CBufferedImageDecoder Class Reference

#include <imageconversion.h>

Link against: imageconversion.lib

class CBufferedImageDecoder : public CBase

Inherits from

CBufferedImageDecoder
- CBase

Public Member Functions
virtual	~CBufferedImageDecoder()
IMPORT_C void	AppendDataL(const TDesC8 &)
IMPORT_C void	Cancel()
IMPORT_C void	ContinueConvert(TRequestStatus *)
IMPORT_C void	ContinueOpenL()
IMPORT_C void	ContinueProcessingHeaderL()
IMPORT_C void	Convert(TRequestStatus *, CFbsBitmap &, TInt)
IMPORT_C void	Convert(TRequestStatus *, CFbsBitmap &, CFbsBitmap &, TInt)
IMPORT_C HBufC *	FrameCommentL(TInt, TInt)
IMPORT_C TInt	FrameCount()
IMPORT_C const CFrameImageData &	FrameData(TInt)
IMPORT_C const TFrameInfo &	FrameInfo(TInt)
IMPORT_C CFrameInfoStrings *	FrameInfoStringsL(TInt)
IMPORT_C CFrameInfoStrings *	FrameInfoStringsLC(TInt)
IMPORT_C HBufC *	ImageCommentL(TInt)
IMPORT_C TUid	ImplementationUid()
IMPORT_C TBool	IsImageHeaderProcessingComplete()
IMPORT_C CBufferedImageDecoder *	NewL(RFs &)
IMPORT_C TInt	NumberOfFrameComments(TInt)
IMPORT_C TInt	NumberOfImageComments()
IMPORT_C void	OpenL(const TDesC8 &, const TDesC8 &, const CImageDecoder::TOptions)
IMPORT_C void	OpenL(const TDesC8 &, const CImageDecoder::TOptions, const TUid, const TUid, const TUid)
IMPORT_C void	Reset()
IMPORT_C TBool	ValidDecoder()

Inherited Functions
	CBase::CBase()
	CBase::Delete(CBase *)
	CBase::Extension_(TUint,TAny &,TAny )
	CBase::operator new(TUint)
	CBase::operator new(TUint,TAny *)
	CBase::operator new(TUint,TLeave)
	CBase::operator new(TUint,TLeave,TUint)
	CBase::operator new(TUint,TUint)
	CBase::~CBase()

Detailed Description

Buffered image conversion library.

Provides a wrapper arround CImageDecoder that enables you to decode multiple images without having to recreate the CBufferedImageDecoder object each time. One of the key features of this class is the ability to append image data to the decoder object as it becomes available; this is done using AppendDataL().

Constructor & Destructor Documentation

~CBufferedImageDecoder ( )

IMPORT_C

~CBufferedImageDecoder

(

)

[virtual]

Destructor for this class.

Stops decoding if it is in progress and frees all resources owned by the object prior to its destruction.

Member Function Documentation

AppendDataL ( const TDesC8 & )

IMPORT_C void

AppendDataL

(

const TDesC8 &

aData

)

Adds new image data.

A copy of the data is held internally, and the caller does not need to retain the data.

Parameters
aData	The new image data to append.

Cancel ( )

IMPORT_C void

Cancel

(

)

Requests an asynchronous decode to terminate.

Cancels any conversions currently in progress.

ContinueConvert ( TRequestStatus * )

IMPORT_C void

ContinueConvert

(

TRequestStatus *

aRequestStatus

)

Continues decoding a frame and/or mask after new image data was added to the source file or descriptor and a previous call to Convert() or ContinueConvert() returned KErrUnderflow.

Parameters
aRequestStatus	The request status. On completion contains an error code. KErrNone if frame was decoded successfully, KErrUnderflow if the frame was partially decoded otherwise another of the system-wide error codes.

ContinueOpenL ( )

IMPORT_C void

ContinueOpenL

(

)

Call this function to retry to create a decoder after OpenL() returned with KErrUnderFlow and extra data was added to the descriptor using AppendDataL(). This function can be recalled until ValidDecoder() return ETrue.

Leave Codes
KErrUnderflow	Not enough data in descriptor to identify which plugin decoder to use.

ContinueProcessingHeaderL ( )

IMPORT_C void

ContinueProcessingHeaderL

(

)

Continues processing image headers after new image data was appended.

This function can be called until IsImageHeaderProcessingComplete() return ETrue.

