tdelibs/kimgio/xcf.cpp

/*
 * qxcfi.cpp: A Qt 3 plug-in for reading GIMP XCF image files
 * Copyright (C) 2001 lignum Computing, Inc. <allen@lignumcomputing.com>
 * Copyright (C) 2004 Melchior FRANZ <mfranz@kde.org>
 *
 * This plug-in is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

#include <stdlib.h>
#include <tqimage.h>
#include <tqiodevice.h>
#include <tqvaluestack.h>
#include <tqvaluevector.h>

#include <kdebug.h>
#include "xcf.h"


///////////////////////////////////////////////////////////////////////////////


KDE_EXPORT void kimgio_xcf_read(TQImageIO *io)
{
	XCFImageFormat xcfif;
	xcfif.readXCF(io);
}


KDE_EXPORT void kimgio_xcf_write(TQImageIO *io)
{
	kdDebug(399) << "XCF: write support not implemented" << endl;
	io->setStatus(-1);
}

///////////////////////////////////////////////////////////////////////////////



int XCFImageFormat::random_table[RANDOM_TABLE_SIZE];

//int XCFImageFormat::add_lut[256][256];


const XCFImageFormat::LayerModes XCFImageFormat::layer_modes[] = {
	{true},		// NORMAL_MODE
	{true},		// DISSOLVE_MODE
	{true},		// BEHIND_MODE
	{false},	// MULTIPLY_MODE
	{false},	// SCREEN_MODE
	{false},	// OVERLAY_MODE
	{false},	// DIFFERENCE_MODE
	{false},	// ADDITION_MODE
	{false},	// SUBTRACT_MODE
	{false},	// DARKEN_ONLY_MODE
	{false},	// LIGHTEN_ONLY_MODE
	{false},	// HUE_MODE
	{false},	// SATURATION_MODE
	{false},	// COLOR_MODE
	{false},	// VALUE_MODE
	{false},	// DIVIDE_MODE
	{true},		// ERASE_MODE
	{true},		// REPLACE_MODE
	{true},		// ANTI_ERASE_MODE
};


//! Change a QRgb value's alpha only.
inline QRgb tqRgba ( QRgb rgb, int a )
{
	return ((a & 0xff) << 24 | (rgb & TQRGB_MASK));
}


/*!
 * The constructor for the XCF image loader. This initializes the
 * tables used in the layer merging routines.
 */
XCFImageFormat::XCFImageFormat()
{
	// From GIMP "paint_funcs.c" v1.2
	srand(RANDOM_SEED);

	for (int i = 0; i < RANDOM_TABLE_SIZE; i++)
		random_table[i] = rand();

	for (int i = 0; i < RANDOM_TABLE_SIZE; i++) {
		int tmp;
		int swap = i + rand() % (RANDOM_TABLE_SIZE - i);
		tmp = random_table[i];
		random_table[i] = random_table[swap];
		random_table[swap] = tmp;
	}

//	for (int j = 0; j < 256; j++) {
//		for (int k = 0; k < 256; k++) {
//			int tmp_sum = j + k;
//			if (tmp_sum > 255)
//				tmp_sum = 255;
//			add_lut[j][k] = tmp_sum;
//		}
//	}
}

inline
int XCFImageFormat::add_lut( int a, int b ) {
	return QMIN( a + b, 255 );
}

void XCFImageFormat::readXCF(TQImageIO *io)
{
	XCFImage xcf_image;
	TQDataStream xcf_io(io->ioDevice());

	char tag[14];
	xcf_io.readRawBytes(tag, sizeof(tag));

	if (xcf_io.device()->status() != IO_Ok) {
		kdDebug(399) << "XCF: read failure on header tag" << endl;
		return;
	}

	xcf_io >> xcf_image.width >> xcf_image.height >> xcf_image.type;

	if (xcf_io.device()->status() != IO_Ok) {
		kdDebug(399) << "XCF: read failure on image info" << endl;
		return;
	}

kdDebug() << tag << " " << xcf_image.width << " " << xcf_image.height << " " <<  xcf_image.type << endl;
	if (!loadImageProperties(xcf_io, xcf_image))
		return;

	// The layers appear to be stored in top-to-bottom order. This is
	// the reverse of how a merged image must be computed. So, the layer
	// offsets are pushed onto a LIFO stack (thus, we don't have to load
	// all the data of all layers before beginning to construct the
	// merged image).

	TQValueStack<TQ_INT32> layer_offsets;

	while (true) {
		TQ_INT32 layer_offset;

		xcf_io >> layer_offset;

		if (xcf_io.device()->status() != IO_Ok) {
			kdDebug(399) << "XCF: read failure on layer offsets" << endl;
			return;
		}

		if (layer_offset == 0)
			break;

		layer_offsets.push(layer_offset);
	}

	xcf_image.num_layers = layer_offsets.size();

	if (layer_offsets.size() == 0) {
		kdDebug(399) << "XCF: no layers!" << endl;
		return;
	}

	// Load each layer and add it to the image
	while (!layer_offsets.isEmpty()) {
		TQ_INT32 layer_offset = layer_offsets.pop();

		xcf_io.device()->at(layer_offset);

		if (!loadLayer(xcf_io, xcf_image))
			return;
	}

	if (!xcf_image.initialized) {
		kdDebug(399) << "XCF: no visible layers!" << endl;
		return;
	}

	io->setImage(xcf_image.image);
	io->setStatus(0);
}


/*!
 * An XCF file can contain an arbitrary number of properties associated
 * with the image (and layer and mask).
 * \param xcf_io the data stream connected to the XCF image
 * \param xcf_image XCF image data.
 * \return true if there were no I/O errors.
 */
bool XCFImageFormat::loadImageProperties(TQDataStream& xcf_io, XCFImage& xcf_image)
{
	while (true) {
		PropType type;
		TQByteArray bytes;

		if (!loadProperty(xcf_io, type, bytes)) {
			kdDebug(399) << "XCF: error loading global image properties" << endl;
			return false;
		}

		TQDataStream property(bytes, IO_ReadOnly);

		switch (type) {
			case PROP_END:
				return true;

			case PROP_COMPRESSION:
				property >> xcf_image.compression;
				break;

			case PROP_RESOLUTION:
				property >> xcf_image.x_resolution >> xcf_image.y_resolution;
				break;

			case PROP_TATTOO:
				property >> xcf_image.tattoo;
				break;

			case PROP_PARASITES:
				while (!property.atEnd()) {
					char* tag;
					TQ_UINT32 size;

					property.readBytes(tag, size);

					TQ_UINT32 flags;
					char* data=0;
					property >> flags >> data;

					if (tag && strncmp(tag, "gimp-comment", strlen("gimp-comment")) == 0)
						xcf_image.image.setText("Comment", 0, data);

					delete[] tag;
					delete[] data;
				}
				break;

				case PROP_UNIT:
					property >> xcf_image.unit;
					break;

				case PROP_PATHS:	// This property is ignored.
					break;

				case PROP_USER_UNIT:	// This property is ignored.
					break;

				case PROP_COLORMAP:
					property >> xcf_image.num_colors;
                                        if(xcf_image.num_colors < 0 || xcf_image.num_colors > 65535)
                                            return false;

					xcf_image.palette.reserve(xcf_image.num_colors);

					for (int i = 0; i < xcf_image.num_colors; i++) {
						uchar r, g, b;
						property >> r >> g >> b;
						xcf_image.palette.push_back( tqRgb(r,g,b) );
					}
					break;

				default:
					kdDebug(399) << "XCF: unimplemented image property" << type
							<< ", size " << bytes.size() << endl;
		}
	}
}


