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//
// PREqualize.m
// PRICE
// Image level equalization
//
// Created by Riccardo Mottola on Fri Dec 05 2003.
// Copyright (c) 2003-2004 Carduus. All rights reserved.
//
// This program is free software; you can redistribute it and/or modify it under the terms of the version 2 of the GNU General Public License as published by the Free Software Foundation.
// This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
#import <math.h>
#import <limits.h>
#import "PREqualize.h"
@implementation PREqualize
- (PRImage *)equalizeImage:(PRImage *)srcImage
{
NSBitmapImageRep *srcImageRep;
PRImage *destImage;
NSBitmapImageRep *destImageRep;
int w, h;
int x, y;
int i;
unsigned char *srcData;
unsigned char *destData;
int bytesPerPixel;
int pixNum;
BOOL isColor;
/* some trace */
printf("levels: %d\n", UCHAR_MAX);
/* get source image representation and associated information */
srcImageRep = [srcImage tiffRep];
w = [srcImageRep pixelsWide];
h = [srcImageRep pixelsHigh];
pixNum = h * w;
printf("pixels: %d\n", pixNum);
bytesPerPixel = [srcImageRep bitsPerPixel] /8;
/* check bith depth and color/greyscale image */
if ([srcImageRep hasAlpha])
{
if ([srcImageRep samplesPerPixel] == 2)
{
printf("Grayscale image\n");
isColor = NO;
}
else
{
printf("Color image\n");
isColor = YES;
}
}
else
{
if ([srcImageRep samplesPerPixel] == 1)
{
printf("Grayscale image\n");
isColor = NO;
}
else
{
printf("Color image\n");
isColor = YES;
}
}
/* allocate destination image and its representation */
destImage = [[PRImage alloc] initWithSize:NSMakeSize(w, h)];
if (isColor)
{
destImageRep = [[NSBitmapImageRep alloc]
initWithBitmapDataPlanes:NULL
pixelsWide:w
pixelsHigh:h
bitsPerSample:8
samplesPerPixel:3
hasAlpha:NO
isPlanar:NO
colorSpaceName:NSCalibratedRGBColorSpace
bytesPerRow:0
bitsPerPixel:0];
} else
{
destImageRep = [[NSBitmapImageRep alloc]
initWithBitmapDataPlanes:NULL
pixelsWide:w
pixelsHigh:h
bitsPerSample:8
samplesPerPixel:1
hasAlpha:NO
isPlanar:NO
colorSpaceName:NSCalibratedWhiteColorSpace
bytesPerRow:0
bitsPerPixel:0];
}
srcData = [srcImageRep bitmapData];
destData = [destImageRep bitmapData];
if (isColor)
{
unsigned long int histogramDenormR[UCHAR_MAX+1]; /* not normalized pixel count for each level */
unsigned long int histogramDenormG[UCHAR_MAX+1]; /* not normalized pixel count for each level */
unsigned long int histogramDenormB[UCHAR_MAX+1]; /* not normalized pixel count for each level */
float histogramR[UCHAR_MAX+1]; /* normalized histogram */
float histogramG[UCHAR_MAX+1]; /* normalized histogram */
float histogramB[UCHAR_MAX+1]; /* normalized histogram */
float cumulativeHistogramR[UCHAR_MAX+1]; /* cumulative histogram */
float cumulativeHistogramG[UCHAR_MAX+1]; /* cumulative histogram */
float cumulativeHistogramB[UCHAR_MAX+1]; /* cumulative histogram */
/* calculate the histogram */
for (i = 0; i <= UCHAR_MAX; i++)
histogramDenormR[i] = histogramDenormG[i] = histogramDenormB[i] = 0;
for (y = 0; y < h; y++)
for (x = 0; x < w*3; x += 3)
{
histogramDenormR[srcData[y*(w*3) + x]]++;
histogramDenormG[srcData[y*(w*3) + x + 1]]++;
histogramDenormB[srcData[y*(w*3) + x + 2]]++;
}
/* normalize histogram */
for (i = 0; i <= UCHAR_MAX; i++)
{
histogramR[i] = (float)histogramDenormR[i] / (float)pixNum;
histogramG[i] = (float)histogramDenormG[i] / (float)pixNum;
histogramB[i] = (float)histogramDenormB[i] / (float)pixNum;
}
/* cumulative histogram */
cumulativeHistogramR[0] = histogramR[0];
cumulativeHistogramG[0] = histogramG[0];
cumulativeHistogramB[0] = histogramB[0];
for (i = 1; i <= UCHAR_MAX; i++)
{
cumulativeHistogramR[i] = cumulativeHistogramR[i-1] + histogramR[i];
cumulativeHistogramG[i] = cumulativeHistogramG[i-1] + histogramG[i];
cumulativeHistogramB[i] = cumulativeHistogramB[i-1] + histogramB[i];
}
/* equalize */
for (y = 0; y < h; y++)
for (x = 0; x < w*3; x += 3)
{
destData[y*(w*3) + x] = floor((UCHAR_MAX+0.9)*cumulativeHistogramR[srcData[y*(w*3) + x]]);
destData[y*(w*3) + x + 1] = floor((UCHAR_MAX+0.9)*cumulativeHistogramG[srcData[y*(w*3) + x + 1]]);
destData[y*(w*3) + x + 2] = floor((UCHAR_MAX+0.9)*cumulativeHistogramB[srcData[y*(w*3) + x + 2]]);
}
} else
{
unsigned long int histogramDenorm[UCHAR_MAX+1]; /* not normalized pixel count for each level */
float histogram[UCHAR_MAX+1]; /* normalized histogram */
float cumulativeHistogram[UCHAR_MAX+1]; /* cumulative histogram */
/* calculate the histogram */
for (i = 0; i <= UCHAR_MAX; i++)
histogramDenorm[i] = 0;
for (y = 0; y < h; y++)
for (x = 0; x < w; x++)
histogramDenorm[srcData[y*w + x]]++;
/* normalize histogram */
for (i = 0; i <= UCHAR_MAX; i++)
histogram[i] = (float)histogramDenorm[i] / (float)pixNum;
/* cumulative histogram */
cumulativeHistogram[0] = histogram[0];
for (i = 1; i <= UCHAR_MAX; i++)
cumulativeHistogram[i] = cumulativeHistogram[i-1] + histogram[i];
/* equalize */
for (y = 0; y < h; y++)
for (x = 0; x < w; x++)
destData[y*w + x] = floor((UCHAR_MAX+0.9)*cumulativeHistogram[srcData[y*w + x]]);
}
[destImage addRepresentation:destImageRep];
[destImageRep release];
[destImage autorelease];
return destImage;
}
@end
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