GetDIBits

The GetDIBits function retrieves the bits of the specified bitmap and copies them into a buffer using the specified format.

int GetDIBits(

HDC hdc,	// handle of device context
HBITMAP hbmp,	// handle of bitmap
UINT uStartScan,	// first scan line to set in destination bitmap
UINT cScanLines,	// number of scan lines to copy
LPVOID lpvBits,	// address of array for bitmap bits
LPBITMAPINFO lpbi,	// address of structure with bitmap data
UINT uUsage	// RGB or palette index
);

Parameters

hdc

Identifies the device context.

hbmp

Identifies the bitmap.

uStartScan

Specifies the first scan line to retrieve.

cScanLines

Specifies the number of scan lines to retrieve.

lpvBits

Points to a buffer to receive the bitmap data. If this parameter is NULL, the function passes the dimensions and format of the bitmap to the BITMAPINFO structure pointed to by the lpbi parameter.

lpbi

Points to a BITMAPINFO structure that specifies the desired format for the device-independent bitmap (DIB) data.

uUsage

Specifies the format of the bmiColors member of the BITMAPINFO structure. It must be one of the following values:

Value	Meaning
DIB_PAL_COLORS	The color table should consist of an array of 16-bit indices into the current logical palette.
DIB_RGB_COLORS	The color table should consist of literal red, green, blue (RGB) values.

Return Values

If the lpvBits parameter is non-NULL and the function succeeds, the return value is the number of scan lines copied from the bitmap.

Windows 95:

If the lpvBits parameter is NULL and GetDIBits successfully fills the BITMAPINFO structure, the return value is the total number of scan lines in the bitmap.

Windows NT:

If the lpvBits parameter is NULL and GetDIBits successfully fills the BITMAPINFO structure, the return value is non-zero.

If the function fails, the return value is zero.

Remarks

If the requested format for the DIB matches its internal format, the RGB values for the bitmap are copied. If the requested format doesn't match the internal format, a color table is synthesized. The following table describes the color table synthesized for each format.

Value	Meaning
BPP	The color table consists of a black and a white entry.
4_BPP	The color table consists of a mix of colors identical to the standard VGA palette.
8_BPP	The color table consists of a general mix of 256 colors defined by GDI. (Included in these 256 colors are the 20 colors found in the default logical palette.)
24_BPP	No color table is returned.

If the lpvBits parameter is a valid pointer, the first six members of the BITMAPINFOHEADER structure must be initialized to specify the size and format of the DIB. Note that a bottom-up DIB is specified by setting the height to a positive number, while a top-down DIB is specified by setting the height to a negative number. The bitmap's color table will be appended to the BITMAPINFO structure.

If lpvBits is NULL, GetDIBits examines the first member of the first structure pointed to by lpbi. This member must specify the size, in bytes, of a BITMAPCOREHEADER or a BITMAPINFOHEADER structure. The function uses the specified size to determine how the remaining members should be initialized.

If lpvBits is NULL and the bit count member of BITMAPINFO is initialized to zero, GetDIBits fills in BITMAPINFOHEADER or BITMAPCOREHEADER without the color table. This technique can be used to query bitmap attributes.

The bitmap identified by the hbmp parameter must not be selected into a device context when the application calls this function.

The origin for a bottom-up DIB is the lower-left corner of the bitmap; the origin for a top-down DIB is the upper-left corner.

See Also

BITMAPCOREHEADER, BITMAPINFO, BITMAPINFOHEADER, SetDIBits

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