Printer Driver Collection User Manuals

The Printer Driver Collection comes with support for some printers. Their usage is described in the following vendor specific manuals.

Content

• Samsung ML Series
  • ML-Series User Manual
• Brother HL Series
  • HL-Series Label Printers User Manual
• Brother QL Series
  • QL-Series Label Printers User Manual

In Detail

Samsung ML-Series Monochrome Laser Printers

This printer driver supports various devices from the Samsung ML series of monochrome laser printers. These devices are so called GDI printers. They accept already rasterized grapics only (like many other printers, too). Thus, the printer driver must do most of the job to prepare a document to be printable.

Note

These printers (or their bussiness) are now part of HP.

Supported are these ML printers, as long as they "understand" the SPL2 language. SPL is the acronym for "Samsung Printer Language" and there was a version 1 as well (e.g. SPL1). That's why the language for these printers is called SPL2 and isn't compatible with the SPL1.

Known ML-Series printer models

Printer	Resolution	Duplex	Trays	Man. Feed	tested
ML1630
ML1640	600/1200		1		X
ML2010
ML2015
ML2240	600/1200		1	X
ML2510

Untested other Laser Printers

Theoretical some other Samsung printers accept the same SPL2 language and this printer driver can support them. Due to the absence of these printers, its untested yet. These printers are:

• ML1630
• ML2010
• ML2015
• ML2240
• ML2510

If you have such a printer, please test it and report if it works for you.

ML-Series Laser Printers User Manual

Overview

• INI file set used by printer drivers
• Paper Jam Recovery
• ECO setting
• Power Save Time Setting
• Altitude setting
• Parallel Processing
• Default Resolution

Overwriting driver's/device's settings

All driver settings can be individually overwritten on a per printer device base via its Device Parameter INI file.

The full settings search order is:

• Printer device's Device Parameter INI file (usually /var/lib/caps/<somedir>/\*)
• Printer driver's Driver Feature Configuration INI file (usually /etc/caps/drivers/samsung-spl2-driver.init)
• Printer drivers default INI file (usually /etc/caps/drivers/capsdriver.ini)
• Printer driver's Device Description INI file (usually /usr/share/caps/drivers)

For the default medium format libpaper is also used as a settings source if not otherwise defined.

Printer Driver Configuration

The following list shows the INI files read-in by the QPDL/SPL2 printer drivers. Some of the shown INI files use generic names, see below.

INI File name	Meaning	Expected Location
caps.ini	Shared initialization	CAPS Configuration Directory
capsdriver.ini	Shared class initialization	CAPS Printer Driver Configuration Directory
devicedriver.ini (see note)	Device Description	CAPS Printer Driver Database Directory
feature.ini (see note)	Driver Feature Configuration	optional, CAPS Printer Driver Configuration Directory
parameter.ini (see note)	Printing Device Parameters	CAPS Printer Device Parameter Directory

Note

The devicedriver.ini is only an example name for a Device Description INI file. Its real name correlates with the printing device.

The feature.ini is only an example name for a Driver Feature Configuration INI file. It is defined in the devicedriver.ini and is optional.

The parameter.ini is only an example for one of the Printing Device Parameters INI files. All INI files from the physical printing device's directory are read-in.

For the caps-samsung-spl2 printer driver the mentioned feature INI file is

• samsung-spl2-driver.ini

The mentioned parameter INI file is always device dependend.

Note

The following configuration parameters get their default values in the mentioned feature INI files shown above. You can change their values in one of these feature INI files (e.g. "once for all" ) or individually in the device's specific parameter INI files (refer the capsprndir tool for the location of these parameter INI files in their CAPS Printer Device Parameter Directory).

Paper Type

It seems the printer adapts its own physical printing parameters depending on the paper type. Thus, a paper type can be defined to use this feature.

Section	Variable
paper	type

Values:

• None: This setting uses some printer internal defaults
• Normal: Ordinary white copy paper (75 g … 90 g per m²)
• Thick: Thick paper (90 g … 105 g per m²)
• Thin: Thin paper (60 g … 70 g per m²)
• Bond: Bonded paper (rag pulp kind of paper)
• OHP: Overhead Foil
• Card: Card (FIXME)
• Label: Label
• Used: Recycled paper (maybe pre-printed is meant instead)
• Color: Ordinary coloured paper (75 g … 90 g per m²)
• Env: Envelope

Note

This is a fixed setting and the user cannot change it when printing.
If the paper type isn't set, a selection list is generated instead and the default_type setting instead comes into play (see below).

Default Paper Type

Section	Variable
paper	default_type

If type (see above) isn't set, the default_type defines the default type in the generated PPD section. Accepted values are the same as for the type variable.

Note

This is a weak fixed setting. The user can change it when printing.

Loaded Medium Format

Defines the expected medium format in the printer's single medium tray.

Section	Variable
paper	format

Accepted are all values the libpaper can handle.

A list of supported format names can be retrieved via the command paperconf :

$ paperconf -a
a4
letter
note
legal
executive
halfletter
halfexecutive
11x17
statement
folio
quarto
10x14
ledger
tabloid
[…]

Refer man paperconf for more details.

This setting is optional. If not set here, a more generic setting is used instead. One source of a generic setting can be the CAPS wide setting in the base driver's INI file, e.g. capsdriver.ini, usually installed to /etc/caps/drivers.

If the base driver's INI file doesn't set the medium format, a second source can be the system wide setting from libpaper. Refer man paperconf how to setup a default system wide medium format.

Paper Jam Recovery

If the printer device is in trouble with its paper way, the printer driver can wait until the issue is solved by the user or can discard the job in this case.

Section	Variable
features	jam_recovery

Values:

• false: If a paper jam happens, the current job gets discarded
• true: If a paper jam happens, the current page gets printed again automatically after recovery

Note

If jam_recovery isn't set it defaults to true

ECO setting

Section	Variable
features	eco

Values:

• Default: Use printer's built-in setting (whatever this means)
• Off: Switch off the ECO mode, by defining this as the default in the PPD
• On: Switch on the ECO mode, by defining this as the default in the PPD

Due to this setting selects the default in the PPD, the user still can change it on a per print base.

Note

If eco isn't set it defaults to Default

Altitude setting

Define altitude when printing.

Section	Variable
features	altitude

Values:

• Low: Operating below 1000 m
• High: Operating above 1000 m

From some internet source:

‍The higher the altitude, the more printing problems you may encounter, including ghost images appearing on documents, loose toner appearing on one or more documents, and the print on all documents appearing light. Certain laser printers include a High Altitude Correction component that eliminates the problems associated with operating a printer in a high altitude location.

