Class CPalette

class CPalette : public CBase;

Description

Provides user-definable palette support to the GDI.

A palette is a user-defined set of colours, which is a subset of the full range of 24-bit colours. This allows users the advantages of having a low bpp colour mode whilst being able to specify the colours available in that mode. To give an example, the EColor16 mode provides a palette of 16 colours as it provides a mapping between an integer index and a TRgb colour (see the table EGA Low-colour constants). Only a palette of 16 colour enables you to change the palette. Palettes are also used to allow 24-bit bitmaps to be stored in a more compressed form by finding the actual number of different colours used in the bitmap, creating a palette to allow the mapping of these colours to a smaller index space, and encoding the bitmaps pixels using indexes to this new index space.

A palette has a size which is set at its creation and cannot be altered the number of entries in the palette. Each entry in a palette is a mapping between that entrys index and a TRgb value. Palette entries can be got and set at any time between the palettes creation and destruction. The GDIs palette support also provides functions to find the nearest palette colour to a requested TRgb colour.

Derivation

• CBase - Base class for all classes to be instantiated on the heap.

• CPalette - Provides user-definable palette support to the GDI.

Members

Defined in CPalette:

• CPalette()
• Clear()Clears all the entries in the palette to TRgb(0).
• Entries()constGets the number of entries in the palette
• GetDataPtr(TInt,TInt,TPtr8 &)Returns a descriptor over the palette entries for the specifed colors. It is des...
• GetEntry(TInt)constGets the RGB value of the palette entry at aPaletteIndex.
• NearestEntry(const TRgb &)constGets the colour in the palette which is closest to the specified colour.
• NearestIndex(const TRgb &)constGets the index of the colour in the palette which is closest to the specified co...
• NewDefaultL(TDisplayMode)Creates a new default palette for the specified display mode. The default palett...
• NewL(TInt)Creates a new palette with the specified number of entries.
• SetEntry(TInt,const TRgb &)Sets the palette entry at aPaletteIndex to the RGB value aPaletteEntry.
• iArray
• iNumEntries
• ~CPalette()Destructor.

Inherited from CBase:

• Delete(CBase *)Deletes the specified object.
• Extension_(TUint,TAny *&,TAny *)Extension function
• operator new(TUint)Allocates the object from the heap and then initialises its contents to binary z...
• operator new(TUint,TAny *)Initialises the object to binary zeroes.
• operator new(TUint,TLeave)Allocates the object from the heap and then initialises its contents to binary z...
• operator new(TUint,TLeave,TUint)Allocates the object from the heap and then initialises its contents to binary z...
• operator new(TUint,TUint)Allocates the object from the heap and then initialises its contents to binary z...

IMPORT_C static CPalette* NewL(TInt aNumberOfEntries);

Description

Creates a new palette with the specified number of entries.

Parameters

Return value

IMPORT_C ~CPalette();

Description

Destructor.

protected: IMPORT_C CPalette();

Description

IMPORT_C static CPalette* NewDefaultL(TDisplayMode aDispMode);

Description

Creates a new default palette for the specified display mode. The default palette for a particular display mode has one entry for each possible colour in that display mode (2 entries for EGray2, 16 entries for EColor16 etc.); the colour of each index p in the default palette is set to its default value according to its display mode (e.g. if the mode is EColor16 then palette[p]==TRgb::Color16(p); if the mode is EGray4 then palette[p]==TRgb::_Gray4(p)).

Parameters

Return value

IMPORT_C void Clear();

Description

Clears all the entries in the palette to TRgb(0).

inline TInt Entries() const;

Description

Gets the number of entries in the palette

Return value

IMPORT_C TRgb GetEntry(TInt aPaletteIndex) const;

Description

Gets the RGB value of the palette entry at aPaletteIndex.

Parameters

Return value

IMPORT_C TRgb NearestEntry(const TRgb &aColor) const;

Description

Gets the colour in the palette which is closest to the specified colour.

Parameters

Return value

IMPORT_C TInt NearestIndex(const TRgb &aColor) const;

Description

Gets the index of the colour in the palette which is closest to the specified colour.

Parameters

Return value

IMPORT_C void SetEntry(TInt aPaletteIndex, const TRgb &aPaletteEntry);

Description

Sets the palette entry at aPaletteIndex to the RGB value aPaletteEntry.

Parameters

IMPORT_C void GetDataPtr(TInt aFirstColor, TInt aNumColors, TPtr8 &aPtr);

Description

Returns a descriptor over the palette entries for the specifed colors. It is designed so that the descriptor can be passed to another thread and that thread copy the relevant entries.

Parameters

protected: TRgb * iArray;

Description

protected: TInt iNumEntries;

Description