xcf.cpp

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/*
 * 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 "xcf.h"

#include <stdlib.h>
#include <QtGui/QImage>
#include <QtGui/QPainter>
#include <QtCore/QIODevice>
#include <QtCore/QStack>
#include <QtCore/QVector>

#include <kdebug.h>


int XCFImageFormat::random_table[RANDOM_TABLE_SIZE];
bool XCFImageFormat::random_table_initialized;

QVector<QRgb> XCFImageFormat::grayTable;


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
    {false},    // DODGE_MODE
    {false},    // BURN_MODE
    {false},    // HARDLIGHT_MODE
    {false},    // SOFTLIGHT_MODE
    {false},    // GRAIN_EXTRACT_MODE
    {false},    // GRAIN_MERGE_MODE
};


inline QRgb qRgba ( const QRgb& rgb, int a )
{
    return ((a & 0xff) << 24 | (rgb & RGB_MASK));
}


XCFImageFormat::XCFImageFormat()
{
}

void XCFImageFormat::initializeRandomTable()
{
    // 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;
    }
}

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

bool XCFImageFormat::readXCF(QIODevice *device, QImage *outImage)
{
    XCFImage xcf_image;
    QDataStream xcf_io(device);

    char tag[14];;

    if (xcf_io.readRawData(tag, sizeof(tag)) != sizeof(tag)) {
            kDebug(399) << "XCF: read failure on header tag";
            return false;
    }
    if (qstrncmp(tag, "gimp xcf", 8) != 0) {
            kDebug(399) << "XCF: read called on non-XCF file";
            return false;
    }

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

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

    // 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).

    QStack<qint32> layer_offsets;

    while (true) {
        qint32 layer_offset;

        xcf_io >> layer_offset;

        if (layer_offset == 0)
            break;

        layer_offsets.push(layer_offset);
    }

    xcf_image.num_layers = layer_offsets.size();

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

    // Load each layer and add it to the image
    while (!layer_offsets.isEmpty()) {
        qint32 layer_offset = layer_offsets.pop();

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

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

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

        *outImage = xcf_image.image;
        return true;
}


bool XCFImageFormat::loadImageProperties(QDataStream& xcf_io, XCFImage& xcf_image)
{
    while (true) {
        PropType type;
        QByteArray bytes;

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

        QDataStream property(bytes);

        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;
                    quint32 size;

                    property.readBytes(tag, size);

                    quint32 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( qRgb(r,g,b) );
                    }
                    break;

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


bool XCFImageFormat::loadProperty(QDataStream& xcf_io, PropType& type, QByteArray& bytes)
{
    quint32 foo;
    xcf_io >> foo;
    type=PropType(foo); // TODO urks

    char* data = 0;
    quint32 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;
                quint32 ncolors;
                xcf_io >> ncolors;

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

        size = 3 * ncolors + 4;
        data = new char[size];

                // since we already read "ncolors" from the stream, we put that data back
                data[0] = 0;
                data[1] = 0;
                data[2] = ncolors >> 8;
                data[3] = ncolors & 255;

                // ... and read the remaining bytes from the stream
        xcf_io.readRawData(data + 4, size - 4);
    } else if (type == PROP_USER_UNIT) {
        // The USER UNIT property size is not correct. I'm not sure why, though.
        float factor;
        qint32 digits;

        xcf_io >> size >> factor >> digits;

        for (int i = 0; i < 5; i++) {
            char* unit_strings;

            xcf_io >> unit_strings;

            delete[] unit_strings;

            if (xcf_io.device()->atEnd()) {
                kDebug(399) << "XCF: read failure on property " << type;
                return false;
            }
        }

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

    if (size != 0 && data)
            bytes = QByteArray(data,size);
    
        delete [] data;

    return true;
}


bool XCFImageFormat::loadLayer(QDataStream& xcf_io, XCFImage& xcf_image)
{
    Layer& layer(xcf_image.layer);
    delete[] layer.name;

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

    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 QImage.

    xcf_io >> layer.hierarchy_offset >> layer.mask_offset;

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

    if( !composeTiles(xcf_image))
        return false;
    xcf_io.device()->seek(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()->seek(layer.mask_offset);

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

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

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

    return true;
}


bool XCFImageFormat::loadLayerProperties(QDataStream& xcf_io, Layer& layer)
{
    while (true) {
        PropType type;
        QByteArray bytes;

