Creating the printer's wire data for bi-coloured print. More...

Data Structures
struct	colour_line_start

Macros
#define	HIGH_ENERGY 0x01

#define	LOW_ENERGY 0x02

Functions
static void	remove_overlapping_dots (size_t cnt, unsigned char black_block[cnt], const unsigned char red_block[cnt])

static void	colour_line_convert (struct line_command *cmd, size_t input_cnt, const signed short inputb[input_cnt], const signed short inputr[input_cnt])

static struct line_command *	colour_command_get (size_t bytes_per_line)

static void	colour_command_put (void *cmd)

static int	cups_ql_colour_line_process (struct qldriver ql, struct halftone_converter cnv_black, struct halftone_converter *cnv_red)

static double	fraction (double no)

static void	rgb2hsv (struct qlhsv hsv, const struct qlrgb rgb_pixel)

static void	red_dot_mark (signed int val, signed short black_pixel, signed short red_pixel)

static void	black_dot_mark (signed int val, signed short black_pixel, signed short red_pixel)

static signed int	to_grey (const struct qlrgb *pixel)

static signed int	is_red (struct qldriver ql, const struct qlrgb pixel)

static int	cups_ql_next_colour_line_read (struct qldriver ql, struct halftone_converter cnv_black, struct halftone_converter *cnv_red)

int	cups_ql_colour_page_print (struct qldriver *ql, int first_time)

Variables
int	terminate

Detailed Description

Creating the printer's wire data for bi-coloured print.

Copyright: GNU General Public License 2.0 or later

Author: Jürgen Borleis

The QL8xx familiy of printers is capable of printing red and black dots on a special medium (e.g. DK2251).

"Colour" here means: black and red on white labels.

In this mode every line must be sent twice. First for low energie to print red dots and second for high energie to print black dots.

The result isn't perfect, since low energy creates red dots, the high energy black dots all have red shadows around them (because the high energy cools down beside the main dot area, the medium tends to red colour). Refer Limitations in bi-colour print for details.

Macro Definition Documentation

◆ HIGH_ENERGY

#define HIGH_ENERGY 0x01

Value to force a black dot. Used in the printer's command to print the black dots, refer colour_line_start for details

◆ LOW_ENERGY

#define LOW_ENERGY 0x02

Value to force a red dot. Used in the printer's command to print the red dots, refer colour_line_start for details

Function Documentation

◆ black_dot_mark()

static void black_dot_mark	(	signed int	val,
		signed short *	black_pixel,
		signed short *	red_pixel
	)

static

Mark a black dot value into both line bufffers

Parameters

[in]	val	The brightness of the dot (-255 = full brightness … 0 = black) (negative value!)
[out]	black_pixel	Where to store the corresponding black value for no black dot at this position
[out]	red_pixel	Where to store the corresponding red value

The black dots scale from 0x00 (black dot!) to 0xff (paper colour!) Red settings depends on red_dot_mark() and its inversion, e.g. both colours scale from 0x00 (dot!) to 0xff (no dot!)

◆ colour_command_get()

static struct line_command* colour_command_get ( size_t bytes_per_line )

static

Allocate the buffer for the colour print command

Parameters

[in] bytes_per_line Expected bytes per line to be sent to the printer

Returns: line_command structure

Todo:: shared component, because the monochrome usecase is only a special usecase of the colour usecase

◆ colour_command_put()

static void colour_command_put ( void * cmd )

static

Free the buffer for the monochrome print command

Parameters

[in] cmd The command buffer to be freed

◆ colour_line_convert()

static void colour_line_convert	(	struct line_command *	cmd,
		size_t	input_cnt,
		const signed short	inputb[input_cnt],
		const signed short	inputr[input_cnt]
	)

static

Create the command to print one dual colour line

Parameters

[out]	cmd	Command data structure where to store the line data
[in]	input_cnt	Count of signed shorts in inputb and inputr (max. 2040 elements, usual 720 elements)
[in]	inputb	Black data to convert
[in]	inputr	Red data to convert

The printer wire colour data format is:

  | command | <bytes_per_line> | command | <bytes_per_line> |

e.g. according to the QL800 datasheet 186 bytes over all (90 bytes per line each).

◆ cups_ql_colour_line_process()

static int cups_ql_colour_line_process	(	struct qldriver *	ql,
		struct halftone_converter *	cnv_black,
		struct halftone_converter *	cnv_red
	)

static

Process one line and send it to the printer

Parameters

[in]	ql	Full job description
[in]	cnv_black	Black data half-tone converter
[in]	cnv_red	Red data half-tone converter

Return values

0	On success

Precondition: The half tone converters must already be filled with two lines; One of the three available half-tone algorithms must already be selected

◆ cups_ql_colour_page_print()

int cups_ql_colour_page_print	(	struct qldriver *	ql,
		int	first_time
	)

Convert the current page into the printer's wire data format

Parameters

[in]	ql	Full job description
[in]	first_time	'1' if called the first time of this job, '0' else

Return values

0	On success
-EINVAL	Unsupported raster input format
-ECANCELED	Termination request from outerspace

The routine loops through all or the remaining lines of the current page and converts them into the printer's colour wire format

Precondition: The format was already checked, e.g. it fits into the printer's media.

