/* Copyright (C) 1993, 1996, 1997, 1998, 1999 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.
 */

/*$Id: gxcht.c $ */
/* Color halftone rendering for Ghostscript imaging library */
#include "memory_.h"
#include "gx.h"
#include "gserrors.h"
#include "gsutil.h"		/* for id generation */
#include "gxarith.h"
#include "gxfixed.h"
#include "gxmatrix.h"
#include "gxdevice.h"
#include "gxcmap.h"
#include "gxdcolor.h"
#include "gxistate.h"
#include "gzht.h"

/* Define whether to force use of the slow code, for testing. */
#define USE_SLOW_CODE 0

/* Define the size of the tile buffer allocated on the stack. */
#define tile_longs_LARGE 256
#define tile_longs_SMALL 64
#if arch_small_memory
#  define tile_longs_allocated tile_longs_SMALL
#  define tile_longs tile_longs_SMALL
#else
#  define tile_longs_allocated tile_longs_LARGE
#  ifdef DEBUG
#    define tile_longs\
       (gs_debug_c('.') ? tile_longs_SMALL : tile_longs_LARGE)
#  else
#    define tile_longs tile_longs_LARGE
#  endif
#endif

/* Define the colored halftone device color type. */
gs_private_st_ptrs1(st_dc_ht_colored, gx_device_color, "dc_ht_colored",
    dc_ht_colored_enum_ptrs, dc_ht_colored_reloc_ptrs, colors.colored.c_ht);
private dev_color_proc_load(gx_dc_ht_colored_load);
private dev_color_proc_fill_rectangle(gx_dc_ht_colored_fill_rectangle);
private dev_color_proc_equal(gx_dc_ht_colored_equal);
const gx_device_color_type_t gx_dc_type_data_ht_colored = {
    &st_dc_ht_colored,
    gx_dc_ht_colored_load, gx_dc_ht_colored_fill_rectangle,
    gx_dc_default_fill_masked, gx_dc_ht_colored_equal
};
#undef gx_dc_type_ht_colored
const gx_device_color_type_t *const gx_dc_type_ht_colored =
    &gx_dc_type_data_ht_colored;
#define gx_dc_type_ht_colored (&gx_dc_type_data_ht_colored)

/* Compare two colored halftones for equality. */
private bool
gx_dc_ht_colored_equal(const gx_device_color * pdevc1,
		       const gx_device_color * pdevc2)
{
    uint num_comp;

    if (pdevc2->type != pdevc1->type ||
	pdevc1->colors.colored.c_ht != pdevc2->colors.colored.c_ht ||
	pdevc1->colors.colored.alpha != pdevc2->colors.colored.alpha ||
	pdevc1->phase.x != pdevc2->phase.x ||
	pdevc1->phase.y != pdevc2->phase.y
	)
	return false;
    num_comp = pdevc1->colors.colored.c_ht->num_comp;
    return
	!memcmp(pdevc1->colors.colored.c_base,
		pdevc2->colors.colored.c_base,
		num_comp * sizeof(pdevc1->colors.colored.c_base[0])) &&
	!memcmp(pdevc1->colors.colored.c_level,
		pdevc2->colors.colored.c_level,
		num_comp * sizeof(pdevc1->colors.colored.c_level[0]));
}

/* Define an abbreviation for a heavily used value. */
#define MAX_DCC GX_DEVICE_COLOR_MAX_COMPONENTS

/* Forward references. */
/* Use a typedef to attempt to work around overly picky compilers. */
typedef gx_color_value gx_color_value_array[MAX_DCC];
typedef struct color_values_pair_s {
    gx_color_value_array values[2];
} color_values_pair_t;
#define SET_HT_COLORS_PROC(proc)\
  int proc(P7(\
	      color_values_pair_t *pvp,\
	      gx_color_index colors[1 << MAX_DCC],\
	      const gx_const_strip_bitmap *sbits[MAX_DCC],\
	      const gx_device_color *pdevc,\
	      gx_device *dev,\
	      gx_ht_cache *caches[MAX_DCC],\
	      int nplanes\
	      ))

private SET_HT_COLORS_PROC(set_ht_colors_le_4);
private SET_HT_COLORS_PROC(set_cmyk_1bit_colors);
private SET_HT_COLORS_PROC(set_ht_colors_gt_4);

#define SET_COLOR_HT_PROC(proc)\
  void proc(P14(\
	        byte *dest_data, /* the output tile */\
		uint dest_raster, /* ibid. */\
		int px,	/* the initial phase of the output tile */\
		int py,\
		int w,	/* how much of the tile to set */\
		int h,\
		int depth,	/* depth of tile (4, 8, 16, 24, 32) */\
		int special,	/* >0 means special 1-bit CMYK */\
		int nplanes,\
		gx_color_index plane_mask,	/* which planes are halftoned */\
		gx_device *dev,		/* in case we are mapping lazily */\
		const color_values_pair_t *pvp,	/* color values ditto */\
		gx_color_index colors[1 << MAX_DCC],	/* the actual colors for the tile, */\
				/* actually [1 << nplanes] */\
		const gx_const_strip_bitmap * sbits[MAX_DCC]	/* the bitmaps for the planes, */\
				/* actually [nplanes] */\
		))

private SET_COLOR_HT_PROC(set_color_ht_le_4);
private SET_COLOR_HT_PROC(set_color_ht_gt_4);

