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 |
|
1_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.2PXNH 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