-#include<stdio.h>
-#include<stdint.h>
-#include<stdlib.h>
-#include<string.h>
-#include<math.h>
-#include "../guicast/linklist.h"
-
-
-
-class HistEq {
- void fit(int *dat, int n, double &a, double &b);
-public:
- void eq(unsigned char *dp, int len);
- HistEq() {}
- ~HistEq() {}
-};
-
-double mean(uint8_t *dat, int n)
-{
- int s = 0;
- for( int i=0; i<n; ++i ) s += *dat++;
- return (double)s / n;
-}
-
-double variance(uint8_t *dat, int n, double m=-1)
-{
- if( m < 0 ) m = mean(dat, n);
- double ss = 0, s = 0;
- for( int i=0; i<n; ++i ) {
- double dx = dat[i]-m;
- s += dx; ss += dx*dx;
- }
- return (ss - s*s / n) / (n-1);
-}
-
-double std_dev(uint8_t *dat, int n, double m=-1)
-{
- return sqrt(variance(dat, n, m));
-}
-
-static inline int clip(int v, int mn, int mx)
-{
- return v<mn ? mn : v>mx ? mx : v;
-}
-
-void HistEq::
-fit(int *dat, int n, double &a, double &b)
-{
- double st2 = 0, sb = 0;
- int64_t sy = 0;
- for( int i=0; i<n; ++i ) sy += dat[i];
- double mx = (n-1)/2., my = (double)sy / n;
- for( int i=0; i<n; ++i ) {
- double t = i - mx;
- st2 += t * t;
- sb += t * dat[i];
- }
- b = sb / st2;
- a = my - mx*b;
-}
-
-void HistEq::
-eq(uint8_t *dp, int len)
-{
- int hist[256], wts[256], map[256];
- for( int i=0; i<256; ++i ) hist[i] = 0;
- uint8_t *bp = dp;
- for( int i=len; --i>=0; ++bp ) ++hist[*bp];
- int t = 0;
- for( int i=0; i<256; ++i ) { t += hist[i]; wts[i] = t; }
- int lmn = len/20, lmx = len-lmn;
- int mn = 0; while( mn < 256 && wts[mn] < lmn ) ++mn;
- int mx = 255; while( mx > mn && wts[mx] > lmx ) --mx;
- double a, b;
- fit(&wts[mn], mx-mn, a, b);
- double r = 256./len;
- double a1 = (a - b*mn) * r, b1 = b * r;
- for( int i=0 ; i<256; ++i ) map[i] = clip(a1 + i*b1, 0, 255);
- bp = dp;
- for( int i=len; --i>=0; ++bp ) *bp = map[*bp];
-}
-
-
-int main(int ac, char **av)
-{
- FILE *ifp = !strcmp(av[1],"-") ? stdin : fopen(av[1],"r");
- FILE *ofp = !strcmp(av[2],"-") ? stdout : fopen(av[2],"w");
- char line[120];
- fgets(line,sizeof(line),ifp); fputs(line,ofp);
- fgets(line,sizeof(line),ifp); fputs(line,ofp);
- int w, h; if( sscanf(line,"%d %d\n",&w,&h) != 2 ) exit(1);
- fgets(line,sizeof(line),ifp); fputs(line,ofp);
- int len = w*h;
- unsigned char data[len], *bp = data;
- for( int ch, i=len; --i>=0 && (ch=getc(ifp)) >= 0; ++bp ) *bp = ch;
- HistEq().eq(data,len);
- bp = data;
- for( int i=len; --i>=0; ++bp ) putc(*bp,ofp);
-
- if( ifp != stdin ) fclose(ifp);
- if( ofp != stdout ) fclose(ofp);
- return 0;
-}
-