Hjg.Pngcs.PngReader Class Reference

Reads a PNG image, line by line More...

Public Member Functions
	PngReader (Stream inputStream)
	Constructs a PngReader from a Stream, with no filename information
	PngReader (Stream inputStream, String filename)
	Constructs a PNGReader objet from a opened Stream
ChunksList	GetChunksList ()
	Returns the ancillary chunks available
PngMetadata	GetMetadata ()
	Returns the ancillary chunks available
ImageLine	ReadRow (int nrow)
	reads the row using ImageLine as buffer
ImageLine	ReadRowInt (int nrow)
ImageLine	ReadRowByte (int nrow)
int[]	ReadRow (int[] buffer, int nrow)
int[]	ReadRowInt (int[] buffer, int nrow)
byte[]	ReadRowByte (byte[] buffer, int nrow)
ImageLine	GetRow (int nrow)
ImageLines	ReadRowsInt (int rowOffset, int nRows, int rowStep)
ImageLines	ReadRowsInt ()
ImageLines	ReadRowsByte (int rowOffset, int nRows, int rowStep)
ImageLines	ReadRowsByte ()
void	ReadSkippingAllRows ()
override String	ToString ()
void	End ()
	Normally this does nothing, but it can be used to force a premature closing
bool	IsInterlaced ()
void	SetUnpackedMode (bool unPackedMode)
bool	IsUnpackedMode ()
void	SetCrcCheckDisabled ()

Public Attributes
readonly bool	interlaced

Protected Attributes
readonly String	filename
	filename, or description - merely informative, can be empty
ImageLine	imgLine
	buffer: last read line
byte[]	rowb
	raw current row, as array of bytes,counting from 1 (index 0 is reserved for filter type)
byte[]	rowbprev
	previuos raw row
byte[]	rowbfilter
	raw current row, after unfiltered
int	rowNum = -1
	last read row number
Adler32	crctest

Properties
ImageInfo	ImgInfo [get, set]
	Basic image info, inmutable
ChunkLoadBehaviour	ChunkLoadBehaviour [get, set]
	Strategy for chunk loading. Default: LOAD_CHUNK_ALWAYS
bool	ShouldCloseStream [get, set]
	Should close the underlying Input Stream when ends?
long	MaxBytesMetadata [get, set]
	Maximum amount of bytes from ancillary chunks to load in memory
long	MaxTotalBytesRead [get, set]
	Maximum total bytes to read from stream
int	SkipChunkMaxSize [get, set]
	Maximum ancillary chunk size
String[]	SkipChunkIds [get, set]
	Ancillary chunks to skip
int	CurrentChunkGroup [get, set]
	number of chunk group (0-6) last read, or currently reading

Detailed Description

Reads a PNG image, line by line

The typical reading sequence is as follows:

1. At construction time, the header and IHDR chunk are read (basic image info)

2 (Optional) you can set some global options: UnpackedMode CrcCheckDisabled

3. (Optional) If you call GetMetadata() or or GetChunksLisk() before reading the pixels, the chunks before IDAT are automatically loaded and available

4a. The rows are read, one by one, with the ReadRowXXX methods: (ReadRowInt() , ReadRowByte(), etc) in order, from 0 to nrows-1 (you can skip or repeat rows, but not go backwards)

4b. Alternatively, you can read all rows, or a subset, in a single call: see ReadRowsInt(), ReadRowsByte() In general this consumes more memory, but for interlaced images this is equally efficient, and more so if reading a small subset of rows.

5. Read of the last row automatically loads the trailing chunks, and ends the reader.

6. End() forcibly finishes/aborts the reading and closes the stream

Constructor & Destructor Documentation

Hjg.Pngcs.PngReader.PngReader

(

Stream

inputStream

)

Constructs a PngReader from a Stream, with no filename information

Parameters

inputStream

Hjg.Pngcs.PngReader.PngReader	(	Stream	inputStream,
		String	filename
	)

Constructs a PNGReader objet from a opened Stream

The constructor reads the signature and first chunk (IDHR)

See Also

FileHelper.CreatePngReader(string)

Parameters

inputStream
filename	Optional, can be the filename or a description.