/*!
 * Read a single property from the image file. The property type is returned
 * in type and the data is returned in bytes.
 * \param xcf the image file data stream.
 * \param type returns with the property type.
 * \param bytes returns with the property data.
 * \return true if there were no IO errors.  */
bool XCFImageFormat::loadProperty(TQDataStream& xcf_io, PropType& type, TQByteArray& bytes)
{
	TQ_UINT32 foo;
	xcf_io >> foo;
	type=PropType(foo);	// TODO urks

	if (xcf_io.device()->status() != IO_Ok) {
		kdDebug(399) << "XCF: read failure on property type" << type << endl;
		return false;
	}

	char* data;
	TQ_UINT32 size;

	// The colormap property size is not the correct number of bytes:
	// The GIMP source xcf.c has size = 4 + ncolors, but it should be
	// 4 + 3 * ncolors

	if (type == PROP_COLORMAP) {
		xcf_io >> size;

		if (xcf_io.device()->status() != IO_Ok) {
			kdDebug(399) << "XCF: read failure on property " << type << " size" << endl;
			return false;
		}

                if(size > 65535 || size < 4)
                    return false;

		size = 3 * (size - 4) + 4;
		data = new char[size];

		xcf_io.readRawBytes(data, size);
	} else if (type == PROP_USER_UNIT) {
		// The USER UNIT property size is not correct. I'm not sure why, though.
		float factor;
		TQ_INT32 digits;
		char* unit_strings;

		xcf_io >> size >> factor >> digits;

		if (xcf_io.device()->status() != IO_Ok) {
			kdDebug(399) << "XCF: read failure on property " << type << endl;
			return false;
		}

		for (int i = 0; i < 5; i++) {
			xcf_io >> unit_strings;

			if (xcf_io.device()->status() != IO_Ok) {
				kdDebug(399) << "XCF: read failure on property " << type << endl;
				return false;
			}

			delete[] unit_strings;
		}

		size = 0;
	} else {
                xcf_io >> size;
                if(size >256000)
                    return false;
                data = new char[size];
		xcf_io.readRawBytes(data, size);
        }

	if (xcf_io.device()->status() != IO_Ok) {
		kdDebug(399) << "XCF: read failure on property " << type << " data, size " << size << endl;
		return false;
	}

	if (size != 0 && data) {
                bytes.assign(data,size);
	}

	return true;
}


/*!
 * Load a layer from the XCF file. The data stream must be positioned at
 * the beginning of the layer data.
 * \param xcf_io the image file data stream.
 * \param xcf_image contains the layer and the color table
 * (if the image is indexed).
 * \return true if there were no I/O errors.
 */
bool XCFImageFormat::loadLayer(TQDataStream& xcf_io, XCFImage& xcf_image)
{
	Layer& layer(xcf_image.layer);
	delete[] layer.name;

	xcf_io >> layer.width >> layer.height >> layer.type >> layer.name;

	if (xcf_io.device()->status() != IO_Ok) {
		kdDebug(399) << "XCF: read failure on layer" << endl;
		return false;
	}

	if (!loadLayerProperties(xcf_io, layer))
		return false;
#if 0
  cout << "layer: \"" << layer.name << "\", size: " << layer.width << " x "
       << layer.height << ", type: " << layer.type << ", mode: " << layer.mode
       << ", opacity: " << layer.opacity << ", visible: " << layer.visible
       << ", offset: " << layer.x_offset << ", " << layer.y_offset << endl;
#endif
  // Skip reading the rest of it if it is not visible. Typically, when
  // you export an image from the The GIMP it flattens (or merges) only
  // the visible layers into the output image.

	if (layer.visible == 0)
		return true;

	// If there are any more layers, merge them into the final TQImage.

	xcf_io >> layer.hierarchy_offset >> layer.mask_offset;
	if (xcf_io.device()->status() != IO_Ok) {
		kdDebug(399) << "XCF: read failure on layer image offsets" << endl;
		return false;
	}

	// Allocate the individual tile QImages based on the size and type
	// of this layer.

	if( !composeTiles(xcf_image))
		return false;
	xcf_io.device()->at(layer.hierarchy_offset);

	// As tiles are loaded, they are copied into the layers tiles by
	// this routine. (loadMask(), below, uses a slightly different
	// version of assignBytes().)

	layer.assignBytes = assignImageBytes;

	if (!loadHierarchy(xcf_io, layer))
		return false;

	if (layer.mask_offset != 0) {
		xcf_io.device()->at(layer.mask_offset);

		if (!loadMask(xcf_io, layer))
			return false;
	}

	// Now we should have enough information to initialize the final
	// TQImage. The first visible layer determines the attributes
	// of the TQImage.

	if (!xcf_image.initialized) {
		if( !initializeImage(xcf_image))
			return false;
		copyLayerToImage(xcf_image);
		xcf_image.initialized = true;
	} else
		mergeLayerIntoImage(xcf_image);

	return true;
}


/*!
 * An XCF file can contain an arbitrary number of properties associated
 * with a layer.
 * \param xcf_io the data stream connected to the XCF image.
 * \param layer layer to collect the properties.
 * \return true if there were no I/O errors.
 */
bool XCFImageFormat::loadLayerProperties(TQDataStream& xcf_io, Layer& layer)
{
	while (true) {
		PropType type;
		TQByteArray bytes;

		if (!loadProperty(xcf_io, type, bytes)) {
			kdDebug(399) << "XCF: error loading layer properties" << endl;
			return false;
		}

		TQDataStream property(bytes, IO_ReadOnly);

		switch (type) {
			case PROP_END:
				return true;

			case PROP_ACTIVE_LAYER:
				layer.active = true;
				break;

			case PROP_OPACITY:
				property >> layer.opacity;
				break;

			case PROP_VISIBLE:
				property >> layer.visible;
				break;

			case PROP_LINKED:
				property >> layer.linked;
				break;

			case PROP_PRESERVE_TRANSPARENCY:
				property >> layer.preserve_transparency;
				break;

			case PROP_APPLY_MASK:
				property >> layer.apply_mask;
				break;

			case PROP_EDIT_MASK:
				property >> layer.edit_mask;
				break;

			case PROP_SHOW_MASK:
				property >> layer.show_mask;
				break;

			case PROP_OFFSETS:
				property >> layer.x_offset >> layer.y_offset;
				break;

			case PROP_MODE:
				property >> layer.mode;
				break;

			case PROP_TATTOO:
				property >> layer.tattoo;
				break;

			default:
				kdDebug(399) << "XCF: unimplemented layer property " << type
						<< ", size " << bytes.size() << endl;
		}
	}
}


/*!
 * Compute the number of tiles in the current layer and allocate
 * TQImage structures for each of them.
 * \param xcf_image contains the current layer.
 */
bool XCFImageFormat::composeTiles(XCFImage& xcf_image)
{
	Layer& layer(xcf_image.layer);

	layer.nrows = (layer.height + TILE_HEIGHT - 1) / TILE_HEIGHT;
	layer.ncols = (layer.width + TILE_WIDTH - 1) / TILE_WIDTH;

	layer.image_tiles.resize(layer.nrows);

	if (layer.type == GRAYA_GIMAGE || layer.type == INDEXEDA_GIMAGE)
		layer.alpha_tiles.resize(layer.nrows);

	if (layer.mask_offset != 0)
		layer.mask_tiles.resize(layer.nrows);

	for (uint j = 0; j < layer.nrows; j++) {
		layer.image_tiles[j].resize(layer.ncols);

		if (layer.type == GRAYA_GIMAGE || layer.type == INDEXEDA_GIMAGE)
			layer.alpha_tiles[j].resize(layer.ncols);

		if (layer.mask_offset != 0)
			layer.mask_tiles[j].resize(layer.ncols);
	}

	for (uint j = 0; j < layer.nrows; j++) {
		for (uint i = 0; i < layer.ncols; i++) {

			uint tile_width = (i + 1) * TILE_WIDTH <= layer.width
					? TILE_WIDTH : layer.width - i * TILE_WIDTH;

			uint tile_height = (j + 1) * TILE_HEIGHT <= layer.height
					? TILE_HEIGHT : layer.height - j * TILE_HEIGHT;

