QGifHandler Class Reference

#include <qgifhandler_p.h>

Inheritance diagram for QGifHandler:

Public Functions
bool	canRead () const
	Returns true if an image can be read from the device (i. More...
int	currentImageNumber () const
	For image formats that support animation, this function returns the sequence number of the current image in the animation. More...
int	imageCount () const
	For image formats that support animation, this function returns the number of images in the animation. More...
int	loopCount () const
	For image formats that support animation, this function returns the number of times the animation should loop. More...
QByteArray	name () const
	Use format() instead. More...
int	nextImageDelay () const
	For image formats that support animation, this function returns the number of milliseconds to wait until reading the next image. More...
QVariant	option (ImageOption option) const
	Returns the value assigned to option as a QVariant. More...
	QGifHandler ()
bool	read (QImage *image)
	Read an image from the device, and stores it in image. More...
void	setOption (ImageOption option, const QVariant &value)
	Sets the option option with the value value. More...
bool	supportsOption (ImageOption option) const
	Returns true if the QImageIOHandler supports the option option; otherwise returns false. More...
bool	write (const QImage &image)
	Writes the image image to the assigned device. More...
	~QGifHandler ()
Public Functions inherited from QImageIOHandler
virtual QRect	currentImageRect () const
	Returns the rect of the current image. More...
QIODevice *	device () const
	Returns the device currently assigned to the QImageIOHandler. More...
QByteArray	format () const
	Returns the format that is currently assigned to QImageIOHandler. More...
virtual bool	jumpToImage (int imageNumber)
	For image formats that support animation, this function jumps to the image whose sequence number is imageNumber. More...
virtual bool	jumpToNextImage ()
	For image formats that support animation, this function jumps to the next image. More...
	QImageIOHandler ()
	Constructs a QImageIOHandler object. More...
void	setDevice (QIODevice *device)
	Sets the device of the QImageIOHandler to device. More...
void	setFormat (const QByteArray &format)
	Sets the format of the QImageIOHandler to format. More...
void	setFormat (const QByteArray &format) const
	Sets the format of the QImageIOHandler to format. More...
virtual	~QImageIOHandler ()
	Destructs the QImageIOHandler object. More...

Static Public Functions
static bool	canRead (QIODevice *device)

Private Functions
bool	imageIsComing () const

Properties
QByteArray	buffer
QString	fileName
int	frameNumber
QGIFFormat *	gifFormat
QVector< QSize >	imageSizes
QImage	lastImage
int	loopCnt
int	nextDelay
bool	scanIsCached

Additional Inherited Members
Public Types inherited from QImageIOHandler
enum	ImageOption {   Size, ClipRect, Description, ScaledClipRect,   ScaledSize, CompressionRatio, Gamma, Quality,   Name, SubType, IncrementalReading, Endianness,   Animation, BackgroundColor, ImageFormat }
	This enum describes the different options supported by QImageIOHandler. More...
Protected Functions inherited from QImageIOHandler
	QImageIOHandler (QImageIOHandlerPrivate &dd)
	Constructs a QImageIOHandler object, using the private member dd. More...
Protected Variables inherited from QImageIOHandler
QScopedPointer< QImageIOHandlerPrivate >	d_ptr

Detailed Description

Definition at line 57 of file qgifhandler_p.h.

Constructors and Destructors

QGifHandler()

QGifHandler::QGifHandler

(

)

Definition at line 1042 of file qgifhandler.cpp.

{
    gifFormat = new QGIFFormat;
    nextDelay = 100;
    loopCnt = -1;
    frameNumber = -1;
    scanIsCached = false;
}

~QGifHandler()

QGifHandler::~QGifHandler

(

)

Definition at line 1051 of file qgifhandler.cpp.

{
    delete gifFormat;
}

Functions

canRead() [1/2]

bool QGifHandler::canRead ( ) const

virtual

Returns true if an image can be read from the device (i.

e., the image format is supported, the device can be read from and the initial header information suggests that the image can be read); otherwise returns false.

