IThumbnailProvider::GetThumbnail method (thumbcache.h)

Article
02/22/2024

Gets a thumbnail image and alpha type.

Syntax

HRESULT GetThumbnail(
  [in]  UINT          cx,
  [out] HBITMAP       *phbmp,
  [out] WTS_ALPHATYPE *pdwAlpha
);

Parameters

[in] cx

Type: UINT

The maximum thumbnail size, in pixels. The Shell draws the returned bitmap at this size or smaller. The returned bitmap should fit into a square of width and height cx, though it does not need to be a square image. The Shell scales the bitmap to render at lower sizes. For example, if the image has a 6:4 aspect ratio, then the returned bitmap should also have a 6:4 aspect ratio.

[out] phbmp

Type: HBITMAP*

When this method returns, contains a pointer to the thumbnail image handle. The image must be a DIB section and 32 bits per pixel. The Shell scales down the bitmap if its width or height is larger than the size specified by cx. The Shell always respects the aspect ratio and never scales a bitmap larger than its original size.

[out] pdwAlpha

Type: WTS_ALPHATYPE*

When this method returns, contains a pointer to one of the following values from the WTS_ALPHATYPE enumeration:

WTSAT_UNKNOWN (0x0)

0x0. The bitmap is an unknown format. The Shell tries nonetheless to detect whether the image has an alpha channel.

WTSAT_RGB (0x1)

0x1. The bitmap is an RGB image without alpha. The alpha channel is invalid and the Shell ignores it.

WTSAT_ARGB (0x2)

0x2. The bitmap is an ARGB image with a valid alpha channel.

Return value

Type: HRESULT

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

Requirements

Requirement	Value
Minimum supported client	Windows Vista [desktop apps only]
Minimum supported server	Windows Server 2008 [desktop apps only]
Target Platform	Windows
Header	thumbcache.h

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