			// Try to create the most appropriate TQImage (each GIMP layer
			// type is treated slightly differently)

			switch (layer.type) {
				case RGB_GIMAGE:
					layer.image_tiles[j][i] = TQImage(tile_width, tile_height, 32, 0);
					if( layer.image_tiles[j][i].isNull())
						return false;
					layer.image_tiles[j][i].setAlphaBuffer(false);
					break;

				case RGBA_GIMAGE:
					layer.image_tiles[j][i] = TQImage(tile_width, tile_height, 32, 0);
					if( layer.image_tiles[j][i].isNull())
						return false;
					layer.image_tiles[j][i].setAlphaBuffer(true);
					break;

				case GRAY_GIMAGE:
					layer.image_tiles[j][i] = TQImage(tile_width, tile_height, 8, 256);
					if( layer.image_tiles[j][i].isNull())
						return false;
					setGrayPalette(layer.image_tiles[j][i]);
					break;

				case GRAYA_GIMAGE:
					layer.image_tiles[j][i] = TQImage(tile_width, tile_height, 8, 256);
					if( layer.image_tiles[j][i].isNull())
						return false;
					setGrayPalette(layer.image_tiles[j][i]);

					layer.alpha_tiles[j][i] = TQImage( tile_width, tile_height, 8, 256);
					if( layer.alpha_tiles[j][i].isNull())
						return false;
					setGrayPalette(layer.alpha_tiles[j][i]);
					break;

				case INDEXED_GIMAGE:
					layer.image_tiles[j][i] = TQImage(tile_width, tile_height, 8,
							xcf_image.num_colors);
					if( layer.image_tiles[j][i].isNull())
						return false;
					setPalette(xcf_image, layer.image_tiles[j][i]);
					break;

				case INDEXEDA_GIMAGE:
					layer.image_tiles[j][i] = TQImage(tile_width, tile_height,8,
							xcf_image.num_colors);
					if( layer.image_tiles[j][i].isNull())
						return false;
					setPalette(xcf_image, layer.image_tiles[j][i]);

					layer.alpha_tiles[j][i] = TQImage(tile_width, tile_height, 8, 256);
					if( layer.alpha_tiles[j][i].isNull())
						return false;
					setGrayPalette(layer.alpha_tiles[j][i]);
			}

			if (layer.mask_offset != 0) {
				layer.mask_tiles[j][i] = TQImage(tile_width, tile_height, 8, 256);
				if( layer.mask_tiles[j][i].isNull())
					return false;
				setGrayPalette(layer.mask_tiles[j][i]);
			}
		}
	}
	return true;
}


/*!
 * Apply a grayscale palette to the TQImage. Note that Qt does not distinguish
 * between grayscale and indexed images. A grayscale image is just
 * an indexed image with a 256-color, grayscale palette.
 * \param image image to set to a grayscale palette.
 */
void XCFImageFormat::setGrayPalette(TQImage& image)
{
	for (int i = 0; i < 256; i++)
		image.setColor(i, tqRgb(i, i, i));
}


/*!
 * Copy the indexed palette from the XCF image into the TQImage.
 * \param xcf_image XCF image containing the palette read from the data stream.
 * \param image image to apply the palette to.
 */
void XCFImageFormat::setPalette(XCFImage& xcf_image, TQImage& image)
{
	for (int i = 0; i < xcf_image.num_colors; i++)
		image.setColor(i, xcf_image.palette[i]);
}


/*!
 * Copy the bytes from the tile buffer into the image tile TQImage, taking into
 * account all the myriad different modes.
 * \param layer layer containing the tile buffer and the image tile matrix.
 * \param i column index of current tile.
 * \param j row index of current tile.
 */
void XCFImageFormat::assignImageBytes(Layer& layer, uint i, uint j)
{
	uchar* tile = layer.tile;

	switch (layer.type) {
		case RGB_GIMAGE:
			for (int l = 0; l < layer.image_tiles[j][i].height(); l++) {
				for (int k = 0; k < layer.image_tiles[j][i].width(); k++) {
					layer.image_tiles[j][i].setPixel(k, l,
							tqRgb(tile[0], tile[1], tile[2]));
					tile += sizeof(QRgb);
				}
			}
			break;

		case RGBA_GIMAGE:
			for ( int l = 0; l < layer.image_tiles[j][i].height(); l++ ) {
				for ( int k = 0; k < layer.image_tiles[j][i].width(); k++ ) {
					layer.image_tiles[j][i].setPixel(k, l,
							tqRgba(tile[0], tile[1], tile[2], tile[3]));
					tile += sizeof(QRgb);
				}
			}
			break;

		case GRAY_GIMAGE:
		case INDEXED_GIMAGE:
			for (int l = 0; l < layer.image_tiles[j][i].height(); l++) {
				for (int k = 0; k < layer.image_tiles[j][i].width(); k++) {
					layer.image_tiles[j][i].setPixel(k, l, tile[0]);
					tile += sizeof(QRgb);
				}
			}
			break;

		case GRAYA_GIMAGE:
		case INDEXEDA_GIMAGE:
			for (int l = 0; l < layer.image_tiles[j][i].height(); l++) {
				for (int k = 0; k < layer.image_tiles[j][i].width(); k++) {

				// The "if" here should not be necessary, but apparently there
				// are some cases where the image can contain larger indices
				// than there are colors in the palette. (A bug in The GIMP?)

					if (tile[0] < layer.image_tiles[j][i].numColors())
						layer.image_tiles[j][i].setPixel(k, l, tile[0]);

					layer.alpha_tiles[j][i].setPixel(k, l, tile[1]);
					tile += sizeof(QRgb);
				}
			}
			break;
	}
}


/*!
 * The GIMP stores images in a "mipmap"-like hierarchy. As far as the QImage
 * is concerned, however, only the top level (i.e., the full resolution image)
 * is used.
 * \param xcf_io the data stream connected to the XCF image.
 * \param layer the layer to collect the image.
 * \return true if there were no I/O errors.
 */
bool XCFImageFormat::loadHierarchy(TQDataStream& xcf_io, Layer& layer)
{
	TQ_INT32 width;
	TQ_INT32 height;
	TQ_INT32 bpp;
	TQ_UINT32 offset;

	xcf_io >> width >> height >> bpp >> offset;

	if (xcf_io.device()->status() != IO_Ok) {
		kdDebug(399) << "XCF: read failure on layer " << layer.name << " image header" << endl;
		return false;
	}

	// GIMP stores images in a "mipmap"-like format (multiple levels of
	// increasingly lower resolution). Only the top level is used here,
	// however.

	TQ_UINT32 junk;
	do {
		xcf_io >> junk;

		if (xcf_io.device()->status() != IO_Ok) {
			kdDebug(399) << "XCF: read failure on layer " << layer.name << " level offsets" << endl;
			return false;
		}
	} while (junk != 0);

	TQIODevice::Offset saved_pos = xcf_io.device()->at();

	xcf_io.device()->at(offset);
	if (!loadLevel(xcf_io, layer, bpp))
		return false;

	xcf_io.device()->at(saved_pos);
	return true;
}


/*!
 * Load one level of the image hierarchy (but only the top level is ever used).
 * \param xcf_io the data stream connected to the XCF image.
 * \param layer the layer to collect the image.
 * \param bpp the number of bytes in a pixel.
 * \return true if there were no I/O errors.
 * \sa loadTileRLE().
 */
bool XCFImageFormat::loadLevel(TQDataStream& xcf_io, Layer& layer, TQ_INT32 bpp)
{
	TQ_INT32 width;
	TQ_INT32 height;
	TQ_UINT32 offset;

	xcf_io >> width >> height >> offset;

	if (xcf_io.device()->status() != IO_Ok) {
		kdDebug(399) << "XCF: read failure on layer " << layer.name << " level info" << endl;
		return false;
	}

	if (offset == 0)
		return true;

	for (uint j = 0; j < layer.nrows; j++) {
		for (uint i = 0; i < layer.ncols; i++) {

			if (offset == 0) {
				kdDebug(399) << "XCF: incorrect number of tiles in layer " << layer.name << endl;
				return false;
			}

