qicohandler.cpp

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// Copyright (C) 2022 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
// Qt-Security score:critical reason:data-parser
 
/*!
    \class QtIcoHandler
    \since 4.4
    \brief The QtIcoHandler class provides support for the ICO image format.
    \internal
*/
 
 
 
#include "qicohandler.h"
#include <QtCore/qendian.h>
#include <private/qendian_p.h>
#include <QtGui/QImage>
#include <QtCore/QBuffer>
#include <QtCore/QFile>
#include <QtCore/QLoggingCategory>
#include <qvariant.h>
 
QT_BEGIN_NAMESPACE
 
Q_LOGGING_CATEGORY(lcIco, "qt.gui.imageio.ico")
 
namespace {
 
// These next two structs represent how the icon information is stored
// in an ICO file.
typedef struct
{
    quint8  bWidth;               // Width of the image
    quint8  bHeight;              // Height of the image (actual height, not times 2)
    quint8  bColorCount;          // Number of colors in image (0 if >=8bpp) [ not ture ]
    quint8  bReserved;            // Reserved
    quint16_le wPlanes;              // Color Planes
    quint16_le wBitCount;            // Bits per pixel
    quint32_le dwBytesInRes;         // how many bytes in this resource?
    quint32_le dwImageOffset;        // where in the file is this image
} ICONDIRENTRY, *LPICONDIRENTRY;
#define ICONDIRENTRY_SIZE 16
 
typedef struct
{
    quint16_le idReserved;   // Reserved
    quint16_le idType;       // resource type (1 for icons, 2 for cursors)
    quint16_le idCount;      // how many images?
    ICONDIRENTRY    idEntries[1]; // the entries for each image
} ICONDIR, *LPICONDIR;
#define ICONDIR_SIZE    6       // Exclude the idEntries field
 
typedef struct {                    // BMP information header
    quint32_le biSize;                // size of this struct
    quint32_le biWidth;               // pixmap width
    quint32_le biHeight;              // pixmap height     (specifies the combined height of the XOR and AND masks)
    quint16_le biPlanes;              // should be 1
    quint16_le biBitCount;            // number of bits per pixel
    quint32_le biCompression;         // compression method
    quint32_le biSizeImage;           // size of image
    quint32_le biXPelsPerMeter;       // horizontal resolution
    quint32_le biYPelsPerMeter;       // vertical resolution
    quint32_le biClrUsed;             // number of colors used
    quint32_le biClrImportant;        // number of important colors
} BMP_INFOHDR ,*LPBMP_INFOHDR;
#define BMP_INFOHDR_SIZE 40
 
}
 
class ICOReader
{
public:
    ICOReader(QIODevice * iodevice);
    int count();
    QImage iconAt(int index);
    static bool canRead(QIODevice *iodev);
 
    static QList<QImage> read(QIODevice *device);
 
    static bool write(QIODevice *device, const QList<QImage> &images);
 
    bool readIconEntry(int index, ICONDIRENTRY * iconEntry);
 
private:
    bool readHeader();
 
    bool readBMPHeader(quint32 imageOffset, BMP_INFOHDR * header);
    void findColorInfo(QImage & image);
    void readColorTable(QImage & image);
 
    void readBMP(QImage & image);
    void read1BitBMP(QImage & image);
    void read4BitBMP(QImage & image);
    void read8BitBMP(QImage & image);
    void read24_32BMP(QImage &image);
 
    struct IcoAttrib
    {
        int nbits;
        int ncolors;
        int h;
        int w;
        int depth;
    } icoAttrib;
 
    QIODevice * iod;
    qint64 startpos;
    bool headerRead;
    ICONDIR iconDir;
 
};
 
// Data readers and writers that takes care of alignment and endian stuff.
static bool readIconDirEntry(QIODevice *iodev, ICONDIRENTRY *iconDirEntry)
{
    if (iodev)
        return (iodev->read((char*)iconDirEntry, ICONDIRENTRY_SIZE) == ICONDIRENTRY_SIZE);
    return false;
}
 
static bool writeIconDirEntry(QIODevice *iodev, const ICONDIRENTRY &iconEntry)
{
    if (iodev)
        return iodev->write((char*)&iconEntry, ICONDIRENTRY_SIZE) == ICONDIRENTRY_SIZE;
    return false;
}
 
static bool readIconDir(QIODevice *iodev, ICONDIR *iconDir)
{
    if (iodev)
        return (iodev->read((char*)iconDir, ICONDIR_SIZE) == ICONDIR_SIZE);
    return false;
}
 
