Conjecture::PixFilt Class Reference

#include <PixFilt.h>

Inheritance diagram for Conjecture::PixFilt:

List of all members.

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Detailed Description

Provides a generalized pixel filtering mechanism.

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This class acts as a 2d "bit-based regular expression", bitexp. For example, suppose we want to determine whether a particular pixel <tx,ty> within an image matches the following bitexp:

?1? 10? ?1?

In such a situation, we may want to switch the 0 to a 1. Instances of this class can describe this kind of matching and can establish whether it is true for a particular pixel position within an image.

To explain the rather esoteric data-structures, we'll describe the internal state needed to describe the above mask.

• it consists of 3 consecutive row-specific tests
• the first row test involves verifying that a one-pixel sequence matches 1.
• the second row test involves verifying that a two-pixel sequence matches 10. This match is offset by one relative to the first one.
• the third row test involves verifying that a one-pixel sequence matches 1. Same offset as first row.

The state: _rows = 3 _yoffset = 1 _data[0] = (0x1 << 8) | ( ( 0+8)<<4 ) | 1 _data[1] = (0x10 << 8) | ( (-1+8)<<4 ) | 1 _data[2] = (0x1 << 8) | ( ( 0+8)<<4 ) | 1

SUBTLETIES ----------

• There is an unfortute difference between the <x,y> coordinate system defined on images, which places <0,0> in the top-left corner, and the <bx,by> bit position define on bit vectors, which places bit 0 on the right, *not* the left.
• If 'tx' is the target x position, it will be very rare for any of the row masks to have a left position that is to the right of 'tx' (masks usually center 'tx' within them, so the left most part of the mask is usually to the left of 'tx'. We make the common case positive, so the 'offset' value indicates the number of pixels to shift left (positive going left, negative going right).

Public Member Functions
	PixFilt (u1 yoffset)
	PixFilt::PixFilt (u1 yoffset, u1 mask1, int offset1)
	PixFilt::PixFilt (u1 yoffset, u1 mask1, int offset1, u1 mask2, int offset2)
	PixFilt::PixFilt (u1 yoffset, u1 mask1, int offset1, u1 mask2, int offset2, u1 mask3, int offset3)
const u2 *	data () const
const u1 &	rows () const
const u1 &	yoffset () const
void	add (u1 mask, int offset)
std::string	str () const
u1	mask (u1 index) const
int	offset (u1 index) const
u1	size (u1 index) const
bool	match (const std::vector< u4 > &rows, u1 width, u1 x, u1 y)
bool	match (const OptIm &im, u1 x, u1 y)
int	filter (std::vector< u4 > &im, u1 width, bool set=true)
int	filter (OptIm &im, bool set=true)
Static Public Member Functions
static void	test (int argc=0, const char *argv[]=NULL)
Protected Member Functions
void	rowsIs (const u1 &rows)
void	yoffsetIs (const u1 &yoffset)
Static Protected Member Functions
static int	ffs (u1 val)

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Member Function Documentation

int Conjecture::PixFilt::ffs (  u1  val  )  [static, protected]

find-first-set: returns the bit position of the left-most on bit within 'val. Bit 0 is on far right. The value 0x5 would return 2 because 0x5 in binary is 101 (left most 1 is bit 2). The value '0x21' would return 5 because 0x21 is binary 100001 (left most 1 is bit 5).

int Conjecture::PixFilt::filter (  std::vector< u4 > &  im, u1  width, bool  set = true )

Apply this filter to the entire image Parameters: set  True means turning on pixels that are off. False means turning off pixels that are on. Returns the number of pixels changed.

bool Conjecture::PixFilt::match (  const std::vector< u4 > &  rows, u1  width, u1  x, u1  y )

Returns true if this PixFilt matches against <x,y> of 'im'

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The documentation for this class was generated from the following files:

• PixFilt.h
• PixFilt.cc

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