			TQIODevice::Offset saved_pos = xcf_io.device()->at();
			TQ_UINT32 offset2;
			xcf_io >> offset2;

			if (xcf_io.device()->status() != IO_Ok) {
				kdDebug(399) << "XCF: read failure on layer " << layer.name << " level offset look-ahead" << endl;
				return false;
			}

			// Evidently, RLE can occasionally expand a tile instead of compressing it!

			if (offset2 == 0)
				offset2 = offset + (uint)(TILE_WIDTH * TILE_HEIGHT * 4 * 1.5);

			xcf_io.device()->at(offset);
			int size = layer.image_tiles[j][i].width() * layer.image_tiles[j][i].height();

			if (!loadTileRLE(xcf_io, layer.tile, size, offset2 - offset, bpp))
				return false;

			// The bytes in the layer tile are juggled differently depending on
			// the target TQImage. The caller has set layer.assignBytes to the
			// appropriate routine.

			layer.assignBytes(layer, i, j);

			xcf_io.device()->at(saved_pos);
			xcf_io >> offset;

			if (xcf_io.device()->status() != IO_Ok) {
				kdDebug(399) << "XCF: read failure on layer " << layer.name << " level offset" << endl;
				return false;
			}
		}
	}

	return true;
}


/*!
 * A layer can have a one channel image which is used as a mask.
 * \param xcf_io the data stream connected to the XCF image.
 * \param layer the layer to collect the mask image.
 * \return true if there were no I/O errors.
 */
bool XCFImageFormat::loadMask(TQDataStream& xcf_io, Layer& layer)
{
	TQ_INT32 width;
	TQ_INT32 height;
	char* name;

	xcf_io >> width >> height >> name;

	if (xcf_io.device()->status() != IO_Ok) {
		kdDebug(399) << "XCF: read failure on mask info" << endl;
		return false;
	}

	delete name;

	if (!loadChannelProperties(xcf_io, layer))
		return false;

	TQ_UINT32 hierarchy_offset;
	xcf_io >> hierarchy_offset;

	if (xcf_io.device()->status() != IO_Ok) {
		kdDebug(399) << "XCF: read failure on mask image offset" << endl;
		return false;
	}

	xcf_io.device()->at(hierarchy_offset);
	layer.assignBytes = assignMaskBytes;

	if (!loadHierarchy(xcf_io, layer))
		return false;

	return true;
}


/*!
 * This is the routine for which all the other code is simply
 * infrastructure. Read the image bytes out of the file and
 * store them in the tile buffer. This is passed a full 32-bit deep
 * buffer, even if bpp is smaller. The caller can figure out what to
 * do with the bytes.
 *
 * The tile is stored in "channels", i.e. the red component of all
 * pixels, then the green component of all pixels, then blue then
 * alpha, or, for indexed images, the color indices of all pixels then
 * the alpha of all pixels.
 *
 * The data is compressed with "run length encoding". Some simple data
 * integrity checks are made.
 *
 * \param xcf_io the data stream connected to the XCF image.
 * \param tile the buffer to expand the RLE into.
 * \param image_size number of bytes expected to be in the image tile.
 * \param data_length number of bytes expected in the RLE.
 * \param bpp number of bytes per pixel.
 * \return true if there were no I/O errors and no obvious corruption of
 * the RLE data.
 */
bool XCFImageFormat::loadTileRLE(TQDataStream& xcf_io, uchar* tile, int image_size,
		int data_length, TQ_INT32 bpp)
{
	uchar* data;

	uchar* xcfdata;
	uchar* xcfodata;
	uchar* xcfdatalimit;

	xcfdata = xcfodata = new uchar[data_length];

	xcf_io.readRawBytes((char*)xcfdata, data_length);

	if (xcf_io.device()->status() != IO_Ok) {
		delete[] xcfodata;
		kdDebug(399) << "XCF: read failure on tile" << endl;
		return false;
	}

	xcfdatalimit = &xcfodata[data_length - 1];

	for (int i = 0; i < bpp; ++i) {

		data = tile + i;

		int count = 0;
		int size = image_size;

		while (size > 0) {
			if (xcfdata > xcfdatalimit)
				goto bogus_rle;

			uchar val = *xcfdata++;
			uint length = val;

			if (length >= 128) {
				length = 255 - (length - 1);
				if (length == 128) {
					if (xcfdata >= xcfdatalimit)
						goto bogus_rle;

					length = (*xcfdata << 8) + xcfdata[1];

					xcfdata += 2;
				}

				count += length;
				size -= length;

				if (size < 0)
					goto bogus_rle;

				if (&xcfdata[length - 1] > xcfdatalimit)
					goto bogus_rle;

				while (length-- > 0) {
					*data = *xcfdata++;
					data += sizeof(QRgb);
				}
			} else {
				length += 1;
				if (length == 128) {
					if (xcfdata >= xcfdatalimit)
						goto bogus_rle;

					length = (*xcfdata << 8) + xcfdata[1];
					xcfdata += 2;
				}

				count += length;
				size -= length;

				if (size < 0)
					goto bogus_rle;

				if (xcfdata > xcfdatalimit)
					goto bogus_rle;

				val = *xcfdata++;

				while (length-- > 0) {
					*data = val;
					data += sizeof(QRgb);
				}
			}
		}
	}

	delete[] xcfodata;
	return true;

bogus_rle:

	kdDebug(399) << "The run length encoding could not be decoded properly" << endl;
	delete[] xcfodata;
	return false;
}


/*!
 * An XCF file can contain an arbitrary number of properties associated
 * with a channel. Note that this routine only reads mask channel properties.
 * \param xcf_io the data stream connected to the XCF image.
 * \param layer layer containing the mask channel to collect the properties.
 * \return true if there were no I/O errors.
 */
bool XCFImageFormat::loadChannelProperties(TQDataStream& xcf_io, Layer& layer)
{
	while (true) {
		PropType type;
		TQByteArray bytes;

		if (!loadProperty(xcf_io, type, bytes)) {
			kdDebug(399) << "XCF: error loading channel properties" << endl;
			return false;
		}

		TQDataStream property(bytes, IO_ReadOnly);

		switch (type) {
			case PROP_END:
				return true;

			case PROP_OPACITY:
				property >> layer.mask_channel.opacity;
				break;

			case PROP_VISIBLE:
				property >> layer.mask_channel.visible;
				break;

			case PROP_SHOW_MASKED:
				property >> layer.mask_channel.show_masked;
				break;

			case PROP_COLOR:
				property >> layer.mask_channel.red >> layer.mask_channel.green
						>> layer.mask_channel.blue;
				break;

			case PROP_TATTOO:
				property >> layer.mask_channel.tattoo;
				break;

			default:
				kdDebug(399) << "XCF: unimplemented channel property " << type
						<< ", size " << bytes.size() << endl;
		}
	}
}


/*!
 * Copy the bytes from the tile buffer into the mask tile TQImage.
 * \param layer layer containing the tile buffer and the mask tile matrix.
 * \param i column index of current tile.
 * \param j row index of current tile.
 */
void XCFImageFormat::assignMaskBytes(Layer& layer, uint i, uint j)
{
	uchar* tile = layer.tile;

	for (int l = 0; l < layer.image_tiles[j][i].height(); l++) {
		for (int k = 0; k < layer.image_tiles[j][i].width(); k++) {
			layer.mask_tiles[j][i].setPixel(k, l, tile[0]);
			tile += sizeof(QRgb);
		}
	}
}


