wmaker/wrlib/convert.c

/* convert.c - convert RImage to Pixmap
 *
 * Raster graphics library
 *
 * Copyright (c) 1997-2003 Alfredo K. Kojima
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Library General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Library General Public License for more details.
 *
 *  You should have received a copy of the GNU Library General Public
 *  License along with this library; if not, write to the Free
 *  Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
 *  MA 02110-1301, USA.
 */

/* Problems:
 *   1. Using Grayscale visual with Dithering crashes wmaker
 *   2. Ghost dock/appicon is wrong in Pseudocolor, Staticgray, Grayscale
 */

#include <config.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>

#include "wraster.h"
#include "convert.h"


#ifdef USE_XSHM
extern Pixmap R_CreateXImageMappedPixmap(RContext * context, RXImage * ximage);
#endif

#define NFREE(n)  if (n) free(n)

#define HAS_ALPHA(I)	((I)->format == RRGBAFormat)

typedef struct RConversionTable {
	unsigned short table[256];
	unsigned short index;

	struct RConversionTable *next;
} RConversionTable;

typedef struct RStdConversionTable {
	unsigned int table[256];

	unsigned short mult;
	unsigned short max;

	struct RStdConversionTable *next;
} RStdConversionTable;

static RConversionTable *conversionTable = NULL;
static RStdConversionTable *stdConversionTable = NULL;

static void release_conversion_table(void)
{
	RConversionTable *tmp = conversionTable;

	while (tmp) {
		RConversionTable *tmp_to_delete = tmp;

		tmp = tmp->next;
		free(tmp_to_delete);
	}
	conversionTable = NULL;
}

static void release_std_conversion_table(void)
{
	RStdConversionTable *tmp = stdConversionTable;

	while (tmp) {
		RStdConversionTable *tmp_to_delete = tmp;

		tmp = tmp->next;
		free(tmp_to_delete);
	}
	stdConversionTable = NULL;
}

void r_destroy_conversion_tables(void)
{
	release_conversion_table();
	release_std_conversion_table();
}

static unsigned short *computeTable(unsigned short mask)
{
	RConversionTable *tmp = conversionTable;
	int i;

	while (tmp) {
		if (tmp->index == mask)
			break;
		tmp = tmp->next;
	}

	if (tmp)
		return tmp->table;

	tmp = (RConversionTable *) malloc(sizeof(RConversionTable));
	if (tmp == NULL)
		return NULL;

	for (i = 0; i < 256; i++)
		tmp->table[i] = (i * mask + 0x7f) / 0xff;

	tmp->index = mask;
	tmp->next = conversionTable;
	conversionTable = tmp;
	return tmp->table;
}

static unsigned int *computeStdTable(unsigned int mult, unsigned int max)
{
	RStdConversionTable *tmp = stdConversionTable;
	unsigned int i;

	while (tmp) {
		if (tmp->mult == mult && tmp->max == max)
			break;
		tmp = tmp->next;
	}

	if (tmp)
		return tmp->table;

	tmp = (RStdConversionTable *) malloc(sizeof(RStdConversionTable));
	if (tmp == NULL)
		return NULL;

	for (i = 0; i < 256; i++) {
		tmp->table[i] = (i * max) / 0xff * mult;
	}
	tmp->mult = mult;
	tmp->max = max;

	tmp->next = stdConversionTable;
	stdConversionTable = tmp;

	return tmp->table;
}

/***************************************************************************/

static void
convertTrueColor_generic(RXImage * ximg, RImage * image,
			 signed char *err, signed char *nerr,
			 const unsigned short *rtable,
			 const unsigned short *gtable,
			 const unsigned short *btable,
			 const int dr, const int dg, const int db,
			 const unsigned short roffs, const unsigned short goffs, const unsigned short boffs)
{
	signed char *terr;
	int x, y, r, g, b;
	int pixel;
	int rer, ger, ber;
	unsigned char *ptr = image->data;
	int channels = (HAS_ALPHA(image) ? 4 : 3);

	/* convert and dither the image to XImage */
	for (y = 0; y < image->height; y++) {
		nerr[0] = 0;
		nerr[1] = 0;
		nerr[2] = 0;
		for (x = 0; x < image->width; x++, ptr += channels) {

