{"record":{"id":"5c70ec13f543a762","repo":"SixLabors/ImageSharp","slug":"the-ccitt-output-buffer-is-too-small-for-the-encoded-data","errorCode":null,"errorMessage":"The CCITT output buffer is too small for the encoded data.","messagePattern":"The CCITT output buffer is too small for the encoded data\\.","errorType":"exception","errorClass":"InvalidMemoryOperationException","httpStatus":null,"severity":"error","filePath":"src/ImageSharp/Formats/Tiff/Compression/Compressors/TiffCcittCompressor.cs","lineNumber":471,"sourceCode":"        {\n            // Skip padding bits, move to next byte.\n            this.bytePosition++;\n            this.bitPosition = 0;\n        }\n    }\n\n    /// <summary>\n    /// Writes a code to the output.\n    /// </summary>\n    /// <param name=\"codeLength\">The length of the code to write.</param>\n    /// <param name=\"code\">The code to be written.</param>\n    /// <param name=\"compressedData\">The destination buffer to write the code to.</param>\n    protected void WriteCode(uint codeLength, uint code, Span<byte> compressedData)\n    {\n        long availableBits = (((long)compressedData.Length - this.bytePosition) * 8) - this.bitPosition;\n        if (codeLength > availableBits)\n        {\n            throw new InvalidMemoryOperationException(\"The CCITT output buffer is too small for the encoded data.\");\n        }\n\n        while (codeLength > 0)\n        {\n            int bitNumber = (int)codeLength;\n            bool bit = (code & (1 << (bitNumber - 1))) != 0;\n            if (bit)\n            {\n                BitWriterUtils.WriteBit(compressedData, this.bytePosition, this.bitPosition);\n            }\n            else\n            {\n                BitWriterUtils.WriteZeroBit(compressedData, this.bytePosition, this.bitPosition);\n            }\n\n            this.bitPosition++;\n            if (this.bitPosition == 8)\n            {","sourceCodeStart":453,"sourceCodeEnd":489,"githubUrl":"https://github.com/SixLabors/ImageSharp/blob/59ce6af6fc29027cda277ef62d4d1694a8acce91/src/ImageSharp/Formats/Tiff/Compression/Compressors/TiffCcittCompressor.cs#L453-L489","documentation":"The CCITT (T4/T6) TIFF compressor bit-writes encoded runs into a caller-provided destination span. Before writing each Huffman code, WriteCode computes the remaining free bits ((buffer length - bytePosition) * 8 - bitPosition); if the code does not fit, it throws InvalidMemoryOperationException. This is an internal capacity guard: the compressed output would overflow the estimated buffer.","triggerScenarios":"Encoding a TIFF row/strip with CCITT G3/G4 compression where the compressor's pre-allocated compressedData span is smaller than the actual encoded bitstream for that strip — e.g. very wide rows with many short white runs producing more code bits than the allocated bytes*8.","commonSituations":"Encoding black-and-white ( bilevel ) images with TiffCompression.CcittGroup3/4 where row width or strip sizing assumptions in the encoder under-estimate encoded size; custom code calling the compressor internals with a hand-sized buffer.","solutions":["Ensure the image is saved as bilevel (1-bit) or grayscale as expected; CCITT encoding of unexpected pixel data can produce larger codes — convert to a supported pixel type before saving.","Report/upgrade: this indicates an internal buffer-sizing bug in the CCITT compressor; check for a newer ImageSharp version with a fix.","As a workaround, save with TiffCompression.None or Deflate/Lzw instead of CCITT."],"exampleFix":"// before\nimage.Save(path, new TiffEncoder { Compression = TiffCompression.CcittGroup4 });\n// after\n// convert to bilevel-compatible pixel type or use a non-CCITT compression\nimage.Save(path, new TiffEncoder { Compression = TiffCompression.Deflate });","handlingStrategy":"try-catch","validationCode":"if (image.PixelType.PixelTypeInformation?.BitsPerPixel > 8)\n    throw new InvalidOperationException(\"CCITT requires bilevel-compatible input\");","typeGuard":null,"tryCatchPattern":"try\n{\n    image.Save(path, new TiffEncoder { Compression = TiffCompression.CcittGroup4 });\n}\ncatch (InvalidMemoryOperationException ex)\n{\n    // fall back to a non-CCITT compression\n    image.Save(path, new TiffEncoder { Compression = TiffCompression.Deflate });\n}","preventionTips":["Only use CCITT for true bilevel images (1-bit or black-and-white content)","Prefer Deflate/LZW when in doubt","Keep ImageSharp updated — internal sizing bugs get fixed upstream"],"tags":["tiff","ccitt","encoding","buffer-size"],"backgroundTag":"buffer-size-limit-exceeded","analyzedSha":"59ce6af6fc29027cda277ef62d4d1694a8acce91","analyzedAt":"2026-09-13T18:34:59.331Z","contentChangedAt":"2026-09-13T18:34:59.331Z","schemaVersion":2},"datasetVersion":"2026-09-16T04:17:20.429Z"}