C# Class Hjg.Pngcs.PngReader

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

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Public Properties

Property	Type	Description
interlaced	bool

Protected Properties

Property	Type	Description
crctest	Hjg.Pngcs.Zlib.Adler32
filename	String
imgLine	Hjg.Pngcs.ImageLine
rowNum	int
rowb	byte[]
rowbfilter	byte[]
rowbprev	byte[]

Public Methods

Method	Description
End ( ) : void	Normally this does nothing, but it can be used to force a premature closing
GetChunksList ( ) : Hjg.Pngcs.Chunks.ChunksList	Returns the ancillary chunks available If the rows have not yet still been read, this includes only the chunks placed before the pixels (IDAT)
GetMetadata ( ) : Hjg.Pngcs.Chunks.PngMetadata	Returns the ancillary chunks available see GetChunksList
IsInterlaced ( ) : bool
IsUnpackedMode ( ) : bool
PngReader ( Stream inputStream ) : System	Constructs a PngReader from a Stream, with no filename information
PngReader ( Stream inputStream, String filename ) : System	Constructs a PNGReader objet from a opened Stream The constructor reads the signature and first chunk (IDHR)FileHelper.CreatePngReader(string)
ReadRow ( int nrow ) : Hjg.Pngcs.ImageLine	reads the row using ImageLine as buffer
ReadRow ( int buffer, int nrow ) : int[]
ReadRowByte ( int nrow ) : Hjg.Pngcs.ImageLine
ReadRowByte ( byte buffer, int nrow ) : byte[]
ReadRowInt ( int nrow ) : Hjg.Pngcs.ImageLine
ReadRowInt ( int buffer, int nrow ) : int[]
ReadRowsByte ( ) : Hjg.Pngcs.ImageLines
ReadRowsByte ( int rowOffset, int nRows, int rowStep ) : Hjg.Pngcs.ImageLines
ReadRowsInt ( ) : Hjg.Pngcs.ImageLines
ReadRowsInt ( int rowOffset, int nRows, int rowStep ) : Hjg.Pngcs.ImageLines
ReadSkippingAllRows ( ) : void
SetCrcCheckDisabled ( ) : void
SetUnpackedMode ( bool unPackedMode ) : void
ToString ( ) : String

Private Methods

Method	Description
Close ( ) : void
FirstChunksNotYetRead ( ) : bool
GetCrctestVal ( ) : long
GetRow ( int nrow ) : Hjg.Pngcs.ImageLine
InitCrctest ( ) : void
ReadChunk ( byte chunkid, int clen, bool skipforced ) : PngChunk	Reads chunkd from input stream, adds to ChunksList, and returns it. If it's skipped, a PngChunkSkipped object is created
ReadFirstChunks ( ) : void	Reads chunks before first IDAT. Position before: after IDHR (crc included) Position after: just after the first IDAT chunk id Returns length of first IDAT chunk , -1 if not found
ReadLastAndClose ( ) : void	Internally called after having read the last line. It reads extra chunks after IDAT, if present.
ReadLastChunks ( ) : void	Reads (and processes ... up to a point) chunks after last IDAT.
ReadRowRaw ( int nrow ) : int
UnfilterRow ( int nbytes ) : void
UnfilterRowAverage ( int nbytes ) : void
UnfilterRowNone ( int nbytes ) : void
UnfilterRowPaeth ( int nbytes ) : void
UnfilterRowSub ( int nbytes ) : void
UnfilterRowUp ( int nbytes ) : void
decodeLastReadRowToByte ( byte buffer, int bytesRead ) : void
decodeLastReadRowToInt ( int buffer, int bytesRead ) : void
logWarn ( String warn ) : void	Logs/prints a warning. The default behaviour is print to stderr, but it can be overriden. This happens rarely - most errors are fatal.