			/* reduce pixel */
			pixel = *ptr + err[x];
			if (pixel < 0)
				pixel = 0;
			else if (pixel > 0xff)
				pixel = 0xff;
			r = rtable[pixel];
			/* calc error */
			rer = pixel - r * dr;

			/* reduce pixel */
			pixel = *(ptr + 1) + err[x + 1];
			if (pixel < 0)
				pixel = 0;
			else if (pixel > 0xff)
				pixel = 0xff;
			g = gtable[pixel];
			/* calc error */
			ger = pixel - g * dg;

			/* reduce pixel */
			pixel = *(ptr + 2) + err[x + 2];
			if (pixel < 0)
				pixel = 0;
			else if (pixel > 0xff)
				pixel = 0xff;
			b = btable[pixel];
			/* calc error */
			ber = pixel - b * db;

			pixel = (r << roffs) | (g << goffs) | (b << boffs);
			XPutPixel(ximg->image, x, y, pixel);

			/* distribute error */
			r = (rer * 3) / 8;
			g = (ger * 3) / 8;
			b = (ber * 3) / 8;
			/* x+1, y */
			err[x + 3 * 1] += r;
			err[x + 1 + 3 * 1] += g;
			err[x + 2 + 3 * 1] += b;
			/* x, y+1 */
			nerr[x] += r;
			nerr[x + 1] += g;
			nerr[x + 2] += b;
			/* x+1, y+1 */
			nerr[x + 3 * 1] = rer - 2 * r;
			nerr[x + 1 + 3 * 1] = ger - 2 * g;
			nerr[x + 2 + 3 * 1] = ber - 2 * b;
		}
		/* skip to next line */
		terr = err;
		err = nerr;
		nerr = terr;
	}

	/* redither the 1st line to distribute error better */
	ptr = image->data;
	y = 0;
	nerr[0] = 0;
	nerr[1] = 0;
	nerr[2] = 0;
	for (x = 0; x < image->width; x++, ptr += channels) {

		/* reduce pixel */
		pixel = *ptr + err[x];
		if (pixel < 0)
			pixel = 0;
		else if (pixel > 0xff)
			pixel = 0xff;
		r = rtable[pixel];
		/* calc error */
		rer = pixel - r * dr;

		/* reduce pixel */
		pixel = *(ptr + 1) + err[x + 1];
		if (pixel < 0)
			pixel = 0;
		else if (pixel > 0xff)
			pixel = 0xff;
		g = gtable[pixel];
		/* calc error */
		ger = pixel - g * dg;

		/* reduce pixel */
		pixel = *(ptr + 2) + err[x + 2];
		if (pixel < 0)
			pixel = 0;
		else if (pixel > 0xff)
			pixel = 0xff;
		b = btable[pixel];
		/* calc error */
		ber = pixel - b * db;

		pixel = (r << roffs) | (g << goffs) | (b << boffs);
		XPutPixel(ximg->image, x, y, pixel);

		/* distribute error */
		r = (rer * 3) / 8;
		g = (ger * 3) / 8;
		b = (ber * 3) / 8;
		/* x+1, y */
		err[x + 3 * 1] += r;
		err[x + 1 + 3 * 1] += g;
		err[x + 2 + 3 * 1] += b;
		/* x, y+1 */
		nerr[x] += r;
		nerr[x + 1] += g;
		nerr[x + 2] += b;
		/* x+1, y+1 */
		nerr[x + 3 * 1] = rer - 2 * r;
		nerr[x + 1 + 3 * 1] = ger - 2 * g;
		nerr[x + 2 + 3 * 1] = ber - 2 * b;
	}
}

static RXImage *image2TrueColor(RContext * ctx, RImage * image)
{
	RXImage *ximg;
	unsigned short rmask, gmask, bmask;
	unsigned short roffs, goffs, boffs;
	unsigned short *rtable, *gtable, *btable;
	int channels = (HAS_ALPHA(image) ? 4 : 3);

	ximg = RCreateXImage(ctx, ctx->depth, image->width, image->height);
	if (!ximg) {
		return NULL;
	}

