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IDirect3DDevice9 StretchRect

2019-02-01 13:51:25 作者：互联网

IDirect3DDevice9::StretchRect

Copy the contents of the source rectangle to the destination rectangle. The source rectangle can be stretched and filtered by the copy. This function is often used to change the aspect ratio of a video stream.

HRESULT StretchRect(
  IDirect3DSurface9 * pSourceSurface,
  CONST RECT * pSourceRect,
  IDirect3DSurface9 * pDestSurface,
  CONST RECT * pDestRect,
  D3DTEXTUREFILTERTYPE Filter
);

Parameters

pSourceSurface: [in] Pointer to the source surface. See IDirect3DSurface9.
pSourceRect: [in] Pointer to the source rectangle. A NULL for this parameter causes the entire source surface to be used.
pDestSurface: [in] Pointer to the destination surface. See IDirect3DSurface9.
pDestRect: [in] Pointer to the destination rectangle. A NULL for this parameter causes the entire destination surface to be used.
Filter: [in] Filter type. Allowable values are D3DTEXF_NONE, D3DTEXF_POINT, or D3DTEXF_LINEAR. For more information, see D3DTEXTUREFILTERTYPE.

Return Values

If the method succeeds, the return value is D3D_OK. If the method fails, the return value can be: D3DERR_INVALIDCALL.

Remarks

StretchRect Restrictions

Driver support varies. See the section on driver support (below) to see which drivers support which source and destination formats.
The source and destination surfaces must be created in the default memory pool.
If filtering is specified, you must set the appropriate filter caps (see StretchRectFilterCaps in D3DCAPS9).
Stretching is not supported between source and destination rectangles on the same surface.
Stretching is not supported if the destination surface is an off-screen plain surface but the source is not.
You many not stretch between source and destination rectangles if either surface is in a compressed format (see Using Compressed Textures (Direct3D 9)).
Stretching supports color-space conversion from YUV to high-precision RGBA only. Since color conversion support is not supported by software emulation, use IDirect3D9::CheckDeviceFormatConversion to test the hardware for color conversion support.
If the source or destination surface is a texture surface (or a cube texture surface), you must use a Direct3D 9 driver that supports D3DDEVCAPS2_CAN_STRETCHRECT_FROM_TEXTURES (see D3DDEVCAPS2).

Additional Restrictions for Depth and Stencil Surfaces

The source and destination surfaces must be plain depth stencil surfaces (not textures) (see IDirect3DDevice9::CreateDepthStencilSurface).
Neither of the surfaces can be discardable.
The entire surface must be copied (that is: sub-rectangle copies are not allowed).
Format conversion, stretching, and shrinking are not supported.
StretchRect cannot be called inside of a BeginScene/EndScene pair.

Using StretchRect to downsample a Multisample Rendertarget

You can use StretchRect to copy from one rendertarget to another. If the source rendertarget is multisampled, this results in downsampling the source rendertarget. For instance you could:

Create a multisampled rendertarget.
Create a second rendertarget of the same size, that is not multisampled.
Copy (using StretchRect the multisample rendertarget to the second rendertarget.

Note that use of the extra surface involved in using StretchRect to downsample a Multisample Rendertarget will result in a performance hit.

Driver Support

There are many restrictions as to which surface combinations are valid for StretchRect. Factors include whether the driver is a Direct3D 9 driver or older, and whether the operation will result in stretching/shrinking. Since applications are not expected to recognize if the driver is a Direct3D 9 driver or not, the runtime will automatically set a new cap, D3DDEVCAPS2_CAN_STRETCHRECT_FROM_TEXTURES cap (see D3DDEVCAPS2), for Direct3D 9-level drivers and above.

DirectX 8 Driver (no stretching)
		Dest formats
		Texture	RT texture	RT	Off-screen plain
Src formats	Texture	No	No	No	No
	RT texture	No	Yes	Yes	No
	RT	No	Yes	Yes	No
	Off-screen plain	Yes	Yes	Yes	Yes

DirectX 8 Driver (stretching)
		Dest formats
		Texture	RT texture	RT	Off-screen plain
Src formats	Texture	No	No	No	No
	RT texture	No	No	No	No
	RT	No	Yes	Yes	No
	Off-screen plain	No	Yes	Yes	No

Direct3D 9 Driver (no stretching)
		Dest formats
		Texture	RT texture	RT	Off-screen plain
Src formats	Texture	No	Yes	Yes	No
	RT texture	No	Yes	Yes	No
	RT	No	Yes	Yes	No
	Off-screen plain	No	Yes	Yes	Yes

Direct3D 9 Driver (stretching)
		Dest formats
		Texture	RT texture	RT	Off-screen plain
Src formats	Texture	No	Yes	Yes	No
	RT texture	No	Yes	Yes	No
	RT	No	Yes	Yes	No
	Off-screen plain	No	Yes	Yes	No

Requirements

Header: Declared in D3D9.h.