◆ cups_ql_next_colour_line_read()

static int cups_ql_next_colour_line_read	(	struct qldriver *	ql,
		struct halftone_converter *	cnv_black,
		struct halftone_converter *	cnv_red
	)

static

Read in the next line from a CUPS RGB raster right border aligned and separate black (e.g. shades of grey) and red (shades of)

Parameters

[in]	ql	Full job description
[in,out]	cnv_black	The black part of the line
[in,out]	cnv_red	The red part of the line

Precondition: Input Raster is RGB 'chunked', 8 bit per channel (e.g. RGB RGB RGB …)

Todo:: The input raster can be smaller than the required line width. In this case the labels are smaller (for example) and the raster must be right aligned.

Note: Both colours gets scaled to 0x00 (dot) to 0xff (no dot) in both halftone converters

◆ fraction()

static double fraction ( double no )

static

Return the fractional part of a floating point

Parameters

[in] no The full number

Returns: the fractional part of no

Todo:: can lrint() be used here instead?

◆ is_red()

static signed int is_red	(	struct qldriver *	ql,
		const struct qlrgb *	pixel
	)

static

Check, if the given pixel in RGB colour space defines a red pixel

Parameters

[in]	ql	Full job description
[in]	pixel	The RGB pixel to check

Return values

Positive	Black pixel brightness (grey scale value)
Negative	Red pixel brightness (hsv's value)

This is a simple and ugly red dot detection. Since we have an RGB colour space, a red colour is hard to detect. Converting it into an HSV colour space makes it simpler to detect red.
If the hue is below 30° or above 350° it is more or less a red. It then depends on its saturation and value if it is a visible red - or still a black.
All checked values are user defined and part of the qldriver structure.

◆ red_dot_mark()

static void red_dot_mark	(	signed int	val,
		signed short *	black_pixel,
		signed short *	red_pixel
	)

static

Mark a red dot value into both line bufffers

Parameters

[in]	val	The brightness of the dot (-255 = full red brightness … 0 = no colour) (negative value!)
[out]	black_pixel	Where to store the corresponding black value for no black dot at this position
[out]	red_pixel	Where to store the corresponding red value

The input values for the red dots get inverted. A 0x00 input means "no red", so a 255 is stored to keep the paper colour. And a -255 input means a "full red", so a 0 is stored to print a red dot. At the same position, the black pixel is setup to keep the paper colour and to not disturb the red dot printing.

◆ remove_overlapping_dots()

static void remove_overlapping_dots	(	size_t	cnt,
		unsigned char	black_block[cnt],
		const unsigned char	red_block[cnt]
	)

static

Remove dots in the black block, if they are already set in the red block

Parameters

[in]	cnt	Element count in black_block and red_block
[in,out]	black_block	Monochrome data for black dots
[in]	red_block	Monochrome data for red dots

We should not send the command for low energy and high energy at the same dot position. So, remove the black dots (high energy) in favour of the red dots (low energy) if they overlap.

Precondition: Both blocks must have the same data size

◆ rgb2hsv()

static void rgb2hsv	(	struct qlhsv *	hsv,
		const struct qlrgb *	rgb_pixel
	)

static

Convert one pixel from RGB colour space to HSV colour space

Parameters

[out]	hsv	The target HSV colour space
[in]	rgb_pixel	The RGB pixel to convert

all three components equal to '0' will print a black dot.
all three components equal to '0xff' will print no dot.

Note: If the colour is on the vertical axis (e.g. a shade of grey), the qlhsv::hue component is returned as a negative number to mark it as invalid/undefined/do-not-use. But the qlhsv::value component is still valid in this case.

https://github.com/iamh2o/rgbw_colorspace_converter/
https://www.neltnerlabs.com/saikoled/how-to-convert-from-hsi-to-rgb-white

◆ to_grey()

static signed int to_grey ( const struct qlrgb * pixel )

static

Convert an RGB pixel to grey scale

Parameters

[in] pixel The pixel in RGB to convert (scale is 0…255 in each channel)

Returns: Grey value of the coloured RGB pixel (0…255)

Precondition: All colour component values are scaled from 0x00 … 0xff. Still expected scale here is: '0' no-colour, 0xff full colour

https://duckduckgo.com/?q=color%20picker%20%23808080

Variable Documentation

◆ terminate

int terminate

Change to '1' to signal the program should stop

Data Structures

Macros

Functions

Variables

Detailed Description

Macro Definition Documentation

◆ HIGH_ENERGY

◆ LOW_ENERGY

Function Documentation

◆ black_dot_mark()

◆ colour_command_get()

◆ colour_command_put()

◆ colour_line_convert()

◆ cups_ql_colour_line_process()

◆ cups_ql_colour_page_print()

◆ cups_ql_next_colour_line_read()

◆ fraction()

◆ is_red()

◆ red_dot_mark()

◆ remove_overlapping_dots()

◆ rgb2hsv()

◆ to_grey()

Variable Documentation

◆ terminate