gchq/CyberChef · error · OperationError

Invalid file type.

Error message

Invalid file type.

What it means

Thrown by NormaliseImage.run when isImage(input) returns false — the input ArrayBuffer's magic bytes do not match any recognised image signature (png, jpg, gif, bmp, etc.). The operation only colour-normalises images, so non-image data is rejected before invoking Jimp.

Source

Thrown at src/core/operations/NormaliseImage.mjs:40

        this.name = "Normalise Image";
        this.module = "Image";
        this.description = "Normalise the image colours.";
        this.infoURL = "";
        this.inputType = "ArrayBuffer";
        this.outputType = "ArrayBuffer";
        this.presentType = "html";
        this.args = [];
    }

    /**
     * @param {ArrayBuffer} input
     * @param {Object[]} args
     * @returns {byteArray}
     */
    async run(input, args) {
        if (!isImage(input)) {
            throw new OperationError("Invalid file type.");
        }

        let image;
        try {
            image = await Jimp.read(input);
        } catch (err) {
            throw new OperationError(`Error opening image file. (${err})`);
        }

        try {
            image.normalize();

            let imageBuffer;
            if (image.mime === "image/gif") {
                imageBuffer = await image.getBuffer(JimpMime.png);
            } else {
                imageBuffer = await image.getBuffer(image.mime);
            }

View on GitHub (pinned to 4290ea7539)

Solutions

1. Feed an actual image file (PNG/JPG/GIF/BMP) as an ArrayBuffer.
2. Ensure the upstream operation outputs ArrayBuffer (e.g. use 'From Hex' or 'From Base64' before this op).
3. Verify the file is not truncated or zero-length.

Example fix

// before: feeding a string
chef.bake("Normalise Image", [], "not an image");
// after: feed decoded image bytes
chef.bake("Normalise Image", [], imageArrayBuffer);

import { isImage } from "core/lib/FileType.mjs";
if (!isImage(input)) {
  // do not call Normalise Image; provide a real image ArrayBuffer
}

const isImageBuffer = (buf) => Boolean(isImage(buf));

try { await chef.bake("Normalise Image", [], input); }
catch (e) { if (e.message === "Invalid file type.") provideImage(); else throw e; }

When it happens

Trigger: run(input, args) with an ArrayBuffer whose header bytes are not a known image magic number. Feeding text, a PDF, a zip, a truncated image, or an empty buffer all produce this.

Common situations: Wrong file dropped into the input; image with a missing/corrupted header; upstream operation outputs a byteArray or string rather than an ArrayBuffer; empty buffer from a failed fetch; file with the wrong extension but actually a different format.

Related errors

• Invalid file type.
• Invalid file type.
• Invalid file type.
• Unsupported file type (supported: jpg,png,pbm,bmp) or no fil
• Invalid file type.

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/61fd6d2bc4393263. Report an issue: GitHub.