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188 lines
3.8 KiB
188 lines
3.8 KiB
/*- |
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* convert.c |
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* |
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* Last changed in libpng 1.6.0 [February 14, 2013] |
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* |
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* COPYRIGHT: Written by John Cunningham Bowler, 2013. |
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* To the extent possible under law, the author has waived all copyright and |
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* related or neighboring rights to this work. This work is published from: |
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* United States. |
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* |
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* Convert 8-bit sRGB or 16-bit linear values to another format. |
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*/ |
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#define _ISOC99_SOURCE 1 |
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#include <stdlib.h> |
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#include <string.h> |
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#include <math.h> |
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#include <stdio.h> |
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#include <fenv.h> |
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#include "sRGB.h" |
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static void |
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usage(const char *prog) |
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{ |
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fprintf(stderr, |
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"%s: usage: %s [-linear|-sRGB] [-gray|-color] component{1,4}\n", |
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prog, prog); |
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exit(1); |
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} |
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unsigned long |
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component(const char *prog, const char *arg, int issRGB) |
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{ |
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char *ep; |
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unsigned long c = strtoul(arg, &ep, 0); |
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if (ep <= arg || *ep || c > 65535 || (issRGB && c > 255)) |
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{ |
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fprintf(stderr, "%s: %s: invalid component value (%lu)\n", prog, arg, c); |
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usage(prog); |
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} |
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return c; |
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} |
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int |
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main(int argc, const char **argv) |
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{ |
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const char *prog = *argv++; |
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int to_linear = 0, to_gray = 0, to_color = 0; |
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int channels = 0; |
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double c[4]; |
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/* FE_TONEAREST is the IEEE754 round to nearest, preferring even, mode; i.e. |
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* everything rounds to the nearest value except that '.5' rounds to the |
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* nearest even value. |
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*/ |
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fesetround(FE_TONEAREST); |
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c[3] = c[2] = c[1] = c[0] = 0; |
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while (--argc > 0 && **argv == '-') |
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{ |
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const char *arg = 1+*argv++; |
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if (strcmp(arg, "sRGB") == 0) |
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to_linear = 0; |
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else if (strcmp(arg, "linear") == 0) |
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to_linear = 1; |
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else if (strcmp(arg, "gray") == 0) |
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to_gray = 1, to_color = 0; |
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else if (strcmp(arg, "color") == 0) |
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to_gray = 0, to_color = 1; |
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else |
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usage(prog); |
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} |
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switch (argc) |
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{ |
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default: |
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usage(prog); |
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break; |
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case 4: |
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c[3] = component(prog, argv[3], to_linear); |
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++channels; |
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case 3: |
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c[2] = component(prog, argv[2], to_linear); |
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++channels; |
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case 2: |
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c[1] = component(prog, argv[1], to_linear); |
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++channels; |
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case 1: |
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c[0] = component(prog, argv[0], to_linear); |
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++channels; |
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break; |
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} |
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if (to_linear) |
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{ |
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int i; |
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int components = channels; |
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if ((components & 1) == 0) |
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--components; |
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for (i=0; i<components; ++i) c[i] = linear_from_sRGB(c[i] / 255); |
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if (components < channels) |
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c[components] = c[components] / 255; |
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} |
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else |
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{ |
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int i; |
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for (i=0; i<4; ++i) c[i] /= 65535; |
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if ((channels & 1) == 0) |
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{ |
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double alpha = c[channels-1]; |
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if (alpha > 0) |
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for (i=0; i<channels-1; ++i) c[i] /= alpha; |
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else |
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for (i=0; i<channels-1; ++i) c[i] = 1; |
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} |
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} |
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if (to_gray) |
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{ |
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if (channels < 3) |
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{ |
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fprintf(stderr, "%s: too few channels (%d) for -gray\n", |
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prog, channels); |
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usage(prog); |
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} |
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c[0] = YfromRGB(c[0], c[1], c[2]); |
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channels -= 2; |
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} |
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if (to_color) |
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{ |
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if (channels > 2) |
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{ |
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fprintf(stderr, "%s: too many channels (%d) for -color\n", |
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prog, channels); |
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usage(prog); |
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} |
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c[3] = c[1]; /* alpha, if present */ |
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c[2] = c[1] = c[0]; |
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} |
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if (to_linear) |
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{ |
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int i; |
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if ((channels & 1) == 0) |
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{ |
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double alpha = c[channels-1]; |
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for (i=0; i<channels-1; ++i) c[i] *= alpha; |
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} |
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for (i=0; i<channels; ++i) c[i] = nearbyint(c[i] * 65535); |
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} |
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else /* to sRGB */ |
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{ |
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int i = (channels+1)&~1; |
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while (--i >= 0) |
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c[i] = sRGB_from_linear(c[i]); |
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for (i=0; i<channels; ++i) c[i] = nearbyint(c[i] * 255); |
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} |
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{ |
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int i; |
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for (i=0; i<channels; ++i) printf(" %g", c[i]); |
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} |
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printf("\n"); |
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return 0; |
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}
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