Note

If altitude isn't set, it defaults to Low

Default Resolution

Defines the default print resolution in the PPD.

Section	Variable
features	resolution

Values:

• 3: 300 DPI horizontally and vertically
• 6: 600 DPI horizontally and vertically
• 12: 1200 DPI horizontally x 600 DPI vertically

Since it only defines the default, it can be changed on a per print base by the user.

Note

If resolution isn't set, it defaults to the lowest available resoultion the printer device is capable.

The selectable resolutions are printer type dependend.

Power Save Time Setting

Define the time to switch into power save after printing, e.g. when idling.

Section	Variable
features	power_save_time

Values:

• Off: No power saving at all
• 5: 5 Minutes
• 10: 10 Minutes
• 15: 15 Minutes
• 30: 30 Minutes
• 45: 45 Minutes
• 60: One hour

The printer needs a warm drum to print and this consumes a lot of electrical power. If the printer is idle for a long time, it can save a lot of electrical power by switching off the drum's heater. This happens by the cost of more time is required to warm up again the next time the printer should print.

Note

If power_save_time isn't set, power saving defaults to 5 minutes

Parallel Processing

Setup the amount of threads to convert page raster data into the printer data in parallel.

Section	Variable
features	threads

Values:

• '0: Autodetect available CPU cores
• '1…n': Amount of additional threads

The value of '0' will autodetect the available CPU cores, other values are used as is, but clamped to the really available CPU cores.

This setting is related to the worker framework. For details, refer Multi core processing framework

Generic INI Settings

There are more setting which aren't driver features, they are CAPS features instead (handled in a different library for example). They are set in a global manner, but still can be overwritten in a driver specific way or device specific way.

Processing Priority

Section	Variable
features	priority

Values:

• '0': No change in driver's process priority
• '1…19': Adapt the driver's process priority to a lower priority

This entry can lower the priority of the driver. For the time of processing the print job, the driver may consume many CPU cycles, which can disturb other activity in the system. By lowering its priority this can be mitigated. The value set here is the so called nice level. Refer "man nice" for further details on it.

Note

If you don't set this feature, the default is "no change of the priority"

You can never set a higher priority this way.

Memory Buffer Size

Section	Variable
interface	buffer_size

Values:

• A number, unit is kiB, e.g. 1024 means 1024 kiB

If defined, the printer data buffer is extended to this value. E.g. the printer gets the printing data in one turn of this size instead of many small pieces.

Note

Some printers are in trouble if you send the printing data in many small pieces and thus, sometimes time out.

The time out especially can happen if the printer starts printing immediately when the first printing data arrives. Some printers cannot stop a printing activity once it has started. The printer then needs a continuous stream of data to continue and to finish the printing activity. Increase the buffer size if you face this kind of trouble.

The default value is 128 kiB if this setting isn't made in any INI file. It it also limited to max. 8 MiB (refer PRINTER_STREAM_BUFFER_DEFAULT_SIZE and PRINTER_STREAM_BUFFER_MAX_SIZE for the settings).

The printer driver is free when to flush the printing data buffer. It can flush the printing data buffer at the end of each processed page (for simplex print and on demand even for duplex print) or after two processed pages for duplex print. This is printer device dependend and should already be handled by the printer driver.

Note

If the printer driver already sets the buffer_size value, there is no reason to change its value.

Attention

The special value of '0' sets up a fully unbuffered mode. In this case the printer receives the printing data in many small pieces. This could make sense in some rare and special use cases.

Printer Monitoring

Monitoring means the printer's status gets read (periodically) in order to be able to report the printer's state to a user. Think about the paper tray is empty and needs to be refilled. The paper tray can be empty while a new printing job should start or it can be empty while already printing. Thus, it makes sense to monitor the printer's status periodically.

But the world isn't perfect and some printers are in trouble if you retrieve their status too often. There are known printers in the field, where a status read destroys the printer's buffer content which makes the print fail.

Section	Variable
features	monitor

Values:

• always
• never
• idle

always

Monitor the printer device:

• when idle
• prior sending the printing data for each page

never

Never monitor the printer device.

idle

Monitor the printer device:

• when idle

This setting can control how to monitor the printer. A printer which is perfect can live with the always setting. In this case it gets monitored even in idle state. Some printers report their transition into the power save mode while idle for a long period of time. With always this transition will be reported to the printing coordinator and can be retrieved by clients. With this setting an empty paper tray will be reported immediately. The same is valid for all kind of paper jam or other types of errors which can happen at the printer's side while printing.

The never setting is the opposite of always. With this setting there will be no disturbance of any printing activity, but no status reports for clients as well. Even if the paper tray is empty, there will be no warning for a client about this fact.

Some printers are in trouble only if they currently are printing when their status should be read. With the setting idle monitoring is restricted to the idle period only. Monitoring is stopped prior the printing of the first page and continued after the last page was printed, e.g. the next idle period is started.

If this setting isn't made, the default behaviour is always: the printer is expected as perfect.

If an invalid setting is made instead, it defaults to never to be safe.

You can add this INI setting into

• the dedicated printer INI in its CAPS Printer Device Parameter Directory
• a driver specific INI file in the CAPS Printer Driver Configuration Directory (for all printers using this driver)
• or in capsdriver.ini in the CAPS Printer Driver Configuration Directory (once for all printers)

For what events are monitored refer the internal function caps_drv_printer_check().

Halftone Processing

Define the default halftone processing method for monochrome prints.

‍From Wikipedia:
Halftone is the reprographic technique that simulates continuous-tone imagery through the use of dots, varying either in size or in spacing, thus generating a gradient-like effect.

Section	Variable
features	halftone

Values:

• none
• ordered
• fls
• jjn

Value: none

Method: Simple threshhold

This method has no grey scale emulation at all. Pixels below a fixed threshhold are printed, pixels above this threshold aren't.

For simple black text or graphics to print, this method might be sufficient. But for coloured text or grey scale graphics it might skip complete content and the printed result isn't what you expect (at least most of the time).

Left: original, right binary halftone

Value: ordered

Method: Bayer Pattern

Left: original, right ordered halftone

Value: fls

Method: Floyd and Steinberg

This is a so called "error diffusion" halftone method and the most popular one. Its result is very good for text and graphics and it has less visible artefacts on large areas with the same grey scale.

