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/* convert.c
*
* COPYRIGHT: Written by John Cunningham Bowler, 2013.
* To the extent possible under law, the author has waived all copyright and
* related or neighboring rights to this work. This work is published from:
* United States.
*
* Convert 8-bit sRGB or 16-bit linear values to another format.
*/
#define _ISOC99_SOURCE 1
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <stdio.h>
#include <fenv.h>
#include "sRGB.h"
static void
usage(const char *prog)
{
fprintf(stderr,
"%s: usage: %s [-linear|-sRGB] [-gray|-color] component{1,4}\n",
prog, prog);
exit(1);
}
unsigned long
component(const char *prog, const char *arg, int issRGB)
{
char *ep;
unsigned long c = strtoul(arg, &ep, 0);
if (ep <= arg || *ep || c > 65535 || (issRGB && c > 255))
{
fprintf(stderr, "%s: %s: invalid component value (%lu)\n", prog, arg, c);
usage(prog);
}
return c;
}
int
main(int argc, const char **argv)
{
const char *prog = *argv++;
int to_linear = 0, to_gray = 0, to_color = 0;
int channels = 0;
double c[4];
/* FE_TONEAREST is the IEEE754 round to nearest, preferring even, mode; i.e.
* everything rounds to the nearest value except that '.5' rounds to the
* nearest even value.
*/
fesetround(FE_TONEAREST);
c[3] = c[2] = c[1] = c[0] = 0;
while (--argc > 0 && **argv == '-')
{
const char *arg = 1+*argv++;
if (strcmp(arg, "sRGB") == 0)
to_linear = 0;
else if (strcmp(arg, "linear") == 0)
to_linear = 1;
else if (strcmp(arg, "gray") == 0)
to_gray = 1, to_color = 0;
else if (strcmp(arg, "color") == 0)
to_gray = 0, to_color = 1;
else
usage(prog);
}
switch (argc)
{
default:
usage(prog);
break;
case 4:
c[3] = component(prog, argv[3], to_linear);
++channels;
case 3:
c[2] = component(prog, argv[2], to_linear);
++channels;
case 2:
c[1] = component(prog, argv[1], to_linear);
++channels;
case 1:
c[0] = component(prog, argv[0], to_linear);
++channels;
break;
}
if (to_linear)
{
int i;
int components = channels;
if ((components & 1) == 0)
--components;
for (i=0; i<components; ++i) c[i] = linear_from_sRGB(c[i] / 255);
if (components < channels)
c[components] = c[components] / 255;
}
else
{
int i;
for (i=0; i<4; ++i) c[i] /= 65535;
if ((channels & 1) == 0)
{
double alpha = c[channels-1];
if (alpha > 0)
for (i=0; i<channels-1; ++i) c[i] /= alpha;
else
for (i=0; i<channels-1; ++i) c[i] = 1;
}
}
if (to_gray)
{
if (channels < 3)
{
fprintf(stderr, "%s: too few channels (%d) for -gray\n",
prog, channels);
usage(prog);
}
c[0] = YfromRGB(c[0], c[1], c[2]);
channels -= 2;
}
if (to_color)
{
if (channels > 2)
{
fprintf(stderr, "%s: too many channels (%d) for -color\n",
prog, channels);
usage(prog);
}
c[3] = c[1]; /* alpha, if present */
c[2] = c[1] = c[0];
}
if (to_linear)
{
int i;
if ((channels & 1) == 0)
{
double alpha = c[channels-1];
for (i=0; i<channels-1; ++i) c[i] *= alpha;
}
for (i=0; i<channels; ++i) c[i] = nearbyint(c[i] * 65535);
}
else /* to sRGB */
{
int i = (channels+1)&~1;
while (--i >= 0)
c[i] = sRGB_from_linear(c[i]);
for (i=0; i<channels; ++i) c[i] = nearbyint(c[i] * 255);
}
{
int i;
for (i=0; i<channels; ++i) printf(" %g", c[i]);
}
printf("\n");
return 0;
}
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