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/***************************************************************************
gamma.c - code for producing color calibration output
-------------------
begin : Wed Oct 11 2000
copyright : (C) 2000 by pnm2ppa project
email :
***************************************************************************/
/***************************************************************************
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
***************************************************************************/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "global.h"
#include "defaults.h"
#include "image.h"
#include "gamma.h"
int
Make_GammaCurve ( double Gamma_R, double Gamma_G, double Gamma_B)
{
/*color correction curve derived from Gamma_R, Gamma_G, Gamma_B .
Gamma_R = Gamma_G = Gamma_B = 1 gives no correction*/
int i;
for (i = 0; i < 256; i++)
{
gEnh_curve_r[i] = (int) (pow ((double) i / 256, Gamma_R) * 256);
gEnh_curve_g[i] = (int) (pow ((double) i / 256, Gamma_G) * 256);
gEnh_curve_b[i] = (int) (pow ((double) i / 256, Gamma_B) * 256);
}
return 0;
}
double
GammaValue( int i )
{
double Gamma;
Gamma = (double) (1.0 - 0.033 * i);
return Gamma;
}
int
ProduceGamma (image_t *image, unsigned char *line )
{
int i, j, q;
double Gamma_R, Gamma_B, Gamma_G;
/* produces a single line of the gamma calibration output */
/* increase j to the value for this line */
for (j = 0; j * (image->height / 20) < image->bufferCurLine - 150; j++);
Gamma_R = Gamma_B = Gamma_G = GammaValue (j);
Make_GammaCurve ( Gamma_R, Gamma_G, Gamma_B);
memset (line, 0xff, image->width * 3);
if (((image->bufferCurLine - 150) % (image->height / 20) > 64))
{
for (i = 150; i < image->width / 4; i++)
{
q = (unsigned char) (255.0 * (i - 150) / (image->width / 4 - 150));
/* R */
line[3 * i] = q;
line[3 * i + 1] = 0;
line[3 * i + 2] = 0;
/* G */
line[3 * (i + image->width / 4)] = 0;
line[3 * (i + image->width / 4) + 1] = q;
line[3 * (i + image->width / 4) + 2] = 0;
/* B */
line[3 * (i + 2 * image->width / 4)] = 0;
line[3 * (i + 2 * image->width / 4) + 1] = 0;
line[3 * (i + 2 * image->width / 4) + 2] = q;
}
}
else
for (i = 150; i < image->width / 4; i += (image->width / 40 - 15))
{
line[3 * i] =
line[3 * i + 1] =
line[3 * i + 2] = 0;
line[3 * (i + image->width / 4) + 1] =
line[3 * (i + image->width / 4)] =
line[3 * (i + image->width / 4) + 2] = 0;
line[3 * (i + 2 * image->width / 4) + 2] =
line[3 * (i + 2 * image->width / 4)] =
line[3 * (i + 2 * image->width / 4) + 1] = 0;
line[3 * (i + 1)] =
line[3 * (i + 1) + 1] =
line[3 * (i + 1) + 2] = 0;
line[3 * (i + 1 + image->width / 4) + 1] =
line[3 * (i + 1 + image->width / 4)] =
line[3 * (i + 1 + image->width / 4) + 2] = 0;
line[3 * (i + 1 + 2 * image->width / 4) + 2] =
line[3 * (i + 1 + 2 * image->width / 4)] =
line[3 * (i + 1 + 2 * image->width / 4) + 1] = 0;
}
if ((j == 1) || (j == 2 && (image->height / 20) > 64))
{
/* this line should be written to the ppm output file */
return 1;
}
return 0;
}
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