com.mcgath.jhove.module

Class PngModule

java.lang.Object

edu.harvard.hul.ois.jhove.ModuleBase

com.mcgath.jhove.module.PngModule

All Implemented Interfaces:

Module

public class PngModule
extends ModuleBase

Module for validation and metadata extraction on PNG files.

Author:

Gary McGath An earlier PNG module was submitted by Gian Uberto Lauri. A few bits of code are copied from it. It validates files but doesn't do much metadata extraction. I noticed it only after making a significant start on my own version. -- GDM

Field Summary

Fields

Modifier and Type	Field and Description
protected Checksummer	_ckSummer
protected int	_colorType
protected ChecksumInputStream	_cstream
protected DataInputStream	_dstream
protected List<Property>	_keywordPropList
protected Property	_metadata
protected List<Property>	_propList
protected List<Property>	_spltList

Fields inherited from class edu.harvard.hul.ois.jhove.ModuleBase

_app, _bigEndian, _checksumFinished, _countStream, _coverage, _crc32, _date, _defaultParams, _features, _format, _init, _isRandomAccess, _je, _logger, _md5, _mimeType, _name, _nByte, _note, _param, _release, _repInfoNote, _rights, _sha1, _signature, _specification, _validityNote, _vendor, _verbosity, _wellFormedNote

Fields inherited from interface edu.harvard.hul.ois.jhove.Module

MAXIMUM_VERBOSITY, MINIMUM_VERBOSITY

Constructor Summary

Constructors

Constructor and Description
PngModule() Instantiate a PngModule object.

Method Summary

Methods

Modifier and Type	Method and Description
void	addKeyword(String keywd, String val) Add a keyword and value.
void	addKeyword(String keywd, String translatedKeywd, String val, String language) Add a keyword, value, and language.
void	addSplt(String name, int sampleDepth, int numSamples) Add a suggested palette
void	checkSignatures(File file, InputStream stream, RepInfo info) Check if the digital object conforms to this Module's internal signature information.
void	eatChunk(PNGChunk chnk) This lets the module skip over the remainder of a chunk, not including the name, length,and CRC.
int	getColorType() Get the color type that was recorded from the IHDR chunk.
protected void	initParse() Initializes the state of the module for parsing.
boolean	isChunkSeen(int chunkType)
boolean	isIdatFinished() Return true if a non-IDAT chunk has been seen after an IDAT chunk
boolean	isIdatSeen() Return true if IDAT chunk has been seen
boolean	isIhdrSeen() Returns true if IHDR chunk has been seen
boolean	isPlteSeen() Return true if PLTE chunk has been seen
int	parse(InputStream stream, RepInfo info, int parseIndex) Parse the content of a purported JPEG stream digital object and store the results in RepInfo.
void	setChunkSeen(int chunkType)
void	setColorType(int ct) Set the color type.
void	setIdatSeen(boolean b) Note that an IDAT chunk has been seen
void	setIendSeen(boolean b) Note that an IEND chunk has been seen
void	setIhdrSeen(boolean b) Note that an IHDR chunk has been seen
void	setPlteSeen(boolean b) Note that a PLTE chunk has been seen

Methods inherited from class edu.harvard.hul.ois.jhove.ModuleBase

addIntegerProperty, addIntegerProperty, applyDefaultParams, calcRAChecksum, checkSignatures, getApp, getBase, getBufferedDataStream, getCoverage, getCRC32, getDate, getDefaultParams, getFeatures, getFormat, getMimeType, getName, getNByte, getNote, getRelease, getRepInfoNote, getRights, getSignature, getSpecification, getValidityNote, getVendor, getWellFormedNote, hasFeature, init, initFeatures, isBigEndian, isRandomAccess, param, parse, readByteBuf, readDouble, readDouble, readDouble, readFloat, readFloat, readSignedByte, readSignedByte, readSignedByte, readSignedInt, readSignedInt, readSignedInt, readSignedLong, readSignedRational, readSignedRational, readSignedShort, readSignedShort, readSignedShort, readUnsignedByte, readUnsignedByte, readUnsignedByte, readUnsignedInt, readUnsignedInt, readUnsignedInt, readUnsignedRational, readUnsignedRational, readUnsignedRational, readUnsignedShort, readUnsignedShort, readUnsignedShort, resetParams, setApp, setBase, setChecksums, setCRC32, setDefaultParams, setMD5, setNByte, setSHA1, setValidityNote, setVerbosity, show, skipBytes, skipBytes, vectorToPropArray

