DIB

Overview

• Device independent bitmap
  • Can be moved from device to device (hence device independent)
• Normally transported in
  • metafiles
  • bmp files
  • clipboard (CF_DIB data format)
• Contains
  • bits
  • header 
    • describes the format of the bits
      • color format (color table)
      • size of the bitmap
• Supports
  • 1-bit, 4-bit, 8-bit
    • pixels are defined by indexes into color table
  • 24-bit
    • 1 byte each for red, green, and blue
• DIB functions
  • GetDIBits
  • SetDIBits
  • CreateDIBBitmap
  • SetDIBitsToDevice
  • StretchDIBits
  • CreateDIBPatternBrush

DIB Header

• Consists two adjoioning parts
  • header
  • color table
• Combined into the BITMAPINFO structure
  • biSize
  • biWidth
  • biHeight
  • biPlanes
    • Should always be 1
  • biBitCount
    • Color resolution in bits per pixel.
    • Allowed are 1, 4, 8, and 24
  • biCompression
    • Type of compression
    • Can be
      • BI_RGB
      • BI_RLE4
      • BI_RLE8
  • biSizeImage
    • Size of the bitmap proper in bytes
  •  biXPelsPerMeter
  • biYPelsPerMeter
  • biClrUsed
  • biClrImportant 

OS2 Style DIB

• A DIB file has
  • A file header
    
// 14 bytes since each WORD is 2 bytes and DWORD is 4
typedef struct tagBITMAPFILEHEADER // bmfh
{
  WORD bfType ; // signature word "BM" or 0x4D42
  DWORD bfSize ; // entire size of file
  WORD bfReserved1 ; // must be zero
  WORD bfReserved2 ; // must be zero
  DWORD bfOffsetBits ; // offset in file of DIB pixel bits
}
BITMAPFILEHEADER, * PBITMAPFILEHEADER ;

  • An information header
    
typedef struct tagBITMAPCOREHEADER // bmch
{
  DWORD bcSize ; // size of the structure = 12
  WORD bcWidth ; // width of image in pixels
  WORD bcHeight ; // height of image in pixels
  WORD bcPlanes ; // = 1
  WORD bcBitCount ; // bits per pixel (1, 4, 8, or 24)
}
BITMAPCOREHEADER, * PBITMAPCOREHEADER ;// Also defined in WINGDI.H
typedef struct tagBITMAPCOREINFO // bmci
{
  BITMAPCOREHEADER bmciHeader ; // core-header structure
  RGBTRIPLE bmciColors[1] ; // color table array
// Always 2, 16, or 256 RGBTRIPLE structures depending on bits per pixel
// Allocate PBITMAPCOREINFO for an 8-bit DIB
// pbmci = malloc (sizeof (BITMAPCOREINFO) + 255 * sizeof (RGBTRIPLE)) ;
}
BITMAPCOREINFO, * PBITMAPCOREINFO ;
  • An RGB color table (but not always. not with 24 bit/pixel DIB)
    • An array of 3 byte RGBTRIPLE structures
      
typedef struct tagRGBTRIPLE // rgbt
{
  BYTE rgbtBlue ; // blue level
  BYTE rgbtGreen ; // green level
  BYTE rgbtRed ; // red level
}
RGBTRIPLE ;

  • The bitmap pixel bits
• A in memory DIB has exactly as DIB file minus file header

http://support.microsoft.com/kb/q81498/