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gxcmap.c
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1994-01-27
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/* Copyright (C) 1992, 1993 Aladdin Enterprises. All rights reserved.
This file is part of Ghostscript.
Ghostscript is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY. No author or distributor accepts responsibility
to anyone for the consequences of using it or for whether it serves any
particular purpose or works at all, unless he says so in writing. Refer
to the Ghostscript General Public License for full details.
Everyone is granted permission to copy, modify and redistribute
Ghostscript, but only under the conditions described in the Ghostscript
General Public License. A copy of this license is supposed to have been
given to you along with Ghostscript so you can know your rights and
responsibilities. It should be in a file named COPYING. Among other
things, the copyright notice and this notice must be preserved on all
copies. */
/* gxcmap.c */
/* Color mapping and conversion for Ghostscript */
#include "gx.h"
#include "gserrors.h"
#include "gscspace.h"
#include "gxarith.h"
#include "gxfrac.h"
#include "gxlum.h"
#include "gxcolor.h"
#include "gxdevice.h"
#include "gzcolor.h"
#include "gzstate.h"
/* Brought back from a later release.... */
#define color_set_pure(pdc, color)\
((pdc)->color1 = (pdc)->color2 = (color), (pdc)->halftone_level = 0)
/* Convert a frac to a gx_color_value. */
/* This is needed because map_rgb_color still uses gx_color_value. */
#define _cv_bits (sizeof(gx_color_value) * 8)
#define frac2cv(fr)\
( ((fr) << (_cv_bits - frac_bits)) +\
((fr) >> (frac_bits * 2 - _cv_bits)) )
#define cv2frac(cv) ((frac)((cv) >> (_cv_bits - frac_bits)))
/* Note: the color model conversion algorithms are taken from */
/* Rogers, Procedural Elements for Computer Graphics, pp. 401-403. */
/* ------ Conversion between HSB and RGB ------ */
/* Convert RGB to HSB. */
void
color_rgb_to_hsb(floatp r, floatp g, floatp b, float hsb[3])
{ frac red = float2frac(r), green = float2frac(g), blue = float2frac(b);
#define rhue hsb[0]
#define rsat hsb[1]
#define rbri hsb[2]
if ( red == green && green == blue )
{ rhue = 0; /* arbitrary */
rsat = 0;
rbri = r; /* pick any one */
}
else
{ /* Convert rgb to hsb */
frac V, Temp;
long diff, H;
V = (red > green ? red : green);
if ( blue > V ) V = blue;
Temp = (red > green ? green : red);
if ( blue < Temp ) Temp = blue;
diff = V - Temp;
if ( V == red )
H = (green - blue) * frac_1_long / diff;
else if ( V == green )
H = (blue - red) * frac_1_long / diff + 2 * frac_1_long;
else /* V == blue */
H = (red - green) * frac_1_long / diff + 4 * frac_1_long;
if ( H < 0 ) H += 6 * frac_1_long;
rhue = H / (frac_1 * 6.0);
rsat = diff / (float)V;
rbri = frac2float(V);
}
#undef rhue
#undef rsat
#undef rbri
}
/* Convert HSB to RGB. */
void
color_hsb_to_rgb(floatp hue, floatp saturation, floatp brightness, float rgb[3])
{ if ( saturation == 0 )
{ rgb[0] = rgb[1] = rgb[2] = brightness;
}
else
{ /* Convert hsb to rgb. */
/* We rely on the fact that the product of two */
/* fracs fits into an unsigned long. */
floatp h6 = hue * 6;
ulong V = float2frac(brightness); /* force arithmetic to long */
frac S = float2frac(saturation);
int I = (int)h6;
ulong F = float2frac(h6 - I); /* ditto */
/* M = V*(1-S), N = V*(1-S*F), K = V*(1-S*(1-F)) = M-N+V */
frac M = V * (frac_1_long - S) / frac_1_long;
frac N = V * (frac_1_long - S * F / frac_1_long) / frac_1_long;
frac K = M - N + V;
frac R, G, B;
switch ( I )
{
default: R = V; G = K; B = M; break;
case 1: R = N; G = V; B = M; break;
case 2: R = M; G = V; B = K; break;
case 3: R = M; G = N; B = V; break;
case 4: R = K; G = M; B = V; break;
case 5: R = V; G = M; B = N; break;
}
rgb[0] = frac2float(R);
rgb[1] = frac2float(G);
rgb[2] = frac2float(B);
#ifdef DEBUG
if ( debug_c('c') )
{ dprintf7("[c]hsb(%g,%g,%g)->VSFI(%ld,%d,%ld,%d)->\n",
hue, saturation, brightness, V, S, F, I);
dprintf6(" RGB(%d,%d,%d)->rgb(%g,%g,%g)\n",
