gchq/CyberChef · error · OperationError

Error converting image format. (${err})

Error message

Error converting image format. (${err})

What it means

Convert Image Format's transcode step calls image.getBuffer(mime, options) for the selected target format (with jpeg quality, PNG filter/deflate settings, or defaults). Any encode failure is caught and re-thrown as 'Error converting image format.' Causes include an unsupported target format, out-of-range encoder options, or source content the target codec cannot represent.

Source

Thrown at src/core/operations/ConvertImageFormat.mjs:114

                case JimpMime.jpeg:
                    buffer = await image.getBuffer(mime, {
                        quality: jpegQuality,
                    });
                    break;
                case JimpMime.png:
                    buffer = await image.getBuffer(mime, {
                        filterType: pngFilterMap[pngFilterType],
                        deflateLevel: pngDeflateLevel,
                    });
                    break;
                default:
                    buffer = await image.getBuffer(mime);
                    break;
            }

            return buffer.buffer;
        } catch (err) {
            throw new OperationError(`Error converting image format. (${err})`);
        }
    }

    /**
     * Displays the converted image using HTML for web apps
     *
     * @param {ArrayBuffer} data
     * @returns {html}
     */
    present(data) {
        if (!data.byteLength) return "";
        const dataArray = new Uint8Array(data);

        const type = isImage(dataArray);
        if (!type) {
            throw new OperationError("Invalid file type.");
        }

View on GitHub (pinned to 4290ea7539)

Solutions

1. Choose a well-supported target format (PNG or JPEG).
2. Keep jpegQuality within 1–100 and PNG deflate/filter at defaults unless you know the valid ranges.
3. If conversion fails, fall back to PNG (lossless, broad support) and retry.
4. Check the bundled Jimp version supports the chosen output codec.

Example fix

// before: jpegQuality passed as 0 or >100
const args = [..., 0, ...];
// after
const args = [..., 85, ...]; // valid JPEG quality

function validEncodeArgs(format, jpegQuality, pngDeflateLevel) {
  if (!format) return false;
  if (format === "JPEG" && !(jpegQuality >= 1 && jpegQuality <= 100)) return false;
  if (format === "PNG" && !(Number.isInteger(pngDeflateLevel) && pngDeflateLevel >= 0 && pngDeflateLevel <= 9)) return false;
  return true;
}
if (!validEncodeArgs(format, jpegQuality, pngDeflateLevel)) {
  throw new Error("Invalid encoder arguments for target format.");
}

function isJpegQuality(v) {
  return typeof v === "number" && v >= 1 && v <= 100;
}

try {
  result = await convertImageFormat.run(input, args);
} catch (err) {
  if (/Error converting image format/.test(err.message)) {
    // Encode failed: try PNG with defaults as a broadly-supported fallback.
  }
  throw err;
}

When it happens

Trigger: Target format not supported by the bundled Jimp; jpegQuality outside 1–100; PNG deflateLevel/filterType invalid; encoding a source (e.g. with alpha) into a format that can't represent it; CMYK source into JPEG.

Common situations: Misconfigured encoder arguments; Jimp version differences in codec support; edge-case source images.

Related errors

• Invalid file type.
• Error loading image. (${err})
• Error containing image. (${err})
• Invalid file format.
• Error opening image file. (${err})

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/7fa43d1ad519a555. Report an issue: GitHub.