	roffs = ctx->red_offset;
	goffs = ctx->green_offset;
	boffs = ctx->blue_offset;

	rmask = ctx->visual->red_mask >> roffs;
	gmask = ctx->visual->green_mask >> goffs;
	bmask = ctx->visual->blue_mask >> boffs;

	rtable = computeTable(rmask);
	gtable = computeTable(gmask);
	btable = computeTable(bmask);

	if (rtable == NULL || gtable == NULL || btable == NULL) {
		RErrorCode = RERR_NOMEMORY;
		RDestroyXImage(ctx, ximg);
		return NULL;
	}

	if (ctx->attribs->render_mode == RBestMatchRendering) {
		int ofs;
		unsigned long r, g, b;
		int x, y;
		unsigned long pixel;
		unsigned char *ptr = image->data;

		/* fake match */
#ifdef WRLIB_DEBUG
		fputs("true color match\n", stderr);
#endif
		if (rmask == 0xff && gmask == 0xff && bmask == 0xff) {
			for (y = 0; y < image->height; y++) {
				for (x = 0; x < image->width; x++, ptr += channels) {
					/* reduce pixel */
					r = ptr[0];
					g = ptr[1];
					b = ptr[2];
					pixel = (r << roffs) | (g << goffs) | (b << boffs);
					XPutPixel(ximg->image, x, y, pixel);
				}
			}
		} else {
			for (y = 0, ofs = 0; y < image->height; y++) {
				for (x = 0; x < image->width; x++, ofs += channels - 3) {
					/* reduce pixel */
					r = rtable[ptr[ofs++]];
					g = gtable[ptr[ofs++]];
					b = btable[ptr[ofs++]];
					pixel = (r << roffs) | (g << goffs) | (b << boffs);
					XPutPixel(ximg->image, x, y, pixel);
				}
			}
		}
	} else {
		/* dither */
		const int dr = 0xff / rmask;
		const int dg = 0xff / gmask;
		const int db = 0xff / bmask;

#ifdef WRLIB_DEBUG
		fputs("true color dither\n", stderr);
#endif

		{
			signed char *err;
			signed char *nerr;
			int ch = (HAS_ALPHA(image) ? 4 : 3);

			err = malloc(ch * (image->width + 2));
			nerr = malloc(ch * (image->width + 2));
			if (!err || !nerr) {
				NFREE(err);
				NFREE(nerr);
				RErrorCode = RERR_NOMEMORY;
				RDestroyXImage(ctx, ximg);
				return NULL;
			}

			memset(err, 0, ch * (image->width + 2));
			memset(nerr, 0, ch * (image->width + 2));

			convertTrueColor_generic(ximg, image, err, nerr,
						 rtable, gtable, btable, dr, dg, db, roffs, goffs, boffs);
			free(err);
			free(nerr);
		}

	}

	return ximg;
}

/***************************************************************************/

static void
convertPseudoColor_to_8(RXImage * ximg, RImage * image,
			signed char *err, signed char *nerr,
			const unsigned short *rtable,
			const unsigned short *gtable,
			const unsigned short *btable,
			const int dr, const int dg, const int db, unsigned long *pixels, int cpc)
{
	signed char *terr;
	int x, y, r, g, b;
	int pixel;
	int rer, ger, ber;
	unsigned char *ptr = image->data;
	unsigned char *optr = (unsigned char *)ximg->image->data;
	int channels = (HAS_ALPHA(image) ? 4 : 3);
	int cpcpc = cpc * cpc;

	/* convert and dither the image to XImage */
	for (y = 0; y < image->height; y++) {
		nerr[0] = 0;
		nerr[1] = 0;
		nerr[2] = 0;
		for (x = 0; x < image->width * 3; x += 3, ptr += channels) {

			/* reduce pixel */
			pixel = *ptr + err[x];
			if (pixel < 0)
				pixel = 0;
			else if (pixel > 0xff)
				pixel = 0xff;
			r = rtable[pixel];
			/* calc error */
			rer = pixel - r * dr;

			/* reduce pixel */
			pixel = *(ptr + 1) + err[x + 1];
			if (pixel < 0)
				pixel = 0;
			else if (pixel > 0xff)
				pixel = 0xff;
			g = gtable[pixel];
			/* calc error */
			ger = pixel - g * dg;

