diff options
Diffstat (limited to 'base/gxdcconv.c')
| -rw-r--r-- | base/gxdcconv.c | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/base/gxdcconv.c b/base/gxdcconv.c new file mode 100644 index 00000000..0b31ea7e --- /dev/null +++ b/base/gxdcconv.c @@ -0,0 +1,159 @@ +/* Copyright (C) 2001-2019 Artifex Software, Inc. + All Rights Reserved. + + This software is provided AS-IS with no warranty, either express or + implied. + + This software is distributed under license and may not be copied, + modified or distributed except as expressly authorized under the terms + of the license contained in the file LICENSE in this distribution. + + Refer to licensing information at http://www.artifex.com or contact + Artifex Software, Inc., 1305 Grant Avenue - Suite 200, Novato, + CA 94945, U.S.A., +1(415)492-9861, for further information. +*/ + + +/* Conversion between device color spaces for Ghostscript */ +#include "gx.h" +#include "gsdcolor.h" /* for gxcmap.h */ +#include "gxdcconv.h" /* interface */ +#include "gxdevice.h" /* for gxcmap.h */ +#include "gxcmap.h" +#include "gxfarith.h" +#include "gxlum.h" +#include "gxgstate.h" +#include "gsstate.h" /* for gs_currentcpsimode */ + +/* + * The CMYK to RGB algorithms specified by Adobe are, e.g., + * R = 1.0 - min(1.0, C + K) + * C = max(0.0, min(1.0, 1 - R - UCR)) + * We got better results on displays with + * R = (1.0 - C) * (1.0 - K) + * C = max(0.0, min(1.0, 1 - R / (1 - UCR))) + * For PLRM compatibility, we use the Adobe algorithms by default, + * but what Adobe says and what they do are two different things. + * Testing on CPSI shows that they use the 'better' algorithm. + */ + +/* ------ Color space conversion ------ */ + +/* Only 4 of the 6 conversions are implemented here; */ +/* the other 2 (Gray to RGB/CMYK) are trivial. */ + +/* Convert RGB to Gray. */ +frac +color_rgb_to_gray(frac r, frac g, frac b, const gs_gstate * 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_gstate * pgs, + frac cmyk[4], gs_memory_t *mem) +{ + 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, + * but they must agree with the ones in gs_init.ps. + */ + frac bg = + (pgs == NULL ? k : pgs->black_generation == NULL ? frac_0 : + gx_map_color_frac(pgs, k, black_generation)); + signed_frac ucr = + (pgs == NULL ? k : pgs->undercolor_removal == NULL ? frac_0 : + gx_map_color_frac(pgs, k, undercolor_removal)); + + if (ucr == frac_1) + cmyk[0] = cmyk[1] = cmyk[2] = 0; + else if (ucr == frac_0) + cmyk[0] = c, cmyk[1] = m, cmyk[2] = y; + else { + if (!gs_currentcpsimode(mem)) { + /* C = max(0.0, min(1.0, 1 - R - UCR)), etc. */ + signed_frac not_ucr = (ucr < 0 ? frac_1 + ucr : frac_1); + + cmyk[0] = (c < ucr ? frac_0 : c > not_ucr ? frac_1 : c - ucr); + cmyk[1] = (m < ucr ? frac_0 : m > not_ucr ? frac_1 : m - ucr); + cmyk[2] = (y < ucr ? frac_0 : y > not_ucr ? frac_1 : y - ucr); + } else { + /* Adobe CPSI method */ + /* C = max(0.0, min(1.0, 1 - R / (1 - UCR))), etc. */ + 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_debug7m('c', mem, "[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_gstate * 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_gstate * pgs, + frac rgb[3], gs_memory_t *mem) +{ + 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: + if (!gs_currentcpsimode(mem)) { + /* R = 1.0 - min(1.0, C + K), etc. */ + frac not_k = frac_1 - k; + + rgb[0] = (c > not_k ? frac_0 : not_k - c); + rgb[1] = (m > not_k ? frac_0 : not_k - m); + rgb[2] = (y > not_k ? frac_0 : not_k - y); + } else { + /* R = (1.0 - C) * (1.0 - K), etc. */ + 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, frac_1_quo(prod)) + rgb[0] = deduct_black(c); + rgb[1] = deduct_black(m); + rgb[2] = deduct_black(y); +#undef deduct_black + } + } + if_debug7m('c', mem, "[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]); +} |