Base class for decoding compressed images into a SkBitmap. More...

#include <SkImageDecoder.h>

Inheritance diagram for SkImageDecoder:

Public Types
enum	Format { kUnknown_Format, kBMP_Format, kGIF_Format, kICO_Format, kJPEG_Format, kPNG_Format, kWBMP_Format, kWEBP_Format, kPKM_Format, kKTX_Format, kASTC_Format, kLastKnownFormat = kKTX_Format }

enum	Mode { kDecodeBounds_Mode, kDecodePixels_Mode }
	Passed to the decode method. More...

enum	Result { kFailure = 0, kPartialSuccess = 1, kSuccess = 2 }
	Result of a decode. More...

Public Member Functions
virtual Format	getFormat () const
	Return the format of image this decoder can decode. More...

bool	decodeYUV8Planes (SkStream stream, SkISize componentSizes[3], void planes[3], size_t rowBytes[3], SkYUVColorSpace *)
	If planes or rowBytes is NULL, decodes the header and computes componentSizes for memory allocation. More...

const char *	getFormatName () const
	Return a readable string of the value returned by getFormat().

bool	getSkipWritingZeroes () const
	Whether the decoder should skip writing zeroes to output if possible.

void	setSkipWritingZeroes (bool skip)
	Set to true if the decoder should skip writing any zeroes when creating the output image. More...

bool	getDitherImage () const
	Returns true if the decoder should try to dither the resulting image. More...

void	setDitherImage (bool dither)
	Set to true if the the decoder should try to dither the resulting image. More...

bool	getPreferQualityOverSpeed () const
	Returns true if the decoder should try to decode the resulting image to a higher quality even at the expense of the decoding speed.

void	setPreferQualityOverSpeed (bool qualityOverSpeed)
	Set to true if the the decoder should try to decode the resulting image to a higher quality even at the expense of the decoding speed.

void	setRequireUnpremultipliedColors (bool request)
	Set to true to require the decoder to return a bitmap with unpremultiplied colors. More...

bool	getRequireUnpremultipliedColors () const
	Returns true if the decoder will only return bitmaps with unpremultiplied colors.

SkPngChunkReader *	getPeeker () const

SkPngChunkReader *	setPeeker (SkPngChunkReader *)

void	setPreserveSrcDepth (bool preserve)
	By default, the codec will try to comply with the "pref" colortype that is passed to decode() or decodeSubset(). More...

SkBitmap::Allocator *	getAllocator () const

SkBitmap::Allocator *	setAllocator (SkBitmap::Allocator *)

int	getSampleSize () const

void	setSampleSize (int size)

void	resetSampleSize ()
	Reset the sampleSize to its default of 1.

void	cancelDecode ()
	Decoding is synchronous, but for long decodes, a different thread can call this method safely. More...

Result	decode (SkStream , SkBitmap bitmap, SkColorType pref, Mode)
	Given a stream, decode it into the specified bitmap. More...

Result	decode (SkStream stream, SkBitmap bitmap, Mode mode)

bool	shouldCancelDecode () const
	Can be queried from within onDecode, to see if the user (possibly in a different thread) has requested the decode to cancel. More...

Static Public Member Functions
static Format	GetStreamFormat (SkStreamRewindable *)
	Return the format of the SkStreamRewindable or kUnknown_Format if it cannot be determined. More...

static const char *	GetFormatName (Format)
	Return a readable string of the Format provided.

static SkImageDecoder *	Factory (SkStreamRewindable *)
	Given a stream, this will try to find an appropriate decoder object. More...

static bool	DecodeFile (const char file[], SkBitmap bitmap, SkColorType pref, Mode, Format format=NULL)
	Decode the image stored in the specified file, and store the result in bitmap. More...

static bool	DecodeFile (const char file[], SkBitmap *bitmap)

static bool	DecodeMemory (const void buffer, size_t size, SkBitmap bitmap, SkColorType pref, Mode, Format *format=NULL)
	Decode the image stored in the specified memory buffer, and store the result in bitmap. More...

static bool	DecodeMemory (const void buffer, size_t size, SkBitmap bitmap)

static bool	DecodeStream (SkStreamRewindable stream, SkBitmap bitmap, SkColorType pref, Mode, Format *format=NULL)
	Decode the image stored in the specified SkStreamRewindable, and store the result in bitmap. More...

static bool	DecodeStream (SkStreamRewindable stream, SkBitmap bitmap)

Protected Types
enum	SrcDepth { kIndex_SrcDepth, k8BitGray_SrcDepth, k32Bit_SrcDepth }
	The raw data of the src image.

