QPictureIO Class Reference

The QPictureIO class contains parameters for loading and saving pictures. More...

#include <qpicture.h>

Public Functions
QString	description () const
	Returns the picture description string. More...
QString	fileName () const
	Returns the file name currently set. More...
const char *	format () const
	Returns the picture format string or 0 if no format has been explicitly set. More...
float	gamma () const
	Returns the gamma value at which the picture will be viewed. More...
QIODevice *	ioDevice () const
	Returns the IO device currently set. More...
const char *	parameters () const
	Returns the picture's parameters string. More...
const QPicture &	picture () const
	Returns the picture currently set. More...
	QPictureIO ()
	Constructs a QPictureIO object with all parameters set to zero. More...
	QPictureIO (QIODevice *ioDevice, const char *format)
	Constructs a QPictureIO object with the I/O device ioDevice and a format tag. More...
	QPictureIO (const QString &fileName, const char *format)
	Constructs a QPictureIO object with the file name fileName and a format tag. More...
int	quality () const
	Returns the quality of the written picture, related to the compression ratio. More...
bool	read ()
	Reads an picture into memory and returns true if the picture was successfully read; otherwise returns false. More...
void	setDescription (const QString &)
	Sets the picture description string for picture handlers that support picture descriptions to description. More...
void	setFileName (const QString &)
	Sets the name of the file to read or write an picture from to fileName. More...
void	setFormat (const char *)
	Sets the picture format to format for the picture to be read or written. More...
void	setGamma (float)
	Sets the gamma value at which the picture will be viewed to gamma. More...
void	setIODevice (QIODevice *)
	Sets the IO device to be used for reading or writing an picture. More...
void	setParameters (const char *)
	Sets the picture's parameter string to parameters. More...
void	setPicture (const QPicture &)
	Sets the picture to picture. More...
void	setQuality (int)
	Sets the quality of the written picture to q, related to the compression ratio. More...
void	setStatus (int)
	Sets the picture IO status to status. More...
int	status () const
	Returns the picture's IO status. More...
bool	write ()
	Writes an picture to an IO device and returns true if the picture was successfully written; otherwise returns false. More...
	~QPictureIO ()
	Destroys the object and all related data. More...

Static Public Functions
static void	defineIOHandler (const char *format, const char *header, const char *flags, picture_io_handler read_picture, picture_io_handler write_picture)
	Defines a picture I/O handler for the picture format called format, which is recognized using the regular expression defined in header, read using readPicture and written using writePicture. More...
static QList< QByteArray >	inputFormats ()
	Returns a sorted list of picture formats that are supported for picture input. More...
static QList< QByteArray >	outputFormats ()
	Returns a sorted list of picture formats that are supported for picture output. More...
static QByteArray	pictureFormat (const QString &fileName)
	Returns a string that specifies the picture format of the file fileName, or null if the file cannot be read or if the format is not recognized. More...
static QByteArray	pictureFormat (QIODevice *)
	Returns a string that specifies the picture format of the picture read from IO device d, or 0 if the device cannot be read or if the format is not recognized. More...

Private Functions
void	init ()
	Contains initialization common to all QPictureIO constructors. More...

Properties
QPictureIOData *	d

Detailed Description

The QPictureIO class contains parameters for loading and saving pictures.

QPictureIO contains a QIODevice object that is used for picture data I/O. The programmer can install new picture file formats in addition to those that Qt provides.

You don't normally need to use this class; QPicture::load(), QPicture::save().

See also

QPicture QPixmap QFile

Definition at line 136 of file qpicture.h.

Constructors and Destructors

QPictureIO() [1/3]

QPictureIO::QPictureIO

(

)

Constructs a QPictureIO object with all parameters set to zero.

Definition at line 1401 of file qpicture.cpp.

{
    init();
}

QPictureIO() [2/3]

QPictureIO::QPictureIO	(	QIODevice *	ioDevice,
		const char *	format
	)

Constructs a QPictureIO object with the I/O device ioDevice and a format tag.

Definition at line 1411 of file qpicture.cpp.

{
    init();
    d->iodev = ioDevice;
    d->frmt = format;
}

QPictureIO() [3/3]

QPictureIO::QPictureIO	(	const QString &	fileName,
		const char *	format
	)

Constructs a QPictureIO object with the file name fileName and a format tag.

Definition at line 1423 of file qpicture.cpp.

{
    init();
    d->frmt = format;
    d->fname = fileName;
}

~QPictureIO()

QPictureIO::~QPictureIO

(

)

Destroys the object and all related data.

Definition at line 1448 of file qpicture.cpp.