static bool writeIconDir(QIODevice *iodev, const ICONDIR &iconDir)
{
    if (iodev)
        return iodev->write((char*)&iconDir, 6) == 6;
    return false;
}
 
static bool readBMPInfoHeader(QIODevice *iodev, BMP_INFOHDR *pHeader)
{
    if (iodev)
        return (iodev->read((char*)pHeader, BMP_INFOHDR_SIZE) == BMP_INFOHDR_SIZE);
    return false;
}
 
static bool writeBMPInfoHeader(QIODevice *iodev, const BMP_INFOHDR &header)
{
    if (iodev)
        return iodev->write((char*)&header, BMP_INFOHDR_SIZE) == BMP_INFOHDR_SIZE;
    return false;
}
 
 
ICOReader::ICOReader(QIODevice * iodevice)
: iod(iodevice)
, startpos(0)
, headerRead(false)
{
}
 
 
int ICOReader::count()
{
    if (readHeader())
        return iconDir.idCount;
    return 0;
}
 
bool ICOReader::canRead(QIODevice *iodev)
{
    bool isProbablyICO = false;
    if (iodev) {
        qint64 oldPos = iodev->pos();
 
        ICONDIR ikonDir;
        if (readIconDir(iodev, &ikonDir)) {
            if (readIconDirEntry(iodev, &ikonDir.idEntries[0])) {
                // ICO format does not have a magic identifier, so we read 6 different values, which will hopefully be enough to identify the file.
                if (   ikonDir.idReserved == 0
                    && (ikonDir.idType == 1 || ikonDir.idType == 2)
                    && ikonDir.idEntries[0].bReserved == 0
                    && (ikonDir.idEntries[0].wPlanes <= 1 || ikonDir.idType == 2)
                    && (ikonDir.idEntries[0].wBitCount <= 32 || ikonDir.idType == 2)     // Bits per pixel
                    && ikonDir.idEntries[0].dwBytesInRes >= 40  // Must be over 40, since sizeof (infoheader) == 40
                    ) {
                    isProbablyICO = true;
                }
 
                if (iodev->isSequential()) {
                    // Our structs might be padded due to alignment, so we need to fetch each member before we ungetChar() !
                    quint32 tmp = ikonDir.idEntries[0].dwImageOffset;
                    iodev->ungetChar((tmp >> 24) & 0xff);
                    iodev->ungetChar((tmp >> 16) & 0xff);
                    iodev->ungetChar((tmp >>  8) & 0xff);
                    iodev->ungetChar(tmp & 0xff);
 
                    tmp = ikonDir.idEntries[0].dwBytesInRes;
                    iodev->ungetChar((tmp >> 24) & 0xff);
                    iodev->ungetChar((tmp >> 16) & 0xff);
                    iodev->ungetChar((tmp >>  8) & 0xff);
                    iodev->ungetChar(tmp & 0xff);
 
                    tmp = ikonDir.idEntries[0].wBitCount;
                    iodev->ungetChar((tmp >>  8) & 0xff);
                    iodev->ungetChar(tmp & 0xff);
 
                    tmp = ikonDir.idEntries[0].wPlanes;
                    iodev->ungetChar((tmp >>  8) & 0xff);
                    iodev->ungetChar(tmp & 0xff);
 
                    iodev->ungetChar(ikonDir.idEntries[0].bReserved);
                    iodev->ungetChar(ikonDir.idEntries[0].bColorCount);
                    iodev->ungetChar(ikonDir.idEntries[0].bHeight);
                    iodev->ungetChar(ikonDir.idEntries[0].bWidth);
                }
            }
 
            if (iodev->isSequential()) {
                // Our structs might be padded due to alignment, so we need to fetch each member before we ungetChar() !
                quint32 tmp = ikonDir.idCount;
                iodev->ungetChar((tmp >>  8) & 0xff);
                iodev->ungetChar(tmp & 0xff);
 
                tmp = ikonDir.idType;
                iodev->ungetChar((tmp >>  8) & 0xff);
                iodev->ungetChar(tmp & 0xff);
 
                tmp = ikonDir.idReserved;
                iodev->ungetChar((tmp >>  8) & 0xff);
                iodev->ungetChar(tmp & 0xff);
            }
        }
        if (!iodev->isSequential()) iodev->seek(oldPos);
    }
 
    return isProbablyICO;
}
 
bool ICOReader::readHeader()
{
    if (iod && !headerRead) {
        startpos = iod->pos();
        if (readIconDir(iod, &iconDir)) {
            if (iconDir.idReserved == 0 && (iconDir.idType == 1 || iconDir.idType == 2))
            headerRead = true;
        }
    }
 
    return headerRead;
}
 
bool ICOReader::readIconEntry(int index, ICONDIRENTRY *iconEntry)
{
    if (readHeader()) {
        if (iod->seek(startpos + ICONDIR_SIZE + (index * ICONDIRENTRY_SIZE))) {
            return readIconDirEntry(iod, iconEntry);
        }
    }
    return false;
}
 