Protected Member Functions
virtual Result	onDecode (SkStream , SkBitmap bitmap, Mode)=0

virtual bool	onDecodeYUV8Planes (SkStream , SkISize[3], void [3], size_t[3], SkYUVColorSpace *)
	If planes or rowBytes is NULL, decodes the header and computes componentSizes for memory allocation. More...

void	copyFieldsToOther (SkImageDecoder *other)
	Copy all fields on this decoder to the other decoder. More...

SkColorType	getDefaultPref ()
	Return the default preference being used by the current or latest call to decode.

bool	allocPixelRef (SkBitmap , SkColorTable ) const

SkColorType	getPrefColorType (SrcDepth, bool hasAlpha) const
	The subclass, inside onDecode(), calls this to determine the colorType of the returned bitmap. More...

Private Attributes
SkPngChunkReader *	fPeeker

SkBitmap::Allocator *	fAllocator

int	fSampleSize

SkColorType	fDefaultPref

bool	fPreserveSrcDepth

bool	fDitherImage

bool	fSkipWritingZeroes

bool	fShouldCancelDecode

bool	fPreferQualityOverSpeed

bool	fRequireUnpremultipliedColors

Detailed Description

Base class for decoding compressed images into a SkBitmap.

Member Enumeration Documentation

enum SkImageDecoder::Mode

Passed to the decode method.

If kDecodeBounds_Mode is passed, then only the bitmap's info need be set. If kDecodePixels_Mode is passed, then the bitmap must have pixels or a pixelRef.

Enumerator
kDecodeBounds_Mode	only return info in bitmap
kDecodePixels_Mode	return entire bitmap (including pixels)

enum SkImageDecoder::Result

Result of a decode.

If read as a boolean, a partial success is considered a success (true).

Enumerator
kFailure	Image failed to decode. bitmap will be.
kPartialSuccess	Part of the image decoded. The rest is.
kSuccess	The entire image was decoded, if Mode is.

Member Function Documentation

void SkImageDecoder::cancelDecode ( )

inline

Decoding is synchronous, but for long decodes, a different thread can call this method safely.

This sets a state that the decoders will periodically check, and if they see it changed to cancel, they will cancel. This will result in decode() returning false. However, there is no guarantee that the decoder will see the state change in time, so it is possible that cancelDecode() will be called, but will be ignored and decode() will return true (assuming no other problems were encountered).

This state is automatically reset at the beginning of decode().

void SkImageDecoder::copyFieldsToOther ( SkImageDecoder * other )

protected

Copy all fields on this decoder to the other decoder.

Used by subclasses to decode a subimage using a different decoder, but with the same settings.

Result SkImageDecoder::decode	(	SkStream *	,
		SkBitmap *	bitmap,
		SkColorType	pref,
		Mode
	)

Given a stream, decode it into the specified bitmap.

If the decoder can decompress the image, it calls bitmap.setInfo(), and then if the Mode is kDecodePixels_Mode, call allocPixelRef(), which will allocated a pixelRef. To access the pixel memory, the codec needs to call lockPixels/unlockPixels on the bitmap. It can then set the pixels with the decompressed image. If the image cannot be decompressed, return kFailure. After the decoding, the function converts the decoded colortype in bitmap to pref if possible. Whether a conversion is feasible is tested by Bitmap::canCopyTo(pref).

If an SkBitmap::Allocator is installed via setAllocator, it will be used to allocate the pixel memory. A clever allocator can be used to allocate the memory from a cache, volatile memory, or even from an existing bitmap's memory.

If an SkPngChunkReader is installed via setPeeker, it may be used to peek into meta data during the decode.

static bool SkImageDecoder::DecodeFile	(	const char	file[],
		SkBitmap *	bitmap,
		SkColorType	pref,
		Mode	,
		Format *	format = `NULL`
	)

static

Decode the image stored in the specified file, and store the result in bitmap.

Return true for success or false on failure.

Parameters

pref	Prefer this colortype.
format	On success, if format is non-null, it is set to the format of the decoded file. On failure it is ignored.

static bool SkImageDecoder::DecodeMemory	(	const void *	buffer,
		size_t	size,
		SkBitmap *	bitmap,
		SkColorType	pref,
		Mode	,
		Format *	format = `NULL`
	)

static

Decode the image stored in the specified memory buffer, and store the result in bitmap.

Return true for success or false on failure.