Left: original, right FLS halftone

Value: jjn

Method: Jarvis, Judice, and Ninke

This is a so called "error diffusion" method and similar to the fls one. Its result is very good for text and graphic, but it has visible artefacts on large areas with the same grey scale.

Left: original, right JJN halftone

Note

If no halftone processing method is defined, Floyd and Steinberg is used as the default.

Attention

This halftone processing method is used only, if the document format's rasterizer doesn't support monochrome raster. In this case libcapsdriver pre-processes the raster data with halftone method selected here.
If the corresponding rasterizer supports monochrome raster, it selects its own halftone method, which can differ from the one selected here.

Brother HL-Series Monochrome Laser Printers

This printer driver supports various devices from the Brother HL series of monochrome laser printers. These devices varies mostly in their available memory and thus, their capabilities regarding the supported resolution. Simple documents can be printed on all devices with high resolution. But expect printing failures at high resolution for devices with 2 MiB memory or less. Please report if you have trouble with high resolutions on your low memory printer device. Refer section Brother HL Laser Printer Trouble shooting for details.

Known HL-Series printer models

Printer	Memory	Resolution	Duplex	2nd Tray	Toner level	tested
HL-1030		3/6/12
HL-1050
HL-1070
HL-1110	1MiB	6/24			1
HL-1112		6/24			1
HL-1230
HL-1240
HL-1250				yes
HL-1270	4MiB			yes	3
HL-1435
HL-1440	2MiB
HL-1450	8MiB			yes
HL-1470	8MiB			yes
HL-1650	8MiB
HL-1670	16MiB
HL-1850	16MiB		yes	yes
HL-1870	32MiB		yes	yes
HL-2030	8MiB					X
HL-2040
HL-2070
HL-2130	8MiB	3/6/12			6	X
HL-2140	8MiB					X
HL-2170

Resolution: '3' means 300x300, '6' means 600x600, '12' means 1200x600 and '24' means 2400x600

Note

This table is really incomplete. Filled with information only from datasheets and manuals. If you know a missing detail, please report it via email to: projects@caps-printing.org

HL-Series Laser Printers User Manual

"HL-Series Label Printers User Manual"

Driver Usage

If the components of the CAPS universe are already present at your host, but no matching printer driver yet, you will get the following systemd journal entry:

CAPS kernel: usb 1-1: new full-speed USB device number 2 using musb-hdrc
CAPS kernel: usblp 1-1:1.0: usblp0: USB Bidirectional printer dev 2 if 0 alt 0 proto 2 vid 0x04F9 pid 0x0027
CAPS systemd[1]: Created slice system-caps\x2dprinter.slice.
CAPS systemd[1]: Starting Printing Driver at /dev/usb/lp0...
CAPS systemd[1]: Reached target Printer.
CAPS caps-printer-prep[150]: Reading config settings from INI file '/etc/caps/caps.ini'
CAPS caps-printer-prep[150]: Parsing file '/etc/caps/caps.ini' at level 'base'
CAPS caps-printer-prep[150]: Merging more config settings from INI file '/etc/caps/capsmanagement.ini'
CAPS caps-printer-prep[150]: Parsing file '/etc/caps/capsmanagement.ini' at level 'base'
CAPS caps-printer-prep[150]: Starting printer discovering process...
CAPS caps-printer-prep[150]: Called for device node '/dev/usb/lp0'
CAPS caps-printer-prep[150]: New printing device discovered.
CAPS caps-printer-prep[150]: No printer driver available for the new printing device
CAPS caps-printer-prep[150]: Found printer device is a 'HL-2030 series' made by 'Brother'
CAPS caps-printer-prep[150]: Its USB vendor ID is 04f9, its USB product ID is 0027
CAPS caps-printer-prep[150]: Its serial number (less important) is: XXXXXXXX
CAPS caps-printer-prep[150]: The printer device's IEEE ID is: MFG:Brother;CMD:PJL,HBP;MDL:HL-2030 series;CLS:PRINTER;
CAPS caps-printer-prep[150]: Install a printer driver for this printer device first
CAPS systemd[1]: caps-printer@-dev-usb-lp0.service: Control process exited, code=exited status=22
CAPS systemd[1]: caps-printer@-dev-usb-lp0.service: Failed with result 'exit-code'.
CAPS systemd[1]: Failed to start Printing Driver at /dev/usb/lp0.

Note

The verbosity setting here was 'info'.

Your journal entry might differ, the shown entry is for my Brother HL-2030 printer device.

If the matching printer driver is already installed, the journal entry differs:

CAPS kernel: usb 1-1: new full-speed USB device number 3 using musb-hdrc
CAPS kernel: usblp 1-1:1.0: usblp0: USB Bidirectional printer dev 3 if 0 alt 0 proto 2 vid 0x04F9 pid 0x0027
CAPS systemd[1]: Starting Printing Driver at /dev/usb/lp0...
CAPS caps-printer-prep[167]: Reading config settings from INI file '/etc/caps/caps.ini'
CAPS caps-printer-prep[167]: Parsing file '/etc/caps/caps.ini' at level 'base'
CAPS caps-printer-prep[167]: Merging more config settings from INI file '/etc/caps/capsmanagement.ini'
CAPS caps-printer-prep[167]: Parsing file '/etc/caps/capsmanagement.ini' at level 'base'
CAPS caps-printer-prep[167]: Starting printer discovering process...
CAPS caps-printer-prep[167]: Called for device node '/dev/usb/lp0'
CAPS caps-printer-prep[167]: New printing device discovered.
CAPS systemd[1]: Started Printing Driver at /dev/usb/lp0.
CAPS caps-printer[169]: Reading config settings from INI file '/etc/caps/caps.ini'
CAPS caps-printer[169]: Parsing file '/etc/caps/caps.ini' at level 'base'
CAPS caps-printer[169]: Merging more config settings from INI file '/etc/caps/capsmanagement.ini'
CAPS caps-printer[169]: Parsing file '/etc/caps/capsmanagement.ini' at level 'base'
CAPS caps-printer[169]: Called for device node '/dev/usb/lp0'
CAPS caps-printer[169]: Launching printer driver ...
CAPS caps-printer[169]: HL series driver is starting
CAPS caps-printer[169]: Parsing file '/etc/caps/drivers/capsdriver.ini' at level 'base'
CAPS caps-printer[169]: Reading the base settings from INI file '/etc/caps/drivers/capsdriver.ini'
CAPS caps-printer[169]: Reading the default settings from INI file '/usr/share/caps/drivers/caps-brother-HL2030-driver.ini'
CAPS caps-printer[169]: Parsing file '/usr/share/caps/drivers/caps-brother-HL2030-driver.ini' at level 'default'
CAPS caps-printer[169]: Merging more default features from INI file '/etc/caps/drivers/hl20-driver.ini'
CAPS caps-printer[169]: Parsing file '/etc/caps/drivers/hl20-driver.ini' at level 'defaults'
CAPS caps-printer[169]: Reading the run-time INI files from parameter directory '/var/lib/caps/printer_6PqHu2'
CAPS caps-printer[169]: Found file: 'service.ini'...
CAPS caps-printer[169]: File 'service.ini' accepted as ini file
CAPS caps-printer[169]: Parsing file '/var/lib/caps/printer_6PqHu2/service.ini' at level 'user'

