QGIFLibHandler Class Reference

#include <qgiflibhandler.h>

Inheritance diagram for QGIFLibHandler:

Public Member Functions
bool	canRead () const override
QVariant	option (ImageOption option) const override
	QGIFLibHandler ()
bool	read (QImage *image) override
void	setOption (ImageOption option, const QVariant &value) override
bool	supportsOption (ImageOption option) const override
bool	write (const QImage &image) override

Static Public Member Functions
static bool	canRead (QIODevice *device)

Private Attributes
QString	m_description

Detailed Description

Definition at line 14 of file qgiflibhandler.h.

Constructor & Destructor Documentation

QGIFLibHandler()

QGIFLibHandler::QGIFLibHandler

(

)

Definition at line 32 of file qgiflibhandler.cpp.

    : QImageIOHandler()
{
}

Member Function Documentation

canRead() [1/2]

bool QGIFLibHandler::canRead ( ) const

override

Definition at line 37 of file qgiflibhandler.cpp.

{
    if (canRead(device())) {
        setFormat("gif");
        return true;
    }
    return false;
}

References canRead().

canRead() [2/2]

bool QGIFLibHandler::canRead ( QIODevice * device )

static

Definition at line 209 of file qgiflibhandler.cpp.

{
    if (!device) {
        qWarning("QGIFLibHandler::canRead() called with no device");
        return false;
    }
 
    char head[6];
    if (device->peek(head, sizeof(head)) == sizeof(head))
        return qstrncmp(head, "GIF87a", 6) == 0
                || qstrncmp(head, "GIF89a", 6) == 0;
    return false;
}

option()

QVariant QGIFLibHandler::option ( ImageOption option ) const

override

Todo

Todo

Definition at line 339 of file qgiflibhandler.cpp.

{
    switch (option)
    {
    case QImageIOHandler::ImageFormat:
        return QVariant();  
        break;
    case QImageIOHandler::Size:
        return QVariant();  
        break;
    case QImageIOHandler::Description:
        return QVariant(m_description);
        break;
    default:
        return QVariant();
    }
}

References m_description, and option().

read()

bool QGIFLibHandler::read ( QImage * image )

override

Todo

is it correct to override default fill color?

Definition at line 46 of file qgiflibhandler.cpp.

{
    // The contents of this function are based on gif2rgb.c, from the giflib source.
//    qDebug("QGIFLibHandler::read into image with size %d x %d", image->size().width(), image->size().height());
 
    int err;
    GifFileType* gifFile = DGifOpen(device(), doInput, &err);
    if (!gifFile) {
        qWarning() << "Received error code" << err;
        return false;
    }
//    qDebug("dimensions %d x %d", gifFile->SWidth, gifFile->SHeight);
 
    *image = QImage(gifFile->SWidth, gifFile->SHeight, QImage::Format_Indexed8);
 
    GifRecordType recordType;
    ColorMapObject* ColorMap;
 
    int i, row, imageNum = 0, topRow, width, height;
    int transColor = -1;
    do
    {
        DGifGetRecordType(gifFile, &recordType);
        switch (recordType)
        {
        case IMAGE_DESC_RECORD_TYPE:
            if (DGifGetImageDesc(gifFile) == GIF_ERROR)
            {
                qWarning("QGIFLibHandler::read: error %d", gifFile->Error);
                return false;
            }
            topRow = gifFile->Image.Top; /* Image Position relative to Screen. */
            width = gifFile->Image.Width;
            height = gifFile->Image.Height;
            //qDebug("Image %d at (%d, %d) [%dx%d]", ++imageNum, gifFile->Image.Left, topRow, width, height);
            if (gifFile->Image.Left + width > gifFile->SWidth ||
                    gifFile->Image.Top + height > gifFile->SHeight)
            {
                qWarning("Image %d is not confined to screen dimension, aborted.", imageNum);
                return false;
            }
 
            // Pre-fill with background color
//            qDebug("background color is at index %d", gifFile->SBackGroundColor);
            image->fill(gifFile->SBackGroundColor);
 
