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DaVinci Graphics Library
DaVinci Documentation

structure BITMAPV4HEADER

Microsoft's DIB data format underwent an update with Windows 4.0 and Windows 95. DIBs can now optionally use a BITMAPV4HEADER structure in place of a BITMAPINFOHEADER structure. The the new structure starts with the same fields as BITMAPINFOHEADER structure, and additional fields used by the new format follow these standard fields. All other structures (color palettes, bits) are located after this new, larger header. The biSize field ia used to specify whether a DIB is based on BITMAPINFOHEADER or BITMAPV4HEADER.

BiSize	Value	Compatibility
Sizeof(BITMAPCOREHEADER)	0x0c	DIB OS/2 1.3 compatible
Sizeof(BITMAPINFOHEADER)	0x28	DIB Windows 3.1 compatible
Sizeof(BITMAPV4HEADER)	0x6c	Windows 95 / DIB NT 4.0
Sizeof(BITMAPV5HEADER)		Windows 98 / DIB NT 5.0

BITMAPINFOHEADER
type definition

BITMAPV4HEADER
type definition

typedef struct
tagBITMAPINFOHEADER{ 
   DWORD  biSize; 
   LONG   biWidth; 
   LONG   biHeight; 
   WORD   biPlanes; 
   WORD   biBitCount 
   DWORD  biCompression;
   DWORD  biSizeImage;
   LONG   biXPelsPerMeter;
   LONG   biYPelsPerMeter;
   DWORD  biClrUsed;
   DWORD  biClrImportant;
} BITMAPINFOHEADER;

typedef struct 
{
 DWORD        bV4Size;
 LONG         bV4Width;
 LONG         bV4Height;
 WORD         bV4Planes;
 WORD         bV4BitCount;
 DWORD        bV4V4Compression;
 DWORD        bV4SizeImage;
 LONG         bV4XPelsPerMeter;
 LONG         bV4YPelsPerMeter;
 DWORD        bV4ClrUsed;
 DWORD        bV4ClrImportant;
 DWORD        bV4RedMask;
 DWORD        bV4GreenMask;
 DWORD        bV4BlueMask;
 DWORD        bV4AlphaMask;
 DWORD        bV4CSType;
 CIEXYZTRIPLE bV4Endpoints;
 DWORD        bV4GammaRed;
 DWORD        bV4GammaGreen;
 DWORD        bV4GammaBlue;
} BITMAPV4HEADER, FAR *LPBITMAPV4HEADER, *PBITMAPV4HEADER;

The fields used by the BITMAPV4HEADER structure correspond to those of BITMAPINFOHEADER structure with the addition of a few supplementary fields as shown above.

Use in DaVinci

DaVinci uses the BITMAPV4HEADER structure when it needs to work with DIBs in special formats which need to contain information which cannot be recorded in the BITMAPINFOHEADER structure:

Identifier of a CMYK-DIB

The field bV4CSType, which takes the following (Color Space Type) values, can identify the DIB as CMYK, as follows:

Symbolic constant	Value	Meaning
LCS_CALIBRATED_RGB	0	The DIB uses the normalized sRGB colour space defined by ICM
LCS_DEVICE_RGB	1	The DIB uses the device dependent RGB colour space defined by a display device. This is the definition used by the older BITMAPINFOHEADER.
LCS_DEVICE_CMYK	2	The DIB uses the device dependent CMYK colour space defined by a printer.

Since the DIB is stored at 8 bits per CMYK component, bV4BitCount equivalent to biBitCount = 32.

Identifier of a RGBA-DIB

To specify an RGBA DIB, the bV4AlphaMask field is set to a non-zero value. Since the DIB is stored with 8 bits per RGB and alpha component, bV4BitCount equivalent to biBitCount = 32.

RGBA DIBs are treated by Windows functions in the same way as other DIBs. The Alpha channel is being used by the DIBAlphaBlend function.

Comment

The BITMAPV4HEADER structure is defined for newer 32 bit compilers in the WINGDI.H header shipped with the compiler.

For 16-Bit Compilers this structure is not defined in WINDOWS.H, for that reason it was included into the header-file LEONARDO.H header shipped with DaVinci.

structure BITMAPV4HEADER

Use in DaVinci

Identifier of a CMYK-DIB

Identifier of a RGBA-DIB

Comment

See also