/* Copyright (C) 1992, 1993 Aladdin Enterprises.  All rights reserved.
  
  This file is part of Aladdin Ghostscript.
  
  Aladdin Ghostscript is distributed with NO WARRANTY OF ANY KIND.  No author
  or distributor accepts any responsibility for the consequences of using it,
  or for whether it serves any particular purpose or works at all, unless he
  or she says so in writing.  Refer to the Aladdin Ghostscript Free Public
  License (the "License") for full details.
  
  Every copy of Aladdin Ghostscript must include a copy of the License,
  normally in a plain ASCII text file named PUBLIC.  The License grants you
  the right to copy, modify and redistribute Aladdin Ghostscript, but only
  under certain conditions described in the License.  Among other things, the
  License requires that the copyright notice and this notice be preserved on
  all copies.
*/

/* gdevpccm.c */
/* Support routines for PC color mapping */
#include "gx.h"
#include "gsmatrix.h"			/* for gxdevice.h */
#include "gxdevice.h"
#include "gdevpccm.h"			/* interface */

/* Color mapping routines for EGA/VGA-style color. */
/* Colors are 4 bits: 8=intensity, 4=R, 2=G, 1=B. */

/* Define the color spectrum */
#define v_black 0
#define v_blue 1
#define v_green 2
#define v_cyan 3
#define v_red 4
#define v_magenta 5
#define v_brown 6
#define v_white 7
#define v_dgray 8			/* dark gray is not very usable */
#define v_lblue 9
#define v_lgreen 10
#define v_lcyan 11
#define v_lred 12
#define v_lmagenta 13
#define v_yellow 14
#define v_bwhite 15

/* ------ EGA/VGA (4-bit) color mapping ------ */

gx_color_index
pc_4bit_map_rgb_color(gx_device *dev, gx_color_value r, gx_color_value g,
  gx_color_value b)
{
#define Nb gx_color_value_bits
	static const byte grays[4] = { v_black, v_dgray, v_white, v_bwhite };
#define tab3(v0,v1,v23) { v0, v1, v23, v23 }
	static const byte g0r0[4] = tab3(v_black,v_blue,v_lblue);
	static const byte g0r1[4] = tab3(v_red,v_magenta,v_lmagenta);
	static const byte g0r2[4] = tab3(v_lred,v_lmagenta,v_lmagenta);
	static const byte _ds *g0[4] = tab3(g0r0, g0r1, g0r2);
	static const byte g1r0[4] = tab3(v_green,v_cyan,v_lcyan);
	static const byte g1r1[4] = tab3(v_brown,v_white,v_lcyan);
	static const byte g1r2[4] = tab3(v_yellow,v_lred,v_lmagenta);
	static const byte _ds *g1[4] = tab3(g1r0, g1r1, g1r2);
	static const byte g2r0[4] = tab3(v_lgreen,v_lgreen,v_lcyan);
	static const byte g2r1[4] = tab3(v_lgreen,v_lgreen,v_lcyan);
	static const byte g2r2[4] = tab3(v_yellow,v_yellow,v_bwhite);
	static const byte _ds *g2[4] = tab3(g2r0, g2r1, g2r2);
	static const byte _ds * _ds *ga[4] = tab3(g0, g1, g2);
#undef tab3
#define q4mask (-1 << (Nb - 2))
	if ( !((r ^ g) & q4mask) && !((g ^ b) & q4mask) )	/* gray */
#undef q4mask
		return (gx_color_index)grays[r >> (Nb - 2)];
	else
#define q3cv(v) ((v - (v >> 2)) >> (Nb - 2))
		return (gx_color_index)ga[q3cv(g)][q3cv(r)][q3cv(b)];
#undef q3cv
#undef Nb
}
int
pc_4bit_map_color_rgb(gx_device *dev, gx_color_index color,
  gx_color_value prgb[3])
{
#define icolor (int)color
	gx_color_value one;
	switch ( icolor )
	{
	case v_white:			/* "dark white" */
		prgb[0] = prgb[1] = prgb[2] =
		  gx_max_color_value - (gx_max_color_value / 3);
		return 0;
	case v_dgray:
		prgb[0] = prgb[1] = prgb[2] = gx_max_color_value / 3;
		return 0;
	}
	one = (icolor & 8 ? gx_max_color_value : gx_max_color_value / 2);
	prgb[0] = (icolor & 4 ? one : 0);
	prgb[1] = (icolor & 2 ? one : 0);
	prgb[2] = (icolor & 1 ? one : 0);
	return 0;
#undef icolor
}

/* ------ SVGA 8-bit color mapping ------ */

/*
 * For 8-bit color, we use a fixed palette with approximately
 * 3 bits of R, 3 bits of G, and 2 bits of B.
 * We have to trade off even spacing of colors along each axis
 * against the desire to have real gray shades;
 * we compromise by using a 7x7x5 "cube" with extra gray shades
 * (1/6, 1/3, 2/3, and 5/6), instead of the obvious 8x8x4.
 */

gx_color_index
pc_8bit_map_rgb_color(gx_device *dev, gx_color_value r, gx_color_value g,
  gx_color_value b)
{	uint rv = r / (gx_max_color_value / 7 + 1);
	uint gv = g / (gx_max_color_value / 7 + 1);
	return (gx_color_index)
		(rv == gv && gv == b / (gx_max_color_value / 7 + 1) ?
		 rv + (256-7) :
		 (rv * 7 + gv) * 5 + b / (gx_max_color_value / 5 + 1));
}
int
pc_8bit_map_color_rgb(gx_device *dev, gx_color_index color,
  gx_color_value prgb[3])
{	static const gx_color_value ramp7[8] =
	{	0,
		gx_max_color_value / 6,
		gx_max_color_value / 3,
		gx_max_color_value / 2,
		gx_max_color_value - (gx_max_color_value / 3),
		gx_max_color_value - (gx_max_color_value / 6),
		gx_max_color_value,
		/* The 8th entry is not actually ever used, */
		/* except to fill out the palette. */
		gx_max_color_value
	};
	static const gx_color_value ramp5[5] =
	{	0,
		gx_max_color_value / 4,
		gx_max_color_value / 2,
		gx_max_color_value - (gx_max_color_value / 4),
		gx_max_color_value
	};
#define icolor (uint)color
	if ( icolor >= 256-7 )
	{	prgb[0] = prgb[1] = prgb[2] = ramp7[icolor - (256-7)];
	}
	else
	{	prgb[0] = ramp7[icolor / 35];
		prgb[1] = ramp7[(icolor / 5) % 7];
		prgb[2] = ramp5[icolor % 5];
	}
#undef icolor
	return 0;
}

/* Write a palette on a file. */
int
pc_write_palette(gx_device *dev, uint max_index, FILE *file)
{	uint i, c;
	gx_color_value rgb[3];
	for ( i = 0; i < max_index; i++ )
	{	(*dev_proc(dev, map_color_rgb))(dev, (gx_color_index)i, rgb);
		for ( c = 0; c < 3; c++ )
		{	byte b = rgb[c] >> (gx_color_value_bits - 8);
			fputc(b, file);
		}
	}
	return 0;
}
