QImageIO(3qt)QImageIO(3qt)NAME
QImageIO - Parameters for loading and saving images
SYNOPSIS
#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
int quality () const
QString description () const
const char * parameters () const
float gamma () const
void setImage ( const QImage & image )
void setStatus ( int status )
void setFormat ( const char * format )
void setIODevice ( QIODevice * ioDevice )
void setFileName ( const QString & fileName )
void setQuality ( int q )
void setDescription ( const QString & description )
void setParameters ( const char * parameters )
void setGamma ( float gamma )
bool read ()
bool write ()
Static Public Members
const char * imageFormat ( const QString & fileName )
const char * imageFormat ( QIODevice * d )
QStrList inputFormats ()
QStrList outputFormats ()
void defineIOHandler ( const char * format, const char * header, const
char * flags, image_io_handler readImage, image_io_handler
writeImage )
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 provides.
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), and PPM (P3 or P6).
You don't normally need to use this class; QPixmap::load(),
QPixmap::save(), and QImage contain sufficient functionality.
For image files that contain sequences of images, only the first is
read. See 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: If you are in a country which recognizes software patents and
in which Unisys holds a patent on LZW compression and/or decompression
and you want to use GIF, Unisys may require you to license the
technology. Such 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, QMovie, Graphics Classes, Image
Processing Classes, and Input/Output and Networking.
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 the I/O device ioDevice and a format
tag.
QImageIO::QImageIO ( const QString & fileName, const char * format )
Constructs a QImageIO object with the file name fileName and a format
tag.
QImageIO::~QImageIO ()
Destroys the object and all related data.
void QImageIO::defineIOHandler ( const char * format, const char * header,
const char * flags, image_io_handler readImage, image_io_handler
writeImage ) [static]
Defines an image I/O handler for the image format called format, which
is recognized using the regular expression header, read using readImage
and written using writeImage.
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 image
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 QImage; header is used to
select a handler to read an image file.
If readImage is a null pointer, the QImageIO will not be able to read
images in format. If writeImage is a null pointer, the QImageIO will
not be able to write images in format. If both are null, the QImageIO
object is valid but useless.
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 );
Before the regex 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 Qt assumes that there is only one handler per format; if two
handlers support the same format, Qt will choose one arbitrarily. It is
not possible to have one handler support reading, and another support
writing.
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.
float QImageIO::gamma () const
Returns the gamma value at which the image will be viewed.
See also setGamma().
const QImage & QImageIO::image () const
Returns the image currently set.
See also setImage().
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 be read or if the format is not recognized.
const char * QImageIO::imageFormat ( QIODevice * d ) [static]
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Returns a string that specifies the image format of the image read from
IO device d, or 0 if the device cannot be read or if the format is not
recognized.
Make sure that d is at the right position in the device (for example,
at the beginning of the file).
See also QIODevice::at().
QStrList QImageIO::inputFormats () [static]
Returns a sorted list of image formats that 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 that are supported for image
output.
Example: scribble/scribble.cpp.
const char * QImageIO::parameters () const
Returns the image's parameters string.
See also setParameters().
int QImageIO::quality () const
Returns the quality of the written image, related to the compression
ratio.
See also setQuality() and QImage::save().
bool QImageIO::read ()
Reads an image into memory and returns TRUE if the image was
successfully read; otherwise returns FALSE.
Before reading an image 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 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( "vegeburger.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 to description.
Currently, no image format supported by Qt uses the description string.
void QImageIO::setFileName ( const QString & fileName )
Sets the name of the file to read or write an image from to fileName.
See also setIODevice().
void QImageIO::setFormat ( const char * format )
Sets the image format to format for the image to be read or written.
It is necessary to specify a format before writing an image, but it is
not necessary to specify a format before reading an image.
If no format has been set, Qt guesses the image format before reading
it. If a format is set the image will only be read if it has that
format.
See also read(), write(), and format().
void QImageIO::setGamma ( float gamma )
Sets the gamma value at which the image will be viewed to gamma. If the
image format stores a gamma value for which the image is intended to be
used, then this setting will be used to modify the image. 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().
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 to image.
See also image().
void QImageIO::setParameters ( const char * parameters )
Sets the image's parameter string to parameters. This is for image
handlers that require special parameters.
Although the current image formats supported by Qt ignore the
parameters string, it may be used in future extensions or by
contributions (for example, JPEG).
See also parameters().
void QImageIO::setQuality ( int q )
Sets the quality of the written image 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() and QImage::save().
void QImageIO::setStatus ( int status )
Sets the image IO status to status. A non-zero value indicates an
error, whereas 0 means that the IO operation was successful.
See also status().
int QImageIO::status () const
Returns the image's IO status. A non-zero value indicates an error,
whereas 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; otherwise returns FALSE.
Before writing an image 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 image will be written using the specified image format.
Example:
QImageIO iio;
QImage im;
im = pixmap; // convert to image
iio.setImage( im );
iio.setFileName( "vegeburger.bmp" );
iio.setFormat( "BMP" );
if ( iio.write() )
// returned TRUE if written successfully
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 1992-2007 Trolltech ASA, 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
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Trolltech AS 2 February 2007 QImageIO(3qt)