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

Macros
#define	DEBUG 0

Functions
static l_float32	normalizeAngleForShear (l_float32 radang, l_float32 mindif)

PIX *	pixHShear (PIX pixd, PIX pixs, l_int32 yloc, l_float32 radang, l_int32 incolor)

PIX *	pixVShear (PIX pixd, PIX pixs, l_int32 xloc, l_float32 radang, l_int32 incolor)

PIX *	pixHShearCorner (PIX pixd, PIX pixs, l_float32 radang, l_int32 incolor)

PIX *	pixVShearCorner (PIX pixd, PIX pixs, l_float32 radang, l_int32 incolor)

PIX *	pixHShearCenter (PIX pixd, PIX pixs, l_float32 radang, l_int32 incolor)

PIX *	pixVShearCenter (PIX pixd, PIX pixs, l_float32 radang, l_int32 incolor)

l_ok	pixHShearIP (PIX *pixs, l_int32 yloc, l_float32 radang, l_int32 incolor)

l_ok	pixVShearIP (PIX *pixs, l_int32 xloc, l_float32 radang, l_int32 incolor)

PIX *	pixHShearLI (PIX *pixs, l_int32 yloc, l_float32 radang, l_int32 incolor)

PIX *	pixVShearLI (PIX *pixs, l_int32 xloc, l_float32 radang, l_int32 incolor)

Variables
static const l_float32	MIN_DIFF_FROM_HALF_PI = 0.04

Detailed Description

   About arbitrary lines
          PIX      *pixHShear()
          PIX      *pixVShear()

   About special 'points': UL corner and center
          PIX      *pixHShearCorner()
          PIX      *pixVShearCorner()
          PIX      *pixHShearCenter()
          PIX      *pixVShearCenter()

   In place about arbitrary lines
          l_int32   pixHShearIP()
          l_int32   pixVShearIP()

   Linear interpolated shear about arbitrary lines
          PIX      *pixHShearLI()
          PIX      *pixVShearLI()

   Static helper
     static l_float32  normalizeAngleForShear()

Definition in file shear.c.

Function Documentation

◆ pixHShear()

PIX* pixHShear	(	PIX *	pixd,
		PIX *	pixs,
		l_int32	yloc,
		l_float32	radang,
		l_int32	incolor
	)

pixHShear()

Parameters

[in]	pixd	[optional], this can be null, equal to pixs, or different from pixs
[in]	pixs	no restrictions on depth
[in]	yloc	location of horizontal line, measured from origin
[in]	radang	angle in radians
[in]	incolor	L_BRING_IN_WHITE, L_BRING_IN_BLACK;

Returns: pixd, always

Notes:
     (1) There are 3 cases:
           (a) pixd == null (make a new pixd)
           (b) pixd == pixs (in-place)
           (c) pixd != pixs
     (2) For these three cases, use these patterns, respectively:
             pixd = pixHShear(NULL, pixs, ...);
             pixHShear(pixs, pixs, ...);
             pixHShear(pixd, pixs, ...);
     (3) This shear leaves the horizontal line of pixels at y = yloc
         invariant.  For a positive shear angle, pixels above this
         line are shoved to the right, and pixels below this line
         move to the left.
     (4) With positive shear angle, this can be used, along with
         pixVShear(), to perform a cw rotation, either with 2 shears
         (for small angles) or in the general case with 3 shears.
     (5) Changing the value of yloc is equivalent to translating
         the result horizontally.
     (6) This brings in 'incolor' pixels from outside the image.
     (7) For in-place operation, pixs cannot be colormapped,
         because the in-place operation only blits in 0 or 1 bits,
         not an arbitrary colormap index.
     (8) The angle is brought into the range [-pi, -pi].  It is
         not permitted to be within MIN_DIFF_FROM_HALF_PI radians
         from either -pi/2 or pi/2.

Definition at line 113 of file shear.c.

References L_BRING_IN_BLACK, and L_BRING_IN_WHITE.

Referenced by pixHShearCenter(), and pixHShearCorner().

◆ pixHShearCenter()

PIX* pixHShearCenter	(	PIX *	pixd,
		PIX *	pixs,
		l_float32	radang,
		l_int32	incolor
	)

pixHShearCenter()

Parameters

[in]	pixd	[optional], if not null, must be equal to pixs
[in]	pixs
[in]	radang	angle in radians
[in]	incolor	L_BRING_IN_WHITE, L_BRING_IN_BLACK;

Returns: pixd, or NULL on error.