/*!
 * Construct the TQImage which will eventually be returned to the QImage
 * loader.
 *
 * There are a couple of situations which require that the TQImage is not
 * exactly the same as The GIMP's representation. The full table is:
 * \verbatim
 *  Grayscale  opaque      :  8 bpp indexed
 *  Grayscale  translucent : 32 bpp + alpha
 *  Indexed    opaque      :  1 bpp if num_colors <= 2
 *                         :  8 bpp indexed otherwise
 *  Indexed    translucent :  8 bpp indexed + alpha if num_colors < 256
 *                         : 32 bpp + alpha otherwise
 *  RGB        opaque      : 32 bpp
 *  RGBA       translucent : 32 bpp + alpha
 * \endverbatim
 * Whether the image is translucent or not is determined by the bottom layer's
 * alpha channel. However, even if the bottom layer lacks an alpha channel,
 * it can still have an opacity < 1. In this case, the TQImage is promoted
 * to 32-bit. (Note this is different from the output from the GIMP image
 * exporter, which seems to ignore this attribute.)
 *
 * Independently, higher layers can be translucent, but the background of
 * the image will not show through if the bottom layer is opaque.
 *
 * For indexed images, translucency is an all or nothing effect.
 * \param xcf_image contains image info and bottom-most layer.
 */
bool XCFImageFormat::initializeImage(XCFImage& xcf_image)
{
	// (Aliases to make the code look a little better.)
	Layer& layer(xcf_image.layer);
	TQImage& image(xcf_image.image);

	switch (layer.type) {
		case RGB_GIMAGE:
			if (layer.opacity == OPAQUE_OPACITY) {
				image.create( xcf_image.width, xcf_image.height, 32);
				if( image.isNull())
					return false;
				image.fill(tqRgb(255, 255, 255));
				break;
			} // else, fall through to 32-bit representation

		case RGBA_GIMAGE:
			image.create(xcf_image.width, xcf_image.height, 32);
			if( image.isNull())
				return false;
			image.fill(tqRgba(255, 255, 255, 0));
			// Turning this on prevents fill() from affecting the alpha channel,
			// by the way.
			image.setAlphaBuffer(true);
			break;

		case GRAY_GIMAGE:
			if (layer.opacity == OPAQUE_OPACITY) {
				image.create(xcf_image.width, xcf_image.height, 8, 256);
				if( image.isNull())
					return false;
				setGrayPalette(image);
				image.fill(255);
				break;
			} // else, fall through to 32-bit representation

		case GRAYA_GIMAGE:
			image.create(xcf_image.width, xcf_image.height, 32);
			if( image.isNull())
				return false;
			image.fill(tqRgba(255, 255, 255, 0));
			image.setAlphaBuffer(true);
			break;

		case INDEXED_GIMAGE:
			// As noted in the table above, there are quite a few combinations
			// which are possible with indexed images, depending on the
			// presense of transparency (note: not translucency, which is not
			// supported by The GIMP for indexed images) and the number of
			// individual colors.

			// Note: Qt treats a bitmap with a Black and White color palette
			// as a mask, so only the "on" bits are drawn, regardless of the
			// order color table entries. Otherwise (i.e., at least one of the
			// color table entries is not black or white), it obeys the one-
			// or two-color palette. Have to ask about this...

			if (xcf_image.num_colors <= 2) {
				image.create(xcf_image.width, xcf_image.height,
						1, xcf_image.num_colors,
						TQImage::LittleEndian);
				if( image.isNull())
					return false;
				image.fill(0);
				setPalette(xcf_image, image);
			} else if (xcf_image.num_colors <= 256) {
				image.create(xcf_image.width, xcf_image.height,
				8, xcf_image.num_colors,
				TQImage::LittleEndian);
				if( image.isNull())
					return false;
				image.fill(0);
				setPalette(xcf_image, image);
			}
			break;

		case INDEXEDA_GIMAGE:
			if (xcf_image.num_colors == 1) {
				// Plenty(!) of room to add a transparent color
				xcf_image.num_colors++;
				xcf_image.palette.resize(xcf_image.num_colors);
				xcf_image.palette[1] = xcf_image.palette[0];
				xcf_image.palette[0] = tqRgba(255, 255, 255, 0);

				image.create(xcf_image.width, xcf_image.height,
						1, xcf_image.num_colors,
						TQImage::LittleEndian);
				if( image.isNull())
					return false;
				image.fill(0);
				setPalette(xcf_image, image);
				image.setAlphaBuffer(true);
			} else if (xcf_image.num_colors < 256) {
				// Plenty of room to add a transparent color
				xcf_image.num_colors++;
				xcf_image.palette.resize(xcf_image.num_colors);
				for (int c = xcf_image.num_colors - 1; c >= 1; c--)
					xcf_image.palette[c] = xcf_image.palette[c - 1];

				xcf_image.palette[0] = tqRgba(255, 255, 255, 0);
				image.create( xcf_image.width, xcf_image.height,
						8, xcf_image.num_colors);
				if( image.isNull())
					return false;
				image.fill(0);
				setPalette(xcf_image, image);
				image.setAlphaBuffer(true);
			} else {
				// No room for a transparent color, so this has to be promoted to
				// true color. (There is no equivalent PNG representation output
				// from The GIMP as of v1.2.)
				image.create(xcf_image.width, xcf_image.height, 32);
				if( image.isNull())
					return false;
				image.fill(tqRgba(255, 255, 255, 0));
				image.setAlphaBuffer(true);
			}
			break;
	}

	image.setDotsPerMeterX((int)(xcf_image.x_resolution * INCHESPERMETER));
	image.setDotsPerMeterY((int)(xcf_image.y_resolution * INCHESPERMETER));
	return true;
}


/*!
 * Copy a layer into an image, taking account of the manifold modes. The
 * contents of the image are replaced.
 * \param xcf_image contains the layer and image to be replaced.
 */
void XCFImageFormat::copyLayerToImage(XCFImage& xcf_image)
{
	Layer& layer(xcf_image.layer);
	TQImage& image(xcf_image.image);
	PixelCopyOperation copy = 0;

	switch (layer.type) {
		case RGB_GIMAGE:
		case RGBA_GIMAGE:
			copy = copyRGBToRGB;
			break;
		case GRAY_GIMAGE:
			if (layer.opacity == OPAQUE_OPACITY)
				copy = copyGrayToGray;
			else
				copy = copyGrayToRGB;
			break;
		case GRAYA_GIMAGE:
			copy = copyGrayAToRGB;
			break;
		case INDEXED_GIMAGE:
			copy = copyIndexedToIndexed;
			break;
		case INDEXEDA_GIMAGE:
			if (xcf_image.image.depth() <= 8)
				copy = copyIndexedAToIndexed;
			else
				copy = copyIndexedAToRGB;
	}

	// For each tile...

	for (uint j = 0; j < layer.nrows; j++) {
		uint y = j * TILE_HEIGHT;

		for (uint i = 0; i < layer.ncols; i++) {
			uint x = i * TILE_WIDTH;

			// This seems the best place to apply the dissolve because it
			// depends on the global position of each tile's
			// pixels. Apparently it's the only mode which can apply to a
			// single layer.

			if (layer.mode == DISSOLVE_MODE) {
				if (layer.type == RGBA_GIMAGE)
					dissolveRGBPixels(layer.image_tiles[j][i], x, y);

				else if (layer.type == GRAYA_GIMAGE)
					dissolveAlphaPixels(layer.alpha_tiles[j][i], x, y);
			}

			for (int l = 0; l < layer.image_tiles[j][i].height(); l++) {
				for (int k = 0; k < layer.image_tiles[j][i].width(); k++) {

					int m = x + k + layer.x_offset;
					int n = y + l + layer.y_offset;

					if (m < 0 || m >= image.width() || n < 0 || n >= image.height())
						continue;

					(*copy)(layer, i, j, k, l, image, m, n);
				}
			}
		}
	}
}


/*!
 * Copy an RGB pixel from the layer to the RGB image. Straight-forward.
 * The only thing this has to take account of is the opacity of the
 * layer. Evidently, the GIMP exporter itself does not actually do this.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::copyRGBToRGB(Layer& layer, uint i, uint j, int k, int l,
		TQImage& image, int m, int n)
{
	QRgb src = layer.image_tiles[j][i].pixel(k, l);
	uchar src_a = layer.opacity;

	if (layer.type == RGBA_GIMAGE)
		src_a = INT_MULT(src_a, tqAlpha(src));