{
    if (d->parameters)
        delete [] (char*)d->parameters;
    delete d;
}

Functions

defineIOHandler()

void QPictureIO::defineIOHandler ( const char *  format, const char *  header, const char *  flags, picture_io_handler  readPicture, picture_io_handler  writePicture  )

static

Defines a picture I/O handler for the picture format called format, which is recognized using the regular expression defined in header, read using readPicture and written using writePicture.

flags is a string of single-character flags for this format. The only flag defined currently is T (upper case), so the only legal value for flags are "T" and the empty string. The "T" flag means that the picture file is a text file, and Qt should treat all newline conventions as equivalent. (XPM files and some PPM files are text files for example.)

format is used to select a handler to write a QPicture; header is used to select a handler to read an picture file.

If readPicture is a null pointer, the QPictureIO will not be able to read pictures in format. If writePicture is a null pointer, the QPictureIO will not be able to write pictures in format. If both are null, the QPictureIO object is valid but useless.

Example:

void readSVG(QPictureIO *picture)
{
    // read the picture using the picture->ioDevice()
}

void writeSVG(QPictureIO *picture)
{
    // write the picture using the picture->ioDevice()
}

    // add the SVG picture handler
    // ...

Before the regular expression test, all the 0 bytes in the file header are converted to 1 bytes. This is done because when Qt was ASCII-based, QRegExp could not handle 0 bytes in strings.

The regexp is only applied on the first 14 bytes of the file.

(Note that if one handlerIO supports writing a format and another supports reading it, Qt supports both reading and writing. If two handlers support the same operation, Qt chooses one arbitrarily.)

Definition at line 1578 of file qpicture.cpp.

{
    qt_init_picture_handlers();
    if (QPHList *list = pictureHandlers()) {
        QPictureHandler *p;
        p = new QPictureHandler(format, header, QByteArray(flags), readPicture, writePicture);
        list->prepend(p);
    }
}

description()

QString QPictureIO::description

(

)

const

Returns the picture description string.

See also

setDescription()

Definition at line 1638 of file qpicture.cpp.

{ return d->descr; }

fileName()

QString QPictureIO::fileName

(

)

const

Returns the file name currently set.

See also

setFileName()

Definition at line 1630 of file qpicture.cpp.

{ return d->fname; }

format()

const char * QPictureIO::format

(

)

const

Returns the picture format string or 0 if no format has been explicitly set.

Definition at line 1616 of file qpicture.cpp.

{ return d->frmt; }

gamma()

float QPictureIO::gamma

(

)

const

Returns the gamma value at which the picture will be viewed.

See also

setGamma()

Definition at line 1783 of file qpicture.cpp.

{
    return d->gamma;
}

init()

void QPictureIO::init ( )

private

Contains initialization common to all QPictureIO constructors.

Definition at line 1434 of file qpicture.cpp.

{
    d = new QPictureIOData();
    d->parameters = 0;
    d->quality = -1; // default quality of the current format
    d->gamma=0.0f;
    d->iostat = 0;
    d->iodev  = 0;
}

inputFormats()

QList< QByteArray > QPictureIO::inputFormats ( )

static

Returns a sorted list of picture formats that are supported for picture input.

Definition at line 1876 of file qpicture.cpp.

Referenced by QPicture::inputFormatList(), and QPicture::inputFormats().

{
    QList<QByteArray> result;

    qt_init_picture_handlers();
    qt_init_picture_plugins();

    if (QPHList *list = pictureHandlers()) {
        for (int i = 0; i < list->size(); ++i) {
            QPictureHandler *p = list->at(i);
            if (p->read_picture && !p->obsolete  && !result.contains(p->format))
                result.append(p->format);
        }
    }
    qSort(result);

    return result;
}

ioDevice()

QIODevice * QPictureIO::ioDevice

(

)

const

Returns the IO device currently set.

See also

setIODevice()

Definition at line 1623 of file qpicture.cpp.

{ return d->iodev; }

outputFormats()

QList< QByteArray > QPictureIO::outputFormats ( )

static

Returns a sorted list of picture formats that are supported for picture output.

Definition at line 1899 of file qpicture.cpp.

Referenced by QPicture::outputFormatList(), and QPicture::outputFormats().

{
    qt_init_picture_handlers();
    qt_init_picture_plugins();

    QList<QByteArray> result;
    if (QPHList *list = pictureHandlers()) {
        for (int i = 0; i < list->size(); ++i) {
            QPictureHandler *p = list->at(i);
            if (p->write_picture && !p->obsolete && !result.contains(p->format))
                result.append(p->format);
        }
    }
    return result;
}

parameters()

const char * QPictureIO::parameters

(

)

const

Returns the picture's parameters string.

See also

setParameters()

Definition at line 1739 of file qpicture.cpp.

{
    return d->parameters;
}

picture()

const QPicture & QPictureIO::picture

(

)

const

Returns the picture currently set.

See also

setPicture()

Definition at line 1602 of file qpicture.cpp.

Referenced by QPicture::load(), and QPicture::save().

