/* Copyright (C) 2001-2006 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 that
   license.  Refer to licensing information at http://www.artifex.com/
   or contact Artifex Software, Inc.,  7 Mt. Lassen Drive - Suite A-134,
   San Rafael, CA  94903, U.S.A., +1(415)492-9861, for further information.
*/
/* $Id: gdevdrop.c 10497 2009-12-12 23:05:18Z ray $ */
/* Default and device-independent RasterOp algorithms */
#include "memory_.h"
#include "gx.h"
#include "gsbittab.h"
#include "gserrors.h"
#include "gsropt.h"
#include "gxcindex.h"
#include "gxdcolor.h"
#include "gxdevice.h"
#include "gxdevmem.h"
#include "gxdevrop.h"
#include "gxgetbit.h"
#include "gdevmem.h"		/* for mem_default_strip_copy_rop prototype */
#include "gdevmrop.h"

/*
 * Define the maximum amount of space we are willing to allocate for a
 * multiple-row RasterOp buffer.  (We are always willing to allocate
 * one row, no matter how wide.)
 */
static const uint max_rop_bitmap = 1000;

/* ---------------- Debugging aids ---------------- */

#ifdef DEBUG

void
trace_copy_rop(const char *cname, gx_device * dev,
	       const byte * sdata, int sourcex, uint sraster, gx_bitmap_id id,
	       const gx_color_index * scolors,
	       const gx_strip_bitmap * textures,
	       const gx_color_index * tcolors,
	       int x, int y, int width, int height,
	       int phase_x, int phase_y, gs_logical_operation_t lop)
{
    dlprintf4("%s: dev=0x%lx(%s) depth=%d\n",
	      cname, (ulong) dev, dev->dname, dev->color_info.depth);
    dlprintf4("  source data=0x%lx x=%d raster=%u id=%lu colors=",
	      (ulong) sdata, sourcex, sraster, (ulong) id);
    if (scolors)
	dprintf2("(%lu,%lu);\n", scolors[0], scolors[1]);
    else
	dputs("none;\n");
    if (textures)
	dlprintf8("  textures=0x%lx size=%dx%d(%dx%d) raster=%u shift=%d(%d)",
		  (ulong) textures, textures->size.x, textures->size.y,
		  textures->rep_width, textures->rep_height,
		  textures->raster, textures->shift, textures->rep_shift);
    else
	dlputs("  textures=none");
    if (tcolors)
	dprintf2(" colors=(%lu,%lu)\n", tcolors[0], tcolors[1]);
    else
	dputs(" colors=none\n");
    dlprintf7("  rect=(%d,%d),(%d,%d) phase=(%d,%d) op=0x%x\n",
	      x, y, x + width, y + height, phase_x, phase_y,
	      (uint) lop);
    if (gs_debug_c('B')) {
	if (sdata)
	    debug_dump_bitmap(sdata, sraster, height, "source bits");
	if (textures && textures->data)
	    debug_dump_bitmap(textures->data, textures->raster,
			      textures->size.y, "textures bits");
    }
}

#endif

/* ---------------- Default copy_rop implementations ---------------- */

/*
 * The default implementation for non-memory devices uses get_bits_rectangle
 * to read out the pixels, the memory device implementation to do the
 * operation, and copy_color to write the pixels back.
 */
int
gx_default_strip_copy_rop(gx_device * dev,
			  const byte * sdata, int sourcex,
			  uint sraster, gx_bitmap_id id,
			  const gx_color_index * scolors,
			  const gx_strip_bitmap * textures,
			  const gx_color_index * tcolors,
			  int x, int y, int width, int height,
			  int phase_x, int phase_y,
			  gs_logical_operation_t lop)
{
    int depth = dev->color_info.depth;
    gs_memory_t *mem = dev->memory;
    const gx_device_memory *mdproto = gdev_mem_device_for_bits(depth);
    gx_device_memory *pmdev;
    uint draster;
    byte *row = 0;
    gs_int_rect rect;
    int max_height;
    int block_height;
    int code;
    int py;