Now the printer driver is running. If you have connected it the very first time, it will create a printer device specific configuration file as well. The journal entry:

CAPS caps-printer-prep[167]: New printing device discovered.

shows this state. And the journal entry:

CAPS caps-printer[169]: Reading the run-time INI files from parameter directory '/var/lib/caps/printer_6PqHu2'

shows where the printer driver expects this configuration file for exact this printer device.

The journal entry slightly differs, if the printer device is already known:

CAPS systemd[1]: Starting Printing Driver at /dev/usb/lp0...
CAPS caps-printer-prep[201]: Reading config settings from INI file '/etc/caps/caps.ini'
CAPS caps-printer-prep[201]: Parsing file '/etc/caps/caps.ini' at level 'base'
CAPS caps-printer-prep[201]: Merging more config settings from INI file '/etc/caps/capsmanagement.ini'
CAPS caps-printer-prep[201]: Parsing file '/etc/caps/capsmanagement.ini' at level 'base'
CAPS caps-printer-prep[201]: Starting printer discovering process...
CAPS caps-printer-prep[201]: Called for device node '/dev/usb/lp0'
CAPS systemd[1]: Started Printing Driver at /dev/usb/lp0.

In this case, the tool 'caps-printer-prep' has found this printer device in its database (usually /var/lib/printer-devices.ini) and just re-use all stored settings.

The content of the newly generated printer device specifc configuration file is generic, since it is generated from some detectable printer information:

$ cat /var/lib/caps/printer_6PqHu2/service.ini
# Automatically created by CAPS. Please adapt the printer device name to your needs
[info]
name = Brother_HL-2030 series_XXXXXXX

You can adapt it to your needs. For the [info] section the keyword 'brief' and 'location' are provided as well.

You can overwrite all settings from the main printer's INI file (for my printer it is /usr/share/caps/drivers/brother-HL2030-driver.ini), the driver's INI file (for my printer it is /etc/caps/drivers/brother-hl2-driver.ini) and these changes are valid only for this specific printer device.

After changing the printer device's configuration file, you must detach and re-attach the printer again, to take effect the changes.

After changing my /etc/caps/drivers/brother-hl2-driver.ini to:

[info]
name = My Brother Printer
brief = Prints fast and nice
location = Office#3

the tool 'capsprinter' shows:

$ capsprinter --list -v
name: 'My Brother Printer'
 description: Prints fast and nice
 location: Office#3
 state: Idle (ID 3)
 reason: Okay (ID 16)
 message: 'Idle'

Printer Device Configuration

Various settings cannot be set via the printing dialouge. They are defined in a printer device corresponding INI file instead.

The following list shows the INI files read-in by the HL1/2 printer drivers. Some of the shown INI files use generic names, see below.

INI File name	Meaning	Expected Location
caps.ini	Shared initialization	CAPS Configuration Directory
capsdriver.ini	Shared class initialization	CAPS Printer Driver Configuration Directory
devicedriver.ini (see note)	Device Description	CAPS Printer Driver Database Directory
feature.ini (see note)	Driver Feature Configuration	optional, CAPS Printer Driver Configuration Directory
parameter.ini (see note)	Printing Device Parameters	CAPS Printer Device Parameter Directory

Note

The devicedriver.ini is only an example name for a Device Description INI file. Its real name correlates with the printing device.

The feature.ini is only an example name for a Driver Feature Configuration INI file. It is defined in the devicedriver.ini and is optional.

The parameter.ini is only an example for one of the Printing Device Parameters INI files. All INI files from the physical printing device's directory are read-in.

For the caps-brother-hl1 printer driver the mentioned feature INI file is

• brother-hl1-driver.ini

For the caps-brother-hl2 printer driver the mentioned feature INI file is

• brother-hl2-driver.ini

The mentioned parameter INI file is always device dependend.

Note

The listed configuration parameters shown below get their default values in the mentioned feature INI files. You can change their values in one of these feature INI files (e.g. "once for all" ) or individually in the device's specific parameter INI files.

Printer Device Specific

The following settings makes sense in a printer device specific way.

In the paper the used paper to print to can be predefined. For example if your printer has only one paper tray, you can define the loaded paper here instead of in the printing dialouge.

The HL printers know a paper format and a paper type.

Paper Type

According to the documentation:

‍Media Type. The temperature of fixing unit is adjusted depending on this setting.

It seems the printer adapts its own physical printing parameters depending on the paper type. Thus, a paper type can be defined to use this feature.

Section	Variable
paper	type

Values:

• Regular: Ordinary white copy paper (75 g … 90 g per m²)
• Thick: Thick paper (90 g … 105 g per m²)
• Thick2: Thick paper
• Transparency: Foil
• Thin: Thin paper (60 g … 70 g per m²)
• Bond: Bonded paper (rag pulp kind of paper)
• Env: Envelope
• Envtck: (FIXME)
• Envtn: (FIXME)
• Used: Recycled paper (maybe pre-printed is meant instead)

Note

This is a fixed setting and the user cannot change it when printing.
If the paper type isn't set, a selection list is generated instead and the default_type setting instead comes into play (see Default Paper Type).

The list of supported values differ from printer to printer. Maybe not all entries of this list are valid for your specific printer.

Default Paper Type

If type (see Paper Type) isn't set, the default_type defines the default type in the generated PPD section. Accepted values are the same as for the type variable.

Section	Variable
paper	default_type

Note

This is a weak fixed setting. The user can change it when printing.

