This is pnmnlfilt.c in view mode; [Download] [Up]
/* pnmnlfilt.c - 4 in 1 (2 non-linear) filter
** - smooth an anyimage
** - do alpha trimmed mean filtering on an anyimage
** - do optimal estimation smoothing on an anyimage
** - do edge enhancement on an anyimage
**
** Version 1.0
**
** The implementation of an alpha-trimmed mean filter
** is based on the description in IEEE CG&A May 1990
** Page 23 by Mark E. Lee and Richard A. Redner.
**
** The paper recommends using a hexagon sampling region around each
** pixel being processed, allowing an effective sub pixel radius to be
** specified. The hexagon values are sythesised by area sampling the
** rectangular pixels with a hexagon grid. The seven hexagon values
** obtained from the 3x3 pixel grid are used to compute the alpha
** trimmed mean. Note that an alpha value of 0.0 gives a conventional
** mean filter (where the radius controls the contribution of
** surrounding pixels), while a value of 0.5 gives a median filter.
** Although there are only seven values to trim from before finding
** the mean, the algorithm has been extended from that described in
** CG&A by using interpolation, to allow a continuous selection of
** alpha value between and including 0.0 to 0.5 The useful values
** for radius are between 0.3333333 (where the filter will have no
** effect because only one pixel is sampled), to 1.0, where all
** pixels in the 3x3 grid are sampled.
**
** The optimal estimation filter is taken from an article "Converting Dithered
** Images Back to Gray Scale" by Allen Stenger, Dr Dobb's Journal, November
** 1992, and this article references "Digital Image Enhancement andNoise Filtering by
** Use of Local Statistics", Jong-Sen Lee, IEEE Transactions on Pattern Analysis and
** Machine Intelligence, March 1980.
**
** Also borrow the technique used in pgmenhance(1) to allow edge
** enhancement if the alpha value is negative.
**
** Author:
** Graeme W. Gill, 30th Jan 1993
** graeme@labtam.oz.au
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation. This software is provided "as is" without express or
** implied warranty.
*/
#include <math.h>
#include "pnm.h"
double hex_area ARGS((double, double, double, double, double));
int atfilt_setup ARGS((double, double, double));
int atfilt0 ARGS((int *)), atfilt1 ARGS((int *)), atfilt2 ARGS((int *));
int atfilt3 ARGS((int *)), atfilt4 ARGS((int *)), atfilt5 ARGS((int *));
int (*atfuncs[6]) ARGS((int *)) = {atfilt0,atfilt1,atfilt2,atfilt3,atfilt4,atfilt5};
xelval omaxval; /* global so that pixel processing code can get at it quickly */
int noisevariance; /* global so that pixel processing code can get at it quickly */
int
main( argc, argv )
int argc;
char* argv[];
{
double radius=0.0,alpha= -1.0;
FILE* ifp;
int rows, cols, format, oformat, row, col;
xelval maxval;
int (*atfunc) ARGS((int *));
char* usage = "alpha radius pnmfile\n\
0.0 <= alpha <= 0.5 for alpha trimmed mean -or- \n\
1.0 <= alpha <= 2.0 for optimal estimation -or- \n\
-0.1 >= alpha >= -0.9 for edge enhancement\n\
