org.riversun.exiguous

Class ExiguousExifLowLevelDecoder

java.lang.Object

org.riversun.exiguous.ExiguousExifLowLevelDecoder

public class ExiguousExifLowLevelDecoder
extends Object

Exif Low Level Decoder


Exif specification one-point description
to understand the code by Tom Misawa :)


[Overview of Exif]
First of all ,the Exif header shows the basic information.
There are blocks to store data called IFD, it is a tree structure as a directory.
The IFD block, it can be a data storage area of ??a fixed length called a field has more.
Link to the child element of the tree structure (child become IFD block) describes in the field. Specifically, it is specified by the offset value of the child element
Since the field is fixed length, since it is not suitable to hold large data, when it is desired to hold large data, specify a data location in the field.

[File structure of Exif]
0xFFD8 = begins with SOI (Start Of Image), and ends in 0xFFD9 = EOI (End Of Image)
ExifJpeg file SOI, APP1, ....., it is recorded in the order of EOI
APP1 is in the leading role of Exif, contents of APP1 is recorded in TIFF format

[Prerequisite knowledge of file structure]
First of all, to the position byte order have a specified byte order, big endian. From there the specified ones.
Although the location that specifies the location in the file are also several places, the offset value is a position that specifies the byte order.

[APP1 header of the structure]
APP1 2byte: fixed value 0xFFE1
Segment length 2byte: APP1 number of bytes
Exif identification code 6byte: fixed value 0x45 78 69 66 00 (Exif \ 0 \ 0)
Byte order (endian) 2byte: selection value 0x49 0x49-> LittleEndian
0x002A 2byte: fixed value (. However, important endian is applied from here)
IFD offset 4byte: offset of the next IFD

[Structure of IFD block]
Count 2byte: the number of fields
Field 12byte: field body (which is present in the IFD block only counts)

[Structure of IFD Field
Tag 2byte: it shows the meaning of the field. For example, we show the example, 'photo of horizontal resolution'.
Type 2byte: field of the data format (such as BYTE or ASCII)
Count 4byte: the length of the data -> For example type is BYTE, if the count is 0x00000020 1byte * 32 = 32 bytes
Offset to the value 4byte: If the length of the data is 4byte below, the data itself, equal to or greater than, the position of the value is stored
[Note]
While Exif is defined as extended format of the JFIF format (JPEG is the compression method),
In this library, JFIF is not treated.

Author:

Tom Misawa (riversun.org@gmail.com)

Field Summary

Fields

Modifier and Type	Field and Description
static int	BIG_ENDIAN
static int	LITTLE_ENDIAN

Constructor Summary

Constructors

Constructor and Description
ExiguousExifLowLevelDecoder()

Method Summary

Modifier and Type	Method and Description
int	getEndianMode()
ExifIFDBlock	getExif_IFD()
ExifIFDBlock	getGPS_IFD()
ExifIFDBlock	getIFD0()
ExifIFDBlock	getIFD1()
long	getLongValue(int[] srcByteArray, int endianMode) Get the long value of the byte array. (You can not put a byte array that exceeds the 8byte is the limit of long.
int[]	getMultiByteFromCurrentFile(long startPos, int len) Get multibytes
boolean	read(String fileName) Read the Exif formatted file
void	setLogging(boolean isLogging) Enabling logging

Methods inherited from class java.lang.Object

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

Field Detail

BIG_ENDIAN

public static final int BIG_ENDIAN

See Also:

Constant Field Values

LITTLE_ENDIAN

public static final int LITTLE_ENDIAN

See Also:

Constant Field Values

Constructor Detail

ExiguousExifLowLevelDecoder

public ExiguousExifLowLevelDecoder()

Method Detail

getEndianMode

public int getEndianMode()

read

public boolean read(String fileName)

Read the Exif formatted file

Parameters:

fileName -

getLongValue

public long getLongValue(int[] srcByteArray,
                         int endianMode)

Get the long value of the byte array.
(You can not put a byte array that exceeds the 8byte is the limit of long. )

Parameters:

srcByteArray -

endianMode - (BIG_ENDIAN=0 / LITTLE_ENDIAN=1)

Returns:

getMultiByteFromCurrentFile

public int[] getMultiByteFromCurrentFile(long startPos,
                                         int len)

Get multibytes

Parameters:

startPos -

len -

Returns:

getIFD0

public ExifIFDBlock getIFD0()

getIFD1

public ExifIFDBlock getIFD1()

getExif_IFD

public ExifIFDBlock getExif_IFD()

getGPS_IFD

public ExifIFDBlock getGPS_IFD()

setLogging

public void setLogging(boolean isLogging)

Enabling logging

Parameters:

isLogging -