            // Now read the image data
            if (gifFile->Image.Interlace)
            {
                /* Need to perform 4 passes on the images: */
                for (i = 0; i < 4; i++)
                    for (row = topRow + InterlacedOffset[i]; row < topRow + height;
                         row += InterlacedJumps[i])
                    {
                        if (DGifGetLine(gifFile, image->scanLine(row), width) == GIF_ERROR)
                        {
                            qWarning("QGIFLibHandler::read: error %d", gifFile->Error);
                            return false;
                        }
                        //                      else
                        //                          qDebug("got row %d: %d %d %d %d %d %d %d %d ...", row,
                        //                              image->scanLine(row)[0], image->scanLine(row)[1], image->scanLine(row)[2], image->scanLine(row)[3],
                        //                              image->scanLine(row)[4], image->scanLine(row)[5], image->scanLine(row)[6], image->scanLine(row)[7]);
                    }
            }
            else
            {
                for (row = 0; row < height; row++)
                {
                    if (DGifGetLine(gifFile, image->scanLine(row), width) == GIF_ERROR)
                    {
                        qWarning("QGIFLibHandler::read: error %d", gifFile->Error);
                        return false;
                    }
                    //                  else
                    //                      qDebug("got row %d: %d %d %d %d %d %d %d %d ...", row,
                    //                          image->scanLine(row)[0], image->scanLine(row)[1], image->scanLine(row)[2], image->scanLine(row)[3],
                    //                          image->scanLine(row)[4], image->scanLine(row)[5], image->scanLine(row)[6], image->scanLine(row)[7]);
                }
            }
            break;
        case EXTENSION_RECORD_TYPE:
        {
            int extCode;
            GifByteType* extData;
            /* Skip any extension blocks in file: */
            if (DGifGetExtension(gifFile, &extCode, &extData) == GIF_ERROR)
            {
                qWarning("QGIFLibHandler::read: error %d", gifFile->Error);
                return false;
            }
            while (extData != NULL)
            {
                int len = extData[0];
                switch (extCode)
                {
                case GRAPHICS_EXT_FUNC_CODE:    // Graphics control extension
//                    qDebug("graphics control: %x %x %x %x %x", extData[0], extData[1], extData[2], extData[3], extData[4]);
                    // Should be block size, packed fields, delay time,
                    // transparent color, block terminator
                    // see doc/gif89.txt in libgif source package
                    // If the trans bit is set in packed fields,
                    // then set the trans color to the one given
                    if (extData[1] & 0x01)
                    {
                        transColor = extData[3];
//                        qDebug("transparent color is at index %d", transColor);
                        //                          image->fill(transColor);
                    }
                    break;
                case COMMENT_EXT_FUNC_CODE:
                {
                    QByteArray comment((char*)(extData + 1), len);
                    //                          qDebug("comment of len %d: \"%s\"", len, comment.constData());
                    image->setText("Description", comment);
                }
                    break;
                case PLAINTEXT_EXT_FUNC_CODE:
                    break;
                }
                if (DGifGetExtensionNext(gifFile, &extData) == GIF_ERROR)
                {
                    qWarning("QGIFLibHandler::read: error %d", gifFile->Error);
                    return false;
                }
            }
        }
            break;
        case TERMINATE_RECORD_TYPE:
            break;
        default:
            break;
        }
    }
    while (recordType != TERMINATE_RECORD_TYPE);
 
    //  BackGround = gifFile->SBackGroundColor;
    ColorMap = (gifFile->Image.ColorMap
                ? gifFile->Image.ColorMap
                : gifFile->SColorMap);
    if (!ColorMap)
    {
        qWarning("QGIFLibHandler::read: Image does not have a colormap");
        return false;
    }
    int ccount = ColorMap->ColorCount;
    image->setColorCount(ccount);
    for (i = 0; i < ccount; ++i)
    {
        GifColorType gifColor = ColorMap->Colors[i];
        QRgb color = gifColor.Blue | (gifColor.Green << 8) | (gifColor.Red << 16);
        // If this is not the transparent color,
        // set the alpha to opaque.
        if (i != transColor)
            color |= 0xff << 24;
        //      qDebug("color %d: 0x%X", i, color);
        image->setColor(i, color);
    }
 
    return true;
}

References doInput(), InterlacedJumps, and InterlacedOffset.

setOption()

void QGIFLibHandler::setOption ( ImageOption option, const QVariant & value )

override

Definition at line 332 of file qgiflibhandler.cpp.

{
    //  qDebug("setOption given option %d, variant of type %d", option, value.type());
    if (option == QImageIOHandler::Description)
        m_description = value.toString();
}

References m_description, option(), and value().

supportsOption()

bool QGIFLibHandler::supportsOption ( ImageOption option ) const

override

Definition at line 315 of file qgiflibhandler.cpp.