{ return d->pi; }

pictureFormat() [1/2]

QByteArray QPictureIO::pictureFormat ( const QString &  fileName )

static

Returns a string that specifies the picture format of the file fileName, or null if the file cannot be read or if the format is not recognized.

Definition at line 1808 of file qpicture.cpp.

Referenced by QPicture::pictureFormat().

{
    QFile file(fileName);
    QByteArray format;
    if (!file.open(QIODevice::ReadOnly))
        return format;
    format = pictureFormat(&file);
    file.close();
    return format;
}

pictureFormat() [2/2]

QByteArray QPictureIO::pictureFormat ( QIODevice *  d )

static

Returns a string that specifies the picture format of the picture read from IO device d, or 0 if the device cannot be read or if the format is not recognized.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Make sure that d is at the right position in the device (for example, at the beginning of the file).

See also

QIODevice::at()

Definition at line 1835 of file qpicture.cpp.

{
    // if you change this change the documentation for defineIOHandler()
    const int buflen = 14;

    char buf[buflen];
    char buf2[buflen];
    qt_init_picture_handlers();
    qt_init_picture_plugins();
    int pos = d->pos();                      // save position
    int rdlen = d->read(buf, buflen);        // read a few bytes

    QByteArray format;
    if (rdlen != buflen)
        return format;

    memcpy(buf2, buf, buflen);

    for (int n = 0; n < rdlen; n++)
        if (buf[n] == '\0')
            buf[n] = '\001';
    if (rdlen > 0) {
        buf[rdlen - 1] = '\0';
        QString bufStr = QString::fromLatin1(buf);
        if (QPHList *list = pictureHandlers()) {
            for (int i = 0; i < list->size(); ++i) {
                if (list->at(i)->header.indexIn(bufStr) != -1) { // try match with headers
                    format = list->at(i)->format;
                    break;
                }
            }
        }
    }
    d->seek(pos);                                // restore position
    return format;
}

quality()

int QPictureIO::quality

(

)

const

Returns the quality of the written picture, related to the compression ratio.

See also

setQuality() QPicture::save()

Definition at line 1712 of file qpicture.cpp.

{
    return d->quality;
}

read()

bool QPictureIO::read

(

)

Reads an picture into memory and returns true if the picture was successfully read; otherwise returns false.

Before reading an picture you must set an IO device or a file name. If both an IO device and a file name have been set, the IO device will be used.

Setting the picture file format string is optional.

Note that this function does not set the format used to read the picture. If you need that information, use the pictureFormat() static functions.

Example:

        QPictureIO iio;
        QPixmap  pixmap;
        iio.setFileName("vegeburger.pic");
        if (iio.read()) {        // OK
            QPicture picture = iio.picture();
            QPainter painter(&pixmap);
            painter.drawPicture(0, 0, picture);
        }

See also

setIODevice() setFileName() setFormat() write() QPixmap::load()

Definition at line 1937 of file qpicture.cpp.

Referenced by QPicture::load().

{
    QFile           file;
    const char          *picture_format;
    QPictureHandler *h;

    if (d->iodev) {                                // read from io device
        // ok, already open
    } else if (!d->fname.isEmpty()) {                // read from file
        file.setFileName(d->fname);
        if (!file.open(QIODevice::ReadOnly))
            return false;                        // cannot open file
        d->iodev = &file;
    } else {                                        // no file name or io device
        return false;
    }
    if (d->frmt.isEmpty()) {
        // Try to guess format
        picture_format = pictureFormat(d->iodev);        // get picture format
        if (!picture_format) {
            if (file.isOpen()) {                        // unknown format
                file.close();
                d->iodev = 0;
            }
            return false;
        }
    } else {
        picture_format = d->frmt;
    }

    h = get_picture_handler(picture_format);
    if (file.isOpen()) {
#if !defined(Q_OS_UNIX)
        if (h && h->text_mode) {                // reopen in translated mode
            file.close();
            file.open(QIODevice::ReadOnly | QIODevice::Text);
        }
        else
#endif
            file.seek(0);                        // position to start
    }
    d->iostat = 1;                                        // assume error

    if (h && h->read_picture)
        (*h->read_picture)(this);

    if (file.isOpen()) {                        // picture was read using file
        file.close();
        d->iodev = 0;
    }
    return d->iostat == 0;                                // picture successfully read?
}

setDescription()

void QPictureIO::setDescription

(

const QString &

description

)

Sets the picture description string for picture handlers that support picture descriptions to description.

Currently, no picture format supported by Qt uses the description string.

Definition at line 1796 of file qpicture.cpp.

{
    d->descr = description;
}

setFileName()

void QPictureIO::setFileName

(

const QString &

fileName

)

Sets the name of the file to read or write an picture from to fileName.

See also

setIODevice()

Definition at line 1701 of file qpicture.cpp.

