qtgafile.cpp

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#include "qtgafile.h"

#include <QtCore/QIODevice>
#include <QtCore/QDebug>
#include <QtCore/QDateTime>

struct TgaReader
{
    virtual ~TgaReader() {}
    virtual QRgb operator()(QIODevice *s) const = 0;
};

struct Tga16Reader : public TgaReader
{
    ~Tga16Reader() {}
    QRgb operator()(QIODevice *s) const
    {
        char ch1, ch2;
        if (s->getChar(&ch1) && s->getChar(&ch2)) {
            quint16 d = (int(ch1) & 0xFF) | ((int(ch2) & 0xFF) << 8);
            QRgb result = (d & 0x8000) ? 0xFF000000 : 0x00000000;
            result |= (d & 0x7C00 << 6) | (d & 0x03E0 << 3) | (d & 0x001F);
            return result;
        } else {
            return 0;
        }
    }
};

struct Tga24Reader : public TgaReader
{
    QRgb operator()(QIODevice *s) const
    {
        char r, g, b;
        if (s->getChar(&b) && s->getChar(&g) && s->getChar(&r))
            return qRgb(uchar(r), uchar(g), uchar(b));
        else
            return 0;
    }
};

struct Tga32Reader : public TgaReader
{
    QRgb operator()(QIODevice *s) const
    {
        char r, g, b, a;
        if (s->getChar(&b) && s->getChar(&g) && s->getChar(&r) && s->getChar(&a))
            return qRgba(uchar(r), uchar(g), uchar(b), uchar(a));
        else
            return 0;
    }
};

QTgaFile::QTgaFile(QIODevice *device)
    : mDevice(device)
{
    ::memset(mHeader, 0, HeaderSize);
    if (!mDevice->isReadable())
    {
        mErrorMessage = QObject::tr("Could not read image data");
        return;
    }
    if (mDevice->isSequential())
    {
        mErrorMessage = QObject::tr("Sequential device (eg socket) for image read not supported");
        return;
    }
    if (!mDevice->seek(0))
    {
        mErrorMessage = QObject::tr("Seek file/device for image read failed");
        return;
    }
    int bytes = device->read((char*)mHeader, HeaderSize);
    if (bytes != HeaderSize)
    {
        mErrorMessage = QObject::tr("Image mHeader read failed");
        device->seek(0);
        return;
    }
    if (mHeader[ImageType] != 2)
    {
        // TODO: should support other image types
        mErrorMessage = QObject::tr("Image type not supported");
        device->seek(0);
        return;
    }
    int bitsPerPixel = mHeader[PixelDepth];
    bool validDepth = (bitsPerPixel == 16 || bitsPerPixel == 24 || bitsPerPixel == 32);
    if (!validDepth)
    {
        mErrorMessage = QObject::tr("Image depth not valid");
    }
    int fileBytes = mDevice->size();
    if (!mDevice->seek(fileBytes - FooterSize))
    {
        mErrorMessage = QObject::tr("Could not seek to image read footer");
        device->seek(0);
        return;
    }
    char footer[FooterSize];
    bytes = mDevice->read((char*)footer, FooterSize);
    if (bytes != FooterSize)
    {
        mErrorMessage = QObject::tr("Could not read footer");
    }
    if (qstrncmp(&footer[SignatureOffset], "TRUEVISION-XFILE", 16) != 0)
    {
        mErrorMessage = QObject::tr("Image type (non-TrueVision 2.0) not supported");
    }
    if (!mDevice->seek(0))
    {
        mErrorMessage = QObject::tr("Could not reset to start position");
    }
}

QTgaFile::~QTgaFile()
{
}

QImage QTgaFile::readImage()
{
    if (!isValid())
        return QImage();

    int offset = mHeader[IdLength];  // Mostly always zero

    // Even in TrueColor files a color pallette may be present
    if (mHeader[ColorMapType] == 1)
        offset += littleEndianInt(&mHeader[CMapLength]) * littleEndianInt(&mHeader[CMapDepth]);

    mDevice->seek(HeaderSize + offset);

    char dummy;
    for (int i = 0; i < offset; ++i)
        mDevice->getChar(&dummy);

    int bitsPerPixel = mHeader[PixelDepth];
    int imageWidth = width();
    int imageHeight = height();

    unsigned char desc = mHeader[ImageDescriptor];
    //unsigned char xCorner = desc & 0x10; // 0 = left, 1 = right
    unsigned char yCorner = desc & 0x20; // 0 = lower, 1 = upper

    QImage im(imageWidth, imageHeight, QImage::Format_ARGB32);
    TgaReader *reader = 0;
    if (bitsPerPixel == 16)
        reader = new Tga16Reader();
    else if (bitsPerPixel == 24)
        reader = new Tga24Reader();
    else if (bitsPerPixel == 32)
        reader = new Tga32Reader();
    TgaReader &read = *reader;

    // For now only deal with yCorner, since no one uses xCorner == 1
    // Also this is upside down, since Qt has the origin flipped
    if (yCorner)
    {
        for (int y = 0; y < imageHeight; ++y)
            for (int x = 0; x < imageWidth; ++x)
                im.setPixel(x, y, read(mDevice));
    }
    else
    {
        for (int y = imageHeight - 1; y >= 0; --y)
            for (int x = 0; x < imageWidth; ++x)
                im.setPixel(x, y, read(mDevice));
    }

    delete reader;

    // TODO: add processing of TGA extension information - ie TGA 2.0 files
    return im;
}