decode_qrcode_data_url

Extract text from QR codes encoded as base64 data URLs. This tool processes image data URLs to decode and retrieve the embedded information.

Instructions

Decode a QR code from a data URL (data:;base64,...)

Input Schema

TableJSON Schema

Name	Required	Description	Default
`imageDataUrl`	Yes	Image data URL (base64) of the QR image.

Implementation Reference

src/services/qrcode-service.ts:38-41 (handler)

Specific handler for decoding QR code from data URL: parses the base64 data and calls buffer decoder.

export async function decodeQrFromDataUrl(dataUrl: string): Promise<DecodeResult> {
  const { buffer } = parseBase64DataUrl(dataUrl);
  return decodeQrFromBuffer(buffer);
}

src/services/qrcode-service.ts:16-33 (handler)

Core implementation: loads image buffer with Jimp, prepares data for jsQR, detects and extracts QR text.

export async function decodeQrFromBuffer(buffer: Buffer): Promise<DecodeResult> {
  const image = await Jimp.read(buffer);
  const { data, width, height } = image.bitmap;

  // Jimp gives a Node Buffer; jsQR expects a Uint8ClampedArray in RGBA order (same layout as Canvas ImageData).
  const clamped = new Uint8ClampedArray(data.buffer, data.byteOffset, data.byteLength);
  const qr = (
    jsQR as unknown as (
      data: Uint8ClampedArray,
      width: number,
      height: number,
    ) => { data: string } | null
  )(clamped, width, height);
  if (!qr) {
    throw new Error('No QR code detected in image');
  }
  return { text: qr.data };
}

src/utils/data-url.ts:6-14 (helper)

Supporting utility to parse data URL and extract the base64 buffer.

export function parseBase64DataUrl(dataUrl: string): { mime: string; buffer: Buffer } {
  const match = /^data:([^;]+);base64,(.+)$/i.exec(dataUrl);
  if (!match) {
    throw new Error('Invalid data URL. Expected format: data:<mime>;base64,<data>');
  }
  const [, mime, data] = match;
  const buffer = Buffer.from(data, 'base64');
  return { mime, buffer };
}

src/server.ts:29-43 (registration)

Tool registration in ListToolsResult: defines name, description, and input schema.

{
  name: 'decode_qrcode_data_url',
  description: 'Decode a QR code from a data URL (data:<mime>;base64,...)',
  inputSchema: {
    type: 'object',
    required: ['imageDataUrl'],
    properties: {
      imageDataUrl: {
        type: 'string',
        description: 'Image data URL (base64) of the QR image.',
      },
    },
    additionalProperties: false,
  },
},

src/server.ts:64-70 (handler)

MCP server CallToolRequest handler: input validation and invocation of service implementation.

if (name === 'decode_qrcode_data_url') {
  if (!args.imageDataUrl || typeof args.imageDataUrl !== 'string') {
    throw new Error('Missing required argument: imageDataUrl');
  }
  const result = await decodeQr({ imageDataUrl: args.imageDataUrl });
  return { content: [{ type: 'text', text: result.text }] };
}

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