Methods inherited from class java.lang.Object

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

Field Detail

_ckSummer

protected Checksummer _ckSummer

_propList

protected List<Property> _propList

_keywordPropList

protected List<Property> _keywordPropList

_spltList

protected List<Property> _spltList

_cstream

protected ChecksumInputStream _cstream

_dstream

protected DataInputStream _dstream

_metadata

protected Property _metadata

_colorType

protected int _colorType

Constructor Detail

PngModule

public PngModule()

Instantiate a PngModule object.

Method Detail

checkSignatures

public void checkSignatures(File file,
                   InputStream stream,
                   RepInfo info)
                     throws IOException

Check if the digital object conforms to this Module's internal signature information.

Specified by:

checkSignatures in interface Module

Overrides:

checkSignatures in class ModuleBase

Parameters:

file - A RandomAccessFile, positioned at its beginning, which is generated from the object to be parsed

stream - An InputStream, positioned at its beginning, which is generated from the object to be parsed

info - A fresh RepInfo object which will be modified to reflect the results of the test

Throws:

IOException

parse

public int parse(InputStream stream,
        RepInfo info,
        int parseIndex)
          throws IOException

Parse the content of a purported JPEG stream digital object and store the results in RepInfo. This function uses the JPEG-L method of detecting a marker following a data stream, checking for a 0 high bit rather than an entire 0 byte. So long at no JPEG markers are defined with a value from 0 through 7F, this is valid for all JPEG files.

Specified by:

parse in interface Module

Overrides:

parse in class ModuleBase

Parameters:

stream - An InputStream, positioned at its beginning, which is generated from the object to be parsed

info - A fresh RepInfo object which will be modified to reflect the results of the parsing

parseIndex - Must be 0 in first call to parse. If parse returns a nonzero value, it must be called again with parseIndex equal to that return value.

Throws:

IOException

eatChunk

public void eatChunk(PNGChunk chnk)
              throws IOException

This lets the module skip over the remainder of a chunk, not including the name, length,and CRC. It updates the CRC.

Throws:

IOException

addKeyword

public void addKeyword(String keywd,
              String val)

Add a keyword and value. Creating arbitrary properties on the fly doesn't go well with JHOVE's approach, so we make each property a Map, with keys Keyword, Value, and optionally Language.

addKeyword

public void addKeyword(String keywd,
              String translatedKeywd,
              String val,
              String language)

Add a keyword, value, and language.

addSplt

public void addSplt(String name,
           int sampleDepth,
           int numSamples)

Add a suggested palette

initParse

protected void initParse()

Initializes the state of the module for parsing.

Overrides:

initParse in class ModuleBase

setIhdrSeen

public void setIhdrSeen(boolean b)

Note that an IHDR chunk has been seen

isIhdrSeen

public boolean isIhdrSeen()

Returns true if IHDR chunk has been seen

setIdatSeen

public void setIdatSeen(boolean b)

Note that an IDAT chunk has been seen

setPlteSeen

public void setPlteSeen(boolean b)

Note that a PLTE chunk has been seen

setIendSeen

public void setIendSeen(boolean b)

Note that an IEND chunk has been seen

isIdatSeen

public boolean isIdatSeen()

Return true if IDAT chunk has been seen

isIdatFinished

public boolean isIdatFinished()

Return true if a non-IDAT chunk has been seen after an IDAT chunk

isPlteSeen

public boolean isPlteSeen()

Return true if PLTE chunk has been seen

setChunkSeen

public void setChunkSeen(int chunkType)

isChunkSeen

public boolean isChunkSeen(int chunkType)

setColorType

public void setColorType(int ct)

Set the color type. The IHDR processing will set this for the benefit of chunks that need it.

getColorType

public int getColorType()

Get the color type that was recorded from the IHDR chunk.