{
    //  qDebug("supportsOption %d", option);
    switch (option)
    {
    // These are relevant only for reading
    case QImageIOHandler::ImageFormat:
    case QImageIOHandler::Size:
        // This is relevant for both reading and writing
    case QImageIOHandler::Description:
        return true;
        break;
    default:
        return false;
    }
}

References option().

write()

bool QGIFLibHandler::write ( const QImage & image )

override

Todo

how to specify dithering method

Todo

based on colorCount (or not? we did ask for Format_Indexed8, so the data is always 8-bit, right?)

Todo

transparent GIFs (use alpha?)

Todo

write to m_device

Todo

how to specify which version, or decide based on features in use

Todo

how to specify background

Todo

foreach of multiple images in an animation...

Definition at line 223 of file qgiflibhandler.cpp.

{
    QImage toWrite(image);
    if (toWrite.colorCount() == 0 || toWrite.colorCount() > 256)
        toWrite = image.convertToFormat(QImage::Format_Indexed8);
 
    QVector<QRgb> colorTable = toWrite.colorTable();
    ColorMapObject cmap;
    // colorCount must be a power of 2
    int colorCount = 1 << GifBitSize(toWrite.colorCount());
    cmap.ColorCount = colorCount;
    cmap.BitsPerPixel = 8;  
    GifColorType* colorValues = (GifColorType*)malloc(cmap.ColorCount * sizeof(GifColorType));
    cmap.Colors = colorValues;
    int c = 0;
    for(; c < toWrite.colorCount(); ++c)
    {
//        qDebug("color %d has %02X%02X%02X", c, qRed(colorTable[c]), qGreen(colorTable[c]), qBlue(colorTable[c]));
        colorValues[c].Red = qRed(colorTable[c]);
        colorValues[c].Green = qGreen(colorTable[c]);
        colorValues[c].Blue = qBlue(colorTable[c]);
    }
    // In case we had an actual number of colors that's not a power of 2,
    // fill the rest with something (black perhaps).
    for (; c < colorCount; ++c)
    {
        colorValues[c].Red = 0;
        colorValues[c].Green = 0;
        colorValues[c].Blue = 0;
    }
 
 
    int err;
    GifFileType *gif = EGifOpen(device(), doOutput, &err);
 
    // Because of this call, libgif is not reentrant
    EGifSetGifVersion(gif, true);
 
    if (EGifPutScreenDesc(gif, toWrite.width(), toWrite.height(), colorCount, 0, &cmap) == GIF_ERROR) {
        qWarning("EGifPutScreenDesc returned error %d", gif->Error);
    }
 
    QVariant descText = option(QImageIOHandler::Description);
    if (descText.type() == QVariant::String)
    {
        QString comment = descText.toString();
        // Will be something like "Description: actual text" or just
        // ": actual text", so remove everything leading up to and
        // including the first colon and the space following it.
        int idx = comment.indexOf(": ");
        if (idx >= 0)
            comment.remove(0, idx + 2);
        //      qDebug() << "comment:" << comment;
        if (!comment.isEmpty())
            EGifPutComment(gif, comment.toUtf8().constData());
    }
    //  else
    //      qDebug("description is of qvariant type %d", descText.type());
 
    if (EGifPutImageDesc(gif, 0, 0, toWrite.width(), toWrite.height(), 0, &cmap) == GIF_ERROR)
        qWarning("EGifPutImageDesc returned error %d", gif->Error);
 
    int lc = toWrite.height();
 
    // NOTE: we suppose that the pixel size is exactly 1 byte, right now we
    //       cannot save anything else
    int llen = toWrite.width();
 
    //  qDebug("will write %d lines, %d bytes each", lc, llen);
 
    for (int l = 0; l < lc; ++l)
    {
        uchar* line = toWrite.scanLine(l);
        if (EGifPutLine(gif, (GifPixelType*)line, llen) == GIF_ERROR)
        {
            int i = gif->Error;
            qWarning("EGifPutLine returned error %d", i);
        }
    }
 
    EGifCloseFile(gif, &err);
    free(colorValues);
 
    return true;
}

References doOutput(), and option().

Member Data Documentation

m_description

QString QGIFLibHandler::m_description

private

Definition at line 27 of file qgiflibhandler.h.

---

The documentation for this class was generated from the following files:

• plugins/impex/gif/qgiflibhandler.h
• plugins/impex/gif/qgiflibhandler.cpp