/* Prepare to use a colored halftone, by loading the default cache. */
private int
gx_dc_ht_colored_load(gx_device_color * pdevc, const gs_imager_state * pis,
		      gx_device * ignore_dev, gs_color_select_t select)
{
    gx_device_halftone *pdht = pdevc->colors.colored.c_ht;
    gx_ht_cache *pcache = pis->ht_cache;
    gx_ht_order *porder =
	(pdht->components ? &pdht->components[0].corder : &pdht->order);

    if (pcache->order.bit_data != porder->bit_data)
	gx_ht_init_cache(pcache, porder);
    /* Set the cache pointers in the default order. */
    pdht->order.cache = porder->cache = pcache;
    return 0;
}

/* Fill a rectangle with a colored halftone. */
/* Note that we treat this as "texture" for RasterOp. */
private int
gx_dc_ht_colored_fill_rectangle(const gx_device_color * pdevc,
				int x, int y, int w, int h,
				gx_device * dev, gs_logical_operation_t lop,
				const gx_rop_source_t * source)
{
    ulong tbits[tile_longs_allocated];
    const uint tile_bytes = tile_longs * size_of(long);
    gx_strip_bitmap tiles;
    gx_rop_source_t no_source;
    const gx_device_halftone *pdht = pdevc->colors.colored.c_ht;
    int depth = dev->color_info.depth;
    int nplanes = dev->color_info.num_components;
    SET_HT_COLORS_PROC((*set_ht_colors)) =
	(
#if USE_SLOW_CODE
	 set_ht_colors_gt_4
#else
	 dev_proc(dev, map_cmyk_color) == cmyk_1bit_map_cmyk_color ?
	   set_cmyk_1bit_colors :
	 nplanes < 4 ? set_ht_colors_le_4 :
	 set_ht_colors_gt_4
#endif
	 );
    SET_COLOR_HT_PROC((*set_color_ht)) =
	(
#if !USE_SLOW_CODE
	 !(pdevc->colors.colored.plane_mask & ~(gx_color_index)15) &&
	  set_ht_colors != set_ht_colors_gt_4 ?
	   set_color_ht_le_4 :
#endif
	 set_color_ht_gt_4);
    color_values_pair_t vp;
    gx_color_index colors[1 << MAX_DCC];
    const gx_const_strip_bitmap *sbits[MAX_DCC];
    gx_ht_cache *caches[MAX_DCC];
    int special;
    int code = 0;
    int raster;
    uint size_x;
    int dw, dh;
    int lw = pdht->lcm_width, lh = pdht->lcm_height;
    bool no_rop;
    int i;

    if (w <= 0 || h <= 0)
	return 0;
    if ((w | h) >= 16) {
	/* It's worth taking the trouble to check the clipping box. */
	gs_fixed_rect cbox;
	int t;

	dev_proc(dev, get_clipping_box)(dev, &cbox);
	if ((t = fixed2int(cbox.p.x)) > x) {
	    if ((w += x - t) <= 0)
		return 0;
	    x = t;
	}
	if ((t = fixed2int(cbox.p.y)) > y) {
	    if ((h += y - t) <= 0)
		return 0;
	    y = t;
	}
	if ((t = fixed2int(cbox.q.x)) < x + w)
	    if ((w = t - x) <= 0)
		return 0;
	if ((t = fixed2int(cbox.q.y)) < y + h)
	    if ((h = t - y) <= 0)
		return 0;
    }
    /* Colored halftone patterns are unconditionally opaque. */
    lop &= ~lop_T_transparent;
    if (pdht->components == 0) {
	caches[0] = caches[1] = caches[2] = caches[3] = pdht->order.cache;
	for (i = 4; i < nplanes; ++i)
	    caches[i] = pdht->order.cache;
    } else {
	gx_ht_order_component *pocs = pdht->components;