 
 
bool ICOReader::readBMPHeader(quint32 imageOffset, BMP_INFOHDR * header)
{
    if (iod) {
        if (iod->seek(startpos + imageOffset)) {
            if (readBMPInfoHeader(iod, header)) {
                return true;
            }
        }
    }
    return false;
}
 
void ICOReader::findColorInfo(QImage & image)
{
    if (icoAttrib.ncolors > 0) {                // set color table
        readColorTable(image);
    }
}
 
void ICOReader::readColorTable(QImage & image)
{
    if (iod) {
        image.setColorCount(icoAttrib.ncolors);
        uchar rgb[4];
        for (int i=0; i<icoAttrib.ncolors; i++) {
            if (iod->read((char*)rgb, 4) != 4) {
            image = QImage();
            break;
            }
            image.setColor(i, qRgb(rgb[2],rgb[1],rgb[0]));
        }
    } else {
        image = QImage();
    }
}
 
void ICOReader::readBMP(QImage & image)
{
    if (icoAttrib.nbits == 1) {                // 1 bit BMP image
        read1BitBMP(image);
    } else if (icoAttrib.nbits == 4) {            // 4 bit BMP image
        read4BitBMP(image);
    } else if (icoAttrib.nbits == 8) {
        read8BitBMP(image);
    } else if (icoAttrib.nbits == 24 || icoAttrib.nbits == 32) { // 24,32 bit BMP image
        read24_32BMP(image);
    }
}
 
 
/**
 * NOTE: A 1 bit BMP is only flipped vertically, and not horizontally like all other color depths!
 * (This is the same with the bitmask)
 *
 */
void ICOReader::read1BitBMP(QImage & image)
{
    if (iod) {
 
        int h = image.height();
        qsizetype bpl = image.bytesPerLine();
 
        while (--h >= 0) {
            if (iod->read((char*)image.scanLine(h),bpl) != bpl) {
                image = QImage();
                break;
            }
        }
    } else {
        image = QImage();
    }
}
 
void ICOReader::read4BitBMP(QImage & image)
{
    if (iod) {
 
        int h = icoAttrib.h;
        int buflen = ((icoAttrib.w+7)/8)*4;
        uchar *buf = new uchar[buflen];
        Q_CHECK_PTR(buf);
 
        while (--h >= 0) {
            if (iod->read((char*)buf,buflen) != buflen) {
                image = QImage();
                break;
            }
            uchar *p = image.scanLine(h);
            uchar *b = buf;
            for (int i=0; i<icoAttrib.w/2; i++) {   // convert nibbles to bytes
                *p++ = *b >> 4;
                *p++ = *b++ & 0x0f;
            }
            if (icoAttrib.w & 1)                    // the last nibble
                *p = *b >> 4;
        }
 
        delete [] buf;
 
    } else {
        image = QImage();
    }
}
 
void ICOReader::read8BitBMP(QImage & image)
{
    if (iod) {
 
        int h = icoAttrib.h;
        qsizetype bpl = image.bytesPerLine();
 
        while (--h >= 0) {
            if (iod->read((char *)image.scanLine(h), bpl) != bpl) {
                image = QImage();
                break;
            }
        }
    } else {
        image = QImage();
    }
}
 
void ICOReader::read24_32BMP(QImage &image)
{
    if (iod) {
        int h = icoAttrib.h;
        QRgb *p;
        QRgb  *end;
        uchar *buf = new uchar[image.bytesPerLine()];
        qsizetype    bpl = ((qsizetype(icoAttrib.w)*icoAttrib.nbits+31)/32)*4;
        uchar *b;
 
        while (--h >= 0) {
            p = (QRgb *)image.scanLine(h);
            end = p + icoAttrib.w;
            if (iod->read((char *)buf, bpl) != bpl) {
                image = QImage();
                break;
            }
            b = buf;
            while (p < end) {
                if (icoAttrib.nbits == 24)
                    *p++ = qRgb(*(b+2), *(b+1), *b);
                else if (icoAttrib.nbits == 32)
                    *p++ = qRgba(*(b+2), *(b+1), *b, *(b+3));
                b += icoAttrib.nbits/8;
            }
        }
 
        delete[] buf;
 
