The BITMAPINFOHEADER structure contains information about the dimensions and color format of a device-independent bitmap (DIB).
Applications developed for Windows NT 4.0 and Windows 95 may use the BITMAPV4HEADER structure. Applications developed for Windows NT 5.0 and Windows 98 may use the BITMAPV5HEADER structure for increased functionality.
typedef struct tagBITMAPINFOHEADER{ // bmih
DWORD biSize;
LONG biWidth;
LONG biHeight;
WORD biPlanes;
WORD biBitCount
DWORD biCompression;
DWORD biSizeImage;
LONG biXPelsPerMeter;
LONG biYPelsPerMeter;
DWORD biClrUsed;
DWORD biClrImportant;
} BITMAPINFOHEADER;
Windows 98, Windows NT 5.0 and later: If biCompression is BI_JPEG, the biWidth member specifies the width of the decompressed JPEG image file.
If biHeight is negative, indicating a top-down DIB, biCompression must be either BI_RGB or BI_BITFIELDS. Top-down DIBs cannot be compressed.
Windows 98, Windows NT 5.0 and later: If biCompression is BI_JPEG, the biHeight member specifies the height of the decompressed JPEG image file.
| Value | Meaning |
|---|---|
| 0 | Windows 98, Windows NT 5.0 and later: The number of bits per pixel is specified or is implied by the JPEG format. |
| 1 | The bitmap is monochrome, and the bmiColors member contains two entries. Each bit in the bitmap array represents a pixel. If the bit is clear, the pixel is displayed with the color of the first entry in the bmiColors table; if the bit is set, the pixel has the color of the second entry in the table. |
| 4 | The bitmap has a maximum of 16 colors, and the bmiColors member contains up to 16 entries. Each pixel in the bitmap is represented by a 4-bit index into the color table. For example, if the first byte in the bitmap is 0x1F, the byte represents two pixels. The first pixel contains the color in the second table entry, and the second pixel contains the color in the sixteenth table entry. |
| 8 | The bitmap has a maximum of 256 colors, and the bmiColors member contains up to 256 entries. In this case, each byte in the array represents a single pixel. |
| 16 | The bitmap has a maximum of 2^16 colors. If the biCompression member of the BITMAPINFOHEADER is BI_RGB, the bmiColors member is NULL. Each WORD in the bitmap array represents a single pixel. The relative intensities of red, green, and blue are represented with 5 bits for each color component. The value for blue is in the least significant 5 bits, followed by 5 bits each for green and red. The most significant bit is not used. The bmiColors color table is used for optimizing colors used on palette-based devices, and must contain the number of entries specified by the biClrUsed member of the BITMAPINFOHEADER. If the biCompression member of the BITMAPINFOHEADER is BI_BITFIELDS, the bmiColors member contains three DWORD color masks that specify the red, green, and blue components, respectively, of each pixel. Each WORD in the bitmap array represents a single pixel. Windows NT: When the biCompression member is BI_BITFIELDS, bits set in each DWORD mask must be contiguous and should not overlap the bits of another mask. All the bits in the pixel do not have to be used. Windows 95 and Windows 98: When the biCompression member is BI_BITFIELDS, the system supports only the following 16bpp color masks: A 5-5-5 16-bit image, where the blue mask is 0x001F, the green mask is 0x03E0, and the red mask is 0x7C00; and a 5-6-5 16-bit image, where the blue mask is 0x001F, the green mask is 0x07E0, and the red mask is 0xF800. |
| 24 | The bitmap has a maximum of 2^24 colors, and the bmiColors member is NULL. Each 3-byte triplet in the bitmap array represents the relative intensities of blue, green, and red, respectively, for a pixel. The bmiColors color table is used for optimizing colors used on palette-based devices, and must contain the number of entries specified by the biClrUsed member of the BITMAPINFOHEADER. |
| 32 | The bitmap has a maximum of 2^32 colors. If the biCompression member of the BITMAPINFOHEADER is BI_RGB, the bmiColors member is NULL. Each DWORD in the bitmap array represents the relative intensities of blue, green, and red, respectively, for a pixel. The high byte in each DWORD is not used. The bmiColors color table is used for optimizing colors used on palette-based devices, and must contain the number of entries specified by the biClrUsed member of the BITMAPINFOHEADER. If the biCompression member of the BITMAPINFOHEADER is BI_BITFIELDS, the bmiColors member contains three DWORD color masks that specify the red, green, and blue components, respectively, of each pixel. Each DWORD in the bitmap array represents a single pixel. Windows NT: When the biCompression member is BI_BITFIELDS, bits set in each DWORD mask must be contiguous and should not overlap the bits of another mask. All the bits in the pixel do not need to be used. Windows 95 and Windows 98: When the biCompression member is BI_BITFIELDS, the system supports only the following 32bpp color mask: The blue mask is 0x000000FF, the green mask is 0x0000FF00, and the red mask is 0x00FF0000. |
| Value | Description |
|---|---|
| BI_RGB | An uncompressed format. |
| BI_RLE8 | A run-length encoded (RLE) format for bitmaps with 8 bits per pixel. The compression format is a 2-byte format consisting of a count byte followed by a byte containing a color index. For more information, see Bitmap Compression. |
| BI_RLE4 | An RLE format for bitmaps with 4 bits per pixel. The compression format is a 2-byte format consisting of a count byte followed by two word-length color indexes. For more information, see Bitmap Compression. |
| BI_BITFIELDS | Specifies that the bitmap is not compressed and that the color table consists of three DWORD color masks that specify the red, green, and blue components, respectively, of each pixel. This is valid when used with 16- and 32-bit-per-pixel bitmaps. |
| BI_JPEG | Windows 98, Windows NT 5.0 and later: Indicates that the image is a JPEG image. |
Windows 98, Windows NT 5.0 and later: If biCompression is JBI_JPEG, biSizeImage indicates the size of the JPEG image buffer.
If biClrUsed is nonzero and the biBitCount member is less than 16, the biClrUsed member specifies the actual number of colors the graphics engine or device driver accesses. If biBitCount is 16 or greater, the biClrUsed member specifies the size of the color table used to optimize performance of the system color palettes. If biBitCount equals 16 or 32, the optimal color palette starts immediately following the three DWORD masks.
If the bitmap is a packed bitmap (a bitmap in which the bitmap array immediately follows the BITMAPINFO header and is referenced by a single pointer), the biClrUsed member must be either zero or the actual size of the color table.
The BITMAPINFO structure combines the BITMAPINFOHEADER structure and a color table to provide a complete definition of the dimensions and colors of a DIB. For more information about DIBs, Device-Independent Bitmaps and BITMAPINFO.
An application should use the information stored in the biSize member to locate the color table in a BITMAPINFO structure, as follows:
pColor = ((LPSTR)pBitmapInfo +
(WORD)(pBitmapInfo->bmiHeader.biSize));
Windows 98, Windows NT 5.0 and later: The BITMAPINFOHEADER structure is extended to allow a JPEG image to be passed as the source image to StretchDIBits.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in wingdi.h.
Bitmaps Overview, Bitmap Structures