	caches[0] = pocs[pdht->color_indices[0]].corder.cache;
	caches[1] = pocs[pdht->color_indices[1]].corder.cache;
	caches[2] = pocs[pdht->color_indices[2]].corder.cache;
	caches[3] = pocs[pdht->color_indices[3]].corder.cache;
	for (i = 4; i < nplanes; ++i)
	    caches[i] = pocs[pdht->color_indices[i]].corder.cache;
    }
    special = set_ht_colors(&vp, colors, sbits, pdevc, dev, caches, nplanes);
    no_rop = source == NULL && lop_no_S_is_T(lop);
    /*
     * If the LCM of the plane cell sizes is smaller than the rectangle
     * being filled, compute a single tile and let tile_rectangle do the
     * replication.
     */
    if ((w > lw || h > lh) &&
	(raster = bitmap_raster(lw * depth)) <= tile_bytes / lh
	) {
	/*
	 * The only reason we need to do fit_fill here is that if the
	 * device is a clipper, the caller might be counting on it to do
	 * all necessary clipping.  Actually, we should clip against the
	 * device's clipping box, not the default....
	 */
	fit_fill(dev, x, y, w, h);
	/* Check to make sure we still have a big rectangle. */
	if (w > lw || h > lh) {
	    tiles.data = (byte *)tbits;
	    tiles.raster = raster;
	    tiles.rep_width = tiles.size.x = lw;
	    tiles.rep_height = tiles.size.y = lh;
	    tiles.id = gs_next_ids(1);
	    tiles.rep_shift = tiles.shift = 0;
	    set_color_ht((byte *)tbits, raster, 0, 0, lw, lh, depth,
			 special, nplanes, pdevc->colors.colored.plane_mask,
			 dev, &vp, colors, sbits);
	    if (no_rop)
		return (*dev_proc(dev, strip_tile_rectangle)) (dev, &tiles,
							       x, y, w, h,
				       gx_no_color_index, gx_no_color_index,
					    pdevc->phase.x, pdevc->phase.y);
	    if (source == NULL)
		set_rop_no_source(source, no_source, dev);
	    return (*dev_proc(dev, strip_copy_rop)) (dev, source->sdata,
			       source->sourcex, source->sraster, source->id,
			     (source->use_scolors ? source->scolors : NULL),
						     &tiles, NULL,
						     x, y, w, h,
					     pdevc->phase.x, pdevc->phase.y,
                                                lop);
	}
    }
    size_x = w * depth;
    raster = bitmap_raster(size_x);
    if (raster > tile_bytes) {
	/*
	 * We can't even do an entire line at once.  See above for
	 * why we do the X equivalent of fit_fill here.
	 */
	if (x < 0)
	    w += x, x = 0;
	if (x > dev->width - w)
	    w = dev->width - x;
	if (w <= 0)
	    return 0;
	size_x = w * depth;
	raster = bitmap_raster(size_x);
	if (raster > tile_bytes) {
	    /* We'll have to do a partial line. */
	    dw = tile_bytes * 8 / depth;
	    size_x = dw * depth;
	    raster = bitmap_raster(size_x);
	    dh = 1;
	    goto fit;
	}
    }
    /* Do as many lines as will fit. */
    dw = w;
    dh = tile_bytes / raster;
    if (dh > h)
	dh = h;
fit:				/* Now the tile will definitely fit. */
    if (!no_rop) {
	tiles.data = (byte *)tbits;
	tiles.id = gx_no_bitmap_id;
	tiles.raster = raster;
	tiles.rep_width = tiles.size.x = size_x / depth;
	tiles.rep_shift = tiles.shift = 0;
    }
    while (w) {
	int cy = y, ch = dh, left = h;

	for (;;) {
	    set_color_ht((byte *)tbits, raster,
			 x + pdevc->phase.x, cy + pdevc->phase.y,
			 dw, ch, depth, special, nplanes,
			 pdevc->colors.colored.plane_mask,
			 dev, &vp, colors, sbits);
	    if (no_rop) {
		code = (*dev_proc(dev, copy_color))
		    (dev, (byte *)tbits, 0, raster, gx_no_bitmap_id,
		     x, cy, dw, ch);
	    } else {
		tiles.rep_height = tiles.size.y = ch;
                if (source == NULL)
                    set_rop_no_source(source, no_source, dev);
		/****** WRONG - MUST ADJUST source VALUES ******/
	        code = (*dev_proc(dev, strip_copy_rop))
		    (dev, source->sdata, source->sourcex, source->sraster,
		     source->id,
		     (source->use_scolors ? source->scolors : NULL),
		     &tiles, NULL, x, cy, dw, ch, 0, 0, lop);
	    }
	    if (code < 0)
		return code;
	    if (!(left -= ch))
		break;
	    cy += ch;
	    if (ch > left)
		ch = left;
	}
	if (!(w -= dw))
	    break;
	x += dw;
	if (dw > w)
	    dw = w;
    }
    return code;
}

/* ---------------- Color table setup ---------------- */

/*
 * We could cache this if we had a place to store it.  Even a 1-element
 * cache would help performance substantially.
 *   Key: device + c_base/c_level of device color
 *   Value: colors table
 */

/*
 * We construct color halftone tiles out of multiple "planes".
 * Each plane specifies halftoning for one component (R/G/B, C/M/Y/K,
 * or DeviceN components).
 */

private const struct {
    ulong pad;			/* to get bytes aligned properly */
    byte bytes[sizeof(ulong) * 8];	/* 8 is arbitrary */
} ht_no_bitmap_data = { 0 };
private const gx_const_strip_bitmap ht_no_bitmap = {
    &ht_no_bitmap_data.bytes[0], sizeof(ulong),
    {sizeof(ulong) * 8, sizeof(ht_no_bitmap_data.bytes) / sizeof(ulong)},
    gx_no_bitmap_id, 1, 1, 0, 0
};