	// Apply the mask (if any)

	if (layer.apply_mask == 1 && layer.mask_tiles.size() > j &&
			layer.mask_tiles[j].size() > i)
		src_a = INT_MULT(src_a, layer.mask_tiles[j][i].pixelIndex(k, l));

	image.setPixel(m, n, tqRgba(src, src_a));
}


/*!
 * Copy a Gray pixel from the layer to the Gray image. Straight-forward.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::copyGrayToGray(Layer& layer, uint i, uint j, int k, int l,
		TQImage& image, int m, int n)
{
	int src = layer.image_tiles[j][i].pixelIndex(k, l);
	image.setPixel(m, n, src);
}


/*!
 * Copy a Gray pixel from the layer to an RGB image. Straight-forward.
 * The only thing this has to take account of is the opacity of the
 * layer. Evidently, the GIMP exporter itself does not actually do this.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::copyGrayToRGB(Layer& layer, uint i, uint j, int k, int l,
		TQImage& image, int m, int n)
{
	QRgb src = layer.image_tiles[j][i].pixel(k, l);
	uchar src_a = layer.opacity;
	image.setPixel(m, n, tqRgba(src, src_a));
}


/*!
 * Copy a GrayA pixel from the layer to an RGB image. Straight-forward.
 * The only thing this has to take account of is the opacity of the
 * layer. Evidently, the GIMP exporter itself does not actually do this.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::copyGrayAToRGB(Layer& layer, uint i, uint j, int k, int l,
				      TQImage& image, int m, int n)
{
	QRgb src = layer.image_tiles[j][i].pixel(k, l);
	uchar src_a = layer.alpha_tiles[j][i].pixelIndex(k, l);
	src_a = INT_MULT(src_a, layer.opacity);

	// Apply the mask (if any)

	if (layer.apply_mask == 1 && layer.mask_tiles.size() > j &&
			layer.mask_tiles[j].size() > i)
		src_a = INT_MULT(src_a, layer.mask_tiles[j][i].pixelIndex(k, l));

	image.setPixel(m, n, tqRgba(src, src_a));
}


/*!
 * Copy an Indexed pixel from the layer to the Indexed image. Straight-forward.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::copyIndexedToIndexed(Layer& layer, uint i, uint j, int k, int l,
		TQImage& image, int m, int n)
{
	int src = layer.image_tiles[j][i].pixelIndex(k, l);
	image.setPixel(m, n, src);
}


/*!
 * Copy an IndexedA pixel from the layer to the Indexed image. Straight-forward.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::copyIndexedAToIndexed(Layer& layer, uint i, uint j, int k, int l,
		TQImage& image, int m, int n)
{
	uchar src = layer.image_tiles[j][i].pixelIndex(k, l);
	uchar src_a = layer.alpha_tiles[j][i].pixelIndex(k, l);
	src_a = INT_MULT(src_a, layer.opacity);

	if (layer.apply_mask == 1 &&
			layer.mask_tiles.size() > j &&
			layer.mask_tiles[j].size() > i)
		src_a = INT_MULT(src_a, layer.mask_tiles[j][i].pixelIndex(k, l));

	if (src_a > 127)
		src++;
	else
		src = 0;

image.setPixel(m, n, src);
}


/*!
 * Copy an IndexedA pixel from the layer to an RGB image. Straight-forward.
 * The only thing this has to take account of is the opacity of the
 * layer. Evidently, the GIMP exporter itself does not actually do this.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::copyIndexedAToRGB(Layer& layer, uint i, uint j, int k, int l,
		TQImage& image, int m, int n)
{
	QRgb src = layer.image_tiles[j][i].pixel(k, l);
	uchar src_a = layer.alpha_tiles[j][i].pixelIndex(k, l);
	src_a = INT_MULT(src_a, layer.opacity);

	// Apply the mask (if any)
	if (layer.apply_mask == 1 && layer.mask_tiles.size() > j &&
			layer.mask_tiles[j].size() > i)
		src_a = INT_MULT(src_a, layer.mask_tiles[j][i].pixelIndex(k, l));

	// This is what appears in the GIMP window
	if (src_a <= 127)
		src_a = 0;
	else
		src_a = OPAQUE_OPACITY;

	image.setPixel(m, n, tqRgba(src, src_a));
}


/*!
 * Merge a layer into an image, taking account of the manifold modes.
 * \param xcf_image contains the layer and image to merge.
 */
void XCFImageFormat::mergeLayerIntoImage(XCFImage& xcf_image)
{
	Layer& layer(xcf_image.layer);
	TQImage& image(xcf_image.image);

	PixelMergeOperation merge = 0;

	switch (layer.type) {
		case RGB_GIMAGE:
		case RGBA_GIMAGE:
			merge = mergeRGBToRGB;
			break;
		case GRAY_GIMAGE:
			if (layer.opacity == OPAQUE_OPACITY)
				merge = mergeGrayToGray;
			else
				merge = mergeGrayToRGB;
			break;
		case GRAYA_GIMAGE:
			if (xcf_image.image.depth() <= 8)
				merge = mergeGrayAToGray;
			else
				merge = mergeGrayAToRGB;
			break;
		case INDEXED_GIMAGE:
			merge = mergeIndexedToIndexed;
			break;
		case INDEXEDA_GIMAGE:
			if (xcf_image.image.depth() <= 8)
				merge = mergeIndexedAToIndexed;
			else
				merge = mergeIndexedAToRGB;
	}

	for (uint j = 0; j < layer.nrows; j++) {
		uint y = j * TILE_HEIGHT;

		for (uint i = 0; i < layer.ncols; i++) {
			uint x = i * TILE_WIDTH;

			// This seems the best place to apply the dissolve because it
			// depends on the global position of each tile's
			// pixels. Apparently it's the only mode which can apply to a
			// single layer.

			if (layer.mode == DISSOLVE_MODE) {
				if (layer.type == RGBA_GIMAGE)
					dissolveRGBPixels(layer.image_tiles[j][i], x, y);

				else if (layer.type == GRAYA_GIMAGE)
					dissolveAlphaPixels(layer.alpha_tiles[j][i], x, y);
			}

			for (int l = 0; l < layer.image_tiles[j][i].height(); l++) {
				for (int k = 0; k < layer.image_tiles[j][i].width(); k++) {

					int m = x + k + layer.x_offset;
					int n = y + l + layer.y_offset;

					if (m < 0 || m >= image.width() || n < 0 || n >= image.height())
						continue;

					(*merge)(layer, i, j, k, l, image, m, n);
				}
			}
		}
	}
}


/*!
 * Merge an RGB pixel from the layer to the RGB image. Straight-forward.
 * The only thing this has to take account of is the opacity of the
 * layer. Evidently, the GIMP exporter itself does not actually do this.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::mergeRGBToRGB(Layer& layer, uint i, uint j, int k, int l,
		TQImage& image, int m, int n)
{
	QRgb src = layer.image_tiles[j][i].pixel(k, l);
	QRgb dst = image.pixel(m, n);

	uchar src_r = tqRed(src);
	uchar src_g = tqGreen(src);
	uchar src_b = tqBlue(src);
	uchar src_a = tqAlpha(src);

	uchar dst_r = tqRed(dst);
	uchar dst_g = tqGreen(dst);
	uchar dst_b = tqBlue(dst);
	uchar dst_a = tqAlpha(dst);