R, G, B, rgb[0], rgb[1], rgb[2]);
}
#endif
}
}
/* ------ Color space conversion ------ */
/* Only 4 of the 6 conversions are implemented here; */
/* the other 2 (Gray to RGB/CMYK) are trivial. */
/* The CMYK to RGB algorithms specified by Adobe are, e.g., */
/* R = 1.0 - min(1.0, C + K) */
/* but we get much better results with */
/* R = (1.0 - C) * (1.0 - K) */
/* Convert RGB to Gray. */
frac
color_rgb_to_gray(frac r, frac g, frac b, const gs_state *pgs)
{ return (r * (unsigned long)lum_red_weight +
g * (unsigned long)lum_green_weight +
b * (unsigned long)lum_blue_weight +
(lum_all_weights / 2))
/ lum_all_weights;
}
/* Convert RGB to CMYK. */
/* Note that this involves black generation and undercolor removal. */
void
color_rgb_to_cmyk(frac r, frac g, frac b, const gs_state *pgs,
frac cmyk[4])
{ frac c = frac_1 - r, m = frac_1 - g, y = frac_1 - b;
frac k = (c < m ? min(c, y) : min(m, y));
/* The default UCR and BG functions are pretty arbitrary.... */
frac bg =
(pgs->black_generation == NULL ? frac_0 :
float2frac((*pgs->black_generation)(pgs, frac2float(k))));
signed_frac ucr =
(pgs->undercolor_removal == NULL ? frac_0 :
float2frac((*pgs->undercolor_removal)(pgs, frac2float(k))));
/* Adobe specifies, e.g., */
/* C = max(0.0, min(1.0, 1 - R - UCR)) */
/* but in order to match our improved CMYK->RGB mapping, we use */
/* C = max(0.0, min(1.0, 1 - R / (1 - UCR)) */
if ( ucr == frac_1 )
cmyk[0] = cmyk[1] = cmyk[2] = 0;
else
{ float denom = frac2float(frac_1 - ucr); /* unscaled */
float v;
v = (float)frac_1 - r / denom; /* unscaled */
cmyk[0] =
(is_fneg(v) ? frac_0 : v >= (float)frac_1 ? frac_1 : (frac)v);
v = (float)frac_1 - g / denom; /* unscaled */
cmyk[1] =
(is_fneg(v) ? frac_0 : v >= (float)frac_1 ? frac_1 : (frac)v);
v = (float)frac_1 - b / denom; /* unscaled */
cmyk[2] =
(is_fneg(v) ? frac_0 : v >= (float)frac_1 ? frac_1 : (frac)v);
}
cmyk[3] = bg;
if_debug7('c', "[c]RGB 0x%x,0x%x,0x%x -> CMYK 0x%x,0x%x,0x%x,0x%x\n",
r, g, b, cmyk[0], cmyk[1], cmyk[2], cmyk[3]);
}
/* Convert CMYK to Gray. */
frac
color_cmyk_to_gray(frac c, frac m, frac y, frac k, const gs_state *pgs)
{ frac not_gray = color_rgb_to_gray(c, m, y, pgs);
return (not_gray > frac_1 - k ? /* gray + k > 1.0 */
frac_0 : frac_1 - (not_gray + k));
}
/* Convert CMYK to RGB. */
void
color_cmyk_to_rgb(frac c, frac m, frac y, frac k, const gs_state *pgs,
frac rgb[3])
{ switch ( k )
{
case frac_0:
rgb[0] = frac_1 - c;
rgb[1] = frac_1 - m;
rgb[2] = frac_1 - y;
break;
case frac_1:
rgb[0] = rgb[1] = rgb[2] = frac_0;
break;
default:
{ ulong not_k = frac_1 - k;
/* Compute not_k * (frac_1 - v) / frac_1 efficiently. */
ulong prod;
#define deduct_black(v)\
(prod = (frac_1 - (v)) * not_k,\
(prod + (prod >> frac_bits) + 1) >> frac_bits)
rgb[0] = deduct_black(c);
rgb[1] = deduct_black(m);
rgb[2] = deduct_black(y);
}
}
if_debug7('c', "[c]CMYK 0x%x,0x%x,0x%x,0x%x -> RGB 0x%x,0x%x,0x%x\n",
c, m, y, k, rgb[0], rgb[1], rgb[2]);
}
/* ------ Device color rendering ------ */
private cmap_proc_gray(cmap_gray_halftoned);
private cmap_proc_gray(cmap_gray_direct);
private cmap_proc_gray(cmap_gray_to_rgb);
private cmap_proc_gray(cmap_gray_to_cmyk);
#define cmap_rgb_halftoned cmap_rgb_direct
private cmap_proc_rgb(cmap_rgb_direct);
private cmap_proc_rgb(cmap_rgb_to_gray);
private cmap_proc_rgb(cmap_rgb_to_cmyk);
#define cmap_cmyk_halftoned cmap_cmyk_direct
private cmap_proc_cmyk(cmap_cmyk_direct);
private cmap_proc_cmyk(cmap_cmyk_to_gray);
private cmap_proc_cmyk(cmap_cmyk_to_rgb);
private const gx_color_map_procs
cmap_gray_few =
{ cmap_gray_halftoned, cmap_rgb_to_gray, cmap_cmyk_to_gray },
cmap_gray_many =
{ cmap_gray_direct, cmap_rgb_to_gray, cmap_cmyk_to_gray },
cmap_rgb_few =
{ cmap_gray_to_rgb, cmap_rgb_halftoned, cmap_cmyk_to_rgb },
cmap_rgb_many =
{ cmap_gray_to_rgb, cmap_rgb_direct, cmap_cmyk_to_rgb },
cmap_cmyk_few =
{ cmap_gray_to_cmyk, cmap_rgb_to_cmyk, cmap_cmyk_halftoned },
cmap_cmyk_many =
{ cmap_gray_to_cmyk, cmap_rgb_to_cmyk, cmap_cmyk_direct };
const gx_color_map_procs *cmap_procs_default =