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

        QDataStream property(bytes);

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


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;

        //kDebug(399) << "IMAGE: height=" << xcf_image.height << ", width=" << xcf_image.width;
        //kDebug(399) << "LAYER: height=" << layer.height << ", width=" << layer.width;
        //kDebug(399) << "LAYER: rows=" << layer.nrows << ", columns=" << layer.ncols;
        
        // SANITY CHECK: Catch corrupted XCF image file where the width or height
        // of a tile is reported are bogus. See Bug# 234030.
        if (layer.height > xcf_image.height || layer.width > xcf_image.width)
              return false;
       
    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 QImage (each GIMP layer
            // type is treated slightly differently)

            switch (layer.type) {
                case RGB_GIMAGE:
                    layer.image_tiles[j][i] = QImage(tile_width, tile_height, QImage::Format_RGB32);
                    layer.image_tiles[j][i].setNumColors(0);
                    if( layer.image_tiles[j][i].isNull())
                        return false;
                    break;

                case RGBA_GIMAGE:
                    layer.image_tiles[j][i] = QImage(tile_width, tile_height, QImage::Format_ARGB32);
                    layer.image_tiles[j][i].setNumColors(0);
                    if( layer.image_tiles[j][i].isNull())
                        return false;
                    break;

                case GRAY_GIMAGE:
                    layer.image_tiles[j][i] = QImage(tile_width, tile_height, QImage::Format_Indexed8);
                    layer.image_tiles[j][i].setNumColors(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] = QImage(tile_width, tile_height, QImage::Format_Indexed8);
                    layer.image_tiles[j][i].setNumColors(256);
                    if( layer.image_tiles[j][i].isNull())
                        return false;
                    setGrayPalette(layer.image_tiles[j][i]);

                    layer.alpha_tiles[j][i] = QImage(tile_width, tile_height, QImage::Format_Indexed8);
                    layer.alpha_tiles[j][i].setNumColors(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] = QImage(tile_width, tile_height, QImage::Format_Indexed8);
                    layer.image_tiles[j][i].setNumColors(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] = QImage(tile_width, tile_height, QImage::Format_Indexed8);
                    layer.image_tiles[j][i].setNumColors(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] = QImage(tile_width, tile_height, QImage::Format_Indexed8);
                    layer.alpha_tiles[j][i].setNumColors(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] = QImage(tile_width, tile_height, QImage::Format_Indexed8);
                layer.mask_tiles[j][i].setNumColors(256);
                if( layer.mask_tiles[j][i].isNull())
                    return false;
                setGrayPalette(layer.mask_tiles[j][i]);
            }
        }
    }
    return true;
}


void XCFImageFormat::setGrayPalette(QImage& image)
{
    if (grayTable.isEmpty()) {
        grayTable.resize(256);

        for (int i = 0; i < 256; i++)
            grayTable[i] = qRgb(i, i, i);
    }

    image.setColorTable(grayTable);
}


void XCFImageFormat::setPalette(XCFImage& xcf_image, QImage& image)
{
    Q_ASSERT (xcf_image.num_colors == xcf_image.palette.size());

    image.setColorTable(xcf_image.palette);
}


void XCFImageFormat::assignImageBytes(Layer& layer, uint i, uint j)
{
    QImage &image = layer.image_tiles[j][i];
    uchar* tile = layer.tile;
    const int width = image.width();
    const int height = image.height();
    const int bytesPerLine = image.bytesPerLine();
    uchar *bits = image.bits();

    switch (layer.type) {
        case RGB_GIMAGE:
            for (int y = 0; y < height; y++) {
                QRgb *dataPtr = (QRgb *) (bits + y * bytesPerLine);
                for (int x = 0; x < width; x++) {
                    *dataPtr++ = qRgb(tile[0], tile[1], tile[2]);
                    tile += sizeof(QRgb);
                }
            }
            break;

        case RGBA_GIMAGE:
            for (int y = 0; y < height; y++) {
                QRgb *dataPtr = (QRgb *) (bits + y * bytesPerLine);
                for (int x = 0; x < width; x++) {
                    *dataPtr++ =    qRgba(tile[0], tile[1], tile[2], tile[3]);
                    tile += sizeof(QRgb);
                }
            }
            break;