			/* reduce pixel */
			pixel = *(ptr + 2) + err[x + 2];
			if (pixel < 0)
				pixel = 0;
			else if (pixel > 0xff)
				pixel = 0xff;
			b = btable[pixel];
			/* calc error */
			ber = pixel - b * db;

			*optr++ = pixels[r * cpcpc + g * cpc + b];

			/* distribute error */
			r = (rer * 3) / 8;
			g = (ger * 3) / 8;
			b = (ber * 3) / 8;

			/* x+1, y */
			err[x + 3 * 1] += r;
			err[x + 1 + 3 * 1] += g;
			err[x + 2 + 3 * 1] += b;
			/* x, y+1 */
			nerr[x] += r;
			nerr[x + 1] += g;
			nerr[x + 2] += b;
			/* x+1, y+1 */
			nerr[x + 3 * 1] = rer - 2 * r;
			nerr[x + 1 + 3 * 1] = ger - 2 * g;
			nerr[x + 2 + 3 * 1] = ber - 2 * b;
		}
		/* skip to next line */
		terr = err;
		err = nerr;
		nerr = terr;

		optr += ximg->image->bytes_per_line - image->width;
	}
}

static RXImage *image2PseudoColor(RContext * ctx, RImage * image)
{
	RXImage *ximg;
	register int x, y, r, g, b;
	unsigned char *ptr;
	unsigned long pixel;
	const int cpc = ctx->attribs->colors_per_channel;
	const unsigned short rmask = cpc - 1;	/* different sizes could be used */
	const unsigned short gmask = rmask;	/* for r,g,b */
	const unsigned short bmask = rmask;
	unsigned short *rtable, *gtable, *btable;
	const int cpccpc = cpc * cpc;
	int channels = (HAS_ALPHA(image) ? 4 : 3);

	ximg = RCreateXImage(ctx, ctx->depth, image->width, image->height);
	if (!ximg) {
		return NULL;
	}

	ptr = image->data;

	/* Tables are same at the moment because rmask==gmask==bmask. */
	rtable = computeTable(rmask);
	gtable = computeTable(gmask);
	btable = computeTable(bmask);

	if (rtable == NULL || gtable == NULL || btable == NULL) {
		RErrorCode = RERR_NOMEMORY;
		RDestroyXImage(ctx, ximg);
		return NULL;
	}

	if (ctx->attribs->render_mode == RBestMatchRendering) {
		/* fake match */
#ifdef WRLIB_DEBUG
		fprintf(stderr, "pseudo color match with %d colors per channel\n", cpc);
#endif
		for (y = 0; y < image->height; y++) {
			for (x = 0; x < image->width; x++, ptr += channels - 3) {
				/* reduce pixel */
				r = rtable[*ptr++];
				g = gtable[*ptr++];
				b = btable[*ptr++];
				pixel = r * cpccpc + g * cpc + b;
				/*data[ofs] = ctx->colors[pixel].pixel; */
				XPutPixel(ximg->image, x, y, ctx->colors[pixel].pixel);
			}
		}
	} else {
		/* dither */
		signed char *err;
		signed char *nerr;
		const int dr = 0xff / rmask;
		const int dg = 0xff / gmask;
		const int db = 0xff / bmask;

#ifdef WRLIB_DEBUG
		fprintf(stderr, "pseudo color dithering with %d colors per channel\n", cpc);
#endif
		err = malloc(4 * (image->width + 3));
		nerr = malloc(4 * (image->width + 3));
		if (!err || !nerr) {
			NFREE(err);
			NFREE(nerr);
			RErrorCode = RERR_NOMEMORY;
			RDestroyXImage(ctx, ximg);
			return NULL;
		}
		memset(err, 0, 4 * (image->width + 3));
		memset(nerr, 0, 4 * (image->width + 3));

		convertPseudoColor_to_8(ximg, image, err + 4, nerr + 4,
					rtable, gtable, btable, dr, dg, db, ctx->pixels, cpc);

