, _height, stride, (float)quality, &imgData);\n      } else {\n        size = WebPEncodeRGBA(rgbaBuffer._data, _width, _height, stride, (float)quality, &imgData);\n      }\n      if (!imgData) {\n        throw CImgIOException(_cimg_instance\n                              \"save_webp(): Failed to encode image to file '%s'.\",\n                              cimg_instance,\n                              filename);\n      }\n      cimg::fwrite(imgData, size, file);\n      cimg::fclose(file);\n      WebPFree(imgData);\n      return *this;\n#endif\n    }\n\n    //! Save image as a JPEG file.\n    /**\n      \\param filename Filename, as a C-string.\n      \\param quality Image quality (in %)\n    **/\n    const CImg<T>& save_jpeg(const char *const filename, const unsigned int quality=100) const {\n      return _save_jpeg(0,filename,quality);","sourceCodeStart":61609,"sourceCodeEnd":61645,"githubUrl":"https://github.com/Yalantis/uCrop/blob/f788b534b48c144edf786c8cddbf0e029e637804/ucrop/src/main/jni/CImg.h#L61609-L61645","documentation":"After WebPEncodeRGB/WebPEncodeRGBA returns, CImg checks whether the encoder produced any data (imgData is null). A null buffer means libwebp failed to encode the image (e.g. invalid dimensions, out of memory, or unsupported pixel setup), so CImg throws CImgIOException before writing the file.","triggerScenarios":"Calling save_webp() when WebPEncodeRGB/RGBA returns size==0 and imgData==nullptr — typically from enormous width*height (memory allocation failure in libwebp) or invalid image dimensions.","commonSituations":"Saving extremely large images that exceed memory limits, images with zero width/height, or environments where the webp encoder cannot allocate the output buffer. Sometimes seen with corrupted/undimensioned image instances.","solutions":["Verify _width>0 and _height>0 before saving; a zero-dimension image cannot be encoded.","Check available memory and image size; reduce image dimensions (resize) before WebP encoding.","Lower the quality parameter is unlikely to help; instead confirm the webp build is intact and dimensions are sane, then retry or use another format (save_png)."],"exampleFix":"// before\nimg.save_webp(\"huge.webp\");\n// after\nif (img.width() == 0 || img.height() == 0) throw std::runtime_error(\"empty image\");\nCImg<float> small = img.get_resize(4096, 4096, -100, -100);\nsmall.save_webp(\"huge.webp\");","handlingStrategy":"try-catch","validationCode":"if (img.is_empty() || img.width() == 0 || img.height() == 0) {\n  throw std::runtime_error(\"cannot save empty image as webp\");\n}","typeGuard":null,"tryCatchPattern":"try {\n  img.save_webp(\"out.webp\");\n} catch (const cimg_library::CImgIOException &e) {\n  std::fprintf(stderr, \"webp encode failed: %s\\n\", e.what());\n  img.save_png(\"out.png\"); // fallback format\n}","preventionTips":["Guard against zero/degenerate dimensions before encoding.","Resize very large images down to a sane maximum before webp.","Keep a non-webp fallback path in save helpers."],"tags":["cimg","image","webp","encode-failure"],"backgroundTag":"file-write-failed","analyzedSha":"f788b534b48c144edf786c8cddbf0e029e637804","analyzedAt":"2026-09-08T08:36:04.887Z","contentChangedAt":"2026-09-08T08:36:04.887Z","schemaVersion":2},"datasetVersion":"2026-09-14T05:17:10.506Z"}