        case GRAY_GIMAGE:
        case INDEXED_GIMAGE:
            for (int y = 0; y < height; y++) {
                uchar *dataPtr = bits + y * bytesPerLine;
                for (int x = 0; x < width; x++) {
                    *dataPtr++ = tile[0];
                    tile += sizeof(QRgb);
                }
            }
            break;

        case GRAYA_GIMAGE:
        case INDEXEDA_GIMAGE:
            for (int y = 0; y < height; y++) {
                uchar *dataPtr = bits + y * bytesPerLine;
                uchar *alphaPtr = layer.alpha_tiles[j][i].scanLine(y);
                for (int x = 0; x < width; x++) {

                // 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] < image.numColors())
                        *dataPtr = tile[0];

                    *alphaPtr = tile[1];
                    dataPtr += 1;
                    alphaPtr += 1;
                    tile += sizeof(QRgb);
                }
            }
            break;
    }
}


bool XCFImageFormat::loadHierarchy(QDataStream& xcf_io, Layer& layer)
{
    qint32 width;
    qint32 height;
    qint32 bpp;
    quint32 offset;

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

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

    quint32 junk;
    do {
        xcf_io >> junk;

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

    qint64 saved_pos = xcf_io.device()->pos();

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

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


bool XCFImageFormat::loadLevel(QDataStream& xcf_io, Layer& layer, qint32 bpp)
{
    qint32 width;
    qint32 height;
    quint32 offset;

    xcf_io >> width >> height >> offset;

    if (offset == 0)
        return true;

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

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

            qint64 saved_pos = xcf_io.device()->pos();
            quint32 offset2;
            xcf_io >> offset2;

            // 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()->seek(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 QImage. The caller has set layer.assignBytes to the
            // appropriate routine.

            layer.assignBytes(layer, i, j);

            xcf_io.device()->seek(saved_pos);
            xcf_io >> offset;
        }
    }

    return true;
}


bool XCFImageFormat::loadMask(QDataStream& xcf_io, Layer& layer)
{
    qint32 width;
    qint32 height;
    char* name;

    xcf_io >> width >> height >> name;

    delete name;

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

    quint32 hierarchy_offset;
    xcf_io >> hierarchy_offset;

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

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

    return true;
}


bool XCFImageFormat::loadTileRLE(QDataStream& xcf_io, uchar* tile, int image_size,
        int data_length, qint32 bpp)
{
    uchar* data;

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

    if (data_length < 0 || data_length > int(TILE_WIDTH * TILE_HEIGHT * 4 * 1.5)) {
        kDebug(399) << "XCF: invalid tile data length" << data_length;
        return false;
    }

    xcfdata = xcfodata = new uchar[data_length];

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

    if (!xcf_io.device()->isOpen()) {
        delete[] xcfodata;
        kDebug(399) << "XCF: read failure on tile";
        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:

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


bool XCFImageFormat::loadChannelProperties(QDataStream& xcf_io, Layer& layer)
{
    while (true) {
        PropType type;
        QByteArray bytes;

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

        QDataStream property(bytes);

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


void XCFImageFormat::assignMaskBytes(Layer& layer, uint i, uint j)
{
    QImage &image = layer.mask_tiles[j][i];
    uchar* tile = layer.tile;
    const int width = image.width();
    const int height = image.height();
    const int bytesPerLine = image.bytesPerLine();
    uchar *bits = image.bits();

    for (int y = 0; y < height; y++) {
        uchar *dataPtr = bits + y * bytesPerLine;
        for (int x = 0; x < width; x++) {
            *dataPtr++ = tile[0];
            tile += sizeof(QRgb);
        }
    }
}


bool XCFImageFormat::initializeImage(XCFImage& xcf_image)
{
    // (Aliases to make the code look a little better.)
    Layer& layer(xcf_image.layer);
    QImage& image(xcf_image.image);

    switch (layer.type) {
        case RGB_GIMAGE:
            if (layer.opacity == OPAQUE_OPACITY) {
                image = QImage( xcf_image.width, xcf_image.height, QImage::Format_RGB32);
                if( image.isNull())
                    return false;
                image.fill(qRgb(255, 255, 255));
                break;
            } // else, fall through to 32-bit representation