Member Function Documentation

ChunksList Hjg.Pngcs.PngReader.GetChunksList

(

)

Returns the ancillary chunks available

If the rows have not yet still been read, this includes only the chunks placed before the pixels (IDAT)

Returns

ChunksList

PngMetadata Hjg.Pngcs.PngReader.GetMetadata

(

)

Returns the ancillary chunks available

see GetChunksList

Returns

PngMetadata

ImageLine Hjg.Pngcs.PngReader.ReadRow

(

int

nrow

)

reads the row using ImageLine as buffer

param name="nrow">row number - just as a check

Returns

the ImageLine that also is available inside this object

ImageLine Hjg.Pngcs.PngReader.ReadRowInt

(

int

nrow

)

ImageLine Hjg.Pngcs.PngReader.ReadRowByte

(

int

nrow

)

int [] Hjg.Pngcs.PngReader.ReadRow	(	int[]	buffer,
		int	nrow
	)

int [] Hjg.Pngcs.PngReader.ReadRowInt	(	int[]	buffer,
		int	nrow
	)

byte [] Hjg.Pngcs.PngReader.ReadRowByte	(	byte[]	buffer,
		int	nrow
	)

ImageLine Hjg.Pngcs.PngReader.GetRow

(

int

nrow

)

Parameters

nrow

Returns

ImageLines Hjg.Pngcs.PngReader.ReadRowsInt	(	int	rowOffset,
		int	nRows,
		int	rowStep
	)

ImageLines Hjg.Pngcs.PngReader.ReadRowsInt

(

)

ImageLines Hjg.Pngcs.PngReader.ReadRowsByte	(	int	rowOffset,
		int	nRows,
		int	rowStep
	)

ImageLines Hjg.Pngcs.PngReader.ReadRowsByte

(

)

void Hjg.Pngcs.PngReader.ReadSkippingAllRows

(

)

override String Hjg.Pngcs.PngReader.ToString

(

)

void Hjg.Pngcs.PngReader.End

(

)

Normally this does nothing, but it can be used to force a premature closing

bool Hjg.Pngcs.PngReader.IsInterlaced

(

)

void Hjg.Pngcs.PngReader.SetUnpackedMode

(

bool

unPackedMode

)

bool Hjg.Pngcs.PngReader.IsUnpackedMode

(

)

See Also

PngReader::setUnpackedMode(boolean)

void Hjg.Pngcs.PngReader.SetCrcCheckDisabled

(

)

Member Data Documentation

readonly String Hjg.Pngcs.PngReader.filename

protected

filename, or description - merely informative, can be empty

ImageLine Hjg.Pngcs.PngReader.imgLine

protected

buffer: last read line

byte [] Hjg.Pngcs.PngReader.rowb

protected

raw current row, as array of bytes,counting from 1 (index 0 is reserved for filter type)

byte [] Hjg.Pngcs.PngReader.rowbprev

protected

previuos raw row

byte [] Hjg.Pngcs.PngReader.rowbfilter

protected

raw current row, after unfiltered

readonly bool Hjg.Pngcs.PngReader.interlaced

int Hjg.Pngcs.PngReader.rowNum = -1

protected

last read row number

Adler32 Hjg.Pngcs.PngReader.crctest

protected

Property Documentation

ImageInfo Hjg.Pngcs.PngReader.ImgInfo

getset

Basic image info, inmutable

ChunkLoadBehaviour Hjg.Pngcs.PngReader.ChunkLoadBehaviour

getset

Strategy for chunk loading. Default: LOAD_CHUNK_ALWAYS

bool Hjg.Pngcs.PngReader.ShouldCloseStream

getset

Should close the underlying Input Stream when ends?

long Hjg.Pngcs.PngReader.MaxBytesMetadata

getset

Maximum amount of bytes from ancillary chunks to load in memory

Default: 5MB. 0: unlimited. If exceeded, chunks will be skipped

long Hjg.Pngcs.PngReader.MaxTotalBytesRead

getset

Maximum total bytes to read from stream

Default: 200MB. 0: Unlimited. If exceeded, an exception will be thrown

int Hjg.Pngcs.PngReader.SkipChunkMaxSize

getset

Maximum ancillary chunk size

Default: 2MB, 0: unlimited. Chunks exceeding this size will be skipped (nor even CRC checked)

String [] Hjg.Pngcs.PngReader.SkipChunkIds

getset

Ancillary chunks to skip

Default: { "fdAT" }. chunks with these ids will be skipped (nor even CRC checked)

int Hjg.Pngcs.PngReader.CurrentChunkGroup

getset

number of chunk group (0-6) last read, or currently reading

see ChunksList.CHUNK_GROUP_NNN