QImageDecoder Class Reference
The QImageDecoder class is an incremental image decoder for all supported image formats.
More...
#include <qasyncimageio.h>
List of all member functions.
Public Members
int
decode ( const uchar * buffer, int length )
Static Public Members
const char *
formatName ( const uchar * buffer, int length )
QImageFormatType *
format ( const char * name )
Detailed Description
The QImageDecoder class is an incremental image decoder for all supported image formats.
New formats are installed by creating objects of class
QImageFormatType; the QMovie class can be used for all installed
incremental image formats. QImageDecoder is only useful for
creating new ways of feeding data to an QImageConsumer.
A QImageDecoder is a machine that decodes images. It takes encoded
image data via its decode() method and expresses its decoding by
supplying information to a QImageConsumer. It implements its
decoding by using a QImageFormat created by one of the
currently-existing QImageFormatType factory objects.
QImageFormatType and QImageFormat are the classes that you might
need to implement support for additional image formats.
Qt supports GIF reading if it is configured that way during
installation (see qgif.h). If it is, we are required to state that
"The Graphics Interchange Format(c) is the Copyright property of
CompuServe Incorporated. GIF(sm) is a Service Mark property of
CompuServe Incorporated."
Warning: If you are in a country that 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 that 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 MNG or PNG format.
See also Graphics Classes, Image Processing Classes, and Multimedia Classes.
Member Function Documentation
QImageDecoder::QImageDecoder ( QImageConsumer * c )
Constructs a QImageDecoder that will send change information to
the QImageConsumer c.
QImageDecoder::~QImageDecoder ()
Destroys a QImageDecoder. The image it built is destroyed. The
decoder built by the factory for the file format is destroyed. The
consumer for which it decoded the image is not destroyed.
int QImageDecoder::decode ( const uchar * buffer, int length )
Call this function to decode some data into image changes. The
data in buffer will be decoded, sending change information to
the QImageConsumer of this QImageDecoder until one of the change
functions of the consumer returns FALSE. The length of the data is
given in length.
Returns the number of bytes consumed: 0 if consumption is
complete, and -1 if decoding fails due to invalid data.
QImageFormatType * QImageDecoder::format ( const char * name ) [static]
Returns a QImageFormatType by name. This might be used when the
user needs to force data to be interpreted as being in a certain
format. name is one of the formats listed by
QImageDecoder::inputFormats(). Note that you will still need to
supply decodable data to result->decoderFor() before you can begin
decoding the data.
const char * QImageDecoder::formatName ( const uchar * buffer, int length ) [static]
Call this function to find the name of the format of the given
header. The returned string is statically allocated. The function
will look at the first length characters in the buffer.
Returns 0 if the format is not recognized.
const QImage & QImageDecoder::image ()
Returns the image currently being decoded.
QStrList QImageDecoder::inputFormats () [static]
Returns a sorted list of formats for which asynchronous loading is
supported.
void QImageDecoder::registerDecoderFactory ( QImageFormatType * f ) [static]
Registers the new QImageFormatType f. This is not needed in
application code because factories call this themselves.
void QImageDecoder::unregisterDecoderFactory ( QImageFormatType * f ) [static]
Unregisters the QImageFormatType f. This is not needed in
application code because factories call this themselves.
This file is part of the Qt toolkit.
Copyright © 1995-2003
Trolltech. All Rights Reserved.
