QImageIO(3qt)QImageIO(3qt)NAMEQImageIO - Parameters for loading and saving images
#include <qimage.h>
Public Members
QImageIO ()
QImageIO ( QIODevice * ioDevice, const char * format )
QImageIO ( const QString & fileName, const char * format )
~QImageIO ()
const QImage& image () const
int status () const
const char* format () const
QIODevice* ioDevice () const
QString fileName () const
const char* parameters () const
QString description () const
void setImage ( const QImage & )
void setStatus ( int )
void setFormat ( const char * )
void setIODevice ( QIODevice * )
void setFileName ( const QString & )
void setParameters ( const char * )
void setDescription ( const QString & )
bool read ()
bool write ()
Static Public Members
const char* imageFormat ( const QString & fileName )
const char* imageFormat ( QIODevice * )
QStrList inputFormats ()
QStrList outputFormats ()
void defineIOHandler ( const char * format, const char *
header, const char * flags, image_io_handler
read_image, image_io_handler write_image )
DESCRIPTION
The QImageIO class contains parameters for loading and
saving images.
QImageIO contains a QIODevice object that is used for
image data I/O. The programmer can install new image file
formats in addition to those that Qt implements.
Qt currently supports the following image file formats:
PNG, BMP, XBM, XPM and PNM. It may also support JPEG, MNG
and GIF, if specially configured during compilation. The
different PNM formats are: PBM (P1 or P4), PGM (P2 or P5),
PPM (P3 or P6).
You will normally not need to use this class,
QPixmap::load(), QPixmap::save() and QImage contain most
of the needed functionality.
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For image files which contain sequences of images, only
the first is read. See the QMovie for loading multiple
images.
PBM, PGM, and PPM format output is always in the more
condensed raw format. PPM and PGM files with more than 256
levels of intensity are scaled down when reading.
Warning: Unisys has changed its position regarding GIF. If
you are in a country where Unisys holds a patent on LZW
compression and/or decompression and you want to use GIF,
Unisys may require you to license that technology. These
countries include Canada, Japan, the USA, France, Germany,
Italy and the UK.
GIF support may be removed completely in a future version
of Qt. We recommend using the PNG format.
See also QImage, QPixmap, QFile and QMovie.
MEMBER FUNCTION DOCUMENTATIONQImageIO::QImageIO ()
Constructs a QImageIO object with all parameters set to
zero.
QImageIO::QImageIO ( QIODevice * ioDevice, const char * format )
Constructs a QImageIO object with an I/O device and a
format tag.
QImageIO::QImageIO ( const QString & fileName, const char *
format )
Constructs a QImageIO object with a file name and a format
tag.
QImageIO::~QImageIO ()
Destructs the object and all related data.
void QImageIO::defineIOHandler ( const char * format, const char
* header, const char * flags, image_io_handler read_image,
image_io_handler write_image ) [static]
Defines a image IO handler for a specified image format.
An image IO handler is responsible for reading and writing
images.
Arguments:
format is the name of the format.
header is a regular expression that recognizes the image
header.
flags is "T" for text formats like PBM; generally you will
want to use 0.
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read_image is a function to read an image of this format.
write_image is a function to write an image of this
format. Both read_image and write_image are of type
image_io_handler, which is a function pointer.
Example:
void readGIF( QImageIO *image )
{
// read the image, using the image->ioDevice()
}
void writeGIF( QImageIO *image )
{
// write the image, using the image->ioDevice()
}
// add the GIF image handler
QImageIO::defineIOHandler( "GIF",
"^GIF[0-9][0-9][a-z]",
0,
readGIF,
writeGIF );
Prior to comparison with the regular expression, the file
header is converted to change all 0 bytes into 1 bytes.
This is done because 0 is such a common header byte yet
regular expressions cannot match it.
For image formats supporting incremental display, such as
sequences of animated frames, see the QImageFormatType
class.
QString QImageIO::description () const
Returns the image description string.
See also setDescription().
QString QImageIO::fileName () const
Returns the file name currently set.