Convert ( TRequestStatus *, CFbsBitmap &, TInt )

IMPORT_C void	Convert	(	TRequestStatus *	aRequestStatus,
			CFbsBitmap &	aDestination,
			TInt	aFrameNumber = 0
		)

Starts decoding an image frame asynchronously.

When converting the operation can complete with KErrUnderflow, if there is insufficient information in the descriptor. In this situation, ContinueConvert() should be called repeatedly until the descriptor has accumulated enough information for ContinueConvert() to complete with KErrNone.

Parameters
aRequestStatus	The request status. On completion contains an error code. KErrNone if frame was decoded successfully, KErrUnderflow if the frame was partially decoded otherwise another of the system-wide error codes.
aDestination	A bitmap that will contain the decoded frame. The bitmap must be created before the call and must be large enough for the frame and set to the required display mode. FrameInfo() can be used to obtain the size and display mode of the frame.
aFrameNumber	The frame in multi-frame image to decode (optional).

Convert ( TRequestStatus *, CFbsBitmap &, CFbsBitmap &, TInt )

IMPORT_C void	Convert	(	TRequestStatus *	aRequestStatus,
			CFbsBitmap &	aDestination,
			CFbsBitmap &	aDestinationMask,
			TInt	aFrameNumber = 0
		)

Starts decoding an image frame and mask asynchronously.

Parameters
aRequestStatus	The request status. On completion contains an error code. KErrNone if frame was decoded successfully, KErrUnderflow if the frame was partially decoded otherwise another of the system-wide error codes.
aDestination	A bitmap that will contain the decoded frame. The bitmap must be created before the call and must be large enough for the frame and set to the required display mode. FrameInfo() can be used to obtain the size and display mode of the frame.
aDestinationMask	A bitmap that will contain the decoded frame mask. The bitmap must be created before the call and must be large enough for the mask. The display mode must be EGray2 or EGray256 and must be EGray256 if the image contains alpha-blending information. This information can be obtained from the iFlags property and TFrameInfoFlags of TFrameInfo obtained from a FrameInfo() call.
aFrameNumber	The frame in multi-frame image to decode (optional).

FrameCommentL ( TInt, TInt )

IMPORT_C HBufC *	FrameCommentL	(	TInt	aFrameNumber,
			TInt	aCommentNumber
		)	const

Returns a particular comment attached to a given frame of the image. Ownership of the returned buffer is transferred to the caller.

Parameters
aFrameNumber	The frame number.
aCommentNumber	The comment number.

Return Value: A buffer containing the comment.

FrameCount ( )

IMPORT_C TInt

FrameCount

(

)

const

Returns the number of frames in the image being decoded. This function can be called immediately after the call to create the decoder, thus enabling the caller to know how many frames need to be converted.

Return Value: The number of frames.

FrameData ( TInt )

IMPORT_C const CFrameImageData &

FrameData

(

TInt

aFrameNumber = 0

)

const

Returns the image data for a specific frame.

Use FrameCount() to determine how many frames are contained in the image before using this function.

Parameters
aFrameNumber	The frame number for which to return frame data.

Return Value: The data for the specified frame.

FrameInfo ( TInt )

IMPORT_C const TFrameInfo &

FrameInfo

(

TInt

aFrameNumber = 0

)

const

Returns the frame info for a specified frame of the image.

This function can be called immediately after the call to create the decoder, thus enabling the caller to know about each frame in advance of converting it.

Parameters
aFrameNumber	The frame number.

Return Value: The information for the specified frame.

FrameInfoStringsL ( TInt )

IMPORT_C CFrameInfoStrings *

FrameInfoStringsL

(

TInt

aFrameNumber = 0

)

Returns the formatted frame information strings for a specific frame.

Ownership is transferred to the caller.

Parameters
aFrameNumber	The frame number.

Return Value: The formatted frame information strings.

FrameInfoStringsLC ( TInt )

IMPORT_C CFrameInfoStrings *

FrameInfoStringsLC

(

TInt

aFrameNumber = 0

)

Returns the formatted frame information strings for a specific frame and leave it on the cleanup stack.

Ownership is transferred to the caller.

Parameters
aFrameNumber	The frame number.

Return Value: The formatted frame information strings.

ImageCommentL ( TInt )

IMPORT_C HBufC *

ImageCommentL

(

TInt

aCommentNumber

)

const

Returns a particular comment attached to the image. Ownership of the returned buffer is transferred to the caller.

Use NumberOfImageComments() to determine how many (if any) comments are contained within the image.

Parameters
aCommentNumber	The comment number.

