opencv/samples/c/demhist.c

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#ifdef _CH_
#pragma package <opencv>
#endif
#define CV_NO_BACKWARD_COMPATIBILITY
#ifndef _EiC
#include "cv.h"
#include "highgui.h"
#include <stdio.h>
#endif
char file_name[] = "baboon.jpg";
int _brightness = 100;
int _contrast = 100;
int hist_size = 64;
float range_0[]={0,256};
float* ranges[] = { range_0 };
IplImage *src_image = 0, *dst_image = 0, *hist_image = 0;
CvHistogram *hist;
uchar lut[256];
CvMat* lut_mat;
/* brightness/contrast callback function */
void update_brightcont( int arg )
{
int brightness = _brightness - 100;
int contrast = _contrast - 100;
int i, bin_w;
float max_value = 0;
/*
* The algorithm is by Werner D. Streidt
* (http://visca.com/ffactory/archives/5-99/msg00021.html)
*/
if( contrast > 0 )
{
double delta = 127.*contrast/100;
double a = 255./(255. - delta*2);
double b = a*(brightness - delta);
for( i = 0; i < 256; i++ )
{
int v = cvRound(a*i + b);
if( v < 0 )
v = 0;
if( v > 255 )
v = 255;
lut[i] = (uchar)v;
}
}
else
{
double delta = -128.*contrast/100;
double a = (256.-delta*2)/255.;
double b = a*brightness + delta;
for( i = 0; i < 256; i++ )
{
int v = cvRound(a*i + b);
if( v < 0 )
v = 0;
if( v > 255 )
v = 255;
lut[i] = (uchar)v;
}
}
cvLUT( src_image, dst_image, lut_mat );
cvShowImage( "image", dst_image );
cvCalcHist( &dst_image, hist, 0, NULL );
cvZero( dst_image );
cvGetMinMaxHistValue( hist, 0, &max_value, 0, 0 );
cvScale( hist->bins, hist->bins, ((double)hist_image->height)/max_value, 0 );
/*cvNormalizeHist( hist, 1000 );*/
cvSet( hist_image, cvScalarAll(255), 0 );
bin_w = cvRound((double)hist_image->width/hist_size);
for( i = 0; i < hist_size; i++ )
cvRectangle( hist_image, cvPoint(i*bin_w, hist_image->height),
cvPoint((i+1)*bin_w, hist_image->height - cvRound(cvGetReal1D(hist->bins,i))),
cvScalarAll(0), -1, 8, 0 );
cvShowImage( "histogram", hist_image );
}
int main( int argc, char** argv )
{
// Load the source image. HighGUI use.
src_image = cvLoadImage( argc == 2 ? argv[1] : file_name, 0 );
if( !src_image )
{
printf("Image was not loaded.\n");
return -1;
}
dst_image = cvCloneImage(src_image);
hist_image = cvCreateImage(cvSize(320,200), 8, 1);
hist = cvCreateHist(1, &hist_size, CV_HIST_ARRAY, ranges, 1);
lut_mat = cvCreateMatHeader( 1, 256, CV_8UC1 );
cvSetData( lut_mat, lut, 0 );
cvNamedWindow("image", 0);
cvNamedWindow("histogram", 0);
cvCreateTrackbar("brightness", "image", &_brightness, 200, update_brightcont);
cvCreateTrackbar("contrast", "image", &_contrast, 200, update_brightcont);
update_brightcont(0);
cvWaitKey(0);
cvReleaseImage(&src_image);
cvReleaseImage(&dst_image);
cvReleaseHist(&hist);
return 0;
}
#ifdef _EiC
main(1,"demhist.c");
#endif