The CreateDIBSection function creates a device-independent bitmap (DIB) that applications can write to directly. The function gives you a pointer to the location of the bitmap’s bit values. You can supply a handle to a file mapping object that the function will use to create the bitmap, or you can let the operating system allocate the memory for the bitmap.
HBITMAP CreateDIBSection(
HDC hdc, |
// handle to device context |
CONST BITMAPINFO *pbmi, |
// pointer to structure containing bitmap size, format, and color data |
UINT iUsage, |
// color data type indicator: RGB values or palette indices |
VOID *ppvBits, |
// pointer to variable to receive a pointer to the bitmap’s bit values |
HANDLE hSection, |
// optional handle to a file mapping object |
DWORD dwOffset |
// offset to the bitmap bit values within the file mapping object |
); |
Value |
Meaning |
DIB_PAL_COLORS |
The bmiColors member is an array of 16-bit indices into the logical palette of the device context specified by hdc. |
DIB_RGB_COLORS |
The BITMAPINFO structure contains an array of literal RGB values. |
If hSection is not NULL, it must be a handle to a file mapping object created by calling the CreateFileMapping function. Handles created by other means will cause CreateDIBSection to fail.
If hSection is not NULL, the CreateDIBSection function locates the bitmap’s bit values at offset dwOffset in the file mapping object referred to by hSection. An application can later retrieve the hSection handle by calling the GetObject function with the HBITMAP returned by CreateDIBSection.
If hSection is NULL, the operating system allocates memory for the
device-independent bitmap. In this case, the CreateDIBSection function
ignores the dwOffset parameter. An application cannot later obtain a
handle to this memory: the dshSection member of the DIBSECTION
structure filled in by calling the GetObject function will be NULL.
If the function succeeds, the return value is a handle to the newly created device-independent bitmap, and *ppvBits points to the bitmap’s bit values.
If the function fails, the return value is NULL, and *ppvBits is NULL. To get extended error information, call GetLastError.
As noted above, if hSection is NULL, the operating system allocates memory for the device-independent bitmap. The operating system closes the handle to that memory when you later delete the device-independent bitmap by calling the DeleteObject function. If hSection is not NULL, you must close the hSection memory handle yourself after calling DeleteObject to delete the bitmap.
Windows NT: You need to guarantee that the GDI subsystem has completed any drawing to a bitmap created by CreateDIBSection before you draw to the bitmap yourself. Access to the bitmap must be synchronized. Do this by calling the GdiFlush function. This applies to any use of the pointer to the bitmap’s bit values, including passing the pointer in calls to functions such as SetDIBits.
BITMAPINFO, CreateFileMapping, DeleteObject, DIBSECTION, GetDIBColorTable, GetObject, GdiFlush, HBITMAP, SetDIBits, SetDIBColorTable
See:
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