#include <string.h>
#include <math.h>
#include "allheaders.h"

Functions
static PIX *	pixFindMinRunsOrthogonal (PIX *pixs, l_float32 angle, l_int32 depth)

PIX *	pixStrokeWidthTransform (PIX *pixs, l_int32 color, l_int32 depth, l_int32 nangles)

PIX *	pixRunlengthTransform (PIX *pixs, l_int32 color, l_int32 direction, l_int32 depth)

l_ok	pixFindHorizontalRuns (PIX pix, l_int32 y, l_int32 xstart, l_int32 xend, l_int32 pn)

l_ok	pixFindVerticalRuns (PIX pix, l_int32 x, l_int32 ystart, l_int32 yend, l_int32 pn)

NUMA *	pixFindMaxRuns (PIX pix, l_int32 direction, NUMA *pnastart)

l_ok	pixFindMaxHorizontalRunOnLine (PIX pix, l_int32 y, l_int32 pxstart, l_int32 *psize)

l_ok	pixFindMaxVerticalRunOnLine (PIX pix, l_int32 x, l_int32 pystart, l_int32 *psize)

l_ok	runlengthMembershipOnLine (l_int32 buffer, l_int32 size, l_int32 depth, l_int32 start, l_int32 *end, l_int32 n)

l_int32 *	makeMSBitLocTab (l_int32 bitval)

Detailed Description


    Label pixels by membership in runs
          PIX         *pixStrokeWidthTransform()
          static PIX  *pixFindMinRunsOrthogonal()
          PIX         *pixRunlengthTransform()

    Find runs along horizontal and vertical lines
          l_int32      pixFindHorizontalRuns()
          l_int32      pixFindVerticalRuns()

    Find max runs along horizontal and vertical lines
          l_int32      pixFindMaxRuns()
          l_int32      pixFindMaxHorizontalRunOnLine()
          l_int32      pixFindMaxVerticalRunOnLine()

    Compute runlength-to-membership transform on a line
          l_int32      runlengthMembershipOnLine()

    Make byte position LUT
          l_int32      makeMSBitLocTab()

 Here we're handling runs of either black or white pixels on 1 bpp
 images.  The directions of the runs in the stroke width transform
 are selectable from given sets of angles.  Most of the other runs
 are oriented either horizontally along the raster lines or
 vertically along pixel columns.

Definition in file runlength.c.

Function Documentation

◆ makeMSBitLocTab()

l_int32 * makeMSBitLocTab ( l_int32 bitval )

makeMSBitLocTab()

Parameters

[in] bitval either 0 or 1

Returns: table: for an input byte, the MS bit location, starting at 0 with the MSBit in the byte, or NULL on error.

Notes:
     (1) If bitval == 1, it finds the leftmost ON pixel in a byte;
         otherwise if bitval == 0, it finds the leftmost OFF pixel.
     (2) If there are no pixels of the indicated color in the byte,
         this returns 8.

Definition at line 774 of file runlength.c.

◆ pixFindHorizontalRuns()

l_ok pixFindHorizontalRuns	(	PIX *	pix,
		l_int32	y,
		l_int32 *	xstart,
		l_int32 *	xend,
		l_int32 *	pn )

pixFindHorizontalRuns()

Parameters

[in]	pix	1 bpp
[in]	y	line to traverse
[in]	xstart	returns array of start positions for fg runs
[in]	xend	returns array of end positions for fg runs
[out]	pn	the number of runs found

Returns: 0 if OK; 1 on error

Notes:
     (1) This finds foreground horizontal runs on a single scanline.
     (2) To find background runs, use pixInvert() before applying
         this function.
     (3) xstart and xend arrays are input.  They should be
         of size w/2 + 1 to insure that they can hold
         the maximum number of runs in the raster line.

Definition at line 369 of file runlength.c.

References GET_DATA_BIT.

Referenced by pixRunlengthTransform().