/* Set the color value(s) and halftone mask for one plane. */

/* Free variables: pvp, pdc, sbits */
#define SET_PLANE_COLOR_CONSTANT(i)\
  BEGIN\
    pvp->values[1][i] = pvp->values[0][i] = pdc->colors.colored.c_base[i];\
    sbits[i] = &ht_no_bitmap;\
  END

/* Free variables: pvp, pdc, sbits, caches, invert, max_color */
#define SET_PLANE_COLOR(i)\
  BEGIN\
    uint q = pdc->colors.colored.c_base[i];\
    uint r = pdc->colors.colored.c_level[i];\
\
    pvp->values[0][i] = fractional_color(q, max_color);\
    if (r == 0)\
	pvp->values[1][i] = pvp->values[0][i], sbits[i] = &ht_no_bitmap;\
    else if (!invert) {\
	pvp->values[1][i] = fractional_color(q + 1, max_color);\
	sbits[i] = (const gx_const_strip_bitmap *)\
	    &gx_render_ht(caches[i], r)->tiles;\
    } else {                                                        \
	const gx_device_halftone *pdht = pdc->colors.colored.c_ht;  \
	int nlevels =\
	    (pdht->components ?\
	     pdht->components[pdht->color_indices[i]].corder.num_levels :\
	     pdht->order.num_levels);\
\
	pvp->values[1][i] = pvp->values[0][i];                   \
	pvp->values[0][i] = fractional_color(q + 1, max_color);   \
	sbits[i] = (const gx_const_strip_bitmap *)\
	    &gx_render_ht(caches[i], nlevels - r)->tiles;    \
    }\
  END

/* Set up the colors and the individual plane halftone bitmaps. */
private int
set_ht_colors_le_4(color_values_pair_t *pvp /* only used internally */,
		   gx_color_index colors[1 << MAX_DCC],
		   const gx_const_strip_bitmap * sbits[MAX_DCC],
		   const gx_device_color * pdc, gx_device * dev,
		   gx_ht_cache * caches[MAX_DCC], int nplanes)
{
    gx_color_value max_color = dev->color_info.dither_colors - 1;
    /*
     * NB: the halftone orders are all set up for an additive color space.
     *     To make these work with a subtractive device space such as CMYK,
     *     it is necessary to invert both the color level and the color
     *     pair. Note that if the original color was provided an additive
     *     space, this will reverse (in an approximate sense) the color
     *     conversion performed to express the color in the device space.
     */
    bool invert = dev->color_info.num_components >= 4;  /****** HACK ******/

    SET_PLANE_COLOR(0);
    SET_PLANE_COLOR(1);
    SET_PLANE_COLOR(2);
    if (nplanes == 3) {
	gx_color_value alpha = pdc->colors.colored.alpha;

	if (alpha == gx_max_color_value) {
#ifndef DEBUG
#  undef gx_map_rgb_color
	    dev_proc_map_rgb_color((*gx_map_rgb_color)) =
		dev_proc(dev, map_rgb_color);
#endif
#define M(i)\
  colors[i] = gx_map_rgb_color(dev, pvp->values[(i) & 1][0],\
			       pvp->values[((i) & 2) >> 1][1],\
			       pvp->values[(i) >> 2][2])
	    M(0); M(1); M(2); M(3); M(4); M(5); M(6); M(7);
#undef M
	} else {
#ifndef DEBUG
#  undef gx_map_rgb_alpha_color
	    dev_proc_map_rgb_alpha_color((*gx_map_rgb_alpha_color)) =
		dev_proc(dev, map_rgb_alpha_color);
#endif
#define M(i)\
  colors[i] = gx_map_rgb_alpha_color(dev, pvp->values[(i) & 1][0],\
				     pvp->values[((i) & 2) >> 1][1],\
				     pvp->values[(i) >> 2][2], alpha)
	    M(0); M(1); M(2); M(3); M(4); M(5); M(6); M(7);
#undef M
	}
    } else {
#ifdef DEBUG
#  define do_map_cmyk_color(dev, c, m, y, k) gx_map_cmyk_color(dev, c, m, y, k)
#else
	dev_proc_map_cmyk_color((*do_map_cmyk_color)) =
	    dev_proc(dev, map_cmyk_color);
#endif
	SET_PLANE_COLOR(3);
	if (nplanes > 4) {
	    /*
	     * Set colors for any planes beyond the 4th.  Since this code
	     * only handles the case of at most 4 active planes, we know
	     * that any further planes are constant.
	     */
	    /****** DOESN'T MAP COLORS RIGHT, DOESN'T HANDLE ALPHA ******/
	    int pi;

	    for (pi = 4; pi < nplanes; ++pi)
		SET_PLANE_COLOR_CONSTANT(pi);
	}
	/*
	 * For CMYK output, especially if the input was RGB, it's
	 * common for one or more of the components to be zero.
	 * Each zero component can cut the cost of color mapping in
	 * half, so it's worth doing a little checking here.
	 */