Default Paper Format

Define the expected default paper format in the printer's paper tray. Accepted are all values the libpaper can handle. Refer 'man paperconf' or 'paperconf -a' for a list of supported formats.

Section	Variable
paper	format

This define is optional. If not set here, a more generic setting is used instead. One source of a generic setting can be the CAPS wide setting in the base driver's INI file, e.g. capsdriver.ini, usually installed to /etc/caps/drivers. If the base driver's INI file doesn't define the paper format a second source can be the system wide setting from libpaper. Refer 'man paperconf' how to setup a default system wide paper format.

Eco Mode

Define the toner save feature.

Section	Variable
features	eco

Values:

• Off
• 1
• 2
• 3

Default Print Resolution

The default print resolution can be defined. Its value is always in a short form, like '3' for 300 DPI.

Section	Variable
features	resolution

Values:

• 3 (for 300 DPI)
• 6 (for 600 DPI)
• 12 (for 1200 DPI)

Supported resolutions varies from printer to printer. Refer the brother-h1.driver.ini or brother-hl2-driver.ini (depending on your model) for the supported resolutions.

Note

Since it only defines the default, the user can still select a different resolution in the printing dialouge on a per print job base.

The key word power_save_time sets the time an idling printer enters the power save state. Its value can be a number and is meant in minutes or the keyword Off to disable this feature. Disabling isn't recommended. Refer section Saving Energy about the energy a printer consumes.

Example:

  power_save_time = 5

You can move the print area on the paper by changing offsets.

The keyword x_offset moves the print area horizontally, while the keyword y_offset moves it vertically. Units are 1/72 inch (TODO really?) and both directions are possible by positive or negative values.

Example:

  x_offset = 0
  y_offset = 0

The keyword density TODO

Example:

  density = 0

The keyword image_adapt TODO

Example:

  image_adapt = On

Generic Settings

These settings are derived from the printing framework and thus, are valid for the QL printer drivers as well.

Processing Priority

Section	Variable
features	priority

Values:

• '0': No change in driver's process priority
• '1…19': Adapt the driver's process priority to a lower priority

This entry can lower the priority of the driver. For the time of processing the print job, the driver may consume many CPU cycles, which can disturb other activity in the system. By lowering its priority this can be mitigated. The value set here is the so called nice level. Refer "man nice" for further details on it.

Note

If you don't set this feature, the default is "no change of the priority"

You can never set a higher priority this way.

Memory Buffer Size

Section	Variable
interface	buffer_size

Values:

• A number, unit is kiB, e.g. 1024 means 1024 kiB

If defined, the printer data buffer is extended to this value. E.g. the printer gets the printing data in one turn of this size instead of many small pieces.

Note

Some printers are in trouble if you send the printing data in many small pieces and thus, sometimes time out.

The time out especially can happen if the printer starts printing immediately when the first printing data arrives. Some printers cannot stop a printing activity once it has started. The printer then needs a continuous stream of data to continue and to finish the printing activity. Increase the buffer size if you face this kind of trouble.

The default value is 128 kiB if this setting isn't made in any INI file. It it also limited to max. 8 MiB (refer PRINTER_STREAM_BUFFER_DEFAULT_SIZE and PRINTER_STREAM_BUFFER_MAX_SIZE for the settings).

The printer driver is free when to flush the printing data buffer. It can flush the printing data buffer at the end of each processed page (for simplex print and on demand even for duplex print) or after two processed pages for duplex print. This is printer device dependend and should already be handled by the printer driver.

Note

If the printer driver already sets the buffer_size value, there is no reason to change its value.

Attention

The special value of '0' sets up a fully unbuffered mode. In this case the printer receives the printing data in many small pieces. This could make sense in some rare and special use cases.

Printer Monitoring

Monitoring means the printer's status gets read (periodically) in order to be able to report the printer's state to a user. Think about the paper tray is empty and needs to be refilled. The paper tray can be empty while a new printing job should start or it can be empty while already printing. Thus, it makes sense to monitor the printer's status periodically.

But the world isn't perfect and some printers are in trouble if you retrieve their status too often. There are known printers in the field, where a status read destroys the printer's buffer content which makes the print fail.

Section	Variable
features	monitor

Values:

• always
• never
• idle

always

Monitor the printer device:

• when idle
• prior sending the printing data for each page

never

Never monitor the printer device.

idle

Monitor the printer device:

• when idle

This setting can control how to monitor the printer. A printer which is perfect can live with the always setting. In this case it gets monitored even in idle state. Some printers report their transition into the power save mode while idle for a long period of time. With always this transition will be reported to the printing coordinator and can be retrieved by clients. With this setting an empty paper tray will be reported immediately. The same is valid for all kind of paper jam or other types of errors which can happen at the printer's side while printing.

The never setting is the opposite of always. With this setting there will be no disturbance of any printing activity, but no status reports for clients as well. Even if the paper tray is empty, there will be no warning for a client about this fact.

Some printers are in trouble only if they currently are printing when their status should be read. With the setting idle monitoring is restricted to the idle period only. Monitoring is stopped prior the printing of the first page and continued after the last page was printed, e.g. the next idle period is started.

If this setting isn't made, the default behaviour is always: the printer is expected as perfect.

If an invalid setting is made instead, it defaults to never to be safe.

You can add this INI setting into

• the dedicated printer INI in its CAPS Printer Device Parameter Directory
• a driver specific INI file in the CAPS Printer Driver Configuration Directory (for all printers using this driver)
• or in capsdriver.ini in the CAPS Printer Driver Configuration Directory (once for all printers)

For what events are monitored refer the internal function caps_drv_printer_check().

Halftone Processing

Define the default halftone processing method for monochrome prints.

‍From Wikipedia:
Halftone is the reprographic technique that simulates continuous-tone imagery through the use of dots, varying either in size or in spacing, thus generating a gradient-like effect.

Section	Variable
features	halftone

Values:

• none
• ordered
• fls
• jjn

Value: none

Method: Simple threshhold

This method has no grey scale emulation at all. Pixels below a fixed threshhold are printed, pixels above this threshold aren't.

For simple black text or graphics to print, this method might be sufficient. But for coloured text or grey scale graphics it might skip complete content and the printed result isn't what you expect (at least most of the time).

Left: original, right binary halftone

Value: ordered

Method: Bayer Pattern

Left: original, right ordered halftone

Value: fls

Method: Floyd and Steinberg

This is a so called "error diffusion" halftone method and the most popular one. Its result is very good for text and graphics and it has less visible artefacts on large areas with the same grey scale.