        case RGBA_GIMAGE:
            image = QImage(xcf_image.width, xcf_image.height, QImage::Format_ARGB32);
            if( image.isNull())
                return false;
            image.fill(qRgba(255, 255, 255, 0));
            break;

        case GRAY_GIMAGE:
            if (layer.opacity == OPAQUE_OPACITY) {
                image = QImage(xcf_image.width, xcf_image.height, QImage::Format_Indexed8);
                image.setNumColors(256);
                if( image.isNull())
                    return false;
                setGrayPalette(image);
                image.fill(255);
                break;
            } // else, fall through to 32-bit representation

        case GRAYA_GIMAGE:
            image = QImage(xcf_image.width, xcf_image.height, QImage::Format_ARGB32);
            if( image.isNull())
                return false;
            image.fill(qRgba(255, 255, 255, 0));
            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
            // presence 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 = QImage(xcf_image.width, xcf_image.height, QImage::Format_MonoLSB);
                image.setNumColors(xcf_image.num_colors);
                if( image.isNull())
                    return false;
                image.fill(0);
                setPalette(xcf_image, image);
            } else if (xcf_image.num_colors <= 256) {
                image = QImage(xcf_image.width, xcf_image.height, QImage::Format_Indexed8);
                image.setNumColors(xcf_image.num_colors);
                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] = qRgba(255, 255, 255, 0);

                image = QImage(xcf_image.width, xcf_image.height, QImage::Format_MonoLSB);
                image.setNumColors(xcf_image.num_colors);
                if( image.isNull())
                    return false;
                image.fill(0);
                setPalette(xcf_image, image);
            } 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] = qRgba(255, 255, 255, 0);
                image = QImage( xcf_image.width, xcf_image.height, QImage::Format_Indexed8);
                image.setNumColors(xcf_image.num_colors);
                if( image.isNull())
                    return false;
                image.fill(0);
                setPalette(xcf_image, image);
            } 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 = QImage(xcf_image.width, xcf_image.height, QImage::Format_ARGB32);
                if( image.isNull())
                    return false;
                image.fill(qRgba(255, 255, 255, 0));
            }
            break;
    }

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


void XCFImageFormat::copyLayerToImage(XCFImage& xcf_image)
{
    Layer& layer(xcf_image.layer);
    QImage& 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;
    }

    if (!copy) {
        return;
    }

    // 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 (!random_table_initialized) {
                    initializeRandomTable();
                    random_table_initialized = true;
                }
                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);
            }

            // Shortcut for common case
            if (copy == copyRGBToRGB && layer.apply_mask != 1) {
                QPainter painter(&image);
                painter.setOpacity(layer.opacity / 255.0);
                painter.setCompositionMode(QPainter::CompositionMode_Source);
                painter.drawImage(x + layer.x_offset, y + layer.y_offset, layer.image_tiles[j][i]);
                continue;
            }

            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);
                }
            }
        }
    }
}


void XCFImageFormat::copyRGBToRGB(Layer& layer, uint i, uint j, int k, int l,
        QImage& 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, qAlpha(src));

    // Apply the mask (if any)

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

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


void XCFImageFormat::copyGrayToGray(Layer& layer, uint i, uint j, int k, int l,
        QImage& image, int m, int n)
{
    int src = layer.image_tiles[j][i].pixelIndex(k, l);
    image.setPixel(m, n, src);
}


void XCFImageFormat::copyGrayToRGB(Layer& layer, uint i, uint j, int k, int l,
        QImage& image, int m, int n)
{
    QRgb src = layer.image_tiles[j][i].pixel(k, l);
    uchar src_a = layer.opacity;
    image.setPixel(m, n, qRgba(src, src_a));
}


void XCFImageFormat::copyGrayAToRGB(Layer& layer, uint i, uint j, int k, int l,
                      QImage& 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() > (int)j &&
            layer.mask_tiles[j].size() > (int)i)
        src_a = INT_MULT(src_a, layer.mask_tiles[j][i].pixelIndex(k, l));