#define M(i)\
  colors[i] = do_map_cmyk_color(dev, pvp->values[(i) & 1][0],\
				pvp->values[((i) & 2) >> 1][1],\
				pvp->values[((i) & 4) >> 2][2],\
				pvp->values[(i) >> 3][3])

      /* We know that plane_mask <= 15. */
	switch ((int)pdc->colors.colored.plane_mask) {
	    case 15:
		M(15); M(14); M(13); M(12);
		M(11); M(10); M(9); M(8);
	    case 7:
		M(7); M(6); M(5); M(4);
c3:	    case 3:
		M(3); M(2);
c1:	    case 1:
		M(1);
		break;
	    case 14:
		M(14); M(12); M(10); M(8);
	    case 6:
		M(6); M(4);
c2:	    case 2:
		M(2);
		break;
	    case 13:
		M(13); M(12); M(9); M(8);
	    case 5:
		M(5); M(4);
		goto c1;
	    case 12:
		M(12); M(8);
	    case 4:
		M(4);
		break;
	    case 11:
		M(11); M(10); M(9); M(8);
		goto c3;
	    case 10:
		M(10); M(8);
		goto c2;
	    case 9:
		M(9); M(8);
		goto c1;
	    case 8:
		M(8);
		break;
	    case 0:;
	}
	M(0);

#undef M

    }
    return 0;
}

/* Set up colors using the standard 1-bit CMYK mapping. */
private int
set_cmyk_1bit_colors(color_values_pair_t *ignore_pvp,
		     gx_color_index colors[1 << MAX_DCC /*16 used*/],
		     const gx_const_strip_bitmap * sbits[MAX_DCC /*4 used*/],
		     const gx_device_color * pdc, gx_device * dev,
		     gx_ht_cache * caches[MAX_DCC /*4 used*/],
		     int nplanes /*4*/)
{
    const gx_device_halftone *pdht = pdc->colors.colored.c_ht;
    /*
     * By reversing the order of the planes, we make the pixel values
     * line up with the color indices.  Then instead of a lookup, we
     * can compute the pixels directly using a Boolean function.
     *
     * We compute each output bit
     *   out[i] = (in[i] & mask1) | (~in[i] & mask0)
     * We store the two masks in colors[0] and colors[1], since the
     * colors array is otherwise unused in this case.  We duplicate
     * the values in all the nibbles so we can do several pixels at a time.
     */
    bits32 mask0 = 0, mask1 = 0;
#define SET_PLANE_COLOR_CMYK(i, mask)\
  BEGIN\
    uint r = pdc->colors.colored.c_level[i];\
\
    if (r == 0) {\
	if (pdc->colors.colored.c_base[i])\
	    mask0 |= mask, mask1 |= mask;\
	sbits[3 - i] = &ht_no_bitmap;\
    } else {\
	int nlevels =\
	    (pdht->components ?\
	     pdht->components[pdht->color_indices[i]].corder.num_levels :\
	     pdht->order.num_levels);\
\
	mask0 |= mask;\
	sbits[3 - i] = (const gx_const_strip_bitmap *)\
	    &gx_render_ht(caches[i], nlevels - r)->tiles;\
    }\
  END
	 /* Suppress a compiler warning about signed/unsigned constants. */
    SET_PLANE_COLOR_CMYK(0, /*0x88888888*/ (bits32)~0x77777777);
    SET_PLANE_COLOR_CMYK(1, 0x44444444);
    SET_PLANE_COLOR_CMYK(2, 0x22222222);
    SET_PLANE_COLOR_CMYK(3, 0x11111111);
#undef SET_PLANE_COLOR_CMYK
    {
	gx_ht_cache *ctemp;

	ctemp = caches[0], caches[0] = caches[3], caches[3] = ctemp;
	ctemp = caches[1], caches[1] = caches[2], caches[2] = ctemp;
    }
    colors[0] = mask0;
    colors[1] = mask1;
    return 1;
}

/*
 * Set up colors for >4 planes.  In this case, we compute the colors
 * themselves lazily.
 */
private int
set_ht_colors_gt_4(color_values_pair_t *pvp,
		   gx_color_index colors[1 << MAX_DCC],
		   const gx_const_strip_bitmap * sbits[MAX_DCC],
		   const gx_device_color * pdc, gx_device * dev,
		   gx_ht_cache * caches[MAX_DCC], int nplanes)
{
    gx_color_value max_color = dev->color_info.dither_colors - 1;
    /* See set_ht_color_le_4 for invert. */
    bool invert = true;  /****** HACK ******/
    gx_color_index plane_mask = pdc->colors.colored.plane_mask;
    int i;
    gx_color_index ci;