Left: original, right FLS halftone

Value: jjn

Method: Jarvis, Judice, and Ninke

This is a so called "error diffusion" method and similar to the fls one. Its result is very good for text and graphic, but it has visible artefacts on large areas with the same grey scale.

Left: original, right JJN halftone

Note

If no halftone processing method is defined, Floyd and Steinberg is used as the default.

Attention

This halftone processing method is used only, if the document format's rasterizer doesn't support monochrome raster. In this case libcapsdriver pre-processes the raster data with halftone method selected here.
If the corresponding rasterizer supports monochrome raster, it selects its own halftone method, which can differ from the one selected here. "HL-Series Label Printers User Manual"

Brother QL-Series Label Printers

This printer driver supports various devices from the Brother QL series of easy to use label printers. These printer devices varies in more or less unknown details. A few differ in their print width (more than 62 mm). And one series (the QL8xx) differ in their capability to print in bi-colour mode with a special label cassette (DK2215).

Known QL-Series printer models

Printer	Cutter	300 DPI	600 DPI	bi-colour	> 62mm	tested
QL500	manual	X				X
QL550	auto	X
QL560	auto	X
QL570	auto	X
QL580	auto	X
QL600	auto	X
QL600TD	auto	X
QL700	auto	X
QL710W	auto	X
QL710NW	auto	X
QL800	auto	X	X	X		X
QL810W	auto	X	X	X
QL820NWB	auto	X	X	X
QL1050	auto	X			X
QL1060N	auto	X			X

Note

For QL models with an auto cutter, it is possible to print multipage documents and each page gets cut by default. For QL models with a manual cutter multipage documents are printed at once and at the end the user can manually cut the whole page sequence.

Reading the printer's datasheets is confusing regarding their print data compression capabilities. Most datasheets state, compression isn't supported or (at least) with some restrictions (limited to the "serial interface" for example). But printer data records from different drivers still show they use the RLE compression method. On the other hand, data compression on a full speed USB link doesn't makes sense for this small amount of data. Thus, this filter doesn't use compression at all.

Various printers listed above can print vertically at 600 DPI. But the driver doesn't support it, yet.

QL-Series Label Printers User Manual

"QL-Series Label Printers User Manual"

How to define labels

Continuous Labels

Continuous labels are simple to create: Just create a label with the exact size of your continuous roll paper. E.g. with its exact width.

Attention

The length of your label must be shorter than some hard limits the printer has. All I know yet is, you should not exceed a length of 1000 mm per single label (or: between cuts).

There is also a minimal limit for the length of your label: it is about 13 mm or 25 mm (depending on the QL model. Read the manual of your printer!).

The margin at the left and right borders you should not print to, are about 0.5 mm. There are no margin requirements at the top and bottom borders.

Attention

The printer will always add 3 mm at the top and bottom to your label. Then it will cut the roll.

Example:

You are using a DK2113 roll. It provides a medium width of 62 mm. You define a label with 62 mm width and 100 mm length.

Some label defined on a continuous medium

Your printable area on this label is 61 mm wide and has a length of 100 mm.

The size of this label after the printer has spit it out is 62 mm wide and has a length of 106 mm.

Pre-cut Labels

Pre-cut labels are a bit more complicated. The printers have some annoying behaviours, which we must honor to get an expected result.

First we must create a label of the exact size of the pre-cut labels of our DK roll. Since the printer adds some margins by itself, we now need to define exact margins. We need to know, the printer will always add 3 mm at the top and the bottom of each label. So it depends on the orientation of our label, where we need to honor these margins.

If we use a pre-cut label DK roll oriented in portrait, the 3 mm margins are at the short edges. For DK rolls oriented in landscape, the 3mm margins are at their long edges.

Some kind of labels in portrait orientation

Some kind of labels in landscape orientation

The margins at the other edges are about 0.5 mm (drop me a note, if this isn't always true). But refer Assumptions about the Print Head for more details.

With this rule it should be easy to define the correct margins, independently of your label's orientation.

You may also read the How the driver deals with margins

Example:

You are using a DK1201 roll. It provides pre-cut labels of the size 29 mm by 90 mm. Orientation on the roll is portrait. Thus, you need the 3 mm margins at the 29 mm edge.

Landscape label, but printed in portrait orientation

You can create a label in landscape (29 mm height, 90 mm width), with 3 mm margins at its left and right edge and 0.5 mm at its top and bottom edge. But regarding the top and bottom margins also refer Assumptions about the Print Head for more details.

Wrong Size for a pre-cut Label

What happens, if you create a larger label than the pre-cut label is? The printer won't be able to cut inbetween labels! It will cut inside the next label instead.

Wrong cut due to wrong vertical size

After that is happen, you must manually remove this remaining label, else the printer can no longer feed it correctly.
Solution: Pull out the DK roll from the printer and manually cut the tape at the intended position, and insert it into the printer again.

How to setup margins correctly

Here a more specific description how to setup the margins if you want to use labels in landscape orientation, but the DK roll provides only portrait orientation.

Landscape label margins on clockwise or counter clockwise rotation

How the driver deals with margins

Horizontal

If the dot count in a line in the raster exceeds the maximum of 720 dots the QL print head has, the filter removes the same amount of dots at the left and right line ends and sends exactly 720 dots to the QL printer device.

If the dot count in a line in the raster is below the maximum of the selected medium (or the maximum dots of the QL print head), it will right align the available dots per line and sends the result to the printer device.

Vertical

For continous labels, all raster lines are sent to the printer device. You do not need margins at the top and bottom edge. The QL printer device itself will add 3 mm at both ends and then cut the label.

For pre-cut labels the filter always ignores 3 mm of data at the top and at the bottom of the raster. At 300 DPI this means 35 lines each and at 600 DPI (only some QL models) 70 lines each. The remaining raster lines are sent to the printer device. For this case you need to add these 3 mm margins to your label, e.g. it must provide lines for the full size of the label.

Bi-coloured print

With the QL8xx printer models and the special DK roll DK2251 a nice feature came in - bi-colour print: black and red dots on white paper.

A friend's comment :-)

In order to print in this mode you need:

• one of the QL8xx printer models
• the DK2251 62 mm continous label roll
• documents which makes use of the red and black colours (refer QL8_What_Is_Red)
• switching to the RGB colour space when printing (monochrome is the default else)
• don't use the 600 DPI print resolution (doesn't work in conjunction with bi-colour)

Limitations in bi-colour print

Bi-colour print mode ins't perfect. See what you can expect.

