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java.lang.Objectcom.trolltech.qt.QSignalEmitter
com.trolltech.qt.QtJambiObject
com.trolltech.qt.gui.QImageIOHandler
public abstract class QImageIOHandler
The QImageIOHandler class defines the common image I/O interface for all image formats in Qt.
Qt uses QImageIOHandler for reading and writing images through QImageReader and QImageWriter. You can also derive from this class to write your own image format handler using Qt's plugin mechanism.
Call setDevice to assign a device to the handler, and setFormat to assign a format to it. One QImageIOHandler may support more than one image format. canRead returns true if an image can be read from the device, and read and write return true if reading or writing an image was completed successfully.
QImageIOHandler also has support for animations formats, through the functions loopCount, imageCount, nextImageDelay and currentImageNumber.
In order to determine what options an image handler supports, Qt will call supportsOption and setOption. Make sure to reimplement these functions if you can provide support for any of the options in the ImageOption enum.
To write your own image handler, you must at least reimplement canRead and read. Then create a QImageIOPlugin that can create the handler. Finally, install your plugin, and QImageReader and QImageWriter will then automatically load the plugin, and start using it.
Nested Class Summary | |
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static class |
QImageIOHandler.ImageOption
This enum describes the different options supported by QImageIOHandler. |
Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter |
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QSignalEmitter.Signal0, QSignalEmitter.Signal1<A>, QSignalEmitter.Signal2<A,B>, QSignalEmitter.Signal3<A,B,C>, QSignalEmitter.Signal4<A,B,C,D>, QSignalEmitter.Signal5<A,B,C,D,E>, QSignalEmitter.Signal6<A,B,C,D,E,F>, QSignalEmitter.Signal7<A,B,C,D,E,F,G>, QSignalEmitter.Signal8<A,B,C,D,E,F,G,H>, QSignalEmitter.Signal9<A,B,C,D,E,F,G,H,I> |
Constructor Summary | |
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QImageIOHandler()
Constructs a QImageIOHandler object. |
Method Summary | |
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abstract boolean |
canRead()
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. |
int |
currentImageNumber()
For image formats that support animation, this function returns the sequence number of the current image in the animation. |
QRect |
currentImageRect()
Returns the rect of the current image. |
QIODevice |
device()
Returns the device currently assigned to the QImageIOHandler. |
QByteArray |
format()
Returns the format that is currently assigned to QImageIOHandler. |
static QImageIOHandler |
fromNativePointer(QNativePointer nativePointer)
This function returns the QImageIOHandler instance pointed to by nativePointer |
int |
imageCount()
For image formats that support animation, this function returns the number of images in the animation. |
boolean |
jumpToImage(int imageNumber)
For image formats that support animation, this function jumps to the image whose sequence number is imageNumber. |
boolean |
jumpToNextImage()
For image formats that support animation, this function jumps to the next image. |
int |
loopCount()
For image formats that support animation, this function returns the number of times the animation should loop. |
int |
nextImageDelay()
For image formats that support animation, this function returns the number of milliseconds to wait until reading the next image. |
java.lang.Object |
option(QImageIOHandler.ImageOption option)
Returns the value assigned to option as a QVariant. |
abstract boolean |
read(QImage image)
Read an image from the device, and stores it in image. |
void |
setDevice(QIODevice device)
Sets the device of the QImageIOHandler to device. |
void |
setFormat(QByteArray format)
Sets the format of the QImageIOHandler to format. |
void |
setOption(QImageIOHandler.ImageOption option,
java.lang.Object value)
Sets the option option with the value value. |
boolean |
supportsOption(QImageIOHandler.ImageOption option)
Returns true if the QImageIOHandler supports the option option; otherwise returns false. |
boolean |
write(QImage image)
Writes the image image to the assigned device. |
Methods inherited from class com.trolltech.qt.QtJambiObject |
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dispose, disposed, finalize, reassignNativeResources, tr, tr, tr |
Methods inherited from class com.trolltech.qt.QSignalEmitter |
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blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread |
Methods inherited from class java.lang.Object |
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clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Methods inherited from interface com.trolltech.qt.QtJambiInterface |
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disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership |
Constructor Detail |
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public QImageIOHandler()
Constructs a QImageIOHandler object.
Method Detail |
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public final QIODevice device()
Returns the device currently assigned to the QImageIOHandler. If not device has been assigned, 0 is returned.
public final QByteArray format()
Returns the format that is currently assigned to QImageIOHandler. If no format has been assigned, an empty string is returned.
public final void setDevice(QIODevice device)
Sets the device of the QImageIOHandler to device. The image handler will use this device when reading and writing images.
The device can only be set once and must be set before calling canRead, read, write, etc. If you need to read multiple files, construct multiple instances of the appropriate QImageIOHandler subclass.
public final void setFormat(QByteArray format)
Sets the format of the QImageIOHandler to format. The format is most useful for handlers that support multiple image formats.
public abstract boolean canRead()
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).
public int currentImageNumber()
For image formats that support animation, this function returns the sequence number of the current image in the animation. If the image format does not support animation, or if it is unable to determine the current sequence number, 0 is returned.
public QRect currentImageRect()
Returns the rect of the current image. If no rect is defined for the image, and empty QRect() is returned.
This function is useful for animations, where only parts of the frame may be updated at a time.
public int imageCount()
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.
public boolean jumpToImage(int imageNumber)
For image formats that support animation, this function jumps to the image whose sequence number is imageNumber. The next call to read will attempt to read this image.
The default implementation does nothing, and returns false.
public boolean jumpToNextImage()
For image formats that support animation, this function jumps to the next image.
The default implementation does nothing, and returns false.
public int loopCount()
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.
public int nextImageDelay()
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.
public java.lang.Object option(QImageIOHandler.ImageOption option)
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.
public abstract boolean read(QImage image)
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.
public void setOption(QImageIOHandler.ImageOption option, java.lang.Object value)
Sets the option option with the value value.
public boolean supportsOption(QImageIOHandler.ImageOption option)
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.
public boolean write(QImage image)
Writes the image image to the assigned device. Returns true on success; otherwise returns false.
The default implementation does nothing, and simply returns false.
public static QImageIOHandler fromNativePointer(QNativePointer nativePointer)
nativePointer
- the QNativePointer of which object should be returned.
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