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


void XCFImageFormat::copyIndexedToIndexed(Layer& layer, uint i, uint j, int k, int l,
        QImage& image, int m, int n)
{
    int src = layer.image_tiles[j][i].pixelIndex(k, l);
    image.setPixel(m, n, src);
}


void XCFImageFormat::copyIndexedAToIndexed(Layer& layer, uint i, uint j, int k, int l,
        QImage& 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() > (int)j &&
            layer.mask_tiles[j].size() > (int)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);
}


void XCFImageFormat::copyIndexedAToRGB(Layer& layer, uint i, uint j, int k, int l,
        QImage& 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() > (int)j &&
            layer.mask_tiles[j].size() > (int)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, qRgba(src, src_a));
}


void XCFImageFormat::mergeLayerIntoImage(XCFImage& xcf_image)
{
    Layer& layer(xcf_image.layer);
    QImage& image(xcf_image.image);

    PixelMergeOperation merge = 0;

    if (!layer.opacity) return; // don't bother doing anything

    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;
    }

    if (!merge) {
        return;
    }

    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 (!random_table_initialized) {
                    initializeRandomTable();
                    random_table_initialized = true;
                }
                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);
            }

            // Shortcut for common case
            if (merge == mergeRGBToRGB && layer.apply_mask != 1
                && layer.mode == NORMAL_MODE) {
                QPainter painter(&image);
                painter.setOpacity(layer.opacity / 255.0);
                painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
                painter.drawImage(x + layer.x_offset, y + layer.y_offset, layer.image_tiles[j][i]);
                continue;
            }

            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);
                }
            }
        }
    }
}


void XCFImageFormat::mergeRGBToRGB(Layer& layer, uint i, uint j, int k, int l,
        QImage& image, int m, int n)
{
    QRgb src = layer.image_tiles[j][i].pixel(k, l);
    QRgb dst = image.pixel(m, n);

    uchar src_r = qRed(src);
    uchar src_g = qGreen(src);
    uchar src_b = qBlue(src);
    uchar src_a = qAlpha(src);

    uchar dst_r = qRed(dst);
    uchar dst_g = qGreen(dst);
    uchar dst_b = qBlue(dst);
    uchar dst_a = qAlpha(dst);

    if (!src_a) return; // nothing to merge

    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 = qMin(src_a, dst_a);
            }
            break;
        case DIVIDE_MODE: {
            src_r = qMin((dst_r * 256) / (1 + src_r), 255);
            src_g = qMin((dst_g * 256) / (1 + src_g), 255);
            src_b = qMin((dst_b * 256) / (1 + src_b), 255);
            src_a = qMin(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 = qMin(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 = qMin(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 = qMin(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 = qMin(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 = qMin(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 = qMin( 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 = qMin(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 = qMin( 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 = qMin(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 = qMin(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 = qMin(src_a, dst_a);
            }
            break;
        case DODGE_MODE: {
            uint tmp;

            tmp = dst_r << 8;
            tmp /= 256 - src_r;
            src_r = (uchar) qMin(tmp, 255u);

            tmp = dst_g << 8;
            tmp /= 256 - src_g;
            src_g = (uchar) qMin(tmp, 255u);

            tmp = dst_b << 8;
            tmp /= 256 - src_b;
            src_b = (uchar) qMin(tmp, 255u);

            src_a = qMin(src_a, dst_a);
            }
            break;
        case BURN_MODE: {
            uint tmp;

            tmp = (255 - dst_r) << 8;
            tmp /= src_r + 1;
            src_r = (uchar) qMin(tmp, 255u);
            src_r = 255 - src_r;

            tmp = (255 - dst_g) << 8;
            tmp /= src_g + 1;
            src_g = (uchar) qMin(tmp, 255u);
            src_g = 255 - src_g;

            tmp = (255 - dst_b) << 8;
            tmp /= src_b + 1;
            src_b = (uchar) qMin(tmp, 255u);
            src_b = 255 - src_b;

            src_a = qMin(src_a, dst_a);
            }
            break;
        case HARDLIGHT_MODE: {
            uint tmp;
            if (src_r > 128) {
                tmp = ((int)255-dst_r) * ((int) 255 - ((src_r-128) << 1));
                src_r = (uchar) qMin(255 - (tmp >> 8), 255u);
            } else {
                tmp = (int) dst_r * ((int) src_r << 1);
                src_r = (uchar) qMin(tmp >> 8, 255u);
            }

            if (src_g > 128) {
                tmp = ((int)255-dst_g) * ((int) 255 - ((src_g-128) << 1));
                src_g = (uchar) qMin(255 - (tmp >> 8), 255u);
            } else {
                tmp = (int) dst_g * ((int) src_g << 1);
                src_g = (uchar) qMin(tmp >> 8, 255u);
            }