0.3333 <= radius <= 1.0 specify effective radius\n";
pnm_init( &argc, argv );
if ( argc < 3 || argc > 4 )
pm_usage( usage );
if ( sscanf( argv[1], "%lf", &alpha ) != 1 )
pm_usage( usage );
if ( sscanf( argv[2], "%lf", &radius ) != 1 )
pm_usage( usage );
if ((alpha > -0.1 && alpha < 0.0) || (alpha > 0.5 && alpha < 1.0))
pm_error( "Alpha must be in range 0.0 <= alpha <= 0.5 for alpha trimmed mean" );
if (alpha > 2.0)
pm_error( "Alpha must be in range 1.0 <= alpha <= 2.0 for optimal estimation" );
if (alpha < -0.9 || (alpha > -0.1 && alpha < 0.0))
pm_error( "Alpha must be in range -0.9 <= alpha <= -0.1 for edge enhancement" );
if (radius < 0.333 || radius > 1.0)
pm_error( "Radius must be in range 0.333333333 <= radius <= 1.0" );
if ( argc == 4 )
ifp = pm_openr( argv[3] );
else
ifp = stdin;
pnm_readpnminit( ifp, &cols, &rows, &maxval, &format );
oformat = PNM_FORMAT_TYPE(format);
omaxval = PPM_MAXMAXVAL; /* force output to max precision */
atfunc = atfuncs[atfilt_setup(alpha,radius,(double)omaxval/(double)maxval)];
if ( oformat < PGM_TYPE )
{
if (PGM_MAXMAXVAL > PPM_MAXMAXVAL)
pm_error( "Can't handle pgm input file as maxval is too big" );
oformat = RPGM_FORMAT;
pm_message( "promoting file to PGM" );
}
pnm_writepnminit( stdout, cols, rows, omaxval, oformat, 0 );
if ( PNM_FORMAT_TYPE(oformat) == PPM_TYPE )
{
xel *irows[3];
xel *irow0, *irow1, *irow2, *orow;
int pr[9],pg[9],pb[9]; /* 3x3 neighbor pixel values */
int r,g,b;
irows[0] = pnm_allocrow( cols );
irows[1] = pnm_allocrow( cols );
irows[2] = pnm_allocrow( cols );
irow0 = irows[0];
irow1 = irows[1];
irow2 = irows[2];
orow = pnm_allocrow( cols );
for ( row = 0; row < rows; row++ )
{
int po,no; /* offsets for left and right colums in 3x3 */
register xel *ip0, *ip1, *ip2, *op;
if (row == 0)
{
irow0 = irow1;
pnm_readpnmrow( ifp, irow1, cols, maxval, format );
}
if (row == (rows-1))
irow2 = irow1;
else
pnm_readpnmrow( ifp, irow2, cols, maxval, format );
for (col = cols-1,po= col>0?1:0,no=0,ip0=irow0,ip1=irow1,ip2=irow2,op=orow;
col >= 0;
col--,ip0++,ip1++,ip2++,op++, no |= 1,po = col!= 0 ? po : 0)
{
/* grab 3x3 pixel values */
pr[0] = PPM_GETR( *ip1 );
pg[0] = PPM_GETG( *ip1 );
pb[0] = PPM_GETB( *ip1 );
pr[1] = PPM_GETR( *(ip1-no) );
pg[1] = PPM_GETG( *(ip1-no) );
pb[1] = PPM_GETB( *(ip1-no) );
pr[5] = PPM_GETR( *(ip1+po) );
pg[5] = PPM_GETG( *(ip1+po) );
pb[5] = PPM_GETB( *(ip1+po) );
pr[3] = PPM_GETR( *(ip2) );
pg[3] = PPM_GETG( *(ip2) );
pb[3] = PPM_GETB( *(ip2) );
pr[2] = PPM_GETR( *(ip2-no) );
pg[2] = PPM_GETG( *(ip2-no) );
pb[2] = PPM_GETB( *(ip2-no) );
pr[4] = PPM_GETR( *(ip2+po) );
pg[4] = PPM_GETG( *(ip2+po) );
pb[4] = PPM_GETB( *(ip2+po) );
pr[6] = PPM_GETR( *(ip0+po) );
pg[6] = PPM_GETG( *(ip0+po) );
pb[6] = PPM_GETB( *(ip0+po) );
pr[8] = PPM_GETR( *(ip0-no) );
pg[8] = PPM_GETG( *(ip0-no) );
pb[8] = PPM_GETB( *(ip0-no) );
pr[7] = PPM_GETR( *(ip0) );
pg[7] = PPM_GETG( *(ip0) );
pb[7] = PPM_GETB( *(ip0) );
r = (*atfunc)(pr);
g = (*atfunc)(pg);
b = (*atfunc)(pb);
PPM_ASSIGN( *op, r, g, b );
}