#ifdef DEBUG
    if (gs_debug_c('b'))
	trace_copy_rop("gx_default_strip_copy_rop",
		       dev, sdata, sourcex, sraster,
		       id, scolors, textures, tcolors,
		       x, y, width, height, phase_x, phase_y, lop);
#endif
    if (mdproto == 0)
	return_error(gs_error_rangecheck);
    if (sdata == 0) {
	fit_fill(dev, x, y, width, height);
    } else {
	fit_copy(dev, sdata, sourcex, sraster, id, x, y, width, height);
    }
    draster = bitmap_raster(width * depth);
    max_height = max_rop_bitmap / draster;
    if (max_height == 0)
	max_height = 1;
    block_height = min(height, max_height);
    gs_make_mem_device_with_copydevice(&pmdev, mdproto, mem, -1, dev);
    pmdev->width = width;
    pmdev->height = block_height;
    pmdev->bitmap_memory = mem;
    pmdev->color_info = dev->color_info;
    code = (*dev_proc(pmdev, open_device))((gx_device *)pmdev);
    pmdev->is_open = true; /* not sure why we need this, but we do. */
    if (code < 0)
	return code;
    if (rop3_uses_D(gs_transparent_rop(lop))) {
	row = gs_alloc_bytes(mem, draster * block_height, "copy_rop row");
	if (row == 0) {
	    code = gs_note_error(gs_error_VMerror);
	    goto out;
	}
    }
    rect.p.x = x;
    rect.q.x = x + width;
    for (py = y; py < y + height; py += block_height) {
	if (block_height > y + height - py)
	    block_height = y + height - py;
	rect.p.y = py;
	rect.q.y = py + block_height;
	if (row /*uses_d*/) {
	    gs_get_bits_params_t bit_params;

	    bit_params.options =
		GB_COLORS_NATIVE | GB_ALPHA_NONE | GB_DEPTH_ALL |
		GB_PACKING_CHUNKY | GB_RETURN_ALL | GB_ALIGN_STANDARD |
		GB_OFFSET_0 | GB_OFFSET_ANY | GB_RASTER_STANDARD;
	    bit_params.data[0] = row;
	    bit_params.x_offset = 0;
	    code = (*dev_proc(dev, get_bits_rectangle))
		(dev, &rect, &bit_params, NULL);
	    if (code < 0)
		break;
	    code = (*dev_proc(pmdev, copy_color))
		((gx_device *)pmdev, bit_params.data[0], bit_params.x_offset,
		 draster, gx_no_bitmap_id, 0, 0, width,
		 block_height);
	    if (code < 0)
		return code;
	}
	code = (*dev_proc(pmdev, strip_copy_rop))
	    ((gx_device *)pmdev,
	     sdata + (py - y) * sraster, sourcex, sraster,
	     gx_no_bitmap_id, scolors, textures, tcolors,
	     0, 0, width, block_height, phase_x + x, phase_y + py, lop);
	if (code < 0)
	    break;
	code = (*dev_proc(dev, copy_color))
	    (dev, scan_line_base(pmdev, 0), 0, draster, gx_no_bitmap_id,
	     x, py, width, block_height);
	if (code < 0)
	    break;
    }
out:
    gs_free_object(mem, row, "copy_rop row");
    gx_device_retain((gx_device *)pmdev, false);
    return code;
}

/* ---------------- Default memory device copy_rop ---------------- */

/* Convert color constants to standard RGB representation. */
static void
unpack_colors_to_standard(gx_device * dev, gx_color_index real_colors[2],
			  const gx_color_index * colors, int depth)
{
    int i;

    for (i = 0; i < 2; ++i) {
	gx_color_value rgb[3];
	gx_color_index pixel;

	(*dev_proc(dev, map_color_rgb)) (dev, colors[i], rgb);
	pixel = gx_color_value_to_byte(rgb[0]);
	if (depth > 8) {
	    pixel = (pixel << 16) +
		(gx_color_value_to_byte(rgb[1]) << 8) +
		gx_color_value_to_byte(rgb[2]);
	}
	real_colors[i] = pixel;
    }
}