Notes:
     (1) See pixHShear() for usage.
     (2) This does a horizontal shear about the center, with (+) shear
         pushing increasingly leftward (-x) with increasing y.

Definition at line 390 of file shear.c.

References pixHShear().

◆ pixHShearCorner()

PIX* pixHShearCorner	(	PIX *	pixd,
		PIX *	pixs,
		l_float32	radang,
		l_int32	incolor
	)

pixHShearCorner()

Parameters

[in]	pixd	[optional], if not null, must be equal to pixs
[in]	pixs
[in]	radang	angle in radians
[in]	incolor	L_BRING_IN_WHITE, L_BRING_IN_BLACK;

Returns: pixd, or NULL on error.

Notes:
     (1) See pixHShear() for usage.
     (2) This does a horizontal shear about the UL corner, with (+) shear
         pushing increasingly leftward (-x) with increasing y.

Definition at line 328 of file shear.c.

References pixHShear().

◆ pixHShearIP()

l_ok pixHShearIP	(	PIX *	pixs,
		l_int32	yloc,
		l_float32	radang,
		l_int32	incolor
	)

pixHShearIP()

Parameters

[in]	pixs
[in]	yloc	location of horizontal line, measured from origin
[in]	radang	angle in radians
[in]	incolor	L_BRING_IN_WHITE, L_BRING_IN_BLACK;

Returns: 0 if OK; 1 on error

Notes:
     (1) This is an in-place version of pixHShear(); see comments there.
     (2) This brings in 'incolor' pixels from outside the image.
     (3) pixs cannot be colormapped, because the in-place operation
         only blits in 0 or 1 bits, not an arbitrary colormap index.
     (4) Does a horizontal full-band shear about the line with (+) shear
         pushing increasingly leftward (-x) with increasing y.

Definition at line 459 of file shear.c.

References L_BRING_IN_BLACK, and L_BRING_IN_WHITE.

Referenced by pixAffineSequential().

◆ pixHShearLI()

PIX* pixHShearLI	(	PIX *	pixs,
		l_int32	yloc,
		l_float32	radang,
		l_int32	incolor
	)

pixHShearLI()

Parameters

[in]	pixs	8 bpp or 32 bpp, or colormapped
[in]	yloc	location of horizontal line, measured from origin
[in]	radang	angle in radians, in range (-pi/2 ... pi/2)
[in]	incolor	L_BRING_IN_WHITE, L_BRING_IN_BLACK;

Returns: pixd sheared, or NULL on error

Notes:
     (1) This does horizontal shear with linear interpolation for
         accurate results on 8 bpp gray, 32 bpp rgb, or cmapped images.
         It is relatively slow compared to the sampled version
         implemented by rasterop, but the result is much smoother.
     (2) This shear leaves the horizontal line of pixels at y = yloc
         invariant.  For a positive shear angle, pixels above this
         line are shoved to the right, and pixels below this line
         move to the left.
     (3) Any colormap is removed.
     (4) The angle is brought into the range [-pi/2 + del, pi/2 - del],
         where del == MIN_DIFF_FROM_HALF_PI.

Definition at line 617 of file shear.c.

References pixGetDimensions().

◆ pixVShear()

PIX* pixVShear	(	PIX *	pixd,
		PIX *	pixs,
		l_int32	xloc,
		l_float32	radang,
		l_int32	incolor
	)

pixVShear()

Parameters

[in]	pixd	[optional], this can be null, equal to pixs, or different from pixs
[in]	pixs	no restrictions on depth
[in]	xloc	location of vertical line, measured from origin
[in]	radang	angle in radians; not too close to +-(pi / 2)
[in]	incolor	L_BRING_IN_WHITE, L_BRING_IN_BLACK;

Returns: pixd, or NULL on error

Notes:
     (1) There are 3 cases:
           (a) pixd == null (make a new pixd)
           (b) pixd == pixs (in-place)
           (c) pixd != pixs
     (2) For these three cases, use these patterns, respectively:
             pixd = pixVShear(NULL, pixs, ...);
             pixVShear(pixs, pixs, ...);
             pixVShear(pixd, pixs, ...);
     (3) This shear leaves the vertical line of pixels at x = xloc
         invariant.  For a positive shear angle, pixels to the right
         of this line are shoved downward, and pixels to the left
         of the line move upward.
     (4) With positive shear angle, this can be used, along with
         pixHShear(), to perform a cw rotation, either with 2 shears
         (for small angles) or in the general case with 3 shears.
     (5) Changing the value of xloc is equivalent to translating
         the result vertically.
     (6) This brings in 'incolor' pixels from outside the image.
     (7) For in-place operation, pixs cannot be colormapped,
         because the in-place operation only blits in 0 or 1 bits,
         not an arbitrary colormap index.
     (8) The angle is brought into the range [-pi, -pi].  It is
         not permitted to be within MIN_DIFF_FROM_HALF_PI radians
         from either -pi/2 or pi/2.

