ChunkHelper (PNGJ 2.0.1 API)

java.lang.Object
- ar.com.hjg.pngj.chunks.ChunkHelper

```
public class ChunkHelper
extends Object
```
Helper methods and constants related to Chunk processing.
This should only be of interest to developers doing special chunk processing or extending the ChunkFactory

Field Summary

Fields
Modifier and Type	Field and Description
`static byte[]`	`b_IDAT`
`static byte[]`	`b_IEND`
`static byte[]`	`b_IHDR`
`static byte[]`	`b_PLTE`
`static String`	`bKGD`
`static String`	`cHRM`
`static String`	`gAMA`
`static String`	`hIST`
`static String`	`iCCP`
`static String`	`IDAT`
`static String`	`IEND`
`static String`	`IHDR`
`static String`	`iTXt`
`static String`	`pHYs`
`static String`	`PLTE`
`static String`	`sBIT`
`static String`	`sPLT`
`static String`	`sRGB`
`static String`	`tEXt`
`static String`	`tIME`
`static String`	`tRNS`
`static String`	`zTXt`

Method Summary

Methods
Modifier and Type	Method and Description
`static PngChunk`	`cloneForWrite(PngChunk chunk, ImageInfo imgInfo)`
`static byte[]`	`compressBytes(byte[] ori, boolean compress)`
`static byte[]`	`compressBytes(byte[] ori, int offset, int len, boolean compress)`
`static boolean`	`equivalent(PngChunk c1, PngChunk c2)` Adhoc criteria: two ancillary chunks are "equivalent" ("practically same type") if they have same id and (perhaps, if multiple are allowed) if the match also in some "internal key" (eg: key for string values, palette for sPLT, etc) When we use this method, we implicitly assume that we don't allow/expect two "equivalent" chunks in a single PNG Notice that the use of this is optional, and that the PNG standard actually allows text chunks that have same key
`static List<PngChunk>`	`filterList(List<PngChunk> target, ChunkPredicate predicateKeep)` Returns only the chunks that "match" the predicate See also trimList()
`static Deflater`	`getDeflater()` thread-local deflater, just reset : this should be only used for short individual chunks decompression
`static Inflater`	`getInflater()` thread-local inflater, just reset : this should be only used for short individual chunks compression
`static boolean`	`isCritical(String id)` critical chunk : first letter is uppercase
`static boolean`	`isPublic(String id)` public chunk: second letter is uppercase
`static boolean`	`isSafeToCopy(String id)` Safe to copy chunk: fourth letter is lower case
`static boolean`	`isText(PngChunk c)`
`static boolean`	`isUnknown(PngChunk c)` "Unknown" just means that our chunk factory (even when it has been augmented by client code) did not recognize its id
`static int`	`posNullByte(byte[] b)` Finds position of null byte in array
`static boolean`	`shouldLoad(String id, ChunkLoadBehaviour behav)` Decides if a chunk should be loaded, according to a ChunkLoadBehaviour
`static byte[]`	`toBytes(String x)` Converts to bytes using Latin1 (ISO-8859-1)
`static byte[]`	`toBytesUTF8(String x)` Converts to bytes using UTF-8
`static String`	`toString(byte[] x)` Converts to String using Latin1 (ISO-8859-1)
`static String`	`toString(byte[] x, int offset, int len)` Converts to String using Latin1 (ISO-8859-1)
`static String`	`toStringUTF8(byte[] x)` Converts to string using UTF-8
`static String`	`toStringUTF8(byte[] x, int offset, int len)` Converts to string using UTF-8
`static int`	`trimList(List<PngChunk> target, ChunkPredicate predicateRemove)` Remove (in place) the chunks that "match" the predicate See also filterList