    /* Set the color values and halftone caches. */
    for (i = 0; i < nplanes; ++i)
	if ((plane_mask >> i) & 1)
	    SET_PLANE_COLOR(i);
        else
	    SET_PLANE_COLOR_CONSTANT(i);

    /*
     * Clear the color table entries that will actually be used, namely,
     * those whose indices are either 0 or 1 in bits selected by plane_mask
     * and 0 in all other bits.
     */
    ci = 0;
    do {
	colors[ci] = gx_no_color_index;
    } while ((ci = ((ci | ~plane_mask) + 1) & plane_mask) != 0);

    return 0;
}

/* ---------------- Color rendering ---------------- */

/* Define the bookkeeping structure for each plane of halftone rendering. */
typedef struct tile_cursor_s {
    int tile_shift;		/* X shift per copy of tile */
    int xoffset;
    int xshift;
    uint xbytes;
    int xbits;
    const byte *row;
    const byte *tdata;
    uint raster;
    const byte *data;
    int bit_shift;
} tile_cursor_t;

/*
 * Initialize one plane cursor, including setting up for the first row
 * (data and bit_shift).
 */
private void
init_tile_cursor(int i, tile_cursor_t *ptc, const gx_const_strip_bitmap *btile,
		 int endx, int lasty)
{
    int tw = btile->size.x;
    int bx = ((ptc->tile_shift = btile->shift) == 0 ? endx :
	      endx + lasty / btile->size.y * ptc->tile_shift) % tw;
    int by = lasty % btile->size.y;

    ptc->xoffset = bx >> 3;
    ptc->xshift = 8 - (bx & 7);
    ptc->xbytes = (tw - 1) >> 3;
    ptc->xbits = ((tw - 1) & 7) + 1;
    ptc->tdata = btile->data;
    ptc->raster = btile->raster;
    ptc->row = ptc->tdata + by * ptc->raster;
    ptc->data = ptc->row + ptc->xoffset;
    ptc->bit_shift = ptc->xshift;
    if_debug6('h', "[h]plane %d: size=%d,%d shift=%d bx=%d by=%dn",
	      i, tw, btile->size.y, btile->shift, bx, by);
}

/* Step a cursor to the next row. */
private void
wrap_shifted_cursor(tile_cursor_t *ptc, const gx_const_strip_bitmap *psbit)
{
    ptc->row += ptc->raster * (psbit->size.y - 1);
    if (ptc->tile_shift) {
	if ((ptc->xshift += ptc->tile_shift) >= 8) {
	    if ((ptc->xoffset -= ptc->xshift >> 3) < 0) {
		/* wrap around in X */
		int bx = (ptc->xoffset << 3) + 8 - (ptc->xshift & 7) +
		    psbit->size.x;

		ptc->xoffset = bx >> 3;
		ptc->xshift = 8 - (bx & 7);
	    } else
		ptc->xshift &= 7;
	}
    }
}
#define STEP_ROW(c, i)\
  BEGIN\
    if (c.row > c.tdata)\
      c.row -= c.raster;\
    else {	/* wrap around to end of tile */\
	wrap_shifted_cursor(&c, sbits[i]);\
    }\
    c.data = c.row + c.xoffset;\
    c.bit_shift = c.xshift;\
  END

/* Define a table for expanding 8x1 bits to 8x4. */
private const bits32 expand_8x1_to_8x4[256] = {
#define X16(c)\
  c+0, c+1, c+0x10, c+0x11, c+0x100, c+0x101, c+0x110, c+0x111,\
  c+0x1000, c+0x1001, c+0x1010, c+0x1011, c+0x1100, c+0x1101, c+0x1110, c+0x1111
    X16(0x00000000), X16(0x00010000), X16(0x00100000), X16(0x00110000),
    X16(0x01000000), X16(0x01010000), X16(0x01100000), X16(0x01110000),
    X16(0x10000000), X16(0x10010000), X16(0x10100000), X16(0x10110000),
    X16(0x11000000), X16(0x11010000), X16(0x11100000), X16(0x11110000)
#undef X16
};

/*
 * Render the combined halftone for nplanes <= 4.
 */
private void
set_color_ht_le_4(byte *dest_data, uint dest_raster, int px, int py,
		  int w, int h, int depth, int special, int nplanes,
		  gx_color_index plane_mask, gx_device *ignore_dev,
		  const color_values_pair_t *ignore_pvp,
		  gx_color_index colors[1 << MAX_DCC],
		  const gx_const_strip_bitmap * sbits[MAX_DCC])
{
    /*
     * Note that the planes are specified in the order RGB or CMYK, but
     * the indices used for the internal colors array are BGR or KYMC,
     * except for the special 1-bit CMYK case.
     */
    int x, y;
    tile_cursor_t cursor[MAX_DCC];
    int dbytes = depth >> 3;
    byte *dest_row =
	dest_data + dest_raster * (h - 1) + (w * depth) / 8;

    if (special > 0) {
	/* Planes are in reverse order. */
	plane_mask =
	    "\000\010\004\014\002\012\006\016\001\011\005\015\003\013\007\017"[plane_mask];
    }
    if_debug6('h',
	      "[h]color_ht: x=%d y=%d w=%d h=%d plane_mask=0x%lu depth=%d\n",
	      px, py, w, h, (ulong)plane_mask, depth);

