Package com.drew.imaging.jpeg

Class JpegSegmentReader

java.lang.Object

com.drew.imaging.jpeg.JpegSegmentReader

public class JpegSegmentReader
extends Object

Performs read functions of JPEG files, returning specific file segments.

JPEG files are composed of a sequence of consecutive JPEG 'segments'. Each is identified by one of a set of byte values, modelled in the JpegSegmentType enumeration. Use readSegments to read out the some or all segments into a JpegSegmentData object, from which the raw JPEG segment byte arrays may be accessed.

Field Summary

Fields

Modifier and Type	Field	Description
private static final byte	MARKER_EOI	Private, because one wouldn't search for it.
private static final byte	SEGMENT_IDENTIFIER	The 0xFF byte that signals the start of a segment.
private static final byte	SEGMENT_SOS	Private, because this segment crashes my algorithm, and searching for it doesn't work (yet).

Constructor Summary

Constructors

Modifier	Constructor	Description
private	JpegSegmentReader()

Method Summary

Modifier and Type	Method	Description
static JpegSegmentData	readSegments(SequentialReader reader, Iterable<JpegSegmentType> segmentTypes)	Processes the provided JPEG data, and extracts the specified JPEG segments into a JpegSegmentData object.
static JpegSegmentData	readSegments(File file, Iterable<JpegSegmentType> segmentTypes)	Processes the provided JPEG data, and extracts the specified JPEG segments into a JpegSegmentData object.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

SEGMENT_IDENTIFIER

private static final byte SEGMENT_IDENTIFIER

The 0xFF byte that signals the start of a segment.

See Also:

• Constant Field Values

SEGMENT_SOS

private static final byte SEGMENT_SOS

Private, because this segment crashes my algorithm, and searching for it doesn't work (yet).

See Also:

• Constant Field Values

MARKER_EOI

private static final byte MARKER_EOI

Private, because one wouldn't search for it.

See Also:

• Constant Field Values

Constructor Details

JpegSegmentReader

private JpegSegmentReader()
                   throws Exception

Throws:

Exception

Method Details

readSegments

public static JpegSegmentData readSegments(File file,
 Iterable<JpegSegmentType> segmentTypes)
                                    throws JpegProcessingException,
IOException

Processes the provided JPEG data, and extracts the specified JPEG segments into a JpegSegmentData object.

Will not return SOS (start of scan) or EOI (end of image) segments.

Parameters:

file - a File from which the JPEG data will be read.

segmentTypes - the set of JPEG segments types that are to be returned. If this argument is null then all found segment types are returned.

Throws:

JpegProcessingException

IOException

readSegments

public static JpegSegmentData readSegments(SequentialReader reader,
 Iterable<JpegSegmentType> segmentTypes)
                                    throws JpegProcessingException,
IOException

Processes the provided JPEG data, and extracts the specified JPEG segments into a JpegSegmentData object.

Will not return SOS (start of scan) or EOI (end of image) segments.

Parameters:

reader - a SequentialReader from which the JPEG data will be read. It must be positioned at the beginning of the JPEG data stream.

segmentTypes - the set of JPEG segments types that are to be returned. If this argument is null then all found segment types are returned.

Throws:

JpegProcessingException

IOException