    } else {
        image = QImage();
    }
}
 
static const char icoOrigDepthKey[] = "_q_icoOrigDepth";
 
QImage ICOReader::iconAt(int index)
{
    QImage img;
 
    if (count() > index) { // forces header to be read
 
        ICONDIRENTRY iconEntry;
        if (readIconEntry(index, &iconEntry)) {
 
            static const uchar pngMagicData[] = { 137, 80, 78, 71, 13, 10, 26, 10 };
 
            if (!iod->seek(startpos + iconEntry.dwImageOffset)
                || iconEntry.dwBytesInRes > iod->bytesAvailable())
                return img;
 
            const QByteArray pngMagic = QByteArray::fromRawData((const char*)pngMagicData, sizeof(pngMagicData));
            const bool isPngImage = (iod->read(pngMagic.size()) == pngMagic);
 
            if (isPngImage) {
                iod->seek(startpos + iconEntry.dwImageOffset);
                QImage image = QImage::fromData(iod->read(iconEntry.dwBytesInRes), "png");
                image.setText(QLatin1String(icoOrigDepthKey), QString::number(iconEntry.wBitCount));
                return image;
            }
 
            BMP_INFOHDR header;
            if (readBMPHeader(iconEntry.dwImageOffset, &header)) {
                icoAttrib.nbits = header.biBitCount ? header.biBitCount : iconEntry.wBitCount;
 
                switch (icoAttrib.nbits) {
                case 32:
                case 24:
                    icoAttrib.depth = 32;
                    break;
                // NB: 15/16 bpp BMP decoding is not implemented, so such images are rejected here
                case 8:
                case 4:
                    icoAttrib.depth = 8;
                    break;
                case 1:
                    icoAttrib.depth = 1;
                    break;
                default:
                    return img;
                    break;
                }
                if (icoAttrib.depth == 32)                // there's no colormap
                    icoAttrib.ncolors = 0;
                else                    // # colors used
                    icoAttrib.ncolors = header.biClrUsed ? uint(header.biClrUsed) : 1 << icoAttrib.nbits;
                if (icoAttrib.ncolors > 256) //color table can't be more than 256
                    return img;
                icoAttrib.w = iconEntry.bWidth;
                if (icoAttrib.w == 0) // means 256 pixels
                    icoAttrib.w = header.biWidth;
                icoAttrib.h = iconEntry.bHeight;
                if (icoAttrib.h == 0) // means 256 pixels
                    icoAttrib.h = header.biHeight/2;
                if (icoAttrib.w > 256 || icoAttrib.h > 256) // Max ico size
                    return img;
 
                QImage::Format format = QImage::Format_ARGB32;
                if (icoAttrib.nbits == 24)
                    format = QImage::Format_RGB32;
                else if (icoAttrib.ncolors == 2 && icoAttrib.depth == 1)
                    format = QImage::Format_Mono;
                else if (icoAttrib.ncolors > 0)
                    format = QImage::Format_Indexed8;
 
                QImage image;
                const QSize size(icoAttrib.w, icoAttrib.h);
                if (QImageIOHandler::allocateImage(size, format, &image)) {
                    findColorInfo(image);
                    if (!image.isNull()) {
                        readBMP(image);
                        if (!image.isNull()) {
                            if (icoAttrib.nbits == 32) {
                                img = std::move(image).convertToFormat(QImage::Format_ARGB32_Premultiplied);
                            } else {
                                QImage mask(image.width(), image.height(), QImage::Format_Mono);
                                if (!mask.isNull()) {
                                    mask.setColorCount(2);
                                    mask.setColor(0, qRgba(255,255,255,0xff));
                                    mask.setColor(1, qRgba(0  ,0  ,0  ,0xff));
                                    read1BitBMP(mask);
                                    if (!mask.isNull()) {
                                        img = image;
                                        img.setAlphaChannel(mask);
                                    }
                                }
                            }
                        }
                    }
                }
                img.setText(QLatin1String(icoOrigDepthKey), QString::number(icoAttrib.nbits));
            }
        }
    }
 
    return img;
}
 
 
/*!
    Reads all the icons from the given \a device, and returns them as
    a list of QImage objects.
 
    Each image has an alpha channel that represents the mask from the
    corresponding icon.
 