◆ pixFindMaxHorizontalRunOnLine()

l_ok pixFindMaxHorizontalRunOnLine	(	PIX *	pix,
		l_int32	y,
		l_int32 *	pxstart,
		l_int32 *	psize )

pixFindMaxHorizontalRunOnLine()

Parameters

[in]	pix	1 bpp
[in]	y	line to traverse
[out]	pxstart	[optional] start position
[out]	psize	the size of the run

Returns: 0 if OK; 1 on error

Notes:
     (1) This finds the longest foreground horizontal run on a scanline.
     (2) To find background runs, use pixInvert() before applying
         this function.

Definition at line 569 of file runlength.c.

References GET_DATA_BIT.

Referenced by pixFindMaxRuns().

◆ pixFindMaxRuns()

NUMA * pixFindMaxRuns	(	PIX *	pix,
		l_int32	direction,
		NUMA **	pnastart )

pixFindMaxRuns()

Parameters

[in]	pix	1 bpp
[in]	direction	L_HORIZONTAL_RUNS or L_VERTICAL_RUNS
[out]	pnastart	[optional] start locations of longest runs

Returns: na of lengths of runs, or NULL on error

Notes:
     (1) This finds the longest foreground runs by row or column
     (2) To find background runs, use pixInvert() before applying
         this function.

Definition at line 518 of file runlength.c.

References L_HORIZONTAL_RUNS, L_VERTICAL_RUNS, pixFindMaxHorizontalRunOnLine(), and pixFindMaxVerticalRunOnLine().

◆ pixFindMaxVerticalRunOnLine()

l_ok pixFindMaxVerticalRunOnLine	(	PIX *	pix,
		l_int32	x,
		l_int32 *	pystart,
		l_int32 *	psize )

pixFindMaxVerticalRunOnLine()

Parameters

[in]	pix	1 bpp
[in]	x	column to traverse
[out]	pystart	[optional] start position
[out]	psize	the size of the run

Returns: 0 if OK; 1 on error

Notes:
     (1) This finds the longest foreground vertical run on a scanline.
     (2) To find background runs, use pixInvert() before applying
         this function.

Definition at line 641 of file runlength.c.

References GET_DATA_BIT.

Referenced by pixFindMaxRuns().

◆ pixFindMinRunsOrthogonal()

static PIX * pixFindMinRunsOrthogonal	(	PIX *	pixs,
		l_float32	angle,
		l_int32	depth )

static

pixFindMinRunsOrthogonal()

Parameters

[in]	pixs	1 bpp
[in]	angle	in radians
[in]	depth	of pixd: 8 or 16 bpp

Returns: pixd 8 or 16 bpp, or NULL on error

Notes:
     (1) This computes, for each fg pixel in pixs, the minimum of
         the runlengths going through that pixel in two orthogonal
         directions: at angle and at (90 + angle).
     (2) We use rotation by shear because the forward and backward
         rotations by the same angle are exact inverse operations.
         As a result, the nonzero pixels in pixd correspond exactly
         to the fg pixels in pixs.  This is not the case with
         sampled rotation, due to spatial quantization.  Nevertheless,
         the result suffers from lack of exact correspondence
         between original and rotated pixels, also due to spatial
         quantization, causing some boundary pixels to be
         shifted from bg to fg or v.v.

Definition at line 197 of file runlength.c.

References L_BRING_IN_WHITE, L_HORIZONTAL_RUNS, L_VERTICAL_RUNS, PIX_SRC, and pixRunlengthTransform().

Referenced by pixStrokeWidthTransform().

◆ pixFindVerticalRuns()

l_ok pixFindVerticalRuns	(	PIX *	pix,
		l_int32	x,
		l_int32 *	ystart,
		l_int32 *	yend,
		l_int32 *	pn )

pixFindVerticalRuns()

Parameters

[in]	pix	1 bpp
[in]	x	line to traverse
[in]	ystart	returns array of start positions for fg runs
[in]	yend	returns array of end positions for fg runs
[out]	pn	the number of runs found

Returns: 0 if OK; 1 on error

Notes:
     (1) This finds foreground vertical runs on a single scanline.
     (2) To find background runs, use pixInvert() before applying
         this function.
     (3) ystart and yend arrays are input.  They should be
         of size h/2 + 1 to insure that they can hold
         the maximum number of runs in the raster line.

Definition at line 444 of file runlength.c.

References GET_DATA_BIT.

Referenced by pixRunlengthTransform().