Definition at line 230 of file shear.c.

References L_BRING_IN_BLACK, and L_BRING_IN_WHITE.

Referenced by pixVShearCenter(), and pixVShearCorner().

◆ pixVShearCenter()

PIX* pixVShearCenter	(	PIX *	pixd,
		PIX *	pixs,
		l_float32	radang,
		l_int32	incolor
	)

pixVShearCenter()

Parameters

[in]	pixd	[optional], if not null, must be equal to pixs
[in]	pixs
[in]	radang	angle in radians
[in]	incolor	L_BRING_IN_WHITE, L_BRING_IN_BLACK;

Returns: pixd, or NULL on error.

Notes:
     (1) See pixVShear() for usage.
     (2) This does a vertical shear about the center, with (+) shear
         pushing increasingly downward (+y) with increasing x.

Definition at line 421 of file shear.c.

References pixVShear().

◆ pixVShearCorner()

PIX* pixVShearCorner	(	PIX *	pixd,
		PIX *	pixs,
		l_float32	radang,
		l_int32	incolor
	)

pixVShearCorner()

Parameters

[in]	pixd	[optional], if not null, must be equal to pixs
[in]	pixs
[in]	radang	angle in radians
[in]	incolor	L_BRING_IN_WHITE, L_BRING_IN_BLACK;

Returns: pixd, or NULL on error.

Notes:
     (1) See pixVShear() for usage.
     (2) This does a vertical shear about the UL corner, with (+) shear
         pushing increasingly downward (+y) with increasing x.

Definition at line 359 of file shear.c.

References pixVShear().

◆ pixVShearIP()

l_ok pixVShearIP	(	PIX *	pixs,
		l_int32	xloc,
		l_float32	radang,
		l_int32	incolor
	)

pixVShearIP()

Parameters

[in]	pixs	all depths; not colormapped
[in]	xloc	location of vertical line, measured from origin
[in]	radang	angle in radians
[in]	incolor	L_BRING_IN_WHITE, L_BRING_IN_BLACK;

Returns: 0 if OK; 1 on error

Notes:
     (1) This is an in-place version of pixVShear(); see comments there.
     (2) This brings in 'incolor' pixels from outside the image.
     (3) pixs cannot be colormapped, because the in-place operation
         only blits in 0 or 1 bits, not an arbitrary colormap index.
     (4) Does a vertical full-band shear about the line with (+) shear
         pushing increasingly downward (+y) with increasing x.

Definition at line 534 of file shear.c.

References L_BRING_IN_BLACK, and L_BRING_IN_WHITE.

Referenced by pixAffineSequential().

◆ pixVShearLI()

PIX* pixVShearLI	(	PIX *	pixs,
		l_int32	xloc,
		l_float32	radang,
		l_int32	incolor
	)

pixVShearLI()

Parameters

[in]	pixs	8 bpp or 32 bpp, or colormapped
[in]	xloc	location of vertical line, measured from origin
[in]	radang	angle in radians, in range (-pi/2 ... pi/2)
[in]	incolor	L_BRING_IN_WHITE, L_BRING_IN_BLACK;

Returns: pixd sheared, or NULL on error

Notes:
     (1) This does vertical shear with linear interpolation for
         accurate results on 8 bpp gray, 32 bpp rgb, or cmapped images.
         It is relatively slow compared to the sampled version
         implemented by rasterop, but the result is much smoother.
     (2) This shear leaves the vertical line of pixels at x = xloc
         invariant.  For a positive shear angle, pixels to the right
         of this line are shoved downward, and pixels to the left
         of the line move upward.
     (3) Any colormap is removed.
     (4) The angle is brought into the range [-pi/2 + del, pi/2 - del],
         where del == MIN_DIFF_FROM_HALF_PI.

Definition at line 729 of file shear.c.

References pixGetDimensions().

Macros

Functions

Variables

Detailed Description

Function Documentation

◆ pixHShear()

◆ pixHShearCenter()

◆ pixHShearCorner()

◆ pixHShearIP()

◆ pixHShearLI()

◆ pixVShear()

◆ pixVShearCenter()

◆ pixVShearCorner()

◆ pixVShearIP()

◆ pixVShearLI()