org.apache.pdfbox.jbig2.decoder

Class GenericRefinementRegionDecodingProcedure

java.lang.Object

org.apache.pdfbox.jbig2.decoder.GenericRefinementRegionDecodingProcedure

public class GenericRefinementRegionDecodingProcedure
extends Object

Implements the JBIG2 Generic Refinement Region decoding procedure as defined in ITU-T T.88, §6.3 including the core decoding loop defined in §6.3.5.6.

This class is purely algorithmic. It has no knowledge of how its inputs are obtained and no dependency on segment headers or input streams. The entry point is the static decode() method; callers supply the ArithmeticDecoder and CX context model directly, so they decide whether to create fresh instances or share existing ones:

• GenericRefinementRegion — creates its own ArithmeticDecoder and CX, then calls decode().
• Symbol dictionary refinement (§6.5.8.2) — passes the parent dictionary's shared ArithmeticDecoder and CX.
• Text region refinement (§6.4) — passes the parent text region's shared ArithmeticDecoder and CX.

This class cannot be instantiated by callers. The private constructor and the internal run(int, int, short, boolean, org.apache.pdfbox.jbig2.Bitmap, int, int, short[], short[]) method exist solely to let the many private helper methods share state through fields rather than through long parameter lists.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	GenericRefinementRegionDecodingProcedure.Template Encapsulates the template-specific operations: context bit formation (GenericRefinementRegionDecodingProcedure.Template.form(short, short, short, short, short)) and initial CX index selection (GenericRefinementRegionDecodingProcedure.Template.setIndex(org.apache.pdfbox.jbig2.decoder.arithmetic.CX)).

Field Summary

Fields

Modifier and Type	Field and Description
static GenericRefinementRegionDecodingProcedure.Template	T0 Singleton template 0 instance (stateless).
static GenericRefinementRegionDecodingProcedure.Template	T1 Singleton template 1 instance (stateless).

Method Summary

Modifier and Type	Method and Description
static Bitmap	decode(ArithmeticDecoder arithDecoder, CX cx, int width, int height, short grTemplate, boolean isTPGROn, Bitmap referenceBitmap, int referenceDX, int referenceDY, short[] grAtX, short[] grAtY) Executes the Generic Refinement Region decoding procedure (§6.3.5.6) and returns the decoded bitmap.

Methods inherited from class java.lang.Object

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

Field Detail

T0

public static final GenericRefinementRegionDecodingProcedure.Template T0

Singleton template 0 instance (stateless).

T1

public static final GenericRefinementRegionDecodingProcedure.Template T1

Singleton template 1 instance (stateless).

Method Detail

decode

public static Bitmap decode(ArithmeticDecoder arithDecoder,
                            CX cx,
                            int width,
                            int height,
                            short grTemplate,
                            boolean isTPGROn,
                            Bitmap referenceBitmap,
                            int referenceDX,
                            int referenceDY,
                            short[] grAtX,
                            short[] grAtY)
                     throws IOException

Executes the Generic Refinement Region decoding procedure (§6.3.5.6) and returns the decoded bitmap.

A short-lived instance is created internally so that the many private helper methods can share state through fields rather than through long parameter lists. No state survives the return of this method.

Parameters:

arithDecoder - the arithmetic decoder — shared with the parent when called from a symbol dictionary or text region, or freshly created when called from a standalone segment; must not be null

cx - the context model — shared or fresh, as above; must not be null

width - decoded bitmap width (GRW); must be > 0

height - decoded bitmap height (GRH); must be > 0

grTemplate - template index: must be 0 or 1 (GRTEMPLATE)

isTPGROn - whether typical prediction is enabled (TPGRON)

referenceBitmap - the reference / base bitmap (GRREFERENCE); must not be null

referenceDX - horizontal offset of reference bitmap (GRREFERENCEDX)

referenceDY - vertical offset of reference bitmap (GRREFERENCEDY)

grAtX - AT pixel X offsets; required for grTemplate == 0, must be a non-null array of length 2 in that case; ignored for grTemplate == 1

grAtY - AT pixel Y offsets; same requirements as grAtX

Returns:

the decoded bitmap

Throws:

IllegalArgumentException - if any parameter constraint above is violated

IOException - if an underlying I/O operation fails