/*
 * Convert RGB to the device's native format.  We special-case this for
 * 1-bit CMYK devices.
 */
static void
pack_cmyk_1bit_from_standard(gx_device * dev, byte * dest, int destx,
			     const byte * src, int width, int depth,
			     int src_depth)
{
    /*
     * This routine is only called if dev_proc(dev, map_cmyk_color) ==
     * cmyk_1bit_map_cmyk_color (implying depth == 4) and src_depth == 24.
     */
    int bit_x = destx * 4;
    byte *dp = dest + (bit_x >> 3);
    bool hi = (bit_x & 4) != 0;	 /* true if last nibble filled was hi */
    byte buf = (hi ? *dp & 0xf0 : 0);
    const byte *sp = src;
    int x;

    for (x = width; --x >= 0; sp += 3) {
	byte r = sp[0], g = sp[1], b = sp[2];
	byte pixel =
	    (r | g | b ?
	     (((r >> 4) & 8) | ((g >> 5) & 4) | ((b >> 6) & 2)) ^ 0xe : 1);

	if ((hi = !hi))
	    buf = pixel << 4;
	else
	    *dp++ = buf | pixel;
    }
    if (hi && width > 0)
	*dp = buf | (*dp & 0xf);

}

static gx_color_index
map_rgb_to_color_via_cmyk(gx_device * dev, const gx_color_value rgbcv[])
{
    gx_color_value cmykcv[4];
    
    cmykcv[0] = gx_max_color_value - rgbcv[0];
    cmykcv[1] = gx_max_color_value - rgbcv[1];
    cmykcv[2] = gx_max_color_value - rgbcv[2];
    cmykcv[3] = (cmykcv[0] < cmykcv[1] ? min(cmykcv[0], cmykcv[2]) : min(cmykcv[1], cmykcv[2]));

    cmykcv[0] -= cmykcv[3];
    cmykcv[1] -= cmykcv[3];
    cmykcv[2] -= cmykcv[3];

    return (*dev_proc(dev, map_cmyk_color)) (dev, cmykcv);
}
static void
pack_from_standard(gx_device * dev, byte * dest, int destx, const byte * src,
		   int width, int depth, int src_depth)
{
    dev_proc_map_rgb_color((*map)) =
	(dev->color_info.num_components == 4 ?
	 map_rgb_to_color_via_cmyk : dev_proc(dev, map_rgb_color));
    int bit_x = destx * depth;
    byte *dp = dest + (bit_x >> 3);
    int shift = (~bit_x & 7) + 1;
    byte buf = (shift == 8 ? 0 : *dp & (0xff00 >> shift));
    const byte *sp = src;
    int x;

    for (x = width; --x >= 0;) {
	byte vr, vg, vb;
	gx_color_index pixel;
	byte chop = 0x1;

	vr = *sp++;
	if (src_depth > 8) {
	    vg = *sp++;
	    vb = *sp++;
	} else
	    vb = vg = vr;
	/*
	 * We have to map back to some pixel value, even if the color
	 * isn't accurate.
	 */
	for (;;) {
            gx_color_value cv[3];
	    cv[0] = gx_color_value_from_byte(vr);
	    cv[1] = gx_color_value_from_byte(vg);
	    cv[2] = gx_color_value_from_byte(vb);
	    pixel = (*map) (dev, cv);
	    if (pixel != gx_no_color_index)
		break;
	    /* Reduce the color accuracy and try again. */
	    vr = (vr >= 0x80 ? vr | chop : vr & ~chop);
	    vg = (vg >= 0x80 ? vg | chop : vg & ~chop);
	    vb = (vb >= 0x80 ? vb | chop : vb & ~chop);
	    chop <<= 1;
	}
	if ((shift -= depth) >= 0)
	    buf += (byte)(pixel << shift);
	else {
	    switch (depth) {
	    default:		/* 1, 2, 4, 8 */
		*dp++ = buf;
		shift += 8;
		buf = (byte)(pixel << shift);
		break;
	    case 32:
		*dp++ = (byte)(pixel >> 24);
		*dp++ = (byte)(pixel >> 16);
	    case 16:
		*dp++ = (byte)(pixel >> 8);
		*dp++ = (byte)pixel;
		shift = 0;
	    }
	}
    }
    if (width > 0 && depth <= 8)
	*dp = (shift == 0 ? buf : buf + (*dp & ((1 << shift) - 1)));
}

