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brother-ql

brother-ql / node/src / BrotherQLPrinter

Class: BrotherQLPrinter ​

Node.js driver for Brother QL label printers.

Implements PrinterAdapter. Callers get a printer instance from discovery.openPrinter() (USB or TCP) and interact solely through the adapter surface: print(rgba, media?, options?), createPreview, getStatus, close.

Multi-ink media (DK-22251) is handled transparently — when the resolved media carries a palette, the driver runs the bitmap library's renderMultiPlaneImage() internally before encoding.

Orientation is auto-decided via pickRotation: landscape input on media tagged defaultOrientation: 'horizontal' rotates 90° CW so the visual reads along the tape feed direction. Override per-call with options.rotate.

Implements ​

Constructors ​

Constructor ​

new BrotherQLPrinter(device, transport, transportType): BrotherQLPrinter

Parameters ​

device ​

DeviceEntry

transport ​

Transport

transportType ​

TransportType

Returns ​

BrotherQLPrinter

Properties ​

device ​

readonly device: DeviceEntry

The device entry for the connected printer.

Useful for logging, diagnostics, and displaying VID/PID. Undefined if the connection was established without device matching (e.g. a raw TCP connection to a known IP).

Implementation of ​

PrinterAdapter.device

family ​

readonly family: "brother-ql"

Driver family identifier, e.g. 'brother-ql' or 'labelwriter'.

Implementation of ​

PrinterAdapter.family

transportType ​

readonly transportType: TransportType

Accessors ​

connected ​

Get Signature ​

get connected(): boolean

Whether the printer is currently connected.

Returns ​

boolean

Implementation of ​

PrinterAdapter.connected

model ​

Get Signature ​

get model(): string

Human-readable model name from the driver's device registry.

Returns ​

string

Implementation of ​

PrinterAdapter.model

Methods ​

close() ​

close(): Promise<void>

Close the connection. Always call in finally blocks.

Returns ​

Promise<void>

Implementation of ​

PrinterAdapter.close

createPreview() ​

createPreview(image, options?): Promise<PreviewResult>

Generate a preview showing how this printer would reproduce the design on the given media. Returns separated 1bpp planes with display colours.

The driver uses its own colour-splitting logic (the same code that print() uses internally) to produce the planes. The consuming app renders whatever planes come back without needing to know the splitting rules.

For offline preview without a live connection, use the static createPreviewOffline() function exported from the driver's *-core package instead.

Parameters ​

image ​

RawImageData

— full RGBA, typically from designer.render().

options? ​

PreviewOptions

— optional media override. If media is omitted, uses detected media from the last getStatus(). If no status is available, the driver defaults to single-colour at the printer's native head width and sets PreviewResult.assumed = true.

Returns ​

Promise<PreviewResult>

Implementation of ​

PrinterAdapter.createPreview

getStatus() ​

getStatus(): Promise<PrinterStatus>

Poll the status endpoint until 32 bytes are available.

The USB transferAsync() call resolves immediately with 0 bytes if the printer hasn't queued a response yet, so retry with a short delay up to STATUS_POLL_ATTEMPTS times.

Returns ​

Promise<PrinterStatus>

Implementation of ​

PrinterAdapter.getStatus

print() ​

print(image, media?, options?): Promise<void>

Print from a full-colour RGBA image.

The driver converts to its native format internally:

  • Single-colour media (media.palette undefined) — threshold/dither RGBA to a single 1bpp plane via renderImage.
  • Multi-ink media (media.palette defined) — split into planes via renderMultiPlaneImage using that palette.

Orientation: drivers compute the rotation via pickRotation (see ./orientation.ts) — the input image is treated as the intended visual; the driver auto-rotates landscape input on media tagged defaultOrientation: 'horizontal'.

Multi-ink splitting: the palette on the media descriptor names every ink the driver should classify pixels into; the contracts package does not pick "red" or "black" — those facts live with the media entry.

Batch printing: call print() once per label. The driver handles job framing internally (e.g. Brother QL page-break commands between sequential print() calls within the same session).

Parameters ​

image ​

RawImageData

— full RGBA, typically from designer.render().

media? ​

MediaDescriptor

— which media to print on. Determines dimensions, margins, and colour mode. If omitted, uses detected media from the last getStatus().

options? ​

BrotherQLPrintOptions

— per-call options (copies, density, etc.).

Returns ​

Promise<void>

Throws ​

MediaNotSpecifiedError if no media is known.

Implementation of ​

PrinterAdapter.print