source/libs/libpng/libpng-src/contrib/tools/cvtcolor.c

   1 /*-
   2  * convert.c
   3  *
   4  * Last changed in libpng 1.6.0 [February 14, 2013]
   5  *
   6  * COPYRIGHT: Written by John Cunningham Bowler, 2013.
   7  * To the extent possible under law, the author has waived all copyright and
   8  * related or neighboring rights to this work.  This work is published from:
   9  * United States.
  10  *
  11  * Convert 8-bit sRGB or 16-bit linear values to another format.
  12  */
  13 #define _ISOC99_SOURCE 1
  14
  15 #include <stdlib.h>
  16 #include <string.h>
  17 #include <math.h>
  18 #include <stdio.h>
  19
  20 #include <fenv.h>
  21
  22 #include "sRGB.h"
  23
  24 static void
  25 usage(const char *prog)
  26 {
  27    fprintf(stderr,
  28       "%s: usage: %s [-linear|-sRGB] [-gray|-color] component{1,4}\n",
  29       prog, prog);
  30    exit(1);
  31 }
  32
  33 unsigned long
  34 component(const char *prog, const char *arg, int issRGB)
  35 {
  36    char *ep;
  37    unsigned long c = strtoul(arg, &ep, 0);
  38
  39    if (ep <= arg || *ep || c > 65535 || (issRGB && c > 255))
  40    {
  41       fprintf(stderr, "%s: %s: invalid component value (%lu)\n", prog, arg, c);
  42       usage(prog);
  43    }
  44
  45    return c;
  46 }
  47
  48 int
  49 main(int argc, const char **argv)
  50 {
  51    const char *prog = *argv++;
  52    int to_linear = 0, to_gray = 0, to_color = 0;
  53    int channels = 0;
  54    double c[4];
  55
  56    /* FE_TONEAREST is the IEEE754 round to nearest, preferring even, mode; i.e.
  57     * everything rounds to the nearest value except that '.5' rounds to the
  58     * nearest even value.
  59     */
  60    fesetround(FE_TONEAREST);
  61
  62    c[3] = c[2] = c[1] = c[0] = 0;
  63
  64    while (--argc > 0 && **argv == '-')
  65    {
  66       const char *arg = 1+*argv++;
  67
  68       if (strcmp(arg, "sRGB") == 0)
  69          to_linear = 0;
  70
  71       else if (strcmp(arg, "linear") == 0)
  72          to_linear = 1;
  73
  74       else if (strcmp(arg, "gray") == 0)
  75          to_gray = 1, to_color = 0;
  76
  77       else if (strcmp(arg, "color") == 0)
  78          to_gray = 0, to_color = 1;
  79
  80       else
  81          usage(prog);
  82    }
  83
  84    switch (argc)
  85    {
  86       default:
  87          usage(prog);
  88          break;
  89
  90       case 4:
  91          c[3] = component(prog, argv[3], to_linear);
  92          ++channels;
  93       case 3:
  94          c[2] = component(prog, argv[2], to_linear);
  95          ++channels;
  96       case 2:
  97          c[1] = component(prog, argv[1], to_linear);
  98          ++channels;
  99       case 1:
 100          c[0] = component(prog, argv[0], to_linear);
 101          ++channels;
 102          break;
 103       }
 104
 105    if (to_linear)
 106    {
 107       int i;
 108       int components = channels;
 109
 110       if ((components & 1) == 0)
 111          --components;
 112
 113       for (i=0; i<components; ++i) c[i] = linear_from_sRGB(c[i] / 255);
 114       if (components < channels)
 115          c[components] = c[components] / 255;
 116    }
 117
 118    else
 119    {
 120       int i;
 121       for (i=0; i<4; ++i) c[i] /= 65535;
 122
 123       if ((channels & 1) == 0)
 124       {
 125          double alpha = c[channels-1];
 126
 127          if (alpha > 0)
 128             for (i=0; i<channels-1; ++i) c[i] /= alpha;
 129          else
 130             for (i=0; i<channels-1; ++i) c[i] = 1;
 131       }
 132    }
 133
 134    if (to_gray)
 135    {
 136       if (channels < 3)
 137       {
 138          fprintf(stderr, "%s: too few channels (%d) for -gray\n",
 139             prog, channels);
 140          usage(prog);
 141       }
 142
 143       c[0] = YfromRGB(c[0], c[1], c[2]);
 144       channels -= 2;
 145    }
 146
 147    if (to_color)
 148    {
 149       if (channels > 2)
 150       {
 151          fprintf(stderr, "%s: too many channels (%d) for -color\n",
 152             prog, channels);
 153          usage(prog);
 154       }
 155
 156       c[3] = c[1]; /* alpha, if present */
 157       c[2] = c[1] = c[0];
 158    }
 159
 160    if (to_linear)
 161    {
 162       int i;
 163       if ((channels & 1) == 0)
 164       {
 165          double alpha = c[channels-1];
 166          for (i=0; i<channels-1; ++i) c[i] *= alpha;
 167       }
 168
 169       for (i=0; i<channels; ++i) c[i] = nearbyint(c[i] * 65535);
 170    }
 171
 172    else /* to sRGB */
 173    {
 174       int i = (channels+1)&~1;
 175       while (--i >= 0)
 176          c[i] = sRGB_from_linear(c[i]);
 177
 178       for (i=0; i<channels; ++i) c[i] = nearbyint(c[i] * 255);
 179    }
 180
 181    {
 182       int i;
 183       for (i=0; i<channels; ++i) printf(" %g", c[i]);
 184    }
 185    printf("\n");
 186
 187    return 0;
 188 }