encode_method_1030.h File Reference

Declarations for the 1030 encoding method. More...

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Data Structures
struct	cm1030_line_header
struct	cm1030_block_header
struct	cm1030_line
struct	cm1030_band

Macros
#define	C1030_MAX_BYTES_IN_ONE_BLOCK   16350
#define	MAX_LINE_LENGTH   1275
#define	C1030_LINE_LENGTH   (MAX_LINE_LENGTH + 16)
#define	C1030_MAX_LINES_IN_ONE_BAND   256
#define	C1030_LINE_IS_EMPTY   0xff
#define	C1030_LINE_IS_EQUAL   0x00

Functions
void	hl_c1030_block_init (struct cm1030_band *block)
void	hl_c1030_block_exit (struct cm1030_band *block)
void	hl_c1030_line_edit (struct cm1030_line *c, size_t cnt, const uint8_t line[cnt], const uint8_t *last)
int	hl_c1030_block_line_add (struct cm1030_band *block, const struct cm1030_line *line, FILE *outstream)
int	hl_c1030_block_flush (struct cm1030_band *band, FILE *outstream)
int	hl_c1030_block_pad (struct cm1030_band *block, unsigned missing_line_cnt, FILE *outstream)

Macro Definition Documentation

C1030_MAX_BYTES_IN_ONE_BLOCK

#define C1030_MAX_BYTES_IN_ONE_BLOCK   16350

After reaching this size limit, a band needs to be split into more than one block of data to still define the whole band data.

MAX_LINE_LENGTH

#define MAX_LINE_LENGTH   1275

Line length for a letter (e.g. 8.5") @ 1200 DPI is 10.200 dots or 1275 byes.

C1030_LINE_LENGTH

#define C1030_LINE_LENGTH   (MAX_LINE_LENGTH + 16)

Line length for a letter (e.g. 8.5") @ 1200 DPI is 10.200 dots or 1275 byes. Plus some reserve for the encoding if the whole line isn't compressable.

C1030_MAX_LINES_IN_ONE_BAND

#define C1030_MAX_LINES_IN_ONE_BAND   256

In the 1030 encoding format, the full page is divided vertically into bands and each band has a maximum count of lines.

The real count depends on the printer device and its available memory. This value is a default only and can be overwritten by the band_line_count_1030 INI variable.

C1030_LINE_IS_EMPTY

#define C1030_LINE_IS_EMPTY   0xff

Special 'edit' count value to mark a line as empty

C1030_LINE_IS_EQUAL

#define C1030_LINE_IS_EQUAL   0x00

Special 'edit' count value to mark a line as the same as the previous one (e.g. no 'edits' required)

Function Documentation

hl_c1030_block_init()

void hl_c1030_block_init

(

struct cm1030_band *

block

)

Init the printer data block as a preparation

Parameters

[in,out]

block

Printer data block info

hl_c1030_block_exit()

void hl_c1030_block_exit

(

struct cm1030_band *

block

)

Free resources allocated when processing

Parameters

[in]

block

Printer data block info

hl_c1030_line_edit()

void hl_c1030_line_edit	(	struct cm1030_line *	c,
		size_t	cnt,
		const uint8_t	line[cnt],
		const uint8_t *	last
	)

Edit one full line as best as possible

Parameters

[in,out]	c	Compression output buffer
[in]	cnt	Count of bytes with active pixel in both lines
[in]	line	Line to achieve
[in]	last	Previous line (can be NULL)

This function creates all required 'edits' to form the current line inside the printer with the help/reference of the previous (and already existing inside the printer) line. It handles special cases, where the current line is empty (all pixel white) or where the current line is identical to the previous line. To avoid useless encodings (full substitute or repeat until the end) it then first shrinks the length of the line to the really required one (by comparing the current and previous line content) backwards from the end. And then starts the 'edit' based encoding.

If a line has no predecessor (e.g. last is NULL) the first approach was to encode it against an empty line. This seemed to solve some visual artefacts on the paper. But there are still some artefacts with vertical lines, where this approach fails. As a result, if there is no reference line the full line must be encoded.

hl_c1030_block_line_add()

int hl_c1030_block_line_add	(	struct cm1030_band *	block,
		const struct cm1030_line *	line,
		FILE *	outstream
	)

Add one line of dot data to the data block

Parameters

[in]	block	The data block to add the line to
[in]	line	Line info
[in,out]	outstream	The stream to send the printer data to

Return values

0	On success
-errno	If the data flushing to the printer's stream has failed
-EAGAIN	Add the line again, because the block was flushed

This function tries to add the given line data to the block data until the max block size limit of C1030_MAX_BYTES_IN_ONE_BLOCK is hit. If hit, it flushes the already accumulated band data into a valid transfer block of data via hl_c1030_block_flush().

Note

In case the already accumulated data hits the block size limit, the line gets ignored and must be added again.

hl_c1030_block_flush()

int hl_c1030_block_flush	(	struct cm1030_band *	band,
		FILE *	outstream
	)

Flush out the current transfer block

Parameters

[in]	band	Band info
[in,out]	outstream	The stream to send the printer data to

Return values

0	On success
-errno	If the data flushing to the printer has failed

This flushes the data out to the printer with a leading PCL command of the form:

• 'band->bused_cnt' as an integer ASCII number (variable length)
• the char 'w' (one byte)
• 'band->blines' as a binary word in big endian (one word, e.g. two bytes)

...and then appends the corresponding dot data to it.

Note

'Flushing' here means only to write the accumulated line encoding data to the printer's stream. It doesn't mean, the printer receives this data immediately. The real stream flush should happen when processing of the current page finishes.

Precondition

Currently at most C1030_MAX_BYTES_IN_ONE_BLOCK should be in the buffer. More this function cannot handle.

hl_c1030_block_pad()

int hl_c1030_block_pad	(	struct cm1030_band *	block,
		unsigned	missing_line_cnt,
		FILE *	outstream
	)

Pad the current data block to the full band line count

Parameters

[in]	block	Current block data info
[in]	missing_line_cnt	Lines to add to pad the current band
[in,out]	outstream	The stream to send the printer data to

Return values

0	On success
-errno	If the data flushing to the printer's stream has failed

The printer only prints in bands of n lines. Bands with less than these n lines are skipped entirely (and silently). This hurts at the bottom edge of a page, where the vertical dot count might not be a multiple of these n lines.

This function pads the current data block up to these n lines on demand with empty lines. It must be called once at the end of each page if you know your last band has less lines than these n lines.

Postcondition

A call to hl_c1030_block_flush()