		free(err);
		free(nerr);
	}

	return ximg;
}

/*
 * For standard colormap
 */
static RXImage *image2StandardPseudoColor(RContext * ctx, RImage * image)
{
	RXImage *ximg;
	register int x, y, r, g, b;
	unsigned char *ptr;
	unsigned long pixel;
	unsigned char *data;
	unsigned int *rtable, *gtable, *btable;
	unsigned int base_pixel = ctx->std_rgb_map->base_pixel;
	int channels = (HAS_ALPHA(image) ? 4 : 3);

	ximg = RCreateXImage(ctx, ctx->depth, image->width, image->height);
	if (!ximg) {
		return NULL;
	}

	ptr = image->data;

	data = (unsigned char *)ximg->image->data;

	rtable = computeStdTable(ctx->std_rgb_map->red_mult, ctx->std_rgb_map->red_max);

	gtable = computeStdTable(ctx->std_rgb_map->green_mult, ctx->std_rgb_map->green_max);

	btable = computeStdTable(ctx->std_rgb_map->blue_mult, ctx->std_rgb_map->blue_max);

	if (rtable == NULL || gtable == NULL || btable == NULL) {
		RErrorCode = RERR_NOMEMORY;
		RDestroyXImage(ctx, ximg);
		return NULL;
	}

	if (ctx->attribs->render_mode == RBestMatchRendering) {
		for (y = 0; y < image->height; y++) {
			for (x = 0; x < image->width; x++, ptr += channels) {
				/* reduce pixel */
				pixel = (rtable[*ptr] + gtable[*(ptr + 1)]
					 + btable[*(ptr + 2)] + base_pixel) & 0xffffffff;

				XPutPixel(ximg->image, x, y, pixel);
			}
		}
	} else {
		/* dither */
		signed short *err, *nerr;
		signed short *terr;
		int rer, ger, ber;
		int x1, ofs;

#ifdef WRLIB_DEBUG
		fprintf(stderr, "pseudo color dithering with %d colors per channel\n",
			ctx->attribs->colors_per_channel);
#endif
		err = (short *)malloc(3 * (image->width + 2) * sizeof(short));
		nerr = (short *)malloc(3 * (image->width + 2) * sizeof(short));
		if (!err || !nerr) {
			NFREE(err);
			NFREE(nerr);
			RErrorCode = RERR_NOMEMORY;
			RDestroyXImage(ctx, ximg);
			return NULL;
		}
		for (x = 0, x1 = 0; x < image->width * 3; x1 += channels - 3) {
			err[x++] = ptr[x1++];
			err[x++] = ptr[x1++];
			err[x++] = ptr[x1++];
		}
		err[x] = err[x + 1] = err[x + 2] = 0;
		/* convert and dither the image to XImage */
		for (y = 0, ofs = 0; y < image->height; y++) {
			if (y < image->height - 1) {
				int x1;
				for (x = 0, x1 = (y + 1) * image->width * channels;
				     x < image->width * 3; x1 += channels - 3) {
					nerr[x++] = ptr[x1++];
					nerr[x++] = ptr[x1++];
					nerr[x++] = ptr[x1++];
				}
				/* last column */
				x1 -= channels;
				nerr[x++] = ptr[x1++];
				nerr[x++] = ptr[x1++];
				nerr[x++] = ptr[x1++];
			}
			for (x = 0; x < image->width * 3; x += 3, ofs++) {
				/* reduce pixel */
				if (err[x] > 0xff)
					err[x] = 0xff;
				else if (err[x] < 0)
					err[x] = 0;
				if (err[x + 1] > 0xff)
					err[x + 1] = 0xff;
				else if (err[x + 1] < 0)
					err[x + 1] = 0;
				if (err[x + 2] > 0xff)
					err[x + 2] = 0xff;
				else if (err[x + 2] < 0)
					err[x + 2] = 0;

				r = rtable[err[x]];
				g = gtable[err[x + 1]];
				b = btable[err[x + 2]];

				pixel = r + g + b;

				data[ofs] = base_pixel + pixel;

				/* calc error */
				rer = err[x] - (ctx->colors[pixel].red >> 8);
				ger = err[x + 1] - (ctx->colors[pixel].green >> 8);
				ber = err[x + 2] - (ctx->colors[pixel].blue >> 8);