pnm_writepnmrow( stdout, orow, cols, omaxval, oformat, 0 );
if (irow1 == irows[2])
{
irow1 = irows[0];
irow2 = irows[1];
irow0 = irows[2];
}
else if (irow1 == irows[1])
{
irow2 = irows[0];
irow0 = irows[1];
irow1 = irows[2];
}
else /* must be at irows[0] */
{
irow0 = irows[0];
irow1 = irows[1];
irow2 = irows[2];
}
}
}
else /* Else must be PGM */
{
xel *irows[3];
xel *irow0, *irow1, *irow2, *orow;
int p[9]; /* 3x3 neighbor pixel values */
int pv;
int promote;
irows[0] = pnm_allocrow( cols );
irows[1] = pnm_allocrow( cols );
irows[2] = pnm_allocrow( cols );
irow0 = irows[0];
irow1 = irows[1];
irow2 = irows[2];
orow = pnm_allocrow( cols );
/* we scale maxval to omaxval */
promote = ( PNM_FORMAT_TYPE(format) != PNM_FORMAT_TYPE(oformat) );
for ( row = 0; row < rows; row++ )
{
int po,no; /* offsets for left and right colums in 3x3 */
register xel *ip0, *ip1, *ip2, *op;
if (row == 0)
{
irow0 = irow1;
pnm_readpnmrow( ifp, irow1, cols, maxval, format );
if ( promote )
pnm_promoteformatrow( irow1, cols, maxval, format, maxval, oformat );
}
if (row == (rows-1))
irow2 = irow1;
else
{
pnm_readpnmrow( ifp, irow2, cols, maxval, format );
if ( promote )
pnm_promoteformatrow( irow2, cols, maxval, format, maxval, oformat );
}
for (col = cols-1,po= col>0?1:0,no=0,ip0=irow0,ip1=irow1,ip2=irow2,op=orow;
col >= 0;
col--,ip0++,ip1++,ip2++,op++, no |= 1,po = col!= 0 ? po : 0)
{
/* grab 3x3 pixel values */
p[0] = PNM_GET1( *ip1 );
p[1] = PNM_GET1( *(ip1-no) );
p[5] = PNM_GET1( *(ip1+po) );
p[3] = PNM_GET1( *(ip2) );
p[2] = PNM_GET1( *(ip2-no) );
p[4] = PNM_GET1( *(ip2+po) );
p[6] = PNM_GET1( *(ip0+po) );
p[8] = PNM_GET1( *(ip0-no) );
p[7] = PNM_GET1( *(ip0) );
pv = (*atfunc)(p);
PNM_ASSIGN1( *op, pv );
}
pnm_writepnmrow( stdout, orow, cols, omaxval, oformat, 0 );
if (irow1 == irows[2])
{
irow1 = irows[0];
irow2 = irows[1];
irow0 = irows[2];
}
else if (irow1 == irows[1])
{
irow2 = irows[0];
irow0 = irows[1];
irow1 = irows[2];
}
else /* must be at irows[0] */
{
irow0 = irows[0];
irow1 = irows[1];
irow2 = irows[2];
}
}
}
pm_close( ifp );
exit( 0 );
}
#define MXIVAL PPM_MAXMAXVAL /* maximum input value */
#define NOIVAL (MXIVAL + 1) /* number of possible input values */
#define SCALEB 8 /* scale bits */
#define SCALE (1 << SCALEB) /* scale factor */
#define MXSVAL (MXIVAL * SCALE) /* maximum scaled values */
#define CSCALEB 2 /* coarse scale bits */
#define CSCALE (1 << CSCALEB) /* coarse scale factor */
#define MXCSVAL (MXIVAL * CSCALE) /* maximum coarse scaled values */
#define NOCSVAL (MXCSVAL + 1) /* number of coarse scaled values */
#define SCTOCSC(x) ((x) >> (SCALEB - CSCALEB)) /* convert from scaled to coarse scaled */
#define CSCTOSC(x) ((x) << (SCALEB - CSCALEB)) /* convert from course scaled to scaled */
#ifndef MAXINT
# define MAXINT 0x7fffffff /* assume this is a 32 bit machine */
#endif
/* round and scale floating point to scaled integer */
#define ROUND(x) ((int)(((x) * (double)SCALE) + 0.5))
/* round and un-scale scaled integer value */
#define RUNSCALE(x) (((x) + (1 << (SCALEB-1))) >> SCALEB) /* rounded un-scale */
