IDXLookupTable Interface

The IDXLookupTable interface is used to change the color balance for a set of samples. Each color in the pixel is used as an index in a table that indicates what the adjusted color value should be.

To use lookup tables, you must first create a lookup table with the IDXLUTBuilder interface, which sets the number and order of the operations performed on the samples. To obtain a pointer to a lookup table, you must call the Component Object Model (COM) QueryInterface method on an IDXLUTBuilder object.

IDXLookupTable* g_pLUT;
    g_pLUTBuilder->QueryInterface( IID_IDXLookupTable, (void **)&g_pLUT );

The pointer returned from this call can be used to obtain the values contained in the lookup table. It can also be used as a parameter to the IDXSurfaceModifier::SetLookup member function, so that the lookup table can be applied to an entire DXSurface.

Lookup tables can be used to adjust an image's brightness, contrast, or to perform gamma correction.

This interface inherits from the IDXBaseObject interface.

IDXLookupTable Methods

ApplyTables Translates a set of samples in place.

GetIndexValues Retrieves the component values for a specific index in the table.

GetTables Retrieves a copy of the lookup tables.

IsChannelIdentity Determines whether the application of a channel's table will have any effect.

IDXLookupTable::ApplyTables

IDXLookupTable Interface

Translates a set of samples in place.

Syntax

HRESULT ApplyTables(
    DXSAMPLE *pSamples,
    ULONG cSamples
);

Parameters

pSamples
[in, out] Pointer to the buffer of samples to be translated.

cSamples
[in] Number of samples to be translated.

Return Value

Returns an HRESULT value that depends on the implementation of the interface.

IDXLookupTable::GetIndexValues

IDXLookupTable Interface

Retrieves the component values for a specific index in the table.

Syntax

HRESULT GetIndexValues(
    ULONG Index,
    DXBASESAMPLE *pSample
);

Parameters

Index
[in] Index into the lookup table from which to retrieve the translation values.

pSample
[out] Pointer to the location in which to store the translation values.

Return Value

Returns an HRESULT value that depends on the implementation of the interface.

Remarks

An ARGB component value will be returned from the table at the given index.

IDXLookupTable::GetTables

IDXLookupTable Interface

Retrieves a copy of the lookup tables.

Syntax

HRESULT GetTables(
     BYTE RedLUT[256],
     BYTE GreenLUT[256],
     BYTE BlueLUT[256],
     BYTE AlphaLUT[256]
);

Parameters

RedLUT
[out] Location to store the red channel translation values.

GreenLUT
[out] Location to store the green channel translation values.

BlueLUT
[out] Location to store the blue channel translation values.

AlphaLUT
[out] Location to store the alpha channel translation values.

Return Value

Returns an HRESULT value that depends on the implementation of the interface.

Remarks

This method is useful for obtaining a snapshot of the tables.

IDXLookupTable::IsChannelIdentity

IDXLookupTable Interface

Determines whether the application of a channel's table will have any effect.

Syntax

HRESULT IsChannelIdentity(
    DXBASESAMPLE *pSampleBools
);

Parameters

pSampleBools
[out] Pointer to a DXBASESAMPLE structure that tells whether a color's lookup table is enabled.

Return Value

Returns an HRESULT value that depends on the implementation of the interface.

Remarks

A TRUE or FALSE value will be stored in each of the color components (alpha, red, green, and blue) of the returned structure. If a component has a return value of TRUE, that color is unaffected by a call to ApplyTables.

ApplyTables	Translates a set of samples in place.
GetIndexValues	Retrieves the component values for a specific index in the table.
GetTables	Retrieves a copy of the lookup tables.
IsChannelIdentity	Determines whether the application of a channel's table will have any effect.