[Overview][Constants][Types][Classes][Procedures and functions][Variables][Index] Reference for unit 'Graphics' (#lcl)

TJPEGImage

[Properties (by Name)] [Methods (by Name)] [Events (by Name)]

TJPEGImage - a class for handling images stored in JPEG (compressed) format

Declaration

Source position: graphics.pp line 1758

type TJPEGImage = class(TFPImageBitmap)

protected

  procedure InitializeReader(); override;

  

InitializeReader - starts up the specified reader to read th especified Image

  procedure InitializeWriter(); override;

  

InitializeWriter - starts up the specified writer to store the specified Image

  procedure FinalizeReader(); override;

  

FinalizeReader - ends the Image reading process

protected

  class function GetReaderClass; override;

  

GetReaderClass - returns the class of reader for acquiring data from a stream

  class function GetWriterClass; override;

  

GetWriterClass - returns the class of writer for storing data to a stream

  class function GetSharedImageClass; override;

  

GetSharedImageClass - returns the class of Shared Raster Image

public

  constructor Create; override;

  

Create - constructor for TJPEGImage: performs inherited Create then initialises local variables for performance, quality and encoding

public

  class function IsStreamFormatSupported(); override;

  class function GetFileExtensions; override;

  

GetFileExtensions - returns a list of the file extensions available

public

  property CompressionQuality: TJPEGQualityRange; [rw]

  

Determine the compression quality for this image

  property GrayScale: Boolean; [r]

  

Is this a grayscale image?

  property ProgressiveEncoding: Boolean; [r]

  

Is progressive encoding used for this JPEG?

  property Performance: TJPEGPerformance; [rw]

  

Set for best quality or best speed

end;

Inheritance

TJPEGImage

  

TJPEGImage - a class for handling images stored in JPEG (compressed) format

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TFPImageBitmap

  

A class of Bitmap using the FPImage reader and writer (ie customised for FreePascal)

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TCustomBitmap

  

TCustomBitMap - the base class for TBitmap

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TRasterImage

  

TRasterImage - base class for a number of graphic controls, including TCustomBitmap and TCustomIcon, which use a raster of dots to display graphic information

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TGraphic

  

TGraphic - Base class for dealing with Graphic images

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TPersistent

?

TObject

Description

JPEG images are very commonly used for storing digital photographs. They can represent detailed colour photos using a high degree of compression, resulting in very efficient storage, though with some loss of quality.

The properties CompressionQuality (an integer between 1 and 100, with 100 representing the best quality) and Performance (an enumerated variable with two states: BestQuality or BestSpeed ie compression) can be used to determine the balance between efficiency of storage and quality of picture.