            if (src_b > 128) {
                tmp = ((int)255-dst_b) * ((int) 255 - ((src_b-128) << 1));
                src_b = (uchar) qMin(255 - (tmp >> 8), 255u);
            } else {
                tmp = (int) dst_b * ((int) src_b << 1);
                src_b = (uchar) qMin(tmp >> 8, 255u);
            }
            src_a = qMin(src_a, dst_a);
            }
            break;
        case SOFTLIGHT_MODE: {
            uint tmpS, tmpM;

            tmpM = INT_MULT(dst_r, src_r);
            tmpS = 255 - INT_MULT((255 - dst_r), (255-src_r));
            src_r = INT_MULT((255 - dst_r), tmpM)
                + INT_MULT(dst_r, tmpS);

            tmpM = INT_MULT(dst_g, src_g);
            tmpS = 255 - INT_MULT((255 - dst_g), (255-src_g));
            src_g = INT_MULT((255 - dst_g), tmpM)
                + INT_MULT(dst_g, tmpS);

            tmpM = INT_MULT(dst_b, src_b);
            tmpS = 255 - INT_MULT((255 - dst_b), (255-src_b));
            src_b = INT_MULT((255 - dst_b), tmpM)
                + INT_MULT(dst_b, tmpS);

            src_a = qMin(src_a, dst_a);
            }
            break;
        case GRAIN_EXTRACT_MODE: {
            int tmp;
            
            tmp = dst_r - src_r + 128;
            tmp = qMin(tmp, 255);
            tmp = qMax(tmp, 0);
            src_r = (uchar) tmp;

            tmp = dst_g - src_g + 128;
            tmp = qMin(tmp, 255);
            tmp = qMax(tmp, 0);
            src_g = (uchar) tmp;

            tmp = dst_b - src_b + 128;
            tmp = qMin(tmp, 255);
            tmp = qMax(tmp, 0);
            src_b = (uchar) tmp;

            src_a = qMin(src_a, dst_a);
            }
            break;
        case GRAIN_MERGE_MODE: {
            int tmp;
            
            tmp = dst_r + src_r - 128;
            tmp = qMin(tmp, 255);
            tmp = qMax(tmp, 0);
            src_r = (uchar) tmp;

            tmp = dst_g + src_g - 128;
            tmp = qMin(tmp, 255);
            tmp = qMax(tmp, 0);
            src_g = (uchar) tmp;

            tmp = dst_b + src_b - 128;
            tmp = qMin(tmp, 255);
            tmp = qMax(tmp, 0);
            src_b = (uchar) tmp;

            src_a = qMin(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() > (int)j &&
            layer.mask_tiles[j].size() > (int)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, qRgba(new_r, new_g, new_b, new_a));
}


void XCFImageFormat::mergeGrayToGray(Layer& layer, uint i, uint j, int k, int l,
        QImage& image, int m, int n)
{
    int src = layer.image_tiles[j][i].pixelIndex(k, l);
    image.setPixel(m, n, src);
}


void XCFImageFormat::mergeGrayAToGray(Layer& layer, uint i, uint j, int k, int l,
        QImage& image, int m, int n)
{
    int src = qGray(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);

    if (!src_a) return; // nothing to merge

    switch (layer.mode) {
        case MULTIPLY_MODE: {
                src = INT_MULT( src, dst );
            }
            break;
        case DIVIDE_MODE: {
                src = qMin((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;
        case DODGE_MODE: {
                uint tmp = dst << 8;
                tmp /= 256 - src;
                src = (uchar) qMin(tmp, 255u);
            }
            break;
        case BURN_MODE: {
                uint tmp = (255-dst) << 8;
                tmp /= src + 1;
                src = (uchar) qMin(tmp, 255u);
                src = 255 - src;
            }
            break;
        case HARDLIGHT_MODE: {
                uint tmp;
                if (src > 128) {
                    tmp = ((int)255-dst) * ((int) 255 - ((src-128) << 1));
                    src = (uchar) qMin(255 - (tmp >> 8), 255u);
                } else {
                    tmp = (int) dst * ((int) src << 1);
                    src = (uchar) qMin(tmp >> 8, 255u);
                }
            }
            break;
        case SOFTLIGHT_MODE: {
                uint tmpS, tmpM;

                tmpM = INT_MULT(dst, src);
                tmpS = 255 - INT_MULT((255-dst), (255-src));
                src = INT_MULT((255 - dst), tmpM)
                    + INT_MULT(dst, tmpS);

