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TJPEGImage - a class for handling images stored in JPEG (compressed) format
Source position: graphics.pp line 1758
type TJPEGImage = class(TFPImageBitmap) |
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procedure InitializeReader(); override; |
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InitializeReader - starts up the specified reader to read th especified Image |
procedure InitializeWriter(); override; |
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InitializeWriter - starts up the specified writer to store the specified Image |
procedure FinalizeReader(); override; |
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FinalizeReader - ends the Image reading process |
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class function GetReaderClass; override; |
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GetReaderClass - returns the class of reader for acquiring data from a stream |
class function GetWriterClass; override; |
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GetWriterClass - returns the class of writer for storing data to a stream |
class function GetSharedImageClass; override; |
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GetSharedImageClass - returns the class of Shared Raster Image |
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constructor Create; override; |
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Create - constructor for TJPEGImage: performs inherited Create then initialises local variables for performance, quality and encoding |
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class function IsStreamFormatSupported(); override; |
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class function GetFileExtensions; override; |
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GetFileExtensions - returns a list of the file extensions available |
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property CompressionQuality: TJPEGQualityRange; [rw] |
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Determine the compression quality for this image |
property GrayScale: Boolean; [r] |
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Is this a grayscale image? |
property ProgressiveEncoding: Boolean; [r] |
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Is progressive encoding used for this JPEG? |
property Performance: TJPEGPerformance; [rw] |
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Set for best quality or best speed |
end; |
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TJPEGImage - a class for handling images stored in JPEG (compressed) format |
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A class of Bitmap using the FPImage reader and writer (ie customised for FreePascal) |
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TCustomBitMap - the base class for TBitmap |
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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 - Base class for dealing with Graphic images |
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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.
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