OnBeginDecode
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OnBeginDecode method

Called by the filter to determine which image formats are supported.

Syntax


HRESULT retVal = object.OnBeginDecode(pdwEvents, pnFormats, ppFormats);

Parameters

pdwEvents [out]

Type: DWORD

The address of a DWORD variable that receives a combination of the following flags.

IMGDECODE_EVENT_PROGRESS (0x01)

The event sink supports IImageDecodeEventSink::OnProgress.

IMGDECODE_EVENT_PALETTE (0x02)

The event sink supports IImageDecodeEventSink::OnPalette.

IMGDECODE_EVENT_BEGINBITS (0x04)

Not currently supported.

IMGDECODE_EVENT_BITSCOMPLETE (0x08)

The event sink supports IImageDecodeEventSink::OnBitsComplete.

IMGDECODE_EVENT_USEDDRAW (0x10)

The event sink surface supports IDirectDrawSurface.

pnFormats [out]

Type: unsigned long

The address of an unsigned long integer variable that receives the number of entries in the buffer returned in ppFormats.

ppFormats [out]

Type: BFID

The address of a pointer variable that receives an array of GUIDs for the supported formats. Preferred formats appear at the beginning of the array. The following formats are defined.

BFID_MONOCHROME

The surface supports a black-and-white (one-bit, one-channel) format.

BFID_RGB_4

The surface supports a 4-bit index, for a 16-color palette.

BFID_RGB_8

The surface supports an 8-bit index, for a 256-color palette.

BFID_RGB_555

The surface supports a 5-bit, three-channel format, or R(5) G(5) B(5).

BFID_RGB_565

The surface supports 16-bit color, or R(5) G(6) B(5).

BFID_RGB_24

The surface supports 24-bit color, or R(8) G(8) B(8).

BFID_RGB_32

The surface supports 32-bit (byte-aligned) color.

BFID_RGBA_32

The surface supports 32-bit color with alpha channel transparency.

BFID_GRAY_8

The surface supports 8-bit grayscale.

BFID_GRAY_16

The surface supports 16-bit grayscale.

BFID_INDEXED_RGB_1

Same as BFID_MONOCHROME.

BFID_INDEXED_RGB_4

Same as BFID_RGB_4.

BFID_INDEXED_RGB_8

Same as BFID_RGB_8.

Return value

Type: HRESULT

If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Remarks

IImageDecodeEventSink::OnBeginDecode is invoked from IImageDecodeFilter::Initialize.

Free the memory associated with the buffer returned in the ppFormats parameter with CoTaskMemFree. See IImageDecodeFilter::Terminate.

See also

IImageDecodeEventSink::GetSurface

 

 

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