            }
            break;
        case GRAIN_EXTRACT_MODE: {
                int tmp;
                
                tmp = dst - src + 128;
                tmp = qMin(tmp, 255);
                tmp = qMax(tmp, 0);

                src = (uchar) tmp;
            }
            break;
        case GRAIN_MERGE_MODE: {
                int tmp;
                
                tmp = dst + src - 128;
                tmp = qMin(tmp, 255);
                tmp = qMax(tmp, 0);

                src = (uchar) tmp;
            }
            break;
    }

    src_a = INT_MULT(src_a, layer.opacity);

    // Apply the mask (if any)

    if (layer.apply_mask == 1 && layer.mask_tiles.size() > (int)j &&
            layer.mask_tiles[j].size() > (int)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);
}


void XCFImageFormat::mergeGrayToRGB(Layer& layer, uint i, uint j, int k, int l,
        QImage& image, int m, int n)
{
    QRgb src = layer.image_tiles[j][i].pixel(k, l);
    uchar src_a = layer.opacity;
    image.setPixel(m, n, qRgba(src, src_a));
}


void XCFImageFormat::mergeGrayAToRGB(Layer& layer, uint i, uint j, int k, int l,
        QImage& image, int m, int n)
{
    int src = qGray(layer.image_tiles[j][i].pixel(k, l));
    int dst = qGray(image.pixel(m, n));

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

    if (!src_a) return; // nothing to merge

    switch (layer.mode) {
        case MULTIPLY_MODE: {
                src = INT_MULT(src, dst);
                src_a = qMin(src_a, dst_a);
            }
            break;
        case DIVIDE_MODE: {
                src = qMin((dst * 256) / (1 + src), 255);
                src_a = qMin(src_a, dst_a);
            }
            break;
        case SCREEN_MODE: {
                src = 255 - INT_MULT(255 - dst, 255 - src);
                src_a = qMin(src_a, dst_a);
            }
            break;
        case OVERLAY_MODE: {
                src = INT_MULT( dst, dst + INT_MULT(2 * src, 255 - dst));
                src_a = qMin(src_a, dst_a);
            }
            break;
        case DIFFERENCE_MODE: {
                src = dst > src ? dst - src : src - dst;
                src_a = qMin(src_a, dst_a);
            }
            break;
        case ADDITION_MODE: {
                src = add_lut(dst,src);
                src_a = qMin(src_a, dst_a);
            }
            break;
        case SUBTRACT_MODE: {
                src = dst > src ? dst - src : 0;
                src_a = qMin(src_a, dst_a);
            }
            break;
        case DARKEN_ONLY_MODE: {
                src = dst < src ? dst : src;
                src_a = qMin(src_a, dst_a);
            }
            break;
        case LIGHTEN_ONLY_MODE: {
                src = dst < src ? src : dst;
                src_a = qMin(src_a, dst_a);
            }
            break;
        case DODGE_MODE: {
                uint tmp = dst << 8;
                tmp /= 256 - src;
                src = (uchar) qMin(tmp, 255u);
                src_a = qMin(src_a, dst_a);
            }
            break;
        case BURN_MODE: {
                uint tmp = (255-dst) << 8;
                tmp /= src + 1;
                src = (uchar) qMin(tmp, 255u);
                src = 255 - src;
                src_a = qMin(src_a, dst_a);
            }
            break;
        case HARDLIGHT_MODE: {
                uint tmp;
                if (src > 128) {
                    tmp = ((int)255-dst) * ((int) 255 - ((src-128) << 1));
                    src = (uchar) qMin(255 - (tmp >> 8), 255u);
                } else {
                    tmp = (int) dst * ((int) src << 1);
                    src = (uchar) qMin(tmp >> 8, 255u);
                }
                src_a = qMin(src_a, dst_a);
            }
            break;
        case SOFTLIGHT_MODE: {
                uint tmpS, tmpM;

                tmpM = INT_MULT(dst, src);
                tmpS = 255 - INT_MULT((255 - dst), (255-src));
                src = INT_MULT((255 - dst), tmpM)
                    + INT_MULT(dst, tmpS);