◆ pixRunlengthTransform()

PIX * pixRunlengthTransform	(	PIX *	pixs,
		l_int32	color,
		l_int32	direction,
		l_int32	depth )

pixRunlengthTransform()

Parameters

[in]	pixs	1 bpp
[in]	color	0 for white runs, 1 for black runs
[in]	direction	L_HORIZONTAL_RUNS, L_VERTICAL_RUNS
[in]	depth	8 or 16 bpp

Returns: pixd 8 or 16 bpp, or NULL on error

Notes:
     (1) The dest Pix is 8 or 16 bpp, with the pixel values
         equal to the runlength in which it is a member.
         The length is clipped to the max pixel value if necessary.
     (2) color determines if we're labelling white or black runs.
     (3) A pixel that is not a member of the chosen color gets
         value 0; it belongs to a run of length 0 of the
         chosen color.
     (4) To convert for maximum dynamic range, either linear or
         log, use pixMaxDynamicRange().

Definition at line 261 of file runlength.c.

References L_HORIZONTAL_RUNS, L_VERTICAL_RUNS, pixFindHorizontalRuns(), pixFindVerticalRuns(), runlengthMembershipOnLine(), SET_DATA_BYTE, and SET_DATA_TWO_BYTES.

Referenced by pixFindMinRunsOrthogonal(), and pixStrokeWidthTransform().

◆ pixStrokeWidthTransform()

PIX * pixStrokeWidthTransform	(	PIX *	pixs,
		l_int32	color,
		l_int32	depth,
		l_int32	nangles )

pixStrokeWidthTransform()

Parameters

[in]	pixs	1 bpp
[in]	color	0 for white runs, 1 for black runs
[in]	depth	of pixd: 8 or 16 bpp
[in]	nangles	2, 4, 6 or 8

Returns: pixd 8 or 16 bpp, or NULL on error

Notes:
     (1) The dest Pix is 8 or 16 bpp, with the pixel values
         equal to the stroke width in which it is a member.
         The values are clipped to the max pixel value if necessary.
     (2) color determines if we're labelling white or black strokes.
     (3) A pixel that is not a member of the chosen color gets
         value 0; it belongs to a width of length 0 of the
         chosen color.
     (4) This chooses, for each dest pixel, the minimum of sets
         of runlengths through each pixel.  Here are the sets:
           nangles    increment          set
           -------    ---------    --------------------------------
              2          90       {0, 90}
              4          45       {0, 45, 90, 135}
              6          30       {0, 30, 60, 90, 120, 150}
              8          22.5     {0, 22.5, 45, 67.5, 90, 112.5, 135, 157.5}
     (5) Runtime scales linearly with (nangles - 2).

Definition at line 102 of file runlength.c.

References L_HORIZONTAL_RUNS, L_VERTICAL_RUNS, pixFindMinRunsOrthogonal(), and pixRunlengthTransform().

◆ runlengthMembershipOnLine()

l_ok runlengthMembershipOnLine	(	l_int32 *	buffer,
		l_int32	size,
		l_int32	depth,
		l_int32 *	start,
		l_int32 *	end,
		l_int32	n )

runlengthMembershipOnLine()

Parameters

[in]	buffer	into which full line of data is placed
[in]	size	full size of line; w or h
[in]	depth	8 or 16 bpp
[in]	start	array of start positions for fg runs
[in]	end	array of end positions for fg runs
[in]	n	the number of runs

Returns: 0 if OK; 1 on error

Notes:
     (1) Converts a set of runlengths into a buffer of
         runlength membership values.
     (2) Initialization of the array gives pixels that are
         not within a run the value 0.

Definition at line 720 of file runlength.c.

Referenced by pixRunlengthTransform().

Functions

Detailed Description

Function Documentation

◆ makeMSBitLocTab()

◆ pixFindHorizontalRuns()

◆ pixFindMaxHorizontalRunOnLine()

◆ pixFindMaxRuns()

◆ pixFindMaxVerticalRunOnLine()

◆ pixFindMinRunsOrthogonal()

◆ pixFindVerticalRuns()

◆ pixRunlengthTransform()

◆ pixStrokeWidthTransform()

◆ runlengthMembershipOnLine()