Package org.monte.media.jpeg

Class JFIFInputStream

  • All Implemented Interfaces:
    Closeable, AutoCloseable
    public class JFIFInputStream
extends FilterInputStream
    JFIFInputStream.

    This InputStream uses two special marker values which do not exist in the JFIF stream:

    • -1: marks junk data at the beginning of the file.
    • 0: marks entropy encoded image data.

    The junk data at the beginning of the file can be accessed by calling the read-methods immediately after opening the stream. Call nextSegment() immediately after opening the stream if you are not interested into this junk data.

    Junk data at the end of the file is delivered as part of the EOI_MARKER segment. Finish reading after encountering the EOI_MARKER segment if you are not interested in this junk data.

    References:
    JPEG File Interchange Format Version 1.02
    http://www.jpeg.org/public/jfif.pdf

    Pennebaker, W., Mitchell, J. (1993).
    JPEG Still Image Data Compression Standard.
    Chapmann & Hall, New York.
    ISBN 0-442-01272-1

    Version:
    $Id: JFIFInputStream.java 348 2015-09-23 17:46:43Z werner $
    Author:
    Werner Randelshofer, Hausmatt 10, CH-6405 Goldau

    • Method Detail

      • getSegment

        public JFIFInputStream.Segment getSegment()
                                   throws IOException
        Gets the current segment from the input stream.
        Returns:
        The current segment. Returns null, if we encountered the end of the stream.
        Throws:
        IOException

      • getNextSegment

        public JFIFInputStream.Segment getNextSegment()
                                       throws IOException
        Gets the next segment from the input stream.
        Returns:
        The next segment. Returns null, if we encountered the end of the stream.
        Throws:
        IOException

      • getStreamPosition

        public long getStreamPosition()

      • read

        public int read()
         throws IOException
        Reads the next byte of data from this input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

        This method simply performs in.read() and returns the result.

        Overrides:
        read in class FilterInputStream
        Returns:
        the next byte of data, or -1 if the end of the stream is reached.
        Throws:
        IOException - if an I/O error occurs.
        See Also:
        FilterInputStream.in

      • read

        public int read​(byte[] b,
                int off,
                int len)
         throws IOException
        Reads up to len b of data from this input stream into an array of b. This method blocks until some input is available.

        This method simply performs in.read(b, off, len) and returns the result.

        Overrides:
        read in class FilterInputStream
        Parameters:
        b - the buffer into which the data is read.
        off - the start offset of the data.
        len - the maximum number of b read.
        Returns:
        the total number of b read into the buffer, or -1 if there is no more data because the end of the stream has been reached.
        Throws:
        IOException - if an I/O error occurs.
        See Also:
        FilterInputStream.in

      • skipFully

        public final void skipFully​(long n)
                     throws IOException
        Fully skips the specified number of bytes.
        Throws:
        IOException

      • skip

        public long skip​(long n)
          throws IOException
        Skips over and discards n b of data from the input stream. The skip method may, for a variety of reasons, end up skipping over some smaller number of b, possibly 0. The actual number of b skipped is returned.

        This method simply performs in.skip(n).

        Overrides:
        skip in class FilterInputStream
        Parameters:
        n - the number of b to be skipped.
        Returns:
        the actual number of b skipped.
        Throws:
        IOException - if an I/O error occurs.

      • mark

        public void mark​(int readlimit)
        Marks the current position in this input stream. A subsequent call to the reset method repositions this stream at the last marked position so that subsequent reads re-read the same b.

        The readlimit argument tells this input stream to allow that many b to be read before the mark position gets invalidated.

        This method simply performs in.mark(readlimit).

        Overrides:
        mark in class FilterInputStream
        Parameters:
        readlimit - the maximum limit of b that can be read before the mark position becomes invalid.
        See Also:
        FilterInputStream.in, FilterInputStream.reset()

      • reset

        public void reset()
           throws IOException
        Repositions this stream to the position at the time the mark method was last called on this input stream.

        This method simply performs in.reset().

        Stream marks are intended to be used in situations where you need to read ahead a little to see what's in the stream. Often this is most easily done by invoking some general parser. If the stream is of the type handled by the parse, it just chugs along happily. If the stream is not of that type, the parser should toss an exception when it fails. If this happens within readlimit b, it allows the outer code to reset the stream and try another parser.

        Overrides:
        reset in class FilterInputStream
        Throws:
        IOException - if the stream has not been marked or if the mark has been invalidated.
        See Also:
        FilterInputStream.in, FilterInputStream.mark(int)