Method Details

End() public method

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

public End ( ) : void
return	void

GetChunksList() public method

Returns the ancillary chunks available

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

public GetChunksList ( ) : Hjg.Pngcs.Chunks.ChunksList
return	Hjg.Pngcs.Chunks.ChunksList

GetMetadata() public method

Returns the ancillary chunks available

see GetChunksList

public GetMetadata ( ) : Hjg.Pngcs.Chunks.PngMetadata
return	Hjg.Pngcs.Chunks.PngMetadata

IsInterlaced() public method

public IsInterlaced ( ) : bool
return	bool

IsUnpackedMode() public method

public IsUnpackedMode ( ) : bool
return	bool

PngReader() public method

Constructs a PngReader from a Stream, with no filename information

public PngReader ( Stream inputStream ) : System
inputStream	Stream
return	System

PngReader() public method

Constructs a PNGReader objet from a opened Stream

The constructor reads the signature and first chunk (IDHR)FileHelper.CreatePngReader(string)

public PngReader ( Stream inputStream, String filename ) : System
inputStream	Stream
filename	String	Optional, can be the filename or a description.
return	System

ReadRow() public method

reads the row using ImageLine as buffer

public ReadRow ( int nrow ) : Hjg.Pngcs.ImageLine
nrow	int	row number - just as a check
return	Hjg.Pngcs.ImageLine

ReadRow() public method

public ReadRow ( int buffer, int nrow ) : int[]
buffer	int
nrow	int
return	int[]

ReadRowByte() public method

public ReadRowByte ( int nrow ) : Hjg.Pngcs.ImageLine
nrow	int
return	Hjg.Pngcs.ImageLine

ReadRowByte() public method

public ReadRowByte ( byte buffer, int nrow ) : byte[]
buffer	byte
nrow	int
return	byte[]

ReadRowInt() public method

public ReadRowInt ( int nrow ) : Hjg.Pngcs.ImageLine
nrow	int
return	Hjg.Pngcs.ImageLine

ReadRowInt() public method

public ReadRowInt ( int buffer, int nrow ) : int[]
buffer	int
nrow	int
return	int[]

ReadRowsByte() public method

public ReadRowsByte ( ) : Hjg.Pngcs.ImageLines
return	Hjg.Pngcs.ImageLines

ReadRowsByte() public method

public ReadRowsByte ( int rowOffset, int nRows, int rowStep ) : Hjg.Pngcs.ImageLines
rowOffset	int
nRows	int
rowStep	int
return	Hjg.Pngcs.ImageLines

ReadRowsInt() public method

public ReadRowsInt ( ) : Hjg.Pngcs.ImageLines
return	Hjg.Pngcs.ImageLines

ReadRowsInt() public method

public ReadRowsInt ( int rowOffset, int nRows, int rowStep ) : Hjg.Pngcs.ImageLines
rowOffset	int
nRows	int
rowStep	int
return	Hjg.Pngcs.ImageLines

ReadSkippingAllRows() public method

public ReadSkippingAllRows ( ) : void
return	void

SetCrcCheckDisabled() public method

public SetCrcCheckDisabled ( ) : void
return	void

SetUnpackedMode() public method

public SetUnpackedMode ( bool unPackedMode ) : void
unPackedMode	bool
return	void

ToString() public method

public ToString ( ) : String
return	String

Property Details

crctest protected_oe property

protected Adler32,Hjg.Pngcs.Zlib crctest
return	Hjg.Pngcs.Zlib.Adler32

filename protected_oe property

filename, or description - merely informative, can be empty

protected String filename
return	String

imgLine protected_oe property

buffer: last read line

protected ImageLine,Hjg.Pngcs imgLine
return	Hjg.Pngcs.ImageLine

interlaced public_oe property

public bool interlaced
return	bool

rowNum protected_oe property

last read row number

protected int rowNum
return	int

rowb protected_oe property

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

protected byte[] rowb
return	byte[]

rowbfilter protected_oe property

raw current row, after unfiltered

protected byte[] rowbfilter
return	byte[]

rowbprev protected_oe property

previuos raw row

protected byte[] rowbprev
return	byte[]