#define UNSCALE(x) ((x) >> SCALEB)
/* We restrict radius to the values: 0.333333 <= radius <= 1.0 */
/* so that no fewer and no more than a 3x3 grid of pixels around */
/* the pixel in question needs to be read. Given this, we only */
/* need 3 or 4 weightings per hexagon, as follows: */
/* _ _ */
/* Virtical hex: |_|_| 1 2 */
/* |X|_| 0 3 */
/* _ */
/* _ _|_| 1 */
/* Middle hex: |_| 1 Horizontal hex: |X|_| 0 2 */
/* |X| 0 |_| 3 */
/* |_| 2 */
/* all filters */
int V0[NOIVAL],V1[NOIVAL],V2[NOIVAL],V3[NOIVAL]; /* vertical hex */
int M0[NOIVAL],M1[NOIVAL],M2[NOIVAL]; /* middle hex */
int H0[NOIVAL],H1[NOIVAL],H2[NOIVAL],H3[NOIVAL]; /* horizontal hex */
/* alpha trimmed and edge enhancement only */
int ALFRAC[NOIVAL * 8]; /* fractional alpha divider table */
/* optimal estimation only */
int AVEDIV[7 * NOCSVAL]; /* divide by 7 to give average value */
int SQUARE[2 * NOCSVAL]; /* scaled square lookup table */
/* Table initialisation function - return alpha range */
int
atfilt_setup(alpha,radius,maxscale)
double alpha,radius,maxscale; /* alpha, radius and amount to scale input pixel values */
{
/* other function variables */
int alpharange; /* alpha range value 0 - 3 */
double meanscale; /* scale for finding mean */
double mmeanscale; /* scale for finding mean - midle hex */
double alphafraction; /* fraction of next largest/smallest to subtract from sum */
/* do setup */
if (alpha >= 0.0 && alpha < 1.0) /* alpha trimmed mean */
{
double noinmean;
/* number of elements (out of a possible 7) used in the mean */
noinmean = ((0.5 - alpha) * 12.0) + 1.0;
mmeanscale = meanscale = maxscale/noinmean;
if (alpha == 0.0) /* mean filter */
{
alpharange = 0;
alphafraction = 0.0; /* not used */
}
else if (alpha < (1.0/6.0)) /* mean of 5 to 7 middle values */
{
alpharange = 1;
alphafraction = (7.0 - noinmean)/2.0;
}
else if (alpha < (1.0/3.0)) /* mean of 3 to 5 middle values */
{
alpharange = 2;
alphafraction = (5.0 - noinmean)/2.0;
}
else /* mean of 1 to 3 middle values */
{ /* alpha == 0.5 == median filter */
alpharange = 3;
alphafraction = (3.0 - noinmean)/2.0;
}
}
else if (alpha > 0.5) /* optimal estimation - alpha controls noise variance threshold. */
{
int i;
double noinmean = 7.0;
alpharange = 5; /* edge enhancement function */
alpha -= 1.0; /* normalise it to 0.0 -> 1.0 */
mmeanscale = meanscale = maxscale; /* compute scaled hex values */
alphafraction = 1.0/noinmean; /* Set up 1:1 division lookup - not used */
noisevariance = alpha * (double)omaxval;
noisevariance = noisevariance * noisevariance / 8.0; /* estimate of noise variance */
/* set yp optimal estimation specific stuff */
for (i=0; i < (7 * NOCSVAL); i++) /* divide scaled value by 7 lookup */
{
AVEDIV[i] = CSCTOSC(i)/7; /* scaled divide by 7 */
}
for (i=0; i < (2 * NOCSVAL); i++) /* compute square and rescale by (val >> (2 * SCALEB + 2)) table */
{
int val;
val = CSCTOSC(i - NOCSVAL); /* NOCSVAL offset to cope with -ve input values */
SQUARE[i] = (val * val) >> (2 * SCALEB + 2);
}
}