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - IHDR
```
public static final String IHDR
```
    See Also:
    Constant Field Values
  - PLTE
```
public static final String PLTE
```
    See Also:
    Constant Field Values
  - IDAT
```
public static final String IDAT
```
    See Also:
    Constant Field Values
  - IEND
```
public static final String IEND
```
    See Also:
    Constant Field Values
  - cHRM
```
public static final String cHRM
```
    See Also:
    Constant Field Values
  - gAMA
```
public static final String gAMA
```
    See Also:
    Constant Field Values
  - iCCP
```
public static final String iCCP
```
    See Also:
    Constant Field Values
  - sBIT
```
public static final String sBIT
```
    See Also:
    Constant Field Values
  - sRGB
```
public static final String sRGB
```
    See Also:
    Constant Field Values
  - bKGD
```
public static final String bKGD
```
    See Also:
    Constant Field Values
  - hIST
```
public static final String hIST
```
    See Also:
    Constant Field Values
  - tRNS
```
public static final String tRNS
```
    See Also:
    Constant Field Values
  - pHYs
```
public static final String pHYs
```
    See Also:
    Constant Field Values
  - sPLT
```
public static final String sPLT
```
    See Also:
    Constant Field Values
  - tIME
```
public static final String tIME
```
    See Also:
    Constant Field Values
  - iTXt
```
public static final String iTXt
```
    See Also:
    Constant Field Values
  - tEXt
```
public static final String tEXt
```
    See Also:
    Constant Field Values
  - zTXt
```
public static final String zTXt
```
    See Also:
    Constant Field Values
  - b_IHDR
```
public static final byte[] b_IHDR
```
  - b_PLTE
```
public static final byte[] b_PLTE
```
  - b_IDAT
```
public static final byte[] b_IDAT
```
  - b_IEND
```
public static final byte[] b_IEND
```
- Method Detail
  - toBytes
```
public static byte[] toBytes(String x)
```
    Converts to bytes using Latin1 (ISO-8859-1)
  - toString
```
public static String toString(byte[] x)
```
    Converts to String using Latin1 (ISO-8859-1)
  - toString
```
public static String toString(byte[] x,
              int offset,
              int len)
```
    Converts to String using Latin1 (ISO-8859-1)
  - toBytesUTF8
```
public static byte[] toBytesUTF8(String x)
```
    Converts to bytes using UTF-8
  - toStringUTF8
```
public static String toStringUTF8(byte[] x)
```
    Converts to string using UTF-8
  - toStringUTF8
```
public static String toStringUTF8(byte[] x,
                  int offset,
                  int len)
```
    Converts to string using UTF-8
  - isCritical
```
public static boolean isCritical(String id)
```
    critical chunk : first letter is uppercase
  - isPublic
```
public static boolean isPublic(String id)
```
    public chunk: second letter is uppercase
  - isSafeToCopy
```
public static boolean isSafeToCopy(String id)
```
    Safe to copy chunk: fourth letter is lower case
  - isUnknown
```
public static boolean isUnknown(PngChunk c)
```
    "Unknown" just means that our chunk factory (even when it has been augmented by client code) did not recognize its id
  - posNullByte
```
public static int posNullByte(byte[] b)
```
    Finds position of null byte in array
    
    Parameters:
    b -
    
    Returns:
    -1 if not found
  - shouldLoad
```
public static boolean shouldLoad(String id,
                 ChunkLoadBehaviour behav)
```
    Decides if a chunk should be loaded, according to a ChunkLoadBehaviour
    
    Parameters:
    id -
    behav -
    
    Returns:
    true/false
  - compressBytes
```
public static final byte[] compressBytes(byte[] ori,
                   boolean compress)
```
  - compressBytes
```
public static byte[] compressBytes(byte[] ori,
                   int offset,
                   int len,
                   boolean compress)
```
  - filterList
```
public static List<PngChunk> filterList(List<PngChunk> target,
                        ChunkPredicate predicateKeep)
```
    Returns only the chunks that "match" the predicate See also trimList()
  - trimList
```
public static int trimList(List<PngChunk> target,
           ChunkPredicate predicateRemove)
```
    Remove (in place) the chunks that "match" the predicate See also filterList
  - equivalent
```
public static final boolean equivalent(PngChunk c1,
                 PngChunk c2)
```
    Adhoc criteria: two ancillary chunks are "equivalent" ("practically same type") if they have same id and (perhaps, if multiple are allowed) if the match also in some "internal key" (eg: key for string values, palette for sPLT, etc) When we use this method, we implicitly assume that we don't allow/expect two "equivalent" chunks in a single PNG Notice that the use of this is optional, and that the PNG standard actually allows text chunks that have same key
    
    Returns:
    true if "equivalent"
  - isText
```
public static boolean isText(PngChunk c)
```
  - getInflater
```
public static Inflater getInflater()
```
    thread-local inflater, just reset : this should be only used for short individual chunks compression
  - getDeflater
```
public static Deflater getDeflater()
```
    thread-local deflater, just reset : this should be only used for short individual chunks decompression
  - cloneForWrite
```
public static PngChunk cloneForWrite(PngChunk chunk,
                     ImageInfo imgInfo)
```

Class ChunkHelper

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

IHDR

PLTE

IDAT

IEND

cHRM

gAMA

iCCP

sBIT

sRGB

bKGD

hIST

tRNS

pHYs

sPLT

tIME

iTXt

tEXt

zTXt

b_IHDR

b_PLTE

b_IDAT

b_IEND

Method Detail

toBytes

toString

toString

toBytesUTF8

toStringUTF8

toStringUTF8

isCritical

isPublic

isSafeToCopy

isUnknown

posNullByte

shouldLoad

compressBytes

compressBytes

filterList

trimList

equivalent

isText

getInflater

getDeflater

cloneForWrite