/*
 * The default implementation for memory devices uses get_bits_rectangle to
 * read out the pixels and convert them to standard (8-bit gray or 24-bit
 * RGB) representation, the standard memory device implementation to do the
 * operation, pack_from_standard to convert them back to the device
 * representation, and copy_color to write the pixels back.
 */
int
mem_default_strip_copy_rop(gx_device * dev,
			  const byte * sdata, int sourcex,
			  uint sraster, gx_bitmap_id id,
			  const gx_color_index * scolors,
			  const gx_strip_bitmap * textures,
			  const gx_color_index * tcolors,
			  int x, int y, int width, int height,
			  int phase_x, int phase_y,
			  gs_logical_operation_t lop)
{
    int depth = dev->color_info.depth;
    int rop_depth = (gx_device_has_color(dev) ? 24 : 8);
    void (*pack)(gx_device *, byte *, int, const byte *, int, int, int) =
	(dev_proc(dev, map_cmyk_color) == cmyk_1bit_map_cmyk_color &&
	 rop_depth == 24 ? pack_cmyk_1bit_from_standard : pack_from_standard);
    const gx_bitmap_format_t no_expand_options =
	GB_COLORS_NATIVE | GB_ALPHA_NONE | GB_DEPTH_ALL |
	GB_PACKING_CHUNKY | GB_RETURN_ALL | GB_ALIGN_STANDARD |
	GB_OFFSET_0 | GB_OFFSET_ANY | GB_RASTER_STANDARD;
    const gx_bitmap_format_t expand_options =
	(rop_depth > 8 ? GB_COLORS_RGB : GB_COLORS_GRAY) |
	GB_ALPHA_NONE | GB_DEPTH_8 |
	GB_PACKING_CHUNKY | GB_RETURN_COPY | GB_ALIGN_STANDARD |
	GB_OFFSET_0 | GB_RASTER_STANDARD;
    gs_memory_t *mem = dev->memory;
    const gx_device_memory *mdproto = gdev_mem_device_for_bits(rop_depth);
    gx_device_memory mdev;
    union { long l; void *p; } mdev_storage[20];
    uint row_raster = bitmap_raster(width * depth);
    ulong size_from_mem_device;
    gs_rop3_t trans_rop = gs_transparent_rop(lop);
    bool uses_d = rop3_uses_D(trans_rop);
    bool uses_s = rop3_uses_S(trans_rop);
    bool uses_t = rop3_uses_T(trans_rop);
    bool expand_s, expand_t;
    byte *row = 0;
    union { long l; void *p; } dest_buffer[16];
    byte *source_row = 0;
    uint source_row_raster;
    union { long l; void *p; } source_buffer[16];
    byte *texture_row = 0;
    uint texture_row_raster;
    union { long l; void *p; } texture_buffer[16];
    gx_color_index source_colors[2];
    const gx_color_index *real_scolors = scolors;
    gx_color_index texture_colors[2];
    const gx_color_index *real_tcolors = tcolors;
    gx_strip_bitmap rop_texture;
    const gx_strip_bitmap *real_texture = textures;
    gs_int_rect rect;
    gs_get_bits_params_t bit_params;
    gs_get_bits_params_t expand_params;
    gs_get_bits_params_t no_expand_params;
    int max_height;
    int block_height, loop_height;
    int code;
    int py;

/*
 * Allocate a temporary row buffer.  Free variables: mem, block_height.
 * Labels used: out.
 */
#define ALLOC_BUF(buf, prebuf, size, cname)\
	BEGIN\
	  uint num_bytes = (size) * block_height;\
\
	  if (num_bytes <= sizeof(prebuf))\
	    buf = (byte *)prebuf;\
	  else {\
	    buf = gs_alloc_bytes(mem, num_bytes, cname);\
	    if (buf == 0) {\
	      code = gs_note_error(gs_error_VMerror);\
	      goto out;\
	    }\
	  }\
	END