else /* edge enhancement function */
{
alpharange = 4; /* edge enhancement function */
alpha = -alpha; /* turn it the right way up */
meanscale = maxscale * (-alpha/((1.0 - alpha) * 7.0)); /* mean of 7 and scaled by -alpha/(1-alpha) */
mmeanscale = maxscale * (1.0/(1.0 - alpha) + meanscale); /* middle pixel has 1/(1-alpha) as well */
alphafraction = 0.0; /* not used */
}
/* Setup pixel weighting tables - note we pre-compute mean division here too. */
{
int i;
double hexhoff,hexvoff;
double tabscale,mtabscale;
double v0,v1,v2,v3,m0,m1,m2,me0,me1,me2,h0,h1,h2,h3;
hexhoff = radius/2; /* horizontal offset of virtical hex centers */
hexvoff = 3.0 * radius/sqrt(12.0); /* virtical offset of virtical hex centers */
/* scale tables to normalise by hexagon area, and number of hexes used in mean */
tabscale = meanscale / (radius * hexvoff);
mtabscale = mmeanscale / (radius * hexvoff);
v0 = hex_area(0.0,0.0,hexhoff,hexvoff,radius) * tabscale;
v1 = hex_area(0.0,1.0,hexhoff,hexvoff,radius) * tabscale;
v2 = hex_area(1.0,1.0,hexhoff,hexvoff,radius) * tabscale;
v3 = hex_area(1.0,0.0,hexhoff,hexvoff,radius) * tabscale;
m0 = hex_area(0.0,0.0,0.0,0.0,radius) * mtabscale;
m1 = hex_area(0.0,1.0,0.0,0.0,radius) * mtabscale;
m2 = hex_area(0.0,-1.0,0.0,0.0,radius) * mtabscale;
h0 = hex_area(0.0,0.0,radius,0.0,radius) * tabscale;
h1 = hex_area(1.0,1.0,radius,0.0,radius) * tabscale;
h2 = hex_area(1.0,0.0,radius,0.0,radius) * tabscale;
h3 = hex_area(1.0,-1.0,radius,0.0,radius) * tabscale;
for (i=0; i <= MXIVAL; i++)
{
double fi;
fi = (double)i;
V0[i] = ROUND(fi * v0);
V1[i] = ROUND(fi * v1);
V2[i] = ROUND(fi * v2);
V3[i] = ROUND(fi * v3);
M0[i] = ROUND(fi * m0);
M1[i] = ROUND(fi * m1);
M2[i] = ROUND(fi * m2);
H0[i] = ROUND(fi * h0);
H1[i] = ROUND(fi * h1);
H2[i] = ROUND(fi * h2);
H3[i] = ROUND(fi * h3);
}
/* set up alpha fraction lookup table used on big/small */
for (i=0; i < (NOIVAL * 8); i++)
{
ALFRAC[i] = ROUND((double)i * alphafraction);
}
}
return alpharange;
}
/* Core pixel processing function - hand it 3x3 pixels and return result. */
/* Mean filter */
int
atfilt0(p)
int *p; /* 9 pixel values from 3x3 neighbors */
{
int retv;
/* map to scaled hexagon values */
retv = M0[p[0]] + M1[p[3]] + M2[p[7]];
retv += H0[p[0]] + H1[p[2]] + H2[p[1]] + H3[p[8]];
retv += V0[p[0]] + V1[p[3]] + V2[p[2]] + V3[p[1]];
retv += V0[p[0]] + V1[p[3]] + V2[p[4]] + V3[p[5]];
retv += H0[p[0]] + H1[p[4]] + H2[p[5]] + H3[p[6]];
retv += V0[p[0]] + V1[p[7]] + V2[p[6]] + V3[p[5]];
retv += V0[p[0]] + V1[p[7]] + V2[p[8]] + V3[p[1]];
return UNSCALE(retv);
}
/* Mean of 5 - 7 middle values */
int
atfilt1(p)
int *p; /* 9 pixel values from 3x3 neighbors */
{
int h0,h1,h2,h3,h4,h5,h6; /* hexagon values 2 3 */
/* 1 0 4 */
/* 6 5 */
int big,small;
/* map to scaled hexagon values */
h0 = M0[p[0]] + M1[p[3]] + M2[p[7]];
h1 = H0[p[0]] + H1[p[2]] + H2[p[1]] + H3[p[8]];
h2 = V0[p[0]] + V1[p[3]] + V2[p[2]] + V3[p[1]];
h3 = V0[p[0]] + V1[p[3]] + V2[p[4]] + V3[p[5]];
h4 = H0[p[0]] + H1[p[4]] + H2[p[5]] + H3[p[6]];
h5 = V0[p[0]] + V1[p[7]] + V2[p[6]] + V3[p[5]];