    /* Do one-time cursor initialization. */
    {
	int endx = w + px;
	int lasty = h - 1 + py;

	if (plane_mask & 1)
	    init_tile_cursor(0, &cursor[0], sbits[0], endx, lasty);
	if (plane_mask & 2)
	    init_tile_cursor(1, &cursor[1], sbits[1], endx, lasty);
	if (plane_mask & 4)
	    init_tile_cursor(2, &cursor[2], sbits[2], endx, lasty);
	if (plane_mask & 8)
	    init_tile_cursor(3, &cursor[3], sbits[3], endx, lasty);
    }

    /* Now compute the actual tile. */
    for (y = h; ; dest_row -= dest_raster) {
	byte *dest = dest_row;

	--y;
	for (x = w; x > 0;) {
	    bits32 indices;
	    int nx, i;
	    register uint bits;

/* Get the next byte's worth of bits.  Note that there may be */
/* excess bits set beyond the 8th. */
#define NEXT_BITS(c)\
  BEGIN\
    if (c.data > c.row) {\
      bits = ((c.data[-1] << 8) | *c.data) >> c.bit_shift;\
      c.data--;\
    } else {\
      bits = *c.data >> c.bit_shift;\
      c.data += c.xbytes;\
      if ((c.bit_shift -= c.xbits) < 0) {\
	bits |= *c.data << -c.bit_shift;\
	c.bit_shift += 8;\
      } else {\
	bits |= ((c.data[-1] << 8) | *c.data) >> c.bit_shift;\
	c.data--;\
      }\
    }\
  END
	    if (plane_mask & 1) {
		NEXT_BITS(cursor[0]);
		indices = expand_8x1_to_8x4[bits & 0xff];
	    } else
		indices = 0;
	    if (plane_mask & 2) {
		NEXT_BITS(cursor[1]);
		indices |= expand_8x1_to_8x4[bits & 0xff] << 1;
	    }
	    if (plane_mask & 4) {
		NEXT_BITS(cursor[2]);
		indices |= expand_8x1_to_8x4[bits & 0xff] << 2;
	    }
	    if (plane_mask & 8) {
		NEXT_BITS(cursor[3]);
		indices |= expand_8x1_to_8x4[bits & 0xff] << 3;
	    }
#undef NEXT_BITS
	    nx = min(x, 8);	/* 1 <= nx <= 8 */
	    x -= nx;
	    switch (dbytes) {
		case 0:	/* 4 */
		    if (special > 0) {
			/* Special 1-bit CMYK. */
			/* Compute all the pixels at once! */
			indices =
			    (indices & colors[1]) | (~indices & colors[0]);
			i = nx;
			if ((x + nx) & 1) {
			    /* First pixel is even nibble. */
			    *dest = (*dest & 0xf) +
				((indices & 0xf) << 4);
			    indices >>= 4;
			    --i;
			}
			/* Now 0 <= i <= 8. */
			for (; (i -= 2) >= 0; indices >>= 8)
			    *--dest = (byte)indices;
			/* Check for final odd nibble. */
			if (i & 1)
			    *--dest = indices & 0xf;
		    } else {
			/* Other 4-bit pixel */
			i = nx;
			if ((x + nx) & 1) {
			    /* First pixel is even nibble. */
			    *dest = (*dest & 0xf) +
				((byte)colors[indices & 0xf] << 4);
			    indices >>= 4;
			    --i;
			}
			/* Now 0 <= i <= 8. */
			for (; (i -= 2) >= 0; indices >>= 8)
			    *--dest =
				(byte)colors[indices & 0xf] +
				((byte)colors[(indices >> 4) & 0xf]
				 << 4);
			/* Check for final odd nibble. */
			if (i & 1)
			    *--dest = (byte)colors[indices & 0xf];
		    }
		    break;
		case 4:	/* 32 */
		    for (i = nx; --i >= 0; indices >>= 4) {
			bits32 tcolor = (bits32)colors[indices & 0xf];

			dest -= 4;
			dest[3] = (byte)tcolor;
			dest[2] = (byte)(tcolor >> 8);
			tcolor >>= 16;
			dest[1] = (byte)tcolor;
			dest[0] = (byte)(tcolor >> 8);
		    }
		    break;
		case 3:	/* 24 */
		    for (i = nx; --i >= 0; indices >>= 4) {
			bits32 tcolor = (bits32)colors[indices & 0xf];

			dest -= 3;
			dest[2] = (byte) tcolor;
			dest[1] = (byte)(tcolor >> 8);
			dest[0] = (byte)(tcolor >> 16);
		    }
		    break;
		case 2:	/* 16 */
		    for (i = nx; --i >= 0; indices >>= 4) {
			uint tcolor =
			    (uint)colors[indices & 0xf];