First how it looks like with black-only capable label. This image shows a DK1201 roll print:

Black on DK1201

The bi-colour DK2251 roll turns to red when the print head applies a low energy to it and still turns to black with high energy.

Since two temperatures (low and high energy) are used to create dots on this special medium, there are some interferences: using high energy (or high temperature) will cool down around the location the high energy was applied to. As a result, the area around a black dot turns to red as well: around all black areas will be some kind of red shadows.

This image shows a DK2251 bi-colour roll with a black area:

Black on DK2251

Vice versa: applying low energy seems not perfect and results in red areas with some black noise in it.

This image shows a DK2251 bi-colour roll with a red area:

Red on DK2251

If you can live with these imperfections, the DK2251 roll is a nice "add-on" for label printing.

What's Red?

In order to print bi-coloured, the printer filter needs to separate black and red areas in your document. And it isn't as such easy to detect a red as it seems at first.

Red from the printer filter's point of view, has in the HSV colour model (https://en.wikipedia.org/wiki/HSL_and_HSV) a:

• hue below 30 ° or above 350 °
• saturation above 32
• value above 32

Note

All these thresholds you can be changed in the INI file belonging to your printer (if it is one of the QL8xx models).

Refer ql_red_detection for details what has to be changed regarding the red detection.

If you change them, you need to restart the printer driver.

Power Saving

At least the QL8 series of printers have some kind of power save features.

Todo:

Please drop me a note, if you know other QL printers which provide this feature as well.

Auto Power Off

When the printer is idle for a while, it switches itself off and disappears from your host's USB.

It is a little bit annoying, since this is called a power save feature. While it is correct (it really saves power!), the printer is silently gone from your host system. You cannot print anymore until you manually switch it on again through its power button.

You can change/adapt this behaviour via a selection from the PPD's Power Off Timeout menu.

You can select a time between 10 minutes and up to 60 minutes (in steps of 10 minutes) in idle after it powers off. And it is possible to disable this feature entirely here as well.

Note

Once set, the printer persists this setting and thus, there is no further need to set it again and again. But: to change the setting you need to print a job.

Auto Power On

Powering the device can lead to an active printer device or a still disabled printer device. Active means, the printer is visible at your host's USB immediately. Still disabled means, it is invisible at the USB and requires an additionally and manually triggered power-on by its local power button.

You can change/adapt this behaviour via a selection from the PPD's Power Connect Behaviour menu.

You can select Default (e.g. don't change), Go online (e.g. active) or Keep offline (e.g. disabled).

Note

Once set, the printer persists this setting and thus, there is no further need to set it again and again. But: to change the setting you need to print a job.

Printer Driver Configuration

List of used INI files

The following list shows the INI files read-in by the QL printer drivers. Some of the shown INI files use generic names, see below.

INI File name	Meaning	Expected Location
caps.ini	Shared initialization	CAPS Configuration Directory
capsdriver.ini	Shared class initialization	CAPS Printer Driver Configuration Directory
devicedriver.ini (see note)	Device Description	CAPS Printer Driver Database Directory
feature.ini (see note)	Driver Feature Configuration	optional, CAPS Printer Driver Configuration Directory
parameter.ini (see note)	Printing Device Parameters	CAPS Printer Device Parameter Directory

Note

The devicedriver.ini is only an example name for a Device Description INI file. Its real name correlates with the printing device.

The feature.ini is only an example name for a Driver Feature Configuration INI file. It is defined in the devicedriver.ini and is optional.

The parameter.ini is only an example for one of the Printing Device Parameters INI files. All INI files from the physical printing device's directory are read-in.

For the caps-brother-ql* printer drivers the mentioned feature INI file is

• brother-ql-driver.ini

The mentioned parameter INI file is always device dependend.

Note

The listed configuration parameters shown below get their default values in the mentioned feature INI files. You can change their values in one of these feature INI files (e.g. "once for all" ) or individually in the device's specific parameter INI files.

Printer Device Specific

The following settings makes sense in a printer device specific way.

Bi-colour medium

The QL8xx printers cannot detect if this special medium is loaded. This setting is for convenience, since you can always select this medium before printing. If you enable this setting, it only changes the defaults.

Section	Variable
features	colourmedium

Values:

• true
• false

Boolean variable. If true, the bi-colour DK225 cassette is loaded instead of a monochrome one. If not defined, the default is a monochrome capable cassette (e.g. false).

Printer Driver Specific

The following settings adapt the behaviour of the printer driver. Most of them are already set in the printer's Device Description INI file (refer CAPS Printer Driver Database Directory) to a useful value to reflect the features a printer has. Most of the time there is no need to change them.

Power Control

Some printers can be configured in their way of power control. This setting

Section	Variable
features	powerctrl

Values:

• true
• false

This boolean key enables an additional selection in the printer description PPD. It enables the user to define the auto power on and auto power off behaviour of the printer. The default of this selection is always "don't change", but can be set to a different value prior a print job.

Note

Only the QL7 and QL8 family of label printers are currently known to support this kind of feature.

Bytes per Line

Internally used to define various buffer sizes and process the print data.

Section	Variable
features	bytesperline

Values:

• 90
• 162

Dot count in one line

Internally used to define various buffer sizes and process the print data. Corresponds more or less to the bytesperline keyword. It defines the dots of the printer's print head.

Section	Variable
features	dotcount

Values:

• 720
• 1296

Leading Bytes in a job

Used to bring the printer device into a well known state, e.g. reset it. Various printer models have different requirements about the amount of empty and leading bytes to be sent before sending the real print data.

Section	Variable
features	leading_bytes

Values:

• 200 (for QL5xx)
• 400 (for QL8xx)

Bi-Colour support

Boolean variable if the printer device has the feature of bi-colour printing support. Currently only the QL8xx family of printer devices has such an feature. If not defined, the default is false

Section	Variable
features	bicolour

Values:

• true
• false

When the bi-colour support is enabled, the printer driver needs additional information to be able to rip black and red dots.

Section	Variable
bicolour	lower_red_angle
bicolour	higher_red_angle
bicolour	lower_red_saturation
bicolour	lower_red_value

Refer What's Red? for useful values of these settings.