h6 = V0[p[0]] + V1[p[7]] + V2[p[8]] + V3[p[1]];
/* sum values and also discover the largest and smallest */
big = small = h0;
#define CHECK(xx) \
h0 += xx; \
if (xx > big) \
big = xx; \
else if (xx < small) \
small = xx;
CHECK(h1)
CHECK(h2)
CHECK(h3)
CHECK(h4)
CHECK(h5)
CHECK(h6)
#undef CHECK
/* Compute mean of middle 5-7 values */
return UNSCALE(h0 -ALFRAC[(big + small)>>SCALEB]);
}
/* Mean of 3 - 5 middle values */
int
atfilt2(p)
int *p; /* 9 pixel values from 3x3 neighbors */
{
int h0,h1,h2,h3,h4,h5,h6; /* hexagon values 2 3 */
/* 1 0 4 */
/* 6 5 */
int big0,big1,small0,small1;
/* map to scaled hexagon values */
h0 = M0[p[0]] + M1[p[3]] + M2[p[7]];
h1 = H0[p[0]] + H1[p[2]] + H2[p[1]] + H3[p[8]];
h2 = V0[p[0]] + V1[p[3]] + V2[p[2]] + V3[p[1]];
h3 = V0[p[0]] + V1[p[3]] + V2[p[4]] + V3[p[5]];
h4 = H0[p[0]] + H1[p[4]] + H2[p[5]] + H3[p[6]];
h5 = V0[p[0]] + V1[p[7]] + V2[p[6]] + V3[p[5]];
h6 = V0[p[0]] + V1[p[7]] + V2[p[8]] + V3[p[1]];
/* sum values and also discover the 2 largest and 2 smallest */
big0 = small0 = h0;
small1 = MAXINT;
big1 = 0;
#define CHECK(xx) \
h0 += xx; \
if (xx > big1) \
{ \
if (xx > big0) \
{ \
big1 = big0; \
big0 = xx; \
} \
else \
big1 = xx; \
} \
if (xx < small1) \
{ \
if (xx < small0) \
{ \
small1 = small0; \
small0 = xx; \
} \
else \
small1 = xx; \
}
CHECK(h1)
CHECK(h2)
CHECK(h3)
CHECK(h4)
CHECK(h5)
CHECK(h6)
#undef CHECK
/* Compute mean of middle 3-5 values */
return UNSCALE(h0 -big0 -small0 -ALFRAC[(big1 + small1)>>SCALEB]);
}
/* Mean of 1 - 3 middle values. If only 1 value, then this is a median filter. */
int
atfilt3(p)
int *p; /* 9 pixel values from 3x3 neighbors */
{
int h0,h1,h2,h3,h4,h5,h6; /* hexagon values 2 3 */
/* 1 0 4 */
/* 6 5 */
int big0,big1,big2,small0,small1,small2;
/* map to scaled hexagon values */
h0 = M0[p[0]] + M1[p[3]] + M2[p[7]];
h1 = H0[p[0]] + H1[p[2]] + H2[p[1]] + H3[p[8]];
h2 = V0[p[0]] + V1[p[3]] + V2[p[2]] + V3[p[1]];
h3 = V0[p[0]] + V1[p[3]] + V2[p[4]] + V3[p[5]];
h4 = H0[p[0]] + H1[p[4]] + H2[p[5]] + H3[p[6]];
h5 = V0[p[0]] + V1[p[7]] + V2[p[6]] + V3[p[5]];
h6 = V0[p[0]] + V1[p[7]] + V2[p[8]] + V3[p[1]];
/* sum values and also discover the 3 largest and 3 smallest */
big0 = small0 = h0;
small1 = small2 = MAXINT;
big1 = big2 = 0;
#define CHECK(xx) \
h0 += xx; \
if (xx > big2) \
{ \
if (xx > big1) \
{ \
if (xx > big0) \
{ \
big2 = big1; \
big1 = big0; \
big0 = xx; \
} \
else \
{ \
big2 = big1; \
big1 = xx; \
} \
} \
else \
big2 = xx; \
} \
if (xx < small2) \
{ \
if (xx < small1) \
{ \
if (xx < small0) \
{ \
small2 = small1; \
small1 = small0; \
small0 = xx; \
} \
else \
{ \
small2 = small1; \
small1 = xx; \
} \
} \
else \
small2 = xx; \
}
CHECK(h1)
CHECK(h2)
CHECK(h3)
CHECK(h4)
CHECK(h5)
CHECK(h6)
#undef CHECK
/* Compute mean of middle 1-3 values */
return UNSCALE(h0 -big0 -big1 -small0 -small1 -ALFRAC[(big2 + small2)>>SCALEB]);
}
/* Edge enhancement */
/* notice we use the global omaxval */
int
atfilt4(p)
int *p; /* 9 pixel values from 3x3 neighbors */
{
int hav;
