Image::Leptonica::Func::shear
version 0.04
shear.c
shear.c 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()
PIX * pixHShear ( PIX *pixd, PIX *pixs, l_int32 yloc, l_float32 radang, l_int32 incolor )
pixHShear() Input: pixd (<optional>, this can be null, equal to pixs, or different from pixs) pixs (no restrictions on depth) yloc (location of horizontal line, measured from origin) angle (in radians) incolor (L_BRING_IN_WHITE, L_BRING_IN_BLACK); Return: 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.
PIX * pixHShearCenter ( PIX *pixd, PIX *pixs, l_float32 radang, l_int32 incolor )
pixHShearCenter() Input: pixd (<optional>, if not null, must be equal to pixs) pixs angle (in radians) incolor (L_BRING_IN_WHITE, L_BRING_IN_BLACK); Return: 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.
PIX * pixHShearCorner ( PIX *pixd, PIX *pixs, l_float32 radang, l_int32 incolor )
pixHShearCorner() Input: pixd (<optional>, if not null, must be equal to pixs) pixs angle (in radians) incolor (L_BRING_IN_WHITE, L_BRING_IN_BLACK); Return: 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.
l_int32 pixHShearIP ( PIX *pixs, l_int32 yloc, l_float32 radang, l_int32 incolor )
pixHShearIP() Input: pixs yloc (location of horizontal line, measured from origin) angle (in radians) incolor (L_BRING_IN_WHITE, L_BRING_IN_BLACK); Return: 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.
PIX * pixHShearLI ( PIX *pixs, l_int32 yloc, l_float32 radang, l_int32 incolor )
pixHShearLI() Input: pixs (8 bpp or 32 bpp, or colormapped) yloc (location of horizontal line, measured from origin) angle (in radians, in range (-pi/2 ... pi/2)) incolor (L_BRING_IN_WHITE, L_BRING_IN_BLACK); Return: 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.
PIX * pixVShear ( PIX *pixd, PIX *pixs, l_int32 xloc, l_float32 radang, l_int32 incolor )
pixVShear() Input: pixd (<optional>, this can be null, equal to pixs, or different from pixs) pixs (no restrictions on depth) xloc (location of vertical line, measured from origin) angle (in radians; not too close to +-(pi / 2)) incolor (L_BRING_IN_WHITE, L_BRING_IN_BLACK); Return: 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.
PIX * pixVShearCenter ( PIX *pixd, PIX *pixs, l_float32 radang, l_int32 incolor )
pixVShearCenter() Input: pixd (<optional>, if not null, must be equal to pixs) pixs angle (in radians) incolor (L_BRING_IN_WHITE, L_BRING_IN_BLACK); Return: 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.
PIX * pixVShearCorner ( PIX *pixd, PIX *pixs, l_float32 radang, l_int32 incolor )
pixVShearCorner() Input: pixd (<optional>, if not null, must be equal to pixs) pixs angle (in radians) incolor (L_BRING_IN_WHITE, L_BRING_IN_BLACK); Return: 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.
l_int32 pixVShearIP ( PIX *pixs, l_int32 xloc, l_float32 radang, l_int32 incolor )
pixVShearIP() Input: pixs (all depths; not colormapped) xloc (location of vertical line, measured from origin) angle (in radians) incolor (L_BRING_IN_WHITE, L_BRING_IN_BLACK); Return: 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.
PIX * pixVShearLI ( PIX *pixs, l_int32 xloc, l_float32 radang, l_int32 incolor )
pixVShearLI() Input: pixs (8 bpp or 32 bpp, or colormapped) xloc (location of vertical line, measured from origin) angle (in radians, in range (-pi/2 ... pi/2)) incolor (L_BRING_IN_WHITE, L_BRING_IN_BLACK); Return: 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.
Zakariyya Mughal <zmughal@cpan.org>
This software is copyright (c) 2014 by Zakariyya Mughal.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.
To install Image::Leptonica, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Image::Leptonica
CPAN shell
perl -MCPAN -e shell install Image::Leptonica
For more information on module installation, please visit the detailed CPAN module installation guide.