                src_a = qMin(src_a, dst_a);
            }
            break;
        case GRAIN_EXTRACT_MODE: {
                int tmp;
                
                tmp = dst - src + 128;
                tmp = qMin(tmp, 255);
                tmp = qMax(tmp, 0);

                src = (uchar) tmp;
                src_a = qMin(src_a, dst_a);
            }
            break;
        case GRAIN_MERGE_MODE: {
                int tmp;
                
                tmp = dst + src - 128;
                tmp = qMin(tmp, 255);
                tmp = qMax(tmp, 0);

                src = (uchar) tmp;
                src_a = qMin(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() > (int)j &&
            layer.mask_tiles[j].size() > (int)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, qRgba(new_g, new_g, new_g, new_a));
}


void XCFImageFormat::mergeIndexedToIndexed(Layer& layer, uint i, uint j, int k, int l,
        QImage& image, int m, int n)
{
    int src = layer.image_tiles[j][i].pixelIndex(k, l);
    image.setPixel(m, n, src);
}


void XCFImageFormat::mergeIndexedAToIndexed(Layer& layer, uint i, uint j, int k, int l,
        QImage& 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() > (int)j &&
            layer.mask_tiles[j].size() > (int)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);
    }
}


void XCFImageFormat::mergeIndexedAToRGB(Layer& layer, uint i, uint j, int k, int l,
        QImage& 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() > (int)j &&
            layer.mask_tiles[j].size() > (int)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, qRgba(src, src_a));
}


void XCFImageFormat::dissolveRGBPixels ( QImage& 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 > qAlpha(pixel)) {
                image.setPixel(k, l, qRgba(pixel, 0));
            }
        }
    }
}


void XCFImageFormat::dissolveAlphaPixels ( QImage& 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);
            }
        }
    }
}



XCFHandler::XCFHandler()
{
}

bool XCFHandler::canRead() const
{
    if (canRead(device())) {
        setFormat("xcf");
        return true;
    }
    return false;
}

bool XCFHandler::read(QImage *image)
{
    XCFImageFormat xcfif;
    return xcfif.readXCF(device(), image);
}

bool XCFHandler::write(const QImage &)
{
    return false;
}

QByteArray XCFHandler::name() const
{
    return "xcf";
}

bool XCFHandler::canRead(QIODevice *device)
{
      if (!device) {
        qWarning("DDSHandler::canRead() called with no device");
        return false;
    }

    qint64 oldPos = device->pos();

    char head[8];
    qint64 readBytes = device->read(head, sizeof(head));
    if (readBytes != sizeof(head)) {
        if (device->isSequential()) {
            while (readBytes > 0)
                device->ungetChar(head[readBytes-- - 1]);
        } else {
            device->seek(oldPos);
        }
        return false;
    }

    if (device->isSequential()) {
        while (readBytes > 0)
            device->ungetChar(head[readBytes-- - 1]);
    } else {
        device->seek(oldPos);
    }

    return qstrncmp(head, "gimp xcf", 8) == 0;
}


class XCFPlugin : public QImageIOPlugin
{
public:
    QStringList keys() const;
    Capabilities capabilities(QIODevice *device, const QByteArray &format) const;
    QImageIOHandler *create(QIODevice *device, const QByteArray &format = QByteArray()) const;
};

QStringList XCFPlugin::keys() const
{
    return QStringList() << "xcf" << "XCF";
}

QImageIOPlugin::Capabilities XCFPlugin::capabilities(QIODevice *device, const QByteArray &format) const
{
    if (format == "xcf" || format == "XCF")
        return Capabilities(CanRead);
    if (!format.isEmpty())
        return 0;
    if (!device->isOpen())
        return 0;

    Capabilities cap;
    if (device->isReadable() && XCFHandler::canRead(device))
        cap |= CanRead;
    return cap;
}

QImageIOHandler *XCFPlugin::create(QIODevice *device, const QByteArray &format) const
{
    QImageIOHandler *handler = new XCFHandler;
    handler->setDevice(device);
    handler->setFormat(format);
    return handler;
}

Q_EXPORT_STATIC_PLUGIN(XCFPlugin)
Q_EXPORT_PLUGIN2(xcf,XCFPlugin)