#ifdef DEBUG
    if (gs_debug_c('b'))
	trace_copy_rop("mem_default_strip_copy_rop",
		       dev, sdata, sourcex, sraster,
		       id, scolors, textures, tcolors,
		       x, y, width, height, phase_x, phase_y, lop);
#endif
    if (mdproto == 0)
	return_error(gs_error_rangecheck);
    if (sdata == 0) {
	fit_fill(dev, x, y, width, height);
    } else {
	fit_copy(dev, sdata, sourcex, sraster, id, x, y, width, height);
    }
    /* Compute max_height conservatively. */
    max_height = max_rop_bitmap / (width * rop_depth);
    if (max_height == 0)
	max_height = 1;
    block_height = min(height, max_height);
    expand_s = scolors == 0 && uses_s;
    expand_t = tcolors == 0 && uses_t;
    no_expand_params.options = no_expand_options;
    if (expand_t) {
	/*
	 * We don't want to wrap around more than once in Y when
	 * copying the texture to the intermediate buffer.
	 */
	if (textures->size.y < block_height)
	    block_height = textures->size.y;
    }
    gs_make_mem_device(&mdev, mdproto, mem, -1, NULL);
    gx_device_retain((gx_device *)&mdev, true);	/* prevent freeing */
    mdev.width = width;
    mdev.height = block_height;
    mdev.color_info.num_components = rop_depth >> 3;
    if (gdev_mem_data_size(&mdev, width, block_height, &size_from_mem_device) >= 0 &&
	size_from_mem_device <= sizeof(mdev_storage)) {
	/* Use the locally allocated storage. */
	mdev.base = (byte *)mdev_storage;
	if ((code = gdev_mem_bits_size(&mdev, mdev.width, mdev.height, &size_from_mem_device)) < 0)
	    return code;
	mdev.line_ptrs = (byte **) (mdev.base + size_from_mem_device);
    } else {
	mdev.bitmap_memory = mem;
    }
    code = (*dev_proc(&mdev, open_device))((gx_device *)&mdev);
    if (code < 0)
	return code;
    ALLOC_BUF(row, dest_buffer, row_raster, "copy_rop row");
    /* We may need intermediate buffers for all 3 operands. */
    if (expand_s) {
	source_row_raster = bitmap_raster(width * rop_depth);
	ALLOC_BUF(source_row, source_buffer, source_row_raster,
		  "copy_rop source_row");
    }
    if (scolors && uses_s) {
	unpack_colors_to_standard(dev, source_colors, scolors, rop_depth);
	real_scolors = source_colors;
    }
    if (expand_t) {
	texture_row_raster = bitmap_raster(textures->rep_width * rop_depth);
	ALLOC_BUF(texture_row, texture_buffer, texture_row_raster,
		  "copy_rop texture_row");
	rop_texture = *textures;
	rop_texture.data = texture_row;
	rop_texture.raster = texture_row_raster;
	rop_texture.size.x = rop_texture.rep_width;
	rop_texture.id = gs_no_bitmap_id;
	real_texture = &rop_texture;
	if (rop_texture.size.y > rop_texture.rep_height)
	    rop_texture.size.y = rop_texture.rep_height;   /* we only allocated one row_raster, no reps */
    }
    if (tcolors && uses_t) {
	unpack_colors_to_standard(dev, texture_colors, tcolors, rop_depth);
	real_tcolors = texture_colors;
    }
    expand_params.options = expand_options;
    expand_params.x_offset = 0;
    rect.p.x = x;
    rect.q.x = x + width;
    for (py = y; py < y + height; py += loop_height) {
	int sx = sourcex;
	const byte *source_data = sdata + (py - y) * sraster;
	uint source_raster = sraster;

	if (block_height > y + height - py)
	    block_height = y + height - py;
	rect.p.y = py;
	if (expand_t) {
	    int rep_y = (phase_y + py) % rop_texture.rep_height;