	switch (layer.mode) {
		case MULTIPLY_MODE: {
			src_r = INT_MULT(src_r, dst_r);
			src_g = INT_MULT(src_g, dst_g);
			src_b = INT_MULT(src_b, dst_b);
			src_a = KMIN(src_a, dst_a);
			}
			break;
		case DIVIDE_MODE: {
			src_r = KMIN((dst_r * 256) / (1 + src_r), 255);
			src_g = KMIN((dst_g * 256) / (1 + src_g), 255);
			src_b = KMIN((dst_b * 256) / (1 + src_b), 255);
			src_a = KMIN(src_a, dst_a);
			}
			break;
		case SCREEN_MODE: {
			src_r = 255 - INT_MULT(255 - dst_r, 255 - src_r);
			src_g = 255 - INT_MULT(255 - dst_g, 255 - src_g);
			src_b = 255 - INT_MULT(255 - dst_b, 255 - src_b);
			src_a = KMIN(src_a, dst_a);
			}
			break;
		case OVERLAY_MODE: {
			src_r = INT_MULT(dst_r, dst_r + INT_MULT(2 * src_r, 255 - dst_r));
			src_g = INT_MULT(dst_g, dst_g + INT_MULT(2 * src_g, 255 - dst_g));
			src_b = INT_MULT(dst_b, dst_b + INT_MULT(2 * src_b, 255 - dst_b));
			src_a = KMIN(src_a, dst_a);
			}
			break;
		case DIFFERENCE_MODE: {
			src_r = dst_r > src_r ? dst_r - src_r : src_r - dst_r;
			src_g = dst_g > src_g ? dst_g - src_g : src_g - dst_g;
			src_b = dst_b > src_b ? dst_b - src_b : src_b - dst_b;
			src_a = KMIN(src_a, dst_a);
			}
			break;
		case ADDITION_MODE: {
			  src_r = add_lut(dst_r,src_r);
			  src_g = add_lut(dst_g,src_g);
			  src_b = add_lut(dst_b,src_b);
			  src_a = KMIN(src_a, dst_a);
			}
			break;
		case SUBTRACT_MODE: {
			src_r = dst_r > src_r ? dst_r - src_r : 0;
			src_g = dst_g > src_g ? dst_g - src_g : 0;
			src_b = dst_b > src_b ? dst_b - src_b : 0;
			src_a = KMIN(src_a, dst_a);
			}
			break;
		case DARKEN_ONLY_MODE: {
			src_r = dst_r < src_r ? dst_r : src_r;
			src_g = dst_g < src_g ? dst_g : src_g;
			src_b = dst_b < src_b ? dst_b : src_b;
			src_a = KMIN( src_a, dst_a );
			}
			break;
		case LIGHTEN_ONLY_MODE: {
			src_r = dst_r < src_r ? src_r : dst_r;
			src_g = dst_g < src_g ? src_g : dst_g;
			src_b = dst_b < src_b ? src_b : dst_b;
			src_a = KMIN(src_a, dst_a);
			}
			break;
		case HUE_MODE: {
			uchar new_r = dst_r;
			uchar new_g = dst_g;
			uchar new_b = dst_b;

			RGBTOHSV(src_r, src_g, src_b);
			RGBTOHSV(new_r, new_g, new_b);

			new_r = src_r;

			HSVTORGB(new_r, new_g, new_b);

			src_r = new_r;
			src_g = new_g;
			src_b = new_b;
			src_a = KMIN( src_a, dst_a );
			}
			break;
		case SATURATION_MODE: {
			uchar new_r = dst_r;
			uchar new_g = dst_g;
			uchar new_b = dst_b;

			RGBTOHSV(src_r, src_g, src_b);
			RGBTOHSV(new_r, new_g, new_b);

			new_g = src_g;

			HSVTORGB(new_r, new_g, new_b);

			src_r = new_r;
			src_g = new_g;
			src_b = new_b;
			src_a = KMIN(src_a, dst_a);
			}
			break;
		case VALUE_MODE: {
			uchar new_r = dst_r;
			uchar new_g = dst_g;
			uchar new_b = dst_b;

			RGBTOHSV(src_r, src_g, src_b);
			RGBTOHSV(new_r, new_g, new_b);

			new_b = src_b;

			HSVTORGB(new_r, new_g, new_b);

			src_r = new_r;
			src_g = new_g;
			src_b = new_b;
			src_a = KMIN(src_a, dst_a);
			}
			break;
		case COLOR_MODE: {
			uchar new_r = dst_r;
			uchar new_g = dst_g;
			uchar new_b = dst_b;

			RGBTOHLS(src_r, src_g, src_b);
			RGBTOHLS(new_r, new_g, new_b);

			new_r = src_r;
			new_b = src_b;

			HLSTORGB(new_r, new_g, new_b);

			src_r = new_r;
			src_g = new_g;
			src_b = new_b;
			src_a = KMIN(src_a, dst_a);
			}
			break;
	}

	src_a = INT_MULT(src_a, layer.opacity);

	// Apply the mask (if any)

	if (layer.apply_mask == 1 && layer.mask_tiles.size() > j &&
			layer.mask_tiles[j].size() > i)
		src_a = INT_MULT(src_a, layer.mask_tiles[j][i].pixelIndex(k, l));

	uchar new_r, new_g, new_b, new_a;
	new_a = dst_a + INT_MULT(OPAQUE_OPACITY - dst_a, src_a);

	float src_ratio = (float)src_a / new_a;
	float dst_ratio = 1.0 - src_ratio;

	new_r = (uchar)(src_ratio * src_r + dst_ratio * dst_r + EPSILON);
	new_g = (uchar)(src_ratio * src_g + dst_ratio * dst_g + EPSILON);
	new_b = (uchar)(src_ratio * src_b + dst_ratio * dst_b + EPSILON);

	if (!layer_modes[layer.mode].affect_alpha)
		new_a = dst_a;

	image.setPixel(m, n, tqRgba(new_r, new_g, new_b, new_a));
}


/*!
 * Merge a Gray pixel from the layer to the Gray image. Straight-forward.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::mergeGrayToGray(Layer& layer, uint i, uint j, int k, int l,
		TQImage& image, int m, int n)
{
	int src = layer.image_tiles[j][i].pixelIndex(k, l);
	image.setPixel(m, n, src);
}


/*!
 * Merge a GrayA pixel from the layer to the Gray image. Straight-forward.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::mergeGrayAToGray(Layer& layer, uint i, uint j, int k, int l,
		TQImage& image, int m, int n)
{
	int src = tqGray(layer.image_tiles[j][i].pixel(k, l));
	int dst = image.pixelIndex(m, n);

	uchar src_a = layer.alpha_tiles[j][i].pixelIndex(k, l);

	switch (layer.mode) {
		case MULTIPLY_MODE: {
				src = INT_MULT( src, dst );
			}
			break;
		case DIVIDE_MODE: {
				src = KMIN((dst * 256) / (1 + src), 255);
			}
			break;
		case SCREEN_MODE: {
				src = 255 - INT_MULT(255 - dst, 255 - src);
			}
			break;
		case OVERLAY_MODE: {
				src = INT_MULT(dst, dst + INT_MULT(2 * src, 255 - dst));
			}
			break;
		case DIFFERENCE_MODE: {
				src = dst > src ? dst - src : src - dst;
			}
			break;
		case ADDITION_MODE: {
				src = add_lut(dst,src);
			}
			break;
		case SUBTRACT_MODE: {
				src = dst > src ? dst - src : 0;
			}
			break;
		case DARKEN_ONLY_MODE: {
				src = dst < src ? dst : src;
			}
			break;
		case LIGHTEN_ONLY_MODE: {
				src = dst < src ? src : dst;
			}
			break;
	}

	src_a = INT_MULT(src_a, layer.opacity);