When reimplementing canRead(), make sure that the I/O device (device()) is left in its original state (e.g., by using peek() rather than read()).

See also

read(), QIODevice::peek()

Implements QImageIOHandler.

Definition at line 1078 of file qgifhandler.cpp.

Referenced by QGifPlugin::capabilities(), and createReadHandlerHelper().

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

    return false;
}

canRead() [2/2]

bool QGifHandler::canRead ( QIODevice *  device )

static

Definition at line 1088 of file qgifhandler.cpp.

{
    if (!device) {
        qWarning("QGifHandler::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;
}

currentImageNumber()

int QGifHandler::currentImageNumber ( ) const

virtual

For image formats that support animation, this function returns the sequence number of the current image in the animation.

If this function is called before any image is read(), -1 is returned. The number of the first image in the sequence is 0.

If the image format does not support animation, 0 is returned.

See also

read()

Reimplemented from QImageIOHandler.

Definition at line 1201 of file qgifhandler.cpp.

{
    return frameNumber;
}

imageCount()

int QGifHandler::imageCount ( ) const

virtual

For image formats that support animation, this function returns the number of images in the animation.

If the image format does not support animation, or if it is unable to determine the number of images, 0 is returned.

The default implementation returns 1 if canRead() returns true; otherwise 0 is returned.

Reimplemented from QImageIOHandler.

Definition at line 1177 of file qgifhandler.cpp.

{
    if (!scanIsCached) {
        QGIFFormat::scan(device(), &imageSizes, &loopCnt);
        scanIsCached = true;
    }
    return imageSizes.count();
}

imageIsComing()

bool QGifHandler::imageIsComing ( ) const

private

Definition at line 1058 of file qgifhandler.cpp.

{
    const int GifChunkSize = 4096;

    while (!gifFormat->partialNewFrame) {
        if (buffer.isEmpty()) {
            buffer += device()->read(GifChunkSize);
            if (buffer.isEmpty())
                break;
        }

        int decoded = gifFormat->decode(&lastImage, (const uchar *)buffer.constData(), buffer.size(),
                                        &nextDelay, &loopCnt);
        if (decoded == -1)
            break;
        buffer.remove(0, decoded);
    }
    return gifFormat->partialNewFrame;
}

loopCount()

int QGifHandler::loopCount ( ) const

virtual

For image formats that support animation, this function returns the number of times the animation should loop.

If the image format does not support animation, 0 is returned.

Reimplemented from QImageIOHandler.

Definition at line 1186 of file qgifhandler.cpp.

{
    if (!scanIsCached) {
        QGIFFormat::scan(device(), &imageSizes, &loopCnt);
        scanIsCached = true;
    }

    if (loopCnt == 0)
        return -1;
    else if (loopCnt == -1)
        return 0;
    else
        return loopCnt;
}

name()

QByteArray QGifHandler::name ( ) const

virtual

Use format() instead.

Reimplemented from QImageIOHandler.

Definition at line 1206 of file qgifhandler.cpp.

{
    return "gif";
}

nextImageDelay()

int QGifHandler::nextImageDelay ( ) const

virtual

For image formats that support animation, this function returns the number of milliseconds to wait until reading the next image.

If the image format does not support animation, 0 is returned.

Reimplemented from QImageIOHandler.

Definition at line 1172 of file qgifhandler.cpp.

{
    return nextDelay;
}

option()

QVariant QGifHandler::option ( ImageOption  option ) const

virtual

Returns the value assigned to option as a QVariant.

The type of the value depends on the option. For example, option(Size) returns a QSize variant.

See also

setOption(), supportsOption()

Reimplemented from QImageIOHandler.

Definition at line 1145 of file qgifhandler.cpp.

