JPEGImageFormat Class Reference

A subclass of ImageFileFormat for reading and writing JPEG files. More...

#include <juce_ImageFileFormat.h>

Inheritance diagram for JPEGImageFormat:

Collaboration diagram for JPEGImageFormat:

Public Member Functions
	JPEGImageFormat ()
	~JPEGImageFormat ()
bool	canUnderstand (InputStream &) override
	Returns true if the given stream seems to contain data that this format understands. More...
Image	decodeImage (InputStream &) override
	Tries to decode and return an image from the given stream. More...
String	getFormatName () override
	Returns a description of this file format. More...
void	setQuality (float newQuality)
	Specifies the quality to be used when writing a JPEG file. More...
bool	usesFileExtension (const File &) override
	Returns true if this format uses the file extension of the given file. More...
bool	writeImageToStream (const Image &, OutputStream &) override
	Attempts to write an image to a stream. More...

Static Public Member Functions
static ImageFileFormat *	findImageFormatForFileExtension (const File &file)
	Looks for a format that can handle the given file extension. More...
static ImageFileFormat *	findImageFormatForStream (InputStream &input)
	Tries the built-in formats to see if it can find one to read this stream. More...
static Image	loadFrom (InputStream &input)
	Tries to load an image from a stream. More...
static Image	loadFrom (const File &file)
	Tries to load an image from a file. More...
static Image	loadFrom (const void *rawData, size_t numBytesOfData)
	Tries to load an image from a block of raw image data. More...

Private Attributes
float	quality

Detailed Description

A subclass of ImageFileFormat for reading and writing JPEG files.

See also

ImageFileFormat, PNGImageFormat

Constructor & Destructor Documentation

JPEGImageFormat()

JPEGImageFormat::JPEGImageFormat

(

)

~JPEGImageFormat()

JPEGImageFormat::~JPEGImageFormat

(

)

Member Function Documentation

canUnderstand()

bool JPEGImageFormat::canUnderstand ( InputStream &  input )

overridevirtual

Returns true if the given stream seems to contain data that this format understands.

The format class should only read the first few bytes of the stream and sniff for header bytes that it understands.

Note that this will advance the stream and leave it in a new position, so if you're planning on re-using it, you may want to rewind it after calling this method.

See also

decodeImage

Implements ImageFileFormat.

decodeImage()

Image JPEGImageFormat::decodeImage ( InputStream &  input )

overridevirtual

Tries to decode and return an image from the given stream.

This will be called for an image format after calling its canUnderStand() method to see if it can handle the stream.

Parameters

input

the stream to read the data from. The stream will be positioned at the start of the image data (but this may not necessarily be position 0)

Returns

the image that was decoded, or an invalid image if it fails.

See also

loadFrom

Implements ImageFileFormat.

findImageFormatForFileExtension()

static ImageFileFormat* ImageFileFormat::findImageFormatForFileExtension ( const File &  file )

staticinherited

Looks for a format that can handle the given file extension.

There are currently built-in formats for PNG, JPEG and GIF formats. The object that is returned should not be deleted by the caller.

findImageFormatForStream()

static ImageFileFormat* ImageFileFormat::findImageFormatForStream ( InputStream &  input )

staticinherited

Tries the built-in formats to see if it can find one to read this stream.

There are currently built-in decoders for PNG, JPEG and GIF formats. The object that is returned should not be deleted by the caller.

See also

canUnderstand, decodeImage, loadFrom

getFormatName()

String JPEGImageFormat::getFormatName ( )

overridevirtual

Returns a description of this file format.

E.g. "JPEG", "PNG"

Implements ImageFileFormat.

loadFrom() [1/3]

static Image ImageFileFormat::loadFrom ( InputStream &  input )

staticinherited

Tries to load an image from a stream.

This will use the findImageFormatForStream() method to locate a suitable codec, and use that to load the image.

Returns

the image that was decoded, or an invalid image if it fails.

Referenced by CameraDevice::Pimpl::handleImageCapture().

loadFrom() [2/3]

static Image ImageFileFormat::loadFrom ( const File &  file )

staticinherited

Tries to load an image from a file.

This will use the findImageFormatForStream() method to locate a suitable codec, and use that to load the image.

Returns

the image that was decoded, or an invalid image if it fails.

loadFrom() [3/3]

static Image ImageFileFormat::loadFrom ( const void *  rawData, size_t  numBytesOfData  )

staticinherited

Tries to load an image from a block of raw image data.

This will use the findImageFormatForStream() method to locate a suitable codec, and use that to load the image.

Returns

the image that was decoded, or an invalid image if it fails.

setQuality()

void JPEGImageFormat::setQuality

(

float

newQuality

)

Specifies the quality to be used when writing a JPEG file.

Parameters

newQuality

a value 0 to 1.0, where 0 is low quality, 1.0 is best, or any negative value is "default" quality

usesFileExtension()

bool JPEGImageFormat::usesFileExtension ( const File &  possibleFile )

overridevirtual

Returns true if this format uses the file extension of the given file.

Implements ImageFileFormat.

writeImageToStream()

bool JPEGImageFormat::writeImageToStream ( const Image &  sourceImage, OutputStream &  destStream  )

overridevirtual

Attempts to write an image to a stream.

To specify extra information like encoding quality, there will be appropriate parameters in the subclasses of the specific file types.

Returns

true if it nothing went wrong.

Implements ImageFileFormat.

Member Data Documentation

quality

float JPEGImageFormat::quality

private

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

• juce_ImageFileFormat.h