	// Apply the mask (if any)

	if (layer.apply_mask == 1 && layer.mask_tiles.size() > j &&
			layer.mask_tiles[j].size() > i)
		src_a = INT_MULT(src_a, layer.mask_tiles[j][i].pixelIndex(k, l));

	uchar new_a = OPAQUE_OPACITY;

	float src_ratio = (float)src_a / new_a;
	float dst_ratio = 1.0 - src_ratio;

	uchar new_g = (uchar)(src_ratio * src + dst_ratio * dst + EPSILON);

	image.setPixel(m, n, new_g);
}


/*!
 * Merge a Gray pixel from the layer to an RGB image. Straight-forward.
 * The only thing this has to take account of is the opacity of the
 * layer. Evidently, the GIMP exporter itself does not actually do this.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::mergeGrayToRGB(Layer& layer, uint i, uint j, int k, int l,
		TQImage& image, int m, int n)
{
	QRgb src = layer.image_tiles[j][i].pixel(k, l);
	uchar src_a = layer.opacity;
	image.setPixel(m, n, tqRgba(src, src_a));
}


/*!
 * Merge a GrayA pixel from the layer to an RGB image. Straight-forward.
 * The only thing this has to take account of is the opacity of the
 * layer. Evidently, the GIMP exporter itself does not actually do this.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::mergeGrayAToRGB(Layer& layer, uint i, uint j, int k, int l,
		TQImage& image, int m, int n)
{
	int src = tqGray(layer.image_tiles[j][i].pixel(k, l));
	int dst = tqGray(image.pixel(m, n));

	uchar src_a = layer.alpha_tiles[j][i].pixelIndex(k, l);
	uchar dst_a = tqAlpha(image.pixel(m, n));

	switch (layer.mode) {
		case MULTIPLY_MODE: {
				src = INT_MULT(src, dst);
				src_a = KMIN(src_a, dst_a);
			}
			break;
		case DIVIDE_MODE: {
				src = KMIN((dst * 256) / (1 + src), 255);
				src_a = KMIN(src_a, dst_a);
			}
			break;
		case SCREEN_MODE: {
				src = 255 - INT_MULT(255 - dst, 255 - src);
				src_a = KMIN(src_a, dst_a);
			}
			break;
		case OVERLAY_MODE: {
				src = INT_MULT( dst, dst + INT_MULT(2 * src, 255 - dst));
				src_a = KMIN(src_a, dst_a);
			}
			break;
		case DIFFERENCE_MODE: {
				src = dst > src ? dst - src : src - dst;
				src_a = KMIN(src_a, dst_a);
			}
			break;
		case ADDITION_MODE: {
				src = add_lut(dst,src);
				src_a = KMIN(src_a, dst_a);
			}
			break;
		case SUBTRACT_MODE: {
				src = dst > src ? dst - src : 0;
				src_a = KMIN(src_a, dst_a);
			}
			break;
		case DARKEN_ONLY_MODE: {
				src = dst < src ? dst : src;
				src_a = KMIN(src_a, dst_a);
			}
			break;
		case LIGHTEN_ONLY_MODE: {
				src = dst < src ? src : dst;
				src_a = KMIN(src_a, dst_a);
			}
			break;
	}

	src_a = INT_MULT(src_a, layer.opacity);

	// Apply the mask (if any)
	if (layer.apply_mask == 1 && layer.mask_tiles.size() > j &&
			layer.mask_tiles[j].size() > i)
		src_a = INT_MULT(src_a, layer.mask_tiles[j][i].pixelIndex(k, l));

	uchar new_a = dst_a + INT_MULT(OPAQUE_OPACITY - dst_a, src_a);

	float src_ratio = (float)src_a / new_a;
	float dst_ratio = 1.0 - src_ratio;

	uchar new_g = (uchar)(src_ratio * src + dst_ratio * dst + EPSILON);

	if (!layer_modes[layer.mode].affect_alpha)
		new_a = dst_a;

	image.setPixel(m, n, tqRgba(new_g, new_g, new_g, new_a));
}


/*!
 * Merge an Indexed pixel from the layer to the Indexed image. Straight-forward.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::mergeIndexedToIndexed(Layer& layer, uint i, uint j, int k, int l,
		TQImage& image, int m, int n)
{
	int src = layer.image_tiles[j][i].pixelIndex(k, l);
	image.setPixel(m, n, src);
}


/*!
 * Merge an IndexedA pixel from the layer to the Indexed image. Straight-forward.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::mergeIndexedAToIndexed(Layer& layer, uint i, uint j, int k, int l,
		TQImage& image, int m, int n)
{
	uchar src = layer.image_tiles[j][i].pixelIndex(k, l);
	uchar src_a = layer.alpha_tiles[j][i].pixelIndex(k, l);
	src_a = INT_MULT( src_a, layer.opacity );

	if ( layer.apply_mask == 1 &&
			layer.mask_tiles.size() > j &&
			layer.mask_tiles[j].size() > i)
		src_a = INT_MULT(src_a, layer.mask_tiles[j][i].pixelIndex(k, l));

	if (src_a > 127) {
		src++;
		image.setPixel(m, n, src);
	}
}


/*!
 * Merge an IndexedA pixel from the layer to an RGB image. Straight-forward.
 * The only thing this has to take account of is the opacity of the
 * layer. Evidently, the GIMP exporter itself does not actually do this.
 * \param layer source layer.
 * \param i x tile index.
 * \param j y tile index.
 * \param k x pixel index of tile i,j.
 * \param l y pixel index of tile i,j.
 * \param image destination image.
 * \param m x pixel of destination image.
 * \param n y pixel of destination image.
 */
void XCFImageFormat::mergeIndexedAToRGB(Layer& layer, uint i, uint j, int k, int l,
		TQImage& image, int m, int n)
{
	QRgb src = layer.image_tiles[j][i].pixel(k, l);
	uchar src_a = layer.alpha_tiles[j][i].pixelIndex(k, l);
	src_a = INT_MULT(src_a, layer.opacity);

	// Apply the mask (if any)
	if (layer.apply_mask == 1 && layer.mask_tiles.size() > j &&
			layer.mask_tiles[j].size() > i)
		src_a = INT_MULT(src_a, layer.mask_tiles[j][i].pixelIndex(k, l));

	// This is what appears in the GIMP window
	if (src_a <= 127)
		src_a = 0;
	else
		src_a = OPAQUE_OPACITY;

	image.setPixel(m, n, tqRgba(src, src_a));
}


/*!
 * Dissolving pixels: pick a random number between 0 and 255. If the pixel's
 * alpha is less than that, make it transparent.
 * \param image the image tile to dissolve.
 * \param x the global x position of the tile.
 * \param y the global y position of the tile.
 */
void XCFImageFormat::dissolveRGBPixels ( TQImage& image, int x, int y )
{
	// The apparently spurious rand() calls are to wind the random
	// numbers up to the same point for each tile.

	for (int l = 0; l < image.height(); l++) {
		srand(random_table[( l + y ) % RANDOM_TABLE_SIZE]);

		for (int k = 0; k < x; k++)
			rand();

		for (int k = 0; k < image.width(); k++) {
			int rand_val = rand() & 0xff;
			QRgb pixel = image.pixel(k, l);

			if (rand_val > tqAlpha(pixel)) {
				image.setPixel(k, l, tqRgba(pixel, 0));
			}
		}
	}
}


/*!
 * Dissolving pixels: pick a random number between 0 and 255. If the pixel's
 * alpha is less than that, make it transparent. This routine works for
 * the GRAYA and INDEXEDA image types where the pixel alpha's are stored
 * separately from the pixel themselves.
 * \param image the alpha tile to dissolve.
 * \param x the global x position of the tile.
 * \param y the global y position of the tile.
 */
void XCFImageFormat::dissolveAlphaPixels ( TQImage& image, int x, int y )
{
	// The apparently spurious rand() calls are to wind the random
	// numbers up to the same point for each tile.

	for (int l = 0; l < image.height(); l++) {
		srand( random_table[(l + y) % RANDOM_TABLE_SIZE]);

		for (int k = 0; k < x; k++)
			rand();

		for (int k = 0; k < image.width(); k++) {
			int rand_val = rand() & 0xff;
			uchar alpha = image.pixelIndex(k, l);

			if (rand_val > alpha) {
				image.setPixel(k, l, 0);
			}
		}
	}
}