/* map to scaled hexagon values and compute enhance value */
hav = M0[p[0]] + M1[p[3]] + M2[p[7]];
hav += H0[p[0]] + H1[p[2]] + H2[p[1]] + H3[p[8]];
hav += V0[p[0]] + V1[p[3]] + V2[p[2]] + V3[p[1]];
hav += V0[p[0]] + V1[p[3]] + V2[p[4]] + V3[p[5]];
hav += H0[p[0]] + H1[p[4]] + H2[p[5]] + H3[p[6]];
hav += V0[p[0]] + V1[p[7]] + V2[p[6]] + V3[p[5]];
hav += V0[p[0]] + V1[p[7]] + V2[p[8]] + V3[p[1]];
if (hav < 0)
hav = 0;
hav = UNSCALE(hav);
if (hav > omaxval)
hav = omaxval;
return hav;
}
/* Optimal estimation - do smoothing in inverse proportion */
/* to the local variance. */
/* notice we use the globals noisevariance and omaxval*/
int
atfilt5(p)
int *p; /* 9 pixel values from 3x3 neighbors */
{
int mean,variance,temp;
int h0,h1,h2,h3,h4,h5,h6; /* hexagon values 2 3 */
/* 1 0 4 */
/* 6 5 */
/* map to scaled hexagon values */
h0 = M0[p[0]] + M1[p[3]] + M2[p[7]];
h1 = H0[p[0]] + H1[p[2]] + H2[p[1]] + H3[p[8]];
h2 = V0[p[0]] + V1[p[3]] + V2[p[2]] + V3[p[1]];
h3 = V0[p[0]] + V1[p[3]] + V2[p[4]] + V3[p[5]];
h4 = H0[p[0]] + H1[p[4]] + H2[p[5]] + H3[p[6]];
h5 = V0[p[0]] + V1[p[7]] + V2[p[6]] + V3[p[5]];
h6 = V0[p[0]] + V1[p[7]] + V2[p[8]] + V3[p[1]];
mean = h0 + h1 + h2 + h3 + h4 + h5 + h6;
mean = AVEDIV[SCTOCSC(mean)]; /* compute scaled mean by dividing by 7 */
temp = (h1 - mean); variance = SQUARE[NOCSVAL + SCTOCSC(temp)]; /* compute scaled variance */
temp = (h2 - mean); variance += SQUARE[NOCSVAL + SCTOCSC(temp)]; /* and rescale to keep */
temp = (h3 - mean); variance += SQUARE[NOCSVAL + SCTOCSC(temp)]; /* within 32 bit limits */
temp = (h4 - mean); variance += SQUARE[NOCSVAL + SCTOCSC(temp)];
temp = (h5 - mean); variance += SQUARE[NOCSVAL + SCTOCSC(temp)];
temp = (h6 - mean); variance += SQUARE[NOCSVAL + SCTOCSC(temp)];
temp = (h0 - mean); variance += SQUARE[NOCSVAL + SCTOCSC(temp)]; /* (temp = h0 - mean) */
if (variance != 0) /* avoid possible divide by 0 */
temp = mean + (variance * temp) / (variance + noisevariance); /* optimal estimate */
else temp = h0;
if (temp < 0)
temp = 0;
temp = RUNSCALE(temp);
if (temp > omaxval)
temp = omaxval;
return temp;
}
/* ************************************************** */
/* Hexagon intersecting square area functions */
/* Compute the area of the intersection of a triangle */
/* and a rectangle */
double triang_area ARGS((double, double, double, double, double, double, double, double, int));
double rectang_area ARGS((double, double, double, double, double, double, double, double));
/* Triangle orientation is per geometric axes (not graphical axies) */
#define NW 0 /* North west triangle /| */
#define NE 1 /* North east triangle |\ */
#define SW 2 /* South west triangle \| */
#define SE 3 /* South east triangle |/ */
#define STH 2
#define EST 1
#define SWAPI(a,b) (t = a, a = -b, b = -t)
/* compute the area of overlap of a hexagon diameter d, */
/* centered at hx,hy, with a unit square of center sx,sy. */
double
hex_area(sx,sy,hx,hy,d)
double sx,sy; /* square center */
double hx,hy,d; /* hexagon center and diameter */
{
double hx0,hx1,hx2,hy0,hy1,hy2,hy3;