				/* distribute error */
				err[x + 3 * 1] += (rer * 7) / 16;
				err[x + 1 + 3 * 1] += (ger * 7) / 16;
				err[x + 2 + 3 * 1] += (ber * 7) / 16;

				nerr[x] += (rer * 5) / 16;
				nerr[x + 1] += (ger * 5) / 16;
				nerr[x + 2] += (ber * 5) / 16;

				if (x > 0) {
					nerr[x - 3 * 1] += (rer * 3) / 16;
					nerr[x - 3 * 1 + 1] += (ger * 3) / 16;
					nerr[x - 3 * 1 + 2] += (ber * 3) / 16;
				}

				nerr[x + 3 * 1] += rer / 16;
				nerr[x + 1 + 3 * 1] += ger / 16;
				nerr[x + 2 + 3 * 1] += ber / 16;
			}
			/* skip to next line */
			terr = err;
			err = nerr;
			nerr = terr;

			ofs += ximg->image->bytes_per_line - image->width;
		}
		free(err);
		free(nerr);
	}
	ximg->image->data = (char *)data;

	return ximg;
}

static RXImage *image2GrayScale(RContext * ctx, RImage * image)
{
	RXImage *ximg;
	register int x, y, g;
	unsigned char *ptr;
	const int cpc = ctx->attribs->colors_per_channel;
	unsigned short gmask;
	unsigned short *table;
	unsigned char *data;
	int channels = (HAS_ALPHA(image) ? 4 : 3);

	ximg = RCreateXImage(ctx, ctx->depth, image->width, image->height);
	if (!ximg) {
		return NULL;
	}

	ptr = image->data;

	data = (unsigned char *)ximg->image->data;

	if (ctx->vclass == StaticGray)
		gmask = (1 << ctx->depth) - 1;	/* use all grays */
	else
		gmask = cpc * cpc * cpc - 1;

	table = computeTable(gmask);

	if (table == NULL) {
		RErrorCode = RERR_NOMEMORY;
		RDestroyXImage(ctx, ximg);
		return NULL;
	}

	if (ctx->attribs->render_mode == RBestMatchRendering) {
		/* fake match */
#ifdef WRLIB_DEBUG
		fprintf(stderr, "grayscale match with %d colors per channel\n", cpc);
#endif
		for (y = 0; y < image->height; y++) {
			for (x = 0; x < image->width; x++) {
				/* reduce pixel */
				g = table[(*ptr * 30 + *(ptr + 1) * 59 + *(ptr + 2) * 11) / 100];
				ptr += channels;
				/*data[ofs] = ctx->colors[g].pixel; */
				XPutPixel(ximg->image, x, y, ctx->colors[g].pixel);
			}
		}
	} else {
		/* dither */
		short *gerr;
		short *ngerr;
		short *terr;
		int ger;
		const int dg = 0xff / gmask;

#ifdef WRLIB_DEBUG
		fprintf(stderr, "grayscale dither with %d colors per channel\n", cpc);
#endif
		gerr = (short *)malloc((image->width + 2) * sizeof(short));
		ngerr = (short *)malloc((image->width + 2) * sizeof(short));
		if (!gerr || !ngerr) {
			NFREE(gerr);
			NFREE(ngerr);
			RErrorCode = RERR_NOMEMORY;
			RDestroyXImage(ctx, ximg);
			return NULL;
		}
		for (x = 0, y = 0; x < image->width; x++, y += channels) {
			gerr[x] = (ptr[y] * 30 + ptr[y + 1] * 59 + ptr[y + 2] * 11) / 100;
		}
		gerr[x] = 0;
		/* convert and dither the image to XImage */
		for (y = 0; y < image->height; y++) {
			if (y < image->height - 1) {
				int x1;
				for (x = 0, x1 = (y + 1) * image->width * channels; x < image->width;
				     x++, x1 += channels) {
					ngerr[x] = (ptr[x1] * 30 + ptr[x1 + 1] * 59 + ptr[x1 + 2] * 11) / 100;
				}
				/* last column */
				x1 -= channels;
				ngerr[x] = (ptr[x1] * 30 + ptr[x1 + 1] * 59 + ptr[x1 + 2] * 11) / 100;
			}
			for (x = 0; x < image->width; x++) {
				/* reduce pixel */
				if (gerr[x] > 0xff)
					gerr[x] = 0xff;
				else if (gerr[x] < 0)
					gerr[x] = 0;

				g = table[gerr[x]];