    \sa write()
*/
QList<QImage> ICOReader::read(QIODevice *device)
{
    QList<QImage> images;
 
    ICOReader reader(device);
    const int N = reader.count();
    images.reserve(N);
    for (int i = 0; i < N; i++)
        images += reader.iconAt(i);
 
    return images;
}
 
 
/*!
    Writes all the QImages in the \a images list to the given \a
    device. Returns \c true if the images are written successfully;
    otherwise returns \c false.
 
    The first image in the list is stored as the first icon in the
    device, and is therefore used as the default icon by applications.
    The alpha channel of each image is converted to a mask for each
    corresponding icon.
 
    \sa read()
*/
bool ICOReader::write(QIODevice *device, const QList<QImage> &images)
{
    bool retValue = false;
 
    if (images.size()) {
 
        qint64 origOffset = device->pos();
 
        ICONDIR id = { };
        id.idReserved = 0;
        id.idType = 1;
        id.idCount = images.size();
 
        ICONDIRENTRY * entries = new ICONDIRENTRY[id.idCount];
        BMP_INFOHDR * bmpHeaders = new BMP_INFOHDR[id.idCount];
        QByteArray * imageData = new QByteArray[id.idCount];
 
        for (int i=0; i<id.idCount; i++) {
 
            QImage image = images[i];
            // Scale down the image if it is larger than 256 pixels in either width or height
            // because this is a maximum size of image in the ICO file.
            if (image.width() > 256 || image.height() > 256)
            {
                image = image.scaled(256, 256, Qt::KeepAspectRatio, Qt::SmoothTransformation);
            }
            QImage maskImage(image.width(), image.height(), QImage::Format_Mono);
            image = image.convertToFormat(QImage::Format_ARGB32);
            maskImage.fill(Qt::color1);
 
            int    nbits = 32;
            int    bpl_bmp = ((image.width()*nbits+31)/32)*4;
 
            entries[i].bColorCount = 0;
            entries[i].bReserved = 0;
            entries[i].wBitCount = nbits;
            entries[i].bHeight = image.height() < 256 ? image.height() : 0;  // 0 means 256
            entries[i].bWidth = image.width() < 256 ? image.width() : 0;     // 0 means 256
            entries[i].dwBytesInRes = BMP_INFOHDR_SIZE + (bpl_bmp * image.height())
                + (maskImage.bytesPerLine() * maskImage.height());
            entries[i].wPlanes = 1;
            if (i == 0)
                entries[i].dwImageOffset = origOffset + ICONDIR_SIZE
                + (id.idCount * ICONDIRENTRY_SIZE);
            else
                entries[i].dwImageOffset = entries[i-1].dwImageOffset + entries[i-1].dwBytesInRes;
 
            bmpHeaders[i].biBitCount = entries[i].wBitCount;
            bmpHeaders[i].biClrImportant = 0;
            bmpHeaders[i].biClrUsed = entries[i].bColorCount;
            bmpHeaders[i].biCompression = 0;
            bmpHeaders[i].biHeight = entries[i].bHeight ? entries[i].bHeight * 2 : 256 * 2; // 2 is for the mask
            bmpHeaders[i].biPlanes = entries[i].wPlanes;
            bmpHeaders[i].biSize = BMP_INFOHDR_SIZE;
            bmpHeaders[i].biSizeImage = entries[i].dwBytesInRes - BMP_INFOHDR_SIZE;
            bmpHeaders[i].biWidth = entries[i].bWidth ? entries[i].bWidth : 256;
            bmpHeaders[i].biXPelsPerMeter = 0;
            bmpHeaders[i].biYPelsPerMeter = 0;
 
            QBuffer buffer(&imageData[i]);
            buffer.open(QIODevice::WriteOnly);
 
            uchar *buf = new uchar[bpl_bmp];
            uchar *b;
            memset( buf, 0, bpl_bmp );
            int y;
            for (y = image.height() - 1; y >= 0; y--) {    // write the image bits
                // 32 bits
                QRgb *p   = (QRgb *)image.scanLine(y);
                QRgb *end = p + image.width();
                b = buf;
                int x = 0;
                while (p < end) {
                    *b++ = qBlue(*p);
                    *b++ = qGreen(*p);
                    *b++ = qRed(*p);
                    *b++ = qAlpha(*p);
                    if (qAlpha(*p) > 0)   // Even mostly transparent pixels must not be masked away
                        maskImage.setPixel(x, y, 0);
                    p++;
                    x++;
                }
                buffer.write((char*)buf, bpl_bmp);
            }
            delete[] buf;
 