Parameters

pref	Prefer this colortype.
format	On success, if format is non-null, it is set to the format of the decoded buffer. On failure it is ignored.

static bool SkImageDecoder::DecodeStream	(	SkStreamRewindable *	stream,
		SkBitmap *	bitmap,
		SkColorType	pref,
		Mode	,
		Format *	format = `NULL`
	)

static

Decode the image stored in the specified SkStreamRewindable, and store the result in bitmap.

Return true for success or false on failure.

Parameters

pref	Prefer this colortype.
format	On success, if format is non-null, it is set to the format of the decoded stream. On failure it is ignored.

bool SkImageDecoder::decodeYUV8Planes	(	SkStream *	stream,
		SkISize	componentSizes[3],
		void *	planes[3],
		size_t	rowBytes[3],
		SkYUVColorSpace *
	)

If planes or rowBytes is NULL, decodes the header and computes componentSizes for memory allocation.

Otherwise, decodes the YUV planes into the provided image planes and updates componentSizes to the final image size. Returns whether the decoding was successful.

static SkImageDecoder* SkImageDecoder::Factory ( SkStreamRewindable * )

static

Given a stream, this will try to find an appropriate decoder object.

If none is found, the method returns NULL.

bool SkImageDecoder::getDitherImage ( ) const

inline

Returns true if the decoder should try to dither the resulting image.

The default setting is true.

virtual Format SkImageDecoder::getFormat ( ) const

virtual

Return the format of image this decoder can decode.

If this decoder can decode multiple formats, kUnknown_Format will be returned.

SkColorType SkImageDecoder::getPrefColorType	(	SrcDepth	,
		bool	hasAlpha
	)		const

protected

The subclass, inside onDecode(), calls this to determine the colorType of the returned bitmap.

SrcDepth and hasAlpha reflect the raw data of the src image. This routine returns the caller's preference given srcDepth and hasAlpha, or kUnknown_SkColorType if there is no preference.

static Format SkImageDecoder::GetStreamFormat ( SkStreamRewindable * )

static

Return the format of the SkStreamRewindable or kUnknown_Format if it cannot be determined.

Rewinds the stream before returning.

virtual bool SkImageDecoder::onDecodeYUV8Planes	(	SkStream *	,
		SkISize	[3],
		void *	[3],
		size_t	[3],
		SkYUVColorSpace *
	)

inlineprotectedvirtual

If planes or rowBytes is NULL, decodes the header and computes componentSizes for memory allocation.

Otherwise, decodes the YUV planes into the provided image planes and updates componentSizes to the final image size. Returns whether the decoding was successful.

void SkImageDecoder::setDitherImage ( bool dither )

inline

Set to true if the the decoder should try to dither the resulting image.

The default setting is true.

void SkImageDecoder::setPreserveSrcDepth ( bool preserve )

inline

By default, the codec will try to comply with the "pref" colortype that is passed to decode() or decodeSubset().

However, this can be called to override that, causing the codec to try to match the src depth instead (as shown below).

src_8Index  -> kIndex_8_SkColorType
src_8Gray   -> kN32_SkColorType
src_8bpc    -> kN32_SkColorType

void SkImageDecoder::setRequireUnpremultipliedColors ( bool request )

inline

Set to true to require the decoder to return a bitmap with unpremultiplied colors.

The default is false, meaning the resulting bitmap will have its colors premultiplied. NOTE: Passing true to this function may result in a bitmap which cannot be properly used by Skia.

void SkImageDecoder::setSkipWritingZeroes ( bool skip )

inline

Set to true if the decoder should skip writing any zeroes when creating the output image.

This is a hint that may not be respected by the decoder. It should only be used if it is known that the memory to write to has already been set to 0; otherwise the resulting image will have garbage. This is ideal for images that contain a lot of completely transparent pixels, but may be a performance hit for an image that has only a few transparent pixels. The default is false.

bool SkImageDecoder::shouldCancelDecode ( ) const

inline

Can be queried from within onDecode, to see if the user (possibly in a different thread) has requested the decode to cancel.

If this returns true, your onDecode() should stop and return false. Each subclass needs to decide how often it can query this, to balance responsiveness with performance.

Calling this outside of onDecode() may return undefined values.

The documentation for this class was generated from the following file:

include/core/SkImageDecoder.h

Public Types

Public Member Functions

Static Public Member Functions

Protected Types

Protected Member Functions

Private Attributes

Detailed Description

Member Enumeration Documentation

Member Function Documentation