				/*data[ofs] = ctx->colors[g].pixel; */
				XPutPixel(ximg->image, x, y, ctx->colors[g].pixel);
				/* calc error */
				ger = gerr[x] - g * dg;

				/* distribute error */
				g = (ger * 3) / 8;
				/* x+1, y */
				gerr[x + 1] += g;
				/* x, y+1 */
				ngerr[x] += g;
				/* x+1, y+1 */
				ngerr[x + 1] += ger - 2 * g;
			}
			/* skip to next line */
			terr = gerr;
			gerr = ngerr;
			ngerr = terr;
		}
		free(gerr);
		free(ngerr);
	}
	ximg->image->data = (char *)data;

	return ximg;
}

static RXImage *image2Bitmap(RContext * ctx, RImage * image, int threshold)
{
	RXImage *ximg;
	unsigned char *alpha;
	int x, y;

	ximg = RCreateXImage(ctx, 1, image->width, image->height);
	if (!ximg) {
		return NULL;
	}
	alpha = image->data + 3;

	for (y = 0; y < image->height; y++) {
		for (x = 0; x < image->width; x++) {
			XPutPixel(ximg->image, x, y, (*alpha <= threshold ? 0 : 1));
			alpha += 4;
		}
	}

	return ximg;
}

int RConvertImage(RContext * context, RImage * image, Pixmap * pixmap)
{
	RXImage *ximg = NULL;
#ifdef USE_XSHM
	Pixmap tmp;
#endif

	assert(context != NULL);
	assert(image != NULL);
	assert(pixmap != NULL);

	switch (context->vclass) {
	case TrueColor:
		ximg = image2TrueColor(context, image);
		break;

	case PseudoColor:
	case StaticColor:
		if (context->attribs->standard_colormap_mode != RIgnoreStdColormap)
			ximg = image2StandardPseudoColor(context, image);
		else
			ximg = image2PseudoColor(context, image);
		break;

	case GrayScale:
	case StaticGray:
		ximg = image2GrayScale(context, image);
		break;
	}

	if (!ximg) {
		return False;
	}

	*pixmap = XCreatePixmap(context->dpy, context->drawable, image->width, image->height, context->depth);

#ifdef USE_XSHM
	if (context->flags.use_shared_pixmap && ximg->is_shared)
		tmp = R_CreateXImageMappedPixmap(context, ximg);
	else
		tmp = None;
	if (tmp) {
		/*
		 * We have to copy the shm Pixmap into a normal Pixmap because
		 * otherwise, we would have to control when Pixmaps are freed so
		 * that we can detach their shm segments. This is a problem if the
		 * program crash, leaving stale shared memory segments in the
		 * system (lots of them). But with some work, we can optimize
		 * things and remove this XCopyArea. This will require
		 * explicitly freeing all pixmaps when exiting or restarting
		 * wmaker.
		 */
		XCopyArea(context->dpy, tmp, *pixmap, context->copy_gc, 0, 0, image->width, image->height, 0, 0);
		XFreePixmap(context->dpy, tmp);
	} else {
		RPutXImage(context, *pixmap, context->copy_gc, ximg, 0, 0, 0, 0, image->width, image->height);
	}
#else				/* !USE_XSHM */
	RPutXImage(context, *pixmap, context->copy_gc, ximg, 0, 0, 0, 0, image->width, image->height);
#endif				/* !USE_XSHM */