double sx0,sx1,sy0,sy1;
/* compute square co-ordinates */
sx0 = sx - 0.5;
sy0 = sy - 0.5;
sx1 = sx + 0.5;
sy1 = sy + 0.5;
/* compute hexagon co-ordinates */
hx0 = hx - d/2.0;
hx1 = hx;
hx2 = hx + d/2.0;
hy0 = hy - 0.5773502692 * d; /* d / sqrt(3) */
hy1 = hy - 0.2886751346 * d; /* d / sqrt(12) */
hy2 = hy + 0.2886751346 * d; /* d / sqrt(12) */
hy3 = hy + 0.5773502692 * d; /* d / sqrt(3) */
return
triang_area(sx0,sy0,sx1,sy1,hx0,hy2,hx1,hy3,NW) +
triang_area(sx0,sy0,sx1,sy1,hx1,hy2,hx2,hy3,NE) +
rectang_area(sx0,sy0,sx1,sy1,hx0,hy1,hx2,hy2) +
triang_area(sx0,sy0,sx1,sy1,hx0,hy0,hx1,hy1,SW) +
triang_area(sx0,sy0,sx1,sy1,hx1,hy0,hx2,hy1,SE);
}
double
triang_area(rx0,ry0,rx1,ry1,tx0,ty0,tx1,ty1,tt)
double rx0,ry0,rx1,ry1; /* rectangle boundaries */
double tx0,ty0,tx1,ty1; /* triangle boundaries */
int tt; /* triangle type */
{
double a,b,c,d;
double lx0,ly0,lx1,ly1;
/* Convert everything to a NW triangle */
if (tt & STH)
{
double t;
SWAPI(ry0,ry1);
SWAPI(ty0,ty1);
}
if (tt & EST)
{
double t;
SWAPI(rx0,rx1);
SWAPI(tx0,tx1);
}
/* Compute overlapping box */
if (tx0 > rx0)
rx0 = tx0;
if (ty0 > ry0)
ry0 = ty0;
if (tx1 < rx1)
rx1 = tx1;
if (ty1 < ry1)
ry1 = ty1;
if (rx1 <= rx0 || ry1 <= ry0)
return 0.0;
/* Need to compute diagonal line intersection with the box */
/* First compute co-efficients to formulas x = a + by and y = c + dx */
b = (tx1 - tx0)/(ty1 - ty0);
a = tx0 - b * ty0;
d = (ty1 - ty0)/(tx1 - tx0);
c = ty0 - d * tx0;
/* compute top or right intersection */
tt = 0;
ly1 = ry1;
lx1 = a + b * ly1;
if (lx1 <= rx0)
return (rx1 - rx0) * (ry1 - ry0);
else if (lx1 > rx1) /* could be right hand side */
{
lx1 = rx1;
ly1 = c + d * lx1;
if (ly1 <= ry0)
return (rx1 - rx0) * (ry1 - ry0);
tt = 1; /* right hand side intersection */
}
/* compute left or bottom intersection */
lx0 = rx0;
ly0 = c + d * lx0;
if (ly0 >= ry1)
return (rx1 - rx0) * (ry1 - ry0);
else if (ly0 < ry0) /* could be right hand side */
{
ly0 = ry0;
lx0 = a + b * ly0;
if (lx0 >= rx1)
return (rx1 - rx0) * (ry1 - ry0);
tt |= 2; /* bottom intersection */
}
if (tt == 0) /* top and left intersection */
{ /* rectangle minus triangle */
return ((rx1 - rx0) * (ry1 - ry0))
- (0.5 * (lx1 - rx0) * (ry1 - ly0));
}
else if (tt == 1) /* right and left intersection */
{
return ((rx1 - rx0) * (ly0 - ry0))
+ (0.5 * (rx1 - rx0) * (ly1 - ly0));
}
else if (tt == 2) /* top and bottom intersection */
{
return ((rx1 - lx1) * (ry1 - ry0))
+ (0.5 * (lx1 - lx0) * (ry1 - ry0));
}
else /* tt == 3 */ /* right and bottom intersection */
{ /* triangle */
return (0.5 * (rx1 - lx0) * (ly1 - ry0));
}
}
/* Compute rectangle area */
double
rectang_area(rx0,ry0,rx1,ry1,tx0,ty0,tx1,ty1)
double rx0,ry0,rx1,ry1; /* rectangle boundaries */
double tx0,ty0,tx1,ty1; /* rectangle boundaries */
{
/* Compute overlapping box */
if (tx0 > rx0)
rx0 = tx0;
if (ty0 > ry0)
ry0 = ty0;
if (tx1 < rx1)
rx1 = tx1;
if (ty1 < ry1)
ry1 = ty1;
if (rx1 <= rx0 || ry1 <= ry0)
return 0.0;
return (rx1 - rx0) * (ry1 - ry0);
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.