{
    d->fname = fileName;
}

setFormat()

void QPictureIO::setFormat

(

const char *

format

)

Sets the picture format to format for the picture to be read or written.

It is necessary to specify a format before writing an picture, but it is not necessary to specify a format before reading an picture.

If no format has been set, Qt guesses the picture format before reading it. If a format is set the picture will only be read if it has that format.

See also

read() write() format()

Definition at line 1674 of file qpicture.cpp.

{
    d->frmt = format;
}

setGamma()

void QPictureIO::setGamma

(

float

gamma

)

Sets the gamma value at which the picture will be viewed to gamma.

If the picture format stores a gamma value for which the picture is intended to be used, then this setting will be used to modify the picture. Setting to 0.0 will disable gamma correction (i.e. any specification in the file will be ignored).

The default value is 0.0.

See also

gamma()

Definition at line 1773 of file qpicture.cpp.

{
    d->gamma=gamma;
}

setIODevice()

void QPictureIO::setIODevice

(

QIODevice *

ioDevice

)

Sets the IO device to be used for reading or writing an picture.

Setting the IO device allows pictures to be read/written to any block-oriented QIODevice.

If ioDevice is not null, this IO device will override file name settings.

See also

setFileName()

Definition at line 1690 of file qpicture.cpp.

{
    d->iodev = ioDevice;
}

setParameters()

void QPictureIO::setParameters

(

const char *

parameters

)

Sets the picture's parameter string to parameters.

This is for picture handlers that require special parameters.

Although the current picture formats supported by Qt ignore the parameters string, it may be used in future extensions or by contributions (for example, JPEG).

See also

parameters()

Definition at line 1755 of file qpicture.cpp.

{
    if (d->parameters)
        delete [] (char*)d->parameters;
    d->parameters = qstrdup(parameters);
}

setPicture()

void QPictureIO::setPicture

(

const QPicture &

picture

)

Sets the picture to picture.

See also

picture()

Definition at line 1645 of file qpicture.cpp.

{
    d->pi = picture;
}

setQuality()

void QPictureIO::setQuality

(

int

q

)

Sets the quality of the written picture to q, related to the compression ratio.

q must be in the range -1..100. Specify 0 to obtain small compressed files, 100 for large uncompressed files. (-1 signifies the default compression.)

See also

quality() QPicture::save()

Definition at line 1728 of file qpicture.cpp.

{
    d->quality = q;
}

setStatus()

void QPictureIO::setStatus

(

int

status

)

Sets the picture IO status to status.

A non-zero value indicates an error, whereas 0 means that the IO operation was successful.

See also

status()

Definition at line 1656 of file qpicture.cpp.

{
    d->iostat = status;
}

status()

int QPictureIO::status

(

)

const

Returns the picture's IO status.

A non-zero value indicates an error, whereas 0 means that the IO operation was successful.

See also

setStatus()

Definition at line 1610 of file qpicture.cpp.

{ return d->iostat; }

write()

bool QPictureIO::write

(

)

Writes an picture to an IO device and returns true if the picture was successfully written; otherwise returns false.

Before writing an picture you must set an IO device or a file name. If both an IO device and a file name have been set, the IO device will be used.

The picture will be written using the specified picture format.

Example:

        QPictureIO iio;
        QPicture   picture;
        QPainter painter(&picture);
        painter.drawPixmap(0, 0, pixmap);
        iio.setPicture(picture);
        iio.setFileName("vegeburger.pic");
        iio.setFormat("PIC");
        if (iio.write())
            return true; // returned true if written successfully

See also

setIODevice() setFileName() setFormat() read() QPixmap::save()

Definition at line 2006 of file qpicture.cpp.

Referenced by QPicture::save().

{
    if (d->frmt.isEmpty())
        return false;
    QPictureHandler *h = get_picture_handler(d->frmt);
    if (!h || !h->write_picture) {
        qWarning("QPictureIO::write: No such picture format handler: %s",
                 format());
        return false;
    }
    QFile file;
    if (!d->iodev && !d->fname.isEmpty()) {
        file.setFileName(d->fname);
        bool translate = h->text_mode==QPictureHandler::TranslateInOut;
        QIODevice::OpenMode fmode = translate ? QIODevice::WriteOnly | QIODevice::Text : QIODevice::OpenMode(QIODevice::WriteOnly);
        if (!file.open(fmode))                // couldn't create file
            return false;
        d->iodev = &file;
    }
    d->iostat = 1;
    (*h->write_picture)(this);
    if (file.isOpen()) {                        // picture was written using file
        file.close();
        d->iodev = 0;
    }
    return d->iostat == 0;                                // picture successfully written?
}

Properties

d

QPictureIOData* QPictureIO::d

private

Definition at line 183 of file qpicture.h.

---

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

• /src/gui/image/qpicture.h
• /src/gui/image/qpicture.cpp