High resolution support

Some printers are capable to print at 600 DPI vertically. If this boolean is set, the printer is capable to print in this higher resolution. If not defined, the default is false

Section	Variable
features	highresolution

Cutter Support

Section	Variable
features	manualcutter

Values:

• true
• false

Section	Variable
features	autocutter

Values:

• true
• false

Bits to encode the loaded cassette

The QL printers cassetts have some encording in their foot. With this feature, the printer can detect the loaded cassette by its own and can report the size and type of label it currently can print to. The printer driver can read-back this encoding and thus, is able to report the correct label size and type to the user.

Over the time, the amount of encoding bits has increased. The QL500 for example comes with 5 bits to encode the loaded cassette, while the QL800 has 6 bits for the same purpose. The value of this setting is used to mask unsupported bits to always report the correct loaded cassette.

Section	Variable
features	cassette

Values:

• 5 (QL5xx)
• 6 (QL8xx)

Left 5 Cassette Sensors at QL500, right 6 Cassette Sensors at QL800

Currently unused settings

Section	Variable
features	minlength
features	maxlength
features	minwidth
features	maxwidth

Section	Variable
margins	margin_large_left

| margin_large_right | margin_large_top | margin_large_bottom

Generic Settings

These settings are derived from the printing framework and thus, are valid for the QL printer drivers as well.

Processing Priority

Section	Variable
features	priority

Values:

• '0': No change in driver's process priority
• '1…19': Adapt the driver's process priority to a lower priority

This entry can lower the priority of the driver. For the time of processing the print job, the driver may consume many CPU cycles, which can disturb other activity in the system. By lowering its priority this can be mitigated. The value set here is the so called nice level. Refer "man nice" for further details on it.

Note

If you don't set this feature, the default is "no change of the priority"

You can never set a higher priority this way.

Memory Buffer Size

Section	Variable
interface	buffer_size

Values:

• A number, unit is kiB, e.g. 1024 means 1024 kiB

If defined, the printer data buffer is extended to this value. E.g. the printer gets the printing data in one turn of this size instead of many small pieces.

Note

Some printers are in trouble if you send the printing data in many small pieces and thus, sometimes time out.

The time out especially can happen if the printer starts printing immediately when the first printing data arrives. Some printers cannot stop a printing activity once it has started. The printer then needs a continuous stream of data to continue and to finish the printing activity. Increase the buffer size if you face this kind of trouble.

The default value is 128 kiB if this setting isn't made in any INI file. It it also limited to max. 8 MiB (refer PRINTER_STREAM_BUFFER_DEFAULT_SIZE and PRINTER_STREAM_BUFFER_MAX_SIZE for the settings).

The printer driver is free when to flush the printing data buffer. It can flush the printing data buffer at the end of each processed page (for simplex print and on demand even for duplex print) or after two processed pages for duplex print. This is printer device dependend and should already be handled by the printer driver.

Note

If the printer driver already sets the buffer_size value, there is no reason to change its value.

Attention

The special value of '0' sets up a fully unbuffered mode. In this case the printer receives the printing data in many small pieces. This could make sense in some rare and special use cases.

Printer Monitoring

Monitoring means the printer's status gets read (periodically) in order to be able to report the printer's state to a user. Think about the paper tray is empty and needs to be refilled. The paper tray can be empty while a new printing job should start or it can be empty while already printing. Thus, it makes sense to monitor the printer's status periodically.

But the world isn't perfect and some printers are in trouble if you retrieve their status too often. There are known printers in the field, where a status read destroys the printer's buffer content which makes the print fail.

Section	Variable
features	monitor

Values:

• always
• never
• idle

always

Monitor the printer device:

• when idle
• prior sending the printing data for each page

never

Never monitor the printer device.

idle

Monitor the printer device:

• when idle

This setting can control how to monitor the printer. A printer which is perfect can live with the always setting. In this case it gets monitored even in idle state. Some printers report their transition into the power save mode while idle for a long period of time. With always this transition will be reported to the printing coordinator and can be retrieved by clients. With this setting an empty paper tray will be reported immediately. The same is valid for all kind of paper jam or other types of errors which can happen at the printer's side while printing.

The never setting is the opposite of always. With this setting there will be no disturbance of any printing activity, but no status reports for clients as well. Even if the paper tray is empty, there will be no warning for a client about this fact.

Some printers are in trouble only if they currently are printing when their status should be read. With the setting idle monitoring is restricted to the idle period only. Monitoring is stopped prior the printing of the first page and continued after the last page was printed, e.g. the next idle period is started.

If this setting isn't made, the default behaviour is always: the printer is expected as perfect.

If an invalid setting is made instead, it defaults to never to be safe.

You can add this INI setting into

• the dedicated printer INI in its CAPS Printer Device Parameter Directory
• a driver specific INI file in the CAPS Printer Driver Configuration Directory (for all printers using this driver)
• or in capsdriver.ini in the CAPS Printer Driver Configuration Directory (once for all printers)

For what events are monitored refer the internal function caps_drv_printer_check().

Halftone Processing

Define the default halftone processing method for monochrome prints.

‍From Wikipedia:
Halftone is the reprographic technique that simulates continuous-tone imagery through the use of dots, varying either in size or in spacing, thus generating a gradient-like effect.

Section	Variable
features	halftone

Values:

• none
• ordered
• fls
• jjn

Value: none

Method: Simple threshhold

This method has no grey scale emulation at all. Pixels below a fixed threshhold are printed, pixels above this threshold aren't.

For simple black text or graphics to print, this method might be sufficient. But for coloured text or grey scale graphics it might skip complete content and the printed result isn't what you expect (at least most of the time).

Left: original, right binary halftone

Value: ordered

Method: Bayer Pattern

Left: original, right ordered halftone

Value: fls

Method: Floyd and Steinberg

This is a so called "error diffusion" halftone method and the most popular one. Its result is very good for text and graphics and it has less visible artefacts on large areas with the same grey scale.

Left: original, right FLS halftone

Value: jjn

Method: Jarvis, Judice, and Ninke

This is a so called "error diffusion" method and similar to the fls one. Its result is very good for text and graphic, but it has visible artefacts on large areas with the same grey scale.

Left: original, right JJN halftone

Note

If no halftone processing method is defined, Floyd and Steinberg is used as the default.

Attention

This halftone processing method is used only, if the document format's rasterizer doesn't support monochrome raster. In this case libcapsdriver pre-processes the raster data with halftone method selected here.
If the corresponding rasterizer supports monochrome raster, it selects its own halftone method, which can differ from the one selected here. "QL-Series Label Printers User Manual"