	    loop_height = min(block_height, rop_texture.size.y - rep_y);
	    rect.q.y = py + loop_height;
	    expand_params.data[0] = texture_row;
	    gx_get_bits_copy(dev, 0, textures->rep_width, loop_height,
			     &expand_params, &no_expand_params,
			     textures->data + rep_y * textures->raster,
			     textures->raster);
	    /*
	     * Compensate for the addition of rep_y * raster
	     * in the subsidiary strip_copy_rop call.
	     */
	    rop_texture.data = texture_row - rep_y * rop_texture.raster;
	} else {
	    loop_height = block_height;
	    rect.q.y = py + block_height;
	}
	if (uses_d) {
	    bit_params.options = expand_options;
	    bit_params.data[0] = scan_line_base(&mdev, 0);
	    bit_params.x_offset = 0;
	    code = (*dev_proc(dev, get_bits_rectangle))
		(dev, &rect, &bit_params, NULL);
	    if (code < 0)
		break;
	}
	/* Convert the source and texture to standard format. */
	if (expand_s) {
	    expand_params.data[0] = source_row;
	    gx_get_bits_copy(dev, sx, width, loop_height, &expand_params,
			     &no_expand_params, source_data, sraster);
	    sx = 0;
	    source_data = source_row;
	    source_raster = source_row_raster;
	}
	code = (*dev_proc(&mdev, strip_copy_rop))
	    ((gx_device *)&mdev, source_data, sx, source_raster,
	     gx_no_bitmap_id, real_scolors, real_texture, real_tcolors,
	     0, 0, width, loop_height, phase_x + x, phase_y + py, lop);
	if (code < 0)
	    break;
	{
	    /*
	     * Convert the result back to the device's format.  We know
	     * the device is a memory device, so we can store the result
	     * directly into its scan lines.
	     */
	    int i;
	    const byte *unpacked = scan_line_base(&mdev, 0);

	    for (i = 0; i < loop_height; unpacked += mdev.raster, ++i) {
		byte *packed = scan_line_base((gx_device_memory *)dev, py + i);

		pack(dev, packed, x, unpacked, width, depth, rop_depth);
	    }
	}
    }
out:
    if (texture_row != 0 && texture_row != (byte *)texture_buffer)
	gs_free_object(mem, texture_row, "copy_rop texture_row");
    if (source_row != 0 && source_row != (byte *)source_buffer)
	gs_free_object(mem, source_row, "copy_rop source_row");
    if (row != 0 && row != (byte *)dest_buffer)
	gs_free_object(mem, row, "copy_rop row");
    (*dev_proc(&mdev, close_device)) ((gx_device *) & mdev);
    return code;
}

/* ------ Implementation of related functions ------ */

int
gx_default_copy_rop(gx_device * dev,
	     const byte * sdata, int sourcex, uint sraster, gx_bitmap_id id,
		    const gx_color_index * scolors,
	     const gx_tile_bitmap * texture, const gx_color_index * tcolors,
		    int x, int y, int width, int height,
		    int phase_x, int phase_y, gs_logical_operation_t lop)
{
    const gx_strip_bitmap *textures;
    gx_strip_bitmap tiles;

    if (texture == 0)
	textures = 0;
    else {
	*(gx_tile_bitmap *) & tiles = *texture;
	tiles.rep_shift = tiles.shift = 0;
	textures = &tiles;
    }
    return (*dev_proc(dev, strip_copy_rop))
	(dev, sdata, sourcex, sraster, id, scolors, textures, tcolors,
	 x, y, width, height, phase_x, phase_y, lop);
}

int
gx_copy_rop_unaligned(gx_device * dev,
	     const byte * sdata, int sourcex, uint sraster, gx_bitmap_id id,
		      const gx_color_index * scolors,
	     const gx_tile_bitmap * texture, const gx_color_index * tcolors,
		      int x, int y, int width, int height,
		      int phase_x, int phase_y, gs_logical_operation_t lop)
{
    const gx_strip_bitmap *textures;
    gx_strip_bitmap tiles;

    if (texture == 0)
	textures = 0;
    else {
	*(gx_tile_bitmap *) & tiles = *texture;
	tiles.rep_shift = tiles.shift = 0;
	textures = &tiles;
    }
    return gx_strip_copy_rop_unaligned
	(dev, sdata, sourcex, sraster, id, scolors, textures, tcolors,
	 x, y, width, height, phase_x, phase_y, lop);
}