            // NOTE! !! The mask is only flipped vertically - not horizontally !!
            for (y = maskImage.height() - 1; y >= 0; y--)
                buffer.write((char*)maskImage.scanLine(y), maskImage.bytesPerLine());
        }
 
        if (writeIconDir(device, id)) {
            int i;
            bool bOK = true;
            for (i = 0; i < id.idCount && bOK; i++) {
                bOK = writeIconDirEntry(device, entries[i]);
            }
            if (bOK) {
                for (i = 0; i < id.idCount && bOK; i++) {
                    bOK = writeBMPInfoHeader(device, bmpHeaders[i]);
                    bOK &= (device->write(imageData[i]) == (int) imageData[i].size());
                }
                retValue = bOK;
            }
        }
 
        delete [] entries;
        delete [] bmpHeaders;
        delete [] imageData;
 
    }
    return retValue;
}
 
/*!
    Constructs an instance of QtIcoHandler initialized to use \a device.
*/
QtIcoHandler::QtIcoHandler(QIODevice *device)
{
    m_currentIconIndex = 0;
    setDevice(device);
    m_pICOReader = new ICOReader(device);
}
 
/*!
    Destructor for QtIcoHandler.
*/
QtIcoHandler::~QtIcoHandler()
{
    delete m_pICOReader;
}
 
QVariant QtIcoHandler::option(ImageOption option) const
{
    if (option == Size || option == ImageFormat) {
        ICONDIRENTRY iconEntry;
        if (m_pICOReader->readIconEntry(m_currentIconIndex, &iconEntry)) {
            switch (option) {
                case Size:
                    return QSize(iconEntry.bWidth ? iconEntry.bWidth : 256,
                                iconEntry.bHeight ? iconEntry.bHeight : 256);
 
                case ImageFormat:
                    switch (iconEntry.wBitCount) {
                        case 2:
                            return QImage::Format_Mono;
                        case 24:
                            return QImage::Format_RGB32;
                        case 32:
                            return QImage::Format_ARGB32;
                        default:
                            return QImage::Format_Indexed8;
                    }
                    break;
                default:
                    break;
            }
        }
    }
    return QVariant();
}
 
bool QtIcoHandler::supportsOption(ImageOption option) const
{
    return (option == Size || option == ImageFormat);
}
 
/*!
 * Verifies if some values (magic bytes) are set as expected in the header of the file.
 * If the magic bytes were found, it is assumed that the QtIcoHandler can read the file.
 *
 */
bool QtIcoHandler::canRead() const
{
    if (knownCanRead)
        return true;
    bool bCanRead = false;
    QIODevice *device = QImageIOHandler::device();
    if (device) {
        bCanRead = ICOReader::canRead(device);
        if (bCanRead)
            setFormat("ico");
    } else {
        qCWarning(lcIco, "QtIcoHandler::canRead() called with no device");
    }
    knownCanRead = bCanRead;
    return bCanRead;
}
 
/*! This static function is used by the plugin code, and is provided for convenience only.
    \a device must be an opened device with pointing to the start of the header data of the ICO file.
*/
bool QtIcoHandler::canRead(QIODevice *device)
{
    Q_ASSERT(device);
    return ICOReader::canRead(device);
}
 
/*! \reimp
 
*/
bool QtIcoHandler::read(QImage *image)
{
    bool bSuccess = false;
    QImage img = m_pICOReader->iconAt(m_currentIconIndex);
 
    // Make sure we only write to \a image when we succeed.
    if (!img.isNull()) {
        bSuccess = true;
        *image = img;
    }
 
    return bSuccess;
}
 
 
/*! \reimp
 
*/
bool QtIcoHandler::write(const QImage &image)
{
    QIODevice *device = QImageIOHandler::device();
    QList<QImage> imgs;
    imgs.append(image);
    return ICOReader::write(device, imgs);
}
 
/*! \reimp
 
*/
int QtIcoHandler::imageCount() const
{
    return m_pICOReader->count();
}
 
/*! \reimp
 
*/
bool QtIcoHandler::jumpToImage(int imageNumber)
{
    if (imageNumber < imageCount()) {
        m_currentIconIndex = imageNumber;
        return true;
    }
 
    return false;
}
 
/*! \reimp
 
*/
bool QtIcoHandler::jumpToNextImage()
{
    return jumpToImage(m_currentIconIndex + 1);
}
 
QT_END_NAMESPACE