See also setFileName().
const char * QImageIO::format () const
Returns the image format string, or 0 if no format has
been explicitly set.
const QImage & QImageIO::image () const
Returns the image currently set.
See also setImage().
const char * QImageIO::imageFormat ( QIODevice * d ) [static]
Returns a string that specifies the image format of the
image read from d, or null if the file cannot be read or
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if the format is not recognized.
const char* QImageIO::imageFormat ( const QString & fileName )
[static]
Returns a string that specifies the image format of the
file fileName, or null if the file cannot not be read or
if the format is not recognized.
QStrList QImageIO::inputFormats () [static]
Returns a sorted list of image formats which are supported
for image input.
QIODevice * QImageIO::ioDevice () const
Returns the IO device currently set.
See also setIODevice().
QStrList QImageIO::outputFormats () [static]
Returns a sorted list of image formats which are supported
for image output.
const char * QImageIO::parameters () const
Returns image parameters string.
See also setParameters().
bool QImageIO::read ()
Reads an image into memory and returns TRUE if the image
was successfully read.
Before reading an image, you must set an IO device or a
file name. If both an IO device and a file name has been
set, then the IO device will be used.
Setting the image file format string is optional.
Note that this function does not set the format used to
read the image. If you need that information, use the
imageFormat() static functions.
Example:
QImageIO iio;
QPixmap pixmap;
iio.setFileName( "burger.bmp" );
if ( image.read() ) // ok
pixmap = iio.image(); // convert to pixmap
See also setIODevice(), setFileName(), setFormat(),
write() and QPixmap::load().
void QImageIO::setDescription ( const QString & description )
Sets the image description string for image handlers that
support image descriptions.
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Currently, no image format supported by Qt use the
description string.
void QImageIO::setFileName ( const QString & fileName )
Sets the name of the file to read or write an image.
See also setIODevice().
void QImageIO::setFormat ( const char * format )
Sets the image format name of the image about to be read
or written.
It is necessary to specify a format before writing an
image.
It is not necessary to specify a format before reading an
image. If not format has been set, Qt guesses the image
format before reading it. If a format is set, but the
image has another (valid) format, the image will not be
read.
See also read(), write() and format().
void QImageIO::setIODevice ( QIODevice * ioDevice )
Sets the IO device to be used for reading or writing an
image.
Setting the IO device allows images 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().
void QImageIO::setImage ( const QImage & image )
Sets the image.
See also image().
void QImageIO::setParameters ( const char * parameters )
Sets the image parameters string for image handlers that
require special parameters.
Although all image formats supported by Qt ignore the
parameters string, it will be useful for future extensions
or contributions (like JPEG).
void QImageIO::setStatus ( int status )
Sets the image IO status. A non-zero value indicates an
error, while 0 means that the IO operation was successful.
See also status().
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QImageIO(3qt)QImageIO(3qt)int QImageIO::status () const
Returns the image IO status. A non-zero value indicates an
error, while 0 means that the IO operation was successful.
See also setStatus().
bool QImageIO::write ()
Writes an image to an IO device and returns TRUE if the
image was successfully written.
Before writing an image, you must set an IO device or a
file name. If both an IO device and a file name has been
set, then the IO device will be used.
The image will be written using the specified image
format.
Example:
QImageIO iio;
QImage im;
im = pixmap; // convert to image
iio.setImage( im );
iio.setFileName( "burger.bmp" );
iio.setFormat( "BMP" );
iio.write(); // TRUE if ok
See also setIODevice(), setFileName(), setFormat(),
read() and QPixmap::save().
SEE ALSO
http://doc.trolltech.com/qimageio.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2001 Trolltech AS,
http://www.trolltech.com. See the license file included
in the distribution for a complete license statement.
AUTHOR
Generated automatically from the source code.
BUGS
If you find a bug in Qt, please report it as described in
http://doc.trolltech.com/bughowto.html. Good bug reports
make our job much simpler. Thank you.
In case of content or formattting problems with this
manual page, please report them to qt-bugs@trolltech.com.
Please include the name of the manual page (qimageio.3qt)
and the Qt version (2.3.1).
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