int
gx_strip_copy_rop_unaligned(gx_device * dev,
	     const byte * sdata, int sourcex, uint sraster, gx_bitmap_id id,
			    const gx_color_index * scolors,
	   const gx_strip_bitmap * textures, const gx_color_index * tcolors,
			    int x, int y, int width, int height,
		       int phase_x, int phase_y, gs_logical_operation_t lop)
{
    dev_proc_strip_copy_rop((*copy_rop)) = dev_proc(dev, strip_copy_rop);
    int depth = (scolors == 0 ? dev->color_info.depth : 1);
    int step = sraster & (align_bitmap_mod - 1);

    /* Adjust the origin. */
    if (sdata != 0) {
	uint offset =
	(uint) (sdata - (const byte *)0) & (align_bitmap_mod - 1);

	/* See copy_color above re the following statement. */
	if (depth == 24)
	    offset += (offset % 3) *
		(align_bitmap_mod * (3 - (align_bitmap_mod % 3)));
	sdata -= offset;
	sourcex += (offset << 3) / depth;
    }
    /* Adjust the raster. */
    if (!step || sdata == 0 ||
	(scolors != 0 && scolors[0] == scolors[1])
	) {			/* No adjustment needed. */
	return (*copy_rop) (dev, sdata, sourcex, sraster, id, scolors,
			    textures, tcolors, x, y, width, height,
			    phase_x, phase_y, lop);
    }
    /* Do the transfer one scan line at a time. */
    {
	const byte *p = sdata;
	int d = sourcex;
	int dstep = (step << 3) / depth;
	int code = 0;
	int i;

	for (i = 0; i < height && code >= 0;
	     ++i, p += sraster - step, d += dstep
	    )
	    code = (*copy_rop) (dev, p, d, sraster, gx_no_bitmap_id, scolors,
				textures, tcolors, x, y + i, width, 1,
				phase_x, phase_y, lop);
	return code;
    }
}

/* ---------------- Internal routines ---------------- */

/* Compute the effective RasterOp for the 1-bit case, */
/* taking transparency into account. */
gs_rop3_t
gs_transparent_rop(gs_logical_operation_t lop)
{
    gs_rop3_t rop = lop_rop(lop);

    /*
     * The algorithm for computing an effective RasterOp is presented,
     * albeit obfuscated, in the H-P PCL5 technical documentation.
     * Define So ("source opaque") and Po ("pattern opaque") as masks
     * that have 1-bits precisely where the source or pattern
     * respectively are not white (transparent).
     * One applies the original RasterOp to compute an intermediate
     * result R, and then computes the final result as
     * (R & M) | (D & ~M) where M depends on transparencies as follows:
     *      s_tr    p_tr    M
     *       0       0      1
     *       0       1      ~So | Po (? Po ?)
     *       1       0      So
     *       1       1      So & Po
     * The s_tr = 0, p_tr = 1 case seems wrong, but it's clearly
     * specified that way in the "PCL 5 Color Technical Reference
     * Manual."
     *
     * In the 1-bit case, So = ~S and Po = ~P, so we can apply the
     * above table directly.
     */
#define So rop3_not(rop3_S)
#define Po rop3_not(rop3_T)
#ifdef TRANSPARENCY_PER_H_P
/*
 * Believe it or not, MPo depends on S in this case even if the original
 * RasterOp didn't depend on S.
 */
#  define MPo (rop3_not(So) | Po)
#else
#  define MPo Po
#endif
    /*
     * If the operation doesn't use S or T, we must disregard the
     * corresponding transparency flag.
     */
#define source_transparent ((lop & lop_S_transparent) && rop3_uses_S(rop))
#define pattern_transparent ((lop & lop_T_transparent) && rop3_uses_T(rop))
    gs_rop3_t mask =
    (source_transparent ?
     (pattern_transparent ? So & Po : So) :
     (pattern_transparent ? MPo : rop3_1));

#undef MPo
    return (rop & mask) | (rop3_D & ~mask);
}