Return Value: A buffer containing the comment.

ImplementationUid ( )

IMPORT_C TUid

ImplementationUid

(

)

const

Returns the implementation UID of the decoder being used to decode the image.

Return Value: The implementation UID of the decoder.

IsImageHeaderProcessingComplete ( )

IMPORT_C TBool

IsImageHeaderProcessingComplete

(

)

const

Returns the status of the image.

If the image is incomplete or not terminated correctly EFalse will be returned

Return Value: A boolean indicating the image status. Returns ETrue if image header processing is complete, otherwise EFalse.

NewL ( RFs & )

IMPORT_C CBufferedImageDecoder *

NewL

(

RFs &

aFs

)

[static]

Creates a buffered decoder.

The function leaves if the decoder object cannot be created or initialised.

Parameters
aFs	A reference to a file server session for the decoder to use.

Return Value: A pointer to the newly created decoder.

NumberOfFrameComments ( TInt )

IMPORT_C TInt

NumberOfFrameComments

(

TInt

aFrameNumber

)

const

Returns the number of comments attached to a given frame of the image as opposed to the whole image.

Use FrameCount() to retrieve the number of frames in the image to ensure that the value you use for aFrameNumber is valid.

Parameters
aFrameNumber	The frame number.

Return Value: The number of comments attached to a given frame of the image.

NumberOfImageComments ( )

IMPORT_C TInt

NumberOfImageComments

(

)

const

Returns the number of comments attached to the image (as opposed to a particular frame).

Return Value: The number of comments attached to the image.

OpenL ( const TDesC8 &, const TDesC8 &, const CImageDecoder::TOptions )

IMPORT_C void	OpenL	(	const TDesC8 &	aSourceData,
			const TDesC8 &	aMIMEType,
			const CImageDecoder::TOptions	aOptions = CImageDecoder::EOptionNone
		)

Creates a decoder for the image in the source buffer. The client supplies a MIME type which will be used to try and select an appropriate plugin decoder. If it finds a decoder it creates it and then goes on to use that decoder to scan the beginning of the image file.

Parameters
aSourceData	The buffer containing the image to be decoded.
aMIMEType	The MIME type of the image in the buffer.
aOptions	The options to use.

Leave Codes
KEComErrNoInterfaceIdentified	No plugin decoder could be found for the specified image.

OpenL ( const TDesC8 &, const CImageDecoder::TOptions, const TUid, const TUid, const TUid )

IMPORT_C void	OpenL	(	const TDesC8 &	aSourceData,
			const CImageDecoder::TOptions	aOptions = CImageDecoder::EOptionNone,
			const TUid	aImageType = TUid::Null(),
			const TUid	aImageSubType = TUid::Null(),
			const TUid	aDecoderUid = TUid::Null()
		)

Creates a decoder for the image in the source buffer.

If the client supplies an image type (and sub-type, if applicable) or decoder uid, these will be used to try and select an appropriate plugin decoder. If not, then the selection will be done by matching the image header from the buffer. If it finds a decoder it creates it and then goes on to use that decoder to scan the beginning of the image buffer. If a decoder could not be created append data using AppendDataL() and call ContinueOpenL().

See also: KUidICLJpegEXIFInterface KUidICLJpegImageFrameInterface

Parameters
aSourceData	The buffer containing the image to be decoded.
aOptions	The decoder options to use.
aImageType	The image type of the image in the file (optional).
aImageSubType	The image sub-type of the image in the file (optional).
aDecoderUid	The implementation UID for a specific codec or a decoder/encoder class UID (optional, defaults to KNullUid). If this option is selected for a specific codec the image type and image sub type for the displayer must be supplied. When loading plugins by class UID the image type and image subtype are not mandatory and the first valid plugin from the list of available plugins with the specified class UID will be loaded.

Leave Codes
KErrUnderflow	Not enough data in descriptor to identify which plugin decoder to use.
KEComErrNoInterfaceIdentified	No plugin decoder could be found for the specified image.
KErrNotFound	The specified codec could not be found.

Reset ( )

IMPORT_C void

Reset

(

)

Reset the decoder for reuse.

Follow this call with OpenL() and new source data.

ValidDecoder ( )

IMPORT_C TBool

ValidDecoder

(

)

const

Determine if enough data was available to determine which plugin decoder to use. If this return EFalse append extra data using AppendDataL() and and call ContinueOpenL()

Return Value: A boolean indicating if the decoder plugin was successful. ETrue if a decoder plugin was created, otherwise EFalse.