{
    if (option == Size) {
        if (!scanIsCached) {
            QGIFFormat::scan(device(), &imageSizes, &loopCnt);
            scanIsCached = true;
        }
        // before the first frame is read, or we have an empty data stream
        if (frameNumber == -1)
            return (imageSizes.count() > 0) ? QVariant(imageSizes.at(0)) : QVariant();
        // after the last frame has been read, the next size is undefined
        if (frameNumber >= imageSizes.count() - 1)
            return QVariant();
        // and the last case: the size of the next frame
        return imageSizes.at(frameNumber + 1);
    } else if (option == Animation) {
        return true;
    }
    return QVariant();
}

read()

bool QGifHandler::read ( QImage *  image )

virtual

Read an image from the device, and stores it in image.

Returns true if the image is successfully read; otherwise returns false.

For image formats that support incremental loading, and for animation formats, the image handler can assume that image points to the previous frame.

See also

canRead()

Implements QImageIOHandler.

Definition at line 1102 of file qgifhandler.cpp.

{
    const int GifChunkSize = 4096;

    while (!gifFormat->newFrame) {
        if (buffer.isEmpty()) {
            buffer += device()->read(GifChunkSize);
            if (buffer.isEmpty())
                break;
        }

        int decoded = gifFormat->decode(&lastImage, (const uchar *)buffer.constData(), buffer.size(),
                                        &nextDelay, &loopCnt);
        if (decoded == -1)
            break;
        buffer.remove(0, decoded);
    }
    if (gifFormat->newFrame || (gifFormat->partialNewFrame && device()->atEnd())) {
        *image = lastImage;
        ++frameNumber;
        gifFormat->newFrame = false;
        gifFormat->partialNewFrame = false;
        return true;
    }

    return false;
}

setOption()

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

virtual

Sets the option option with the value value.

See also

option(), ImageOption

Reimplemented from QImageIOHandler.

Definition at line 1166 of file qgifhandler.cpp.

{
    Q_UNUSED(option);
    Q_UNUSED(value);
}

supportsOption()

bool QGifHandler::supportsOption ( ImageOption  option ) const

virtual

Returns true if the QImageIOHandler supports the option option; otherwise returns false.

For example, if the QImageIOHandler supports the Size option, supportsOption(Size) must return true.

See also

setOption(), option()

Reimplemented from QImageIOHandler.

Definition at line 1136 of file qgifhandler.cpp.

{
    if (!device() || device()->isSequential())
        return option == Animation;
    else
        return option == Size
            || option == Animation;
}

write()

bool QGifHandler::write ( const QImage &  image )

virtual

Writes the image image to the assigned device.

Returns true on success; otherwise returns false.

The default implementation does nothing, and simply returns false.

Reimplemented from QImageIOHandler.

Definition at line 1130 of file qgifhandler.cpp.

{
    Q_UNUSED(image);
    return false;
}

Properties

buffer

QByteArray QGifHandler::buffer

mutableprivate

Definition at line 84 of file qgifhandler_p.h.

fileName

QString QGifHandler::fileName

private

Definition at line 83 of file qgifhandler_p.h.

frameNumber

int QGifHandler::frameNumber

private

Definition at line 89 of file qgifhandler_p.h.

gifFormat

QGIFFormat* QGifHandler::gifFormat

private

Definition at line 82 of file qgifhandler_p.h.

imageSizes

QVector<QSize> QGifHandler::imageSizes

mutableprivate

Definition at line 90 of file qgifhandler_p.h.

lastImage

QImage QGifHandler::lastImage

mutableprivate

Definition at line 85 of file qgifhandler_p.h.

loopCnt

int QGifHandler::loopCnt

mutableprivate

Definition at line 88 of file qgifhandler_p.h.

nextDelay

int QGifHandler::nextDelay

mutableprivate

Definition at line 87 of file qgifhandler_p.h.

scanIsCached

bool QGifHandler::scanIsCached

mutableprivate

Definition at line 91 of file qgifhandler_p.h.

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

• /src/gui/image/qgifhandler_p.h
• /src/gui/image/qgifhandler.cpp