	RDestroyXImage(context, ximg);

	return True;
}

/* make the gc permanent (create with context creation).
 * GC creation is very expensive. altering its properties is not. -Dan
 */
int RConvertImageMask(RContext * context, RImage * image, Pixmap * pixmap, Pixmap * mask, int threshold)
{
	GC gc;
	XGCValues gcv;
	RXImage *ximg = NULL;

	assert(context != NULL);
	assert(image != NULL);
	assert(pixmap != NULL);
	assert(mask != NULL);

	if (!RConvertImage(context, image, pixmap))
		return False;

	if (image->format == RRGBFormat) {
		*mask = None;
		return True;
	}

	ximg = image2Bitmap(context, image, threshold);

	if (!ximg) {
		return False;
	}
	*mask = XCreatePixmap(context->dpy, context->drawable, image->width, image->height, 1);
	gcv.foreground = context->black;
	gcv.background = context->white;
	gcv.graphics_exposures = False;
	gc = XCreateGC(context->dpy, *mask, GCForeground | GCBackground | GCGraphicsExposures, &gcv);
	RPutXImage(context, *mask, gc, ximg, 0, 0, 0, 0, image->width, image->height);
	RDestroyXImage(context, ximg);
	XFreeGC(context->dpy, gc);

	return True;
}

Bool RGetClosestXColor(RContext * context, const RColor * color, XColor * retColor)
{
	if (context->vclass == TrueColor) {
		unsigned short rmask, gmask, bmask;
		unsigned short roffs, goffs, boffs;
		unsigned short *rtable, *gtable, *btable;

		roffs = context->red_offset;
		goffs = context->green_offset;
		boffs = context->blue_offset;

		rmask = context->visual->red_mask >> roffs;
		gmask = context->visual->green_mask >> goffs;
		bmask = context->visual->blue_mask >> boffs;

		rtable = computeTable(rmask);
		gtable = computeTable(gmask);
		btable = computeTable(bmask);

		retColor->pixel = (rtable[color->red] << roffs) |
		    (gtable[color->green] << goffs) | (btable[color->blue] << boffs);

		retColor->red = color->red << 8;
		retColor->green = color->green << 8;
		retColor->blue = color->blue << 8;
		retColor->flags = DoRed | DoGreen | DoBlue;

	} else if (context->vclass == PseudoColor || context->vclass == StaticColor) {

		if (context->attribs->standard_colormap_mode != RIgnoreStdColormap) {
			unsigned int *rtable, *gtable, *btable;

			rtable = computeStdTable(context->std_rgb_map->red_mult, context->std_rgb_map->red_max);

			gtable = computeStdTable(context->std_rgb_map->green_mult,
						 context->std_rgb_map->green_max);

			btable = computeStdTable(context->std_rgb_map->blue_mult, context->std_rgb_map->blue_max);

			if (rtable == NULL || gtable == NULL || btable == NULL) {
				RErrorCode = RERR_NOMEMORY;
				return False;
			}

			retColor->pixel = (rtable[color->red]
					   + gtable[color->green]
					   + btable[color->blue]
					   + context->std_rgb_map->base_pixel) & 0xffffffff;
			retColor->red = color->red << 8;
			retColor->green = color->green << 8;
			retColor->blue = color->blue << 8;
			retColor->flags = DoRed | DoGreen | DoBlue;

		} else {
			const int cpc = context->attribs->colors_per_channel;
			const unsigned short rmask = cpc - 1;	/* different sizes could be used */
			const unsigned short gmask = rmask;	/* for r,g,b */
			const unsigned short bmask = rmask;
			unsigned short *rtable, *gtable, *btable;
			const int cpccpc = cpc * cpc;
			int index;

			rtable = computeTable(rmask);
			gtable = computeTable(gmask);
			btable = computeTable(bmask);

			if (rtable == NULL || gtable == NULL || btable == NULL) {
				RErrorCode = RERR_NOMEMORY;
				return False;
			}
			index = rtable[color->red] * cpccpc + gtable[color->green] * cpc + btable[color->blue];
			*retColor = context->colors[index];
		}

	} else if (context->vclass == GrayScale || context->vclass == StaticGray) {

		const int cpc = context->attribs->colors_per_channel;
		unsigned short gmask;
		unsigned short *table;
		int index;

		if (context->vclass == StaticGray)
			gmask = (1 << context->depth) - 1;	/* use all grays */
		else
			gmask = cpc * cpc * cpc - 1;

		table = computeTable(gmask);
		if (!table)
			return False;

		index = table[(color->red * 30 + color->green * 59 + color->blue * 11) / 100];

		*retColor = context->colors[index];
	} else {
		RErrorCode = RERR_INTERNAL;
		return False;
	}

	return True;
}