BBQr — QR Code Encoding¶

Animated QR code encoding and decoding for transmitting large data (PSBTs, transactions) via QR codes.

Import: package:bull_sdk/bbqr.dart

Overview¶

BBQr splits large binary data into multiple QR frames that can be animated on screen. The receiver collects all frames and reconstructs the original data.

Use cases:

Transmitting PSBTs between air-gapped devices
Sharing transaction data visually
Any large payload that needs QR-based transfer

Encoding¶

Split Data into QR Frames¶

final parts = await bbqr.split(
  data: yourBytes,
  encoding: bbqr.Encoding.zlib,  // best compression
  fileType: bbqr.FileType.psbt,
);

Encoding Options¶

Encoding	Description
`hex`	Hexadecimal encoding
`base32`	Base32 encoding
`zlib`	Zlib compression (recommended — smallest QR codes)

File Types¶

Type	Use case
`psbt`	Partially Signed Bitcoin Transaction
`transaction`	Signed transaction
`other`	Generic binary data

Decoding¶

Join QR Frames¶

final data = await bbqr.join(parts: collectedParts);

Continuous Join (Streaming)¶

For real-time QR scanning where frames arrive one at a time:

final joiner = bbqr.ContinuousJoin();

// As each QR frame is scanned
joiner.addFrame(frame: qrData);

// Check if complete
if (joiner.isComplete) {
  final data = joiner.finish();
}

QR Generation¶

// Generate a QR code image for a single frame
final qrImage = await bbqr.generateQr(
  data: parts[0],
  size: 300,
);

Gotchas¶

Order matters: Frames must be joined in the correct order. BBQr includes sequence numbers in the data.
Encoding choice: Use zlib for smallest QR codes. Use hex if the receiver doesn't support zlib.
Frame count: More data = more frames. Keep individual frames under 100 bytes for reliable scanning.
Error correction: QR codes have built-in error correction, but damaged frames may still fail.