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#ifndef lint
static char SccsId[] = "%W% %G%";
#endif
/* Module: histdist.c (Histogram Equalize Distribute)
* Subroutine: distribute_levels() returns: int
* Copyright: 1989 Smithsonian Astrophysical Observatory
* You may do anything you like with this file except remove
* this copyright. The Smithsonian Astrophysical Observatory
* makes no representations about the suitability of this
* software for any purpose. It is provided "as is" without
* express or implied warranty.
* Modified: {0} Michael VanHilst initial version 30 May 1989
* {1} MVH fixed bug in range_zgroup 7 Dec 1989
* {n} <who> -- <does what> -- <when>
*/
#include <stdio.h>
#include "hfiles/histeq.h" /* define SubrangeLink */
/*
* Subroutine: distribute_levels
* Purpose: Distribute the levels among histogram sub-groups
* Returns: number of groups with no assigned color levels
*/
int distribute_levels ( linklist, pixel_area, color_levels,
pmin, pmax, ncolor )
SubrangeLink *linklist;
int pixel_area, color_levels;
int pmin, pmax, ncolor;
{
int average;
int threshold;
int excess;
int levels, zeroes;
int max_z_excess, max_nz_excess, max_z_range;
SubrangeLink *subrange;
#ifdef DEBUG
int census = 0;
#endif
static int excess_zgroup(), excess_nzgroup(), range_zgroup();
/* if all one group (no strong peaks), allocation is simple */
if( linklist->next == 0 ) {
linklist->color_levels = ncolor;
return( 0 );
}
/* average is rounded strongly upward to be stingy with levels */
average = (pixel_area / color_levels) + 1;
subrange = linklist;
zeroes = 0;
max_z_excess = max_nz_excess = 0;
max_z_range = 0;
/* first pass, simple assignment and some note taking */
while( subrange != 0 ) {
if( subrange->range > 0 ) {
levels = subrange->pixel_area / average;
excess = subrange->pixel_area - (levels * average);
if( levels >= subrange->range ) {
levels = subrange->range;
subrange->range = -subrange->range;
} else {
if( levels == 0 ) {
zeroes++;
if( excess > max_z_excess )
max_z_excess = excess;
if( subrange->range > max_z_range )
max_z_range = subrange->range;
} else {
if( excess > max_nz_excess )
max_nz_excess = excess;
}
}
subrange->color_levels = levels;
subrange->excess_pixels = excess;
color_levels -= levels;
#ifndef DEBUG
}
#else
census += levels;
} else
++census;
#endif
subrange = subrange->next;
}
/* second pass groups with no levels and vals or ranges above limits */
if( zeroes > 0 ) {
/* groups with counts above 1/4 of average */
threshold = average / 4;
while( (zeroes > 0) && (color_levels > 0) && (max_z_excess > threshold) ) {
if( excess_zgroup(linklist, &max_z_excess, &max_z_range, average) ) {
zeroes--;
color_levels--;
#ifndef DEBUG
}
#else
census++;
} else
(void)fprintf(stderr, "Failed to find excess zero.\n");
#endif
}
/* groups with range above 2 * unequalized distribution */
threshold = MAX(((pmax - pmin) / 8) , 4);
while( (zeroes > 0) && (color_levels > 0) && (max_z_range > threshold) ) {
if( range_zgroup(linklist, &max_z_excess, &max_z_range, average) ) {
zeroes--;
color_levels--;
#ifndef DEBUG
}
#else
census++;
} else
(void)fprintf(stderr, "Failed to find range zero.\n");
#endif
}
}
/* third pass, give away any remaining levels by highest excess */
#ifdef DEBUG
if( color_levels != (ncolor - census) ) {
(void)fprintf(stderr, "Allocation waste: %d level(s)\n",
(ncolor - census) - color_levels);
}
#endif
while( color_levels > 0 ) {
if( (zeroes > 0) && (max_z_excess > max_nz_excess) ) {
if( excess_zgroup(linklist, &max_z_excess, &max_z_range, average) ) {
zeroes--;
color_levels--;
}
#ifdef DEBUG
else (void)fprintf(stderr, "Failed to find excess zero.\n");
#endif
} else {
if( excess_nzgroup(linklist, &max_nz_excess, average) )
color_levels--;
#ifdef DEBUG
else (void)fprintf(stderr, "Failed to find excess.\n");
#endif
}
}
return( zeroes );
}
/*
* Subroutine: excess_zgroup
* Purpose: Find subrange with zero allotted levels and specified excess.
* Assign it one level
*/
static int excess_zgroup ( subrange, excess, range, average )
SubrangeLink *subrange;
int *excess, *range;
int average;
{
int max_excess, looking;
max_excess = -32700;
looking = 1;
while( subrange != 0 ) {
if( (subrange->color_levels == 0) && (subrange->range > 0) ) {
if( looking && (subrange->excess_pixels == *excess) ) {
if( subrange->range > 1 ) {
subrange->color_levels = 1;
} else {
subrange->color_levels = 1;
subrange->range = -1;
}
subrange->excess_pixels -= average;
looking = 0;
} else {
if( subrange->excess_pixels > max_excess )
max_excess = subrange->excess_pixels;
if( subrange->range > *range )
*range = subrange->range;
}
}
subrange = subrange->next;
}
*excess = max_excess;
return( !looking );
}
/*
* Subroutine: range_zgroup
* Purpose: Find group with zero allotted levels and specified range.
* Assign it one level.
*/
static int range_zgroup (subrange, excess, range, average)
SubrangeLink *subrange;
int *excess, *range;
int average;
{
int max_range, looking;
max_range = 0;
looking = 1;
while( subrange != 0 ) {
if( (subrange->color_levels == 0) && (subrange->range > 0) ) {
if( looking && (subrange->range == *range) ) {
if( subrange->range > 1 ) {
subrange->color_levels = 1;
} else {
subrange->color_levels = 1;
subrange->range = -1;
}
subrange->excess_pixels -= average;
looking = 0;
} else {
if( subrange->excess_pixels > *excess )
*excess = subrange->excess_pixels;
if( subrange->range > max_range )
max_range = subrange->range;
}
}
subrange = subrange->next;
}
*range = max_range;
return( !looking );
}
/*
* Subroutine: excess_nzgroup
* Purpose: Find group with non-zero allotted levels and specified
* excess value. Assign it one additional level.
*/
static int excess_nzgroup ( subrange, excess, average )
SubrangeLink *subrange;
int *excess;
int average;
{
int looking, max_excess;
looking = 1;
max_excess = -32767;
while( subrange != 0 ) {
if( (subrange->color_levels > 0) && (subrange->range > 1) ) {
if( looking && (subrange->excess_pixels == *excess) &&
(subrange->color_levels < subrange->range) ) {
subrange->color_levels += 1;
subrange->excess_pixels -= average;
if( subrange->color_levels == subrange->range ) {
subrange->color_levels = subrange->range;
subrange->range = -subrange->range;
} else {
if( subrange->excess_pixels > max_excess )
max_excess = subrange->excess_pixels;
}
looking = 0;
} else {
if( subrange->excess_pixels > max_excess )
max_excess = subrange->excess_pixels;
}
}
subrange = subrange->next;
}
*excess = max_excess;
return( !looking );
}
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