packages/initscripts/353/gamma.c

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#include <stdio.h>
#include <math.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#define GAMMA_FN        "gamma.dat"

/*
 * write in resulting file table in format:
 *
 * count: unsigned short
 *
 * gamma value [1]
 * scale value [256]
 * ...
 * value in format 0.00 - 1.0
 * as 0x0000 - 0xFFFF in fixed point format 0.16
 */

inline unsigned short float_to_fp(unsigned char *fp, float val) {
        unsigned long v;
        unsigned short r;

        if(val <= 0.0) {
                fp[0] = 0x00;
                fp[1] = 0x00;
                return 0x0000;
        }
        if(val >= 1.0) {
                fp[0] = 0xFF;
                fp[1] = 0xFF;
                return 0xFFFF;
        }
        float vv = val;
        val *= 0x10000;
        r = (unsigned short)val;
        fp[0] = (unsigned char)(r >> 8);
        fp[1] = (unsigned char)(r & 0xFF);
        return r;
}

int main() {
        int i, j;
        float g;
        unsigned char v[2];
//      unsigned short c = htons(100);
        float gamma;
        int fout;
        unsigned short t;
        
        fout = open(GAMMA_FN, O_RDWR | O_CREAT, S_IROTH | S_IRGRP | S_IRUSR | S_IWUSR);
        if(fout < 0) {
                printf("failed to open \"%s\" file\n", GAMMA_FN);
                return -1;
        }
        for(j = 1; j <= 200; j++) {
                gamma = j;
                if(gamma > 100)
                        gamma = 100;
                gamma /= 100.0;
                t = j;
                write(fout, &t, 2);
                for(i = 0; i < 257; i++) {
                        g = i;
                        g /= 256.0;
                        g = powf(g, gamma);
                        t = float_to_fp(v, g);
                        write(fout, v, 2);
                }
        }
        close(fout);
        return 0;
}

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