			dest -= 2;
			dest[1] = (byte)tcolor;
			dest[0] = (byte)(tcolor >> 8);
		    }
		    break;
		case 1:	/* 8 */
		    for (i = nx; --i >= 0; indices >>= 4)
			*--dest = (byte)colors[indices & 0xf];
		    break;
	    }
	}
	if (y == 0)
	    break;

	if (plane_mask & 1)
	    STEP_ROW(cursor[0], 0);
	if (plane_mask & 2)
	    STEP_ROW(cursor[1], 1);
	if (plane_mask & 4)
	    STEP_ROW(cursor[2], 2);
	if (plane_mask & 8)
	    STEP_ROW(cursor[3], 3);
    }
}

/*
 * Render the combined halftone for nplanes > 4.  We haven't made any
 * attempt to optimize this code.
 */
private void
set_color_ht_gt_4(byte *dest_data, uint dest_raster, int px, int py,
		  int w, int h, int depth, int special, int num_planes,
		  gx_color_index plane_mask, gx_device *dev,
		  const color_values_pair_t *pvp,
		  gx_color_index colors[1 << MAX_DCC],
		  const gx_const_strip_bitmap * sbits[MAX_DCC])
{
    int x, y;
    tile_cursor_t cursor[MAX_DCC];
    int dbytes = depth >> 3;
    byte *dest_row =
	dest_data + dest_raster * (h - 1) + (w * depth) / 8;
    int pmin, pmax;
    gx_color_value cv[MAX_DCC];

    /* Compute the range of active planes. */
    if (plane_mask == 0)
	pmin = 0, pmax = -1;
    else {
	for (pmin = 0; !((plane_mask >> pmin) & 1); )
	    ++pmin;
	for (pmax = 0; (plane_mask >> pmax) > 1; )
	    ++pmax;
    }

    /* Do one-time cursor initialization. */
    {
	int endx = w + px;
	int lasty = h - 1 + py;
	int i;

	for (i = pmin; i <= pmax; ++i)
	    if ((plane_mask >> i) & 1)
		init_tile_cursor(i, &cursor[i], sbits[i], endx, lasty);
    }

    /* Pre-load the color value for the unchanging planes. */
    {
	int i;

	for (i = 0; i < pmin; ++i)
	    cv[i] = pvp->values[0][i];
	for (i = pmax + 1; i < num_planes; ++i)
	    cv[i] = pvp->values[0][i];
    }

    /* Now compute the actual tile. */
    for (y = h; ; dest_row -= dest_raster) {
	byte *dest = dest_row;
	int i;

	--y;
	for (x = w; x > 0;) {
	    gx_color_index index = 0;
	    gx_color_index tcolor;

	    for (i = pmin; i <= pmax; ++i)
		if ((plane_mask >> i) & 1) {
		    /* Get the next bit from an individual mask. */
		    tile_cursor_t *ptc = &cursor[i];
		    byte tile_bit;

b:		    if (ptc->bit_shift < 8)
			tile_bit = *ptc->data >> ptc->bit_shift++;
		    else if (ptc->data > ptc->row) {
			tile_bit = *--(ptc->data);
			ptc->bit_shift = 1;
		    } else {
			/* Wrap around. */
			ptc->data += ptc->xbytes;
			ptc->bit_shift = 8 - ptc->xbits;
			goto b;
		    }
		    index |= (gx_color_index)(tile_bit & 1) << i;
		}
	    tcolor = colors[index];
	    if (tcolor == gx_no_color_index) {
		/* Map the color value now. */
		int i;

		for (i = pmin; i <= pmax; ++i)
		    cv[i] = pvp->values[(index >> i) & 1][i];
		/****** HACK -- NO WAY TO MAP GENERAL COLORS ******/
		tcolor = colors[index] =
		    gx_map_cmyk_color(dev, cv[0], cv[1], cv[2], cv[3]);
	    }
	    --x;
	    switch (dbytes) {
		case 0:	/* 4 -- might be 2, but we don't support this */
		    if (x & 1) { /* odd nibble */
			*--dest = (byte)tcolor;
		    } else {	/* even nibble */
			*dest = (*dest & 0xf) + ((byte)tcolor << 4);
		    }
		    break;
		case 4:	/* 32 */
		    dest[-4] = (byte)(tcolor >> 24);
		case 3:	/* 24 */
		    dest[-3] = (byte)(tcolor >> 16);
		case 2:	/* 16 */
		    dest[-2] = (byte)(tcolor >> 8);
		case 1:	/* 8 */
		    dest[-1] = (byte)tcolor;
		    dest -= dbytes;
		    break;
	    }
	}
	if (y == 0)
	    break;
	for (i = pmin; i <= pmax; ++i)
	    if ((plane_mask >> i) & 1)
		STEP_ROW(cursor[i], i);
    }
}
