PNGImageReader

Returns a default ImageReadParam object appropriate for this format. All subclasses should define a set of default values for all parameters and return them with this call. This method may be called before the input source is set.

The default implementation constructs and returns a new ImageReadParam object that does not allow source scaling (i.e., it returns new ImageReadParam().

Returns the height in pixels of the given image within the input source.

If the image can be rendered to a user-specified size, then this method returns the default height.

Returns an IIOMetadata object containing metadata associated with the given image, or null if the reader does not support reading metadata, is set to ignore metadata, or if no metadata is available.

Returns an Iterator containing possible image types to which the given image may be decoded, in the form of ImageTypeSpecifierss. At least one legal image type will be returned.

The first element of the iterator should be the most "natural" type for decoding the image with as little loss as possible. For example, for a JPEG image the first entry should be an RGB image, even though the image data is stored internally in a YCbCr color space.

Returns the number of images, not including thumbnails, available from the current input source.

Note that some image formats (such as animated GIF) do not specify how many images are present in the stream. Thus determining the number of images will require the entire stream to be scanned and may require memory for buffering. If images are to be processed in order, it may be more efficient to simply call read with increasing indices until an IndexOutOfBoundsException is thrown to indicate that no more images are available. The allowSearch parameter may be set to false to indicate that an exhaustive search is not desired; the return value will be -1 to indicate that a search is necessary. If the input has been specified with seekForwardOnly set to true, this method throws an IllegalStateException if allowSearch is set to true.

Returns an ImageTypeSpecifier indicating the SampleModel and ColorModel which most closely represents the "raw" internal format of the image. For example, for a JPEG image the raw type might have a YCbCr color space even though the image would conventionally be transformed into an RGB color space prior to display. The returned value should also be included in the list of values returned by getImageTypes.

The default implementation simply returns the first entry from the list provided by getImageType.

Returns an IIOMetadata object representing the metadata associated with the input source as a whole (i.e., not associated with any particular image), or null if the reader does not support reading metadata, is set to ignore metadata, or if no metadata is available.

Returns the width in pixels of the given image within the input source.

If the image can be rendered to a user-specified size, then this method returns the default width.

Reads the image indexed by imageIndex and returns it as a complete BufferedImage, using a supplied ImageReadParam.

The actual BufferedImage returned will be chosen using the algorithm defined by the getDestination method.

Any registered IIOReadProgressListener objects will be notified by calling their imageStarted method, followed by calls to their imageProgress method as the read progresses. Finally their imageComplete method will be called. IIOReadUpdateListener objects may be updated at other times during the read as pixels are decoded. Finally, IIOReadWarningListener objects will receive notification of any non-fatal warnings that occur during decoding.

The set of source bands to be read and destination bands to be written is determined by calling getSourceBands and getDestinationBands on the supplied ImageReadParam. If the lengths of the arrays returned by these methods differ, the set of source bands contains an index larger that the largest available source index, or the set of destination bands contains an index larger than the largest legal destination index, an IllegalArgumentException is thrown.

If the supplied ImageReadParam contains optional setting values not supported by this reader (e.g. source render size or any format-specific settings), they will be ignored.

Restores the ImageReader to its initial state.

The default implementation calls setInput(null, false), setLocale(null), removeAllIIOReadUpdateListeners(), removeAllIIOReadWarningListeners(), removeAllIIOReadProgressListeners(), and clearAbortRequest.

Sets the input source to use to the given ImageInputStream or other Object. The input source must be set before any of the query or read methods are used. If input is null, any currently set input source will be removed. In any case, the value of minIndex will be initialized to 0.

The seekForwardOnly parameter controls whether the value returned by getMinIndex will be increased as each image (or thumbnail, or image metadata) is read. If seekForwardOnly is true, then a call to read(index) will throw an IndexOutOfBoundsException if index < this.minIndex; otherwise, the value of minIndex will be set to index. If seekForwardOnly is false, the value of minIndex will remain 0 regardless of any read operations.

The ignoreMetadata parameter, if set to true, allows the reader to disregard any metadata encountered during the read. Subsequent calls to the getStreamMetadata and getImageMetadata methods may return null, and an IIOImage returned from readAll may return null from their getMetadata method. Setting this parameter may allow the reader to work more efficiently. The reader may choose to disregard this setting and return metadata normally.

Subclasses should take care to remove any cached information based on the previous stream, such as header information or partially decoded image data.

Use of a general Object other than an ImageInputStream is intended for readers that interact directly with a capture device or imaging protocol. The set of legal classes is advertised by the reader's service provider's getInputTypes method; most readers will return a single-element array containing only ImageInputStream.class to indicate that they accept only an ImageInputStream.

The default implementation checks the input argument against the list returned by originatingProvider.getInputTypes() and fails if the argument is not an instance of one of the classes in the list. If the originating provider is set to null, the input is accepted only if it is an ImageInputStream.