bitmap format (_bmp).htm

通过bmp图片格式进行数据加密

 maximum number of colors corresponding to the value of the biBitCount member.
 For more information on the maximum sizes of the color table, see the
 description of the BITMAPINFO structure earlier in this topic.

 If the biClrUsed member is nonzero, it specifies the actual number of colors
 that the graphics engine or device driver will access if the biBitCount
 member is less than 24. If biBitCount is set to 24, biClrUsed specifies the
 size of the reference color table used to optimize performance of Windows
 color palettes.  If the bitmap is a packed bitmap (that is, a bitmap in which
 the bitmap array immediately follows the BITMAPINFO header and which is
 referenced by a single pointer), the biClrUsed member must be set to zero or
 to the actual size of the color table.

 biClrImportant  Specifies the number of color indexes that are considered
 important for displaying the bitmap. If this value is zero, all colors are
 important.

 Comments

 The BITMAPINFO structure combines the BITMAPINFOHEADER structure and a color
 table to provide a complete definition of the dimensions and colors of a
 Windows 3.0 or later DIB. For more information about specifying a Windows 3.0
 DIB, see the description of the BITMAPINFO structure.

 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 supports formats for compressing bitmaps that define their colors
 with 8 bits per pixel and with 4 bits per pixel. Compression reduces the disk
 and memory storage required for the bitmap. The following paragraphs describe
 these formats.

 BI_RLE8

 When the biCompression member is set to BI_RLE8, the bitmap is compressed
 using a run-length encoding format for an 8-bit bitmap. This format may be
 compressed in either of two modes: encoded and absolute. Both modes can occur
 anywhere throughout a single bitmap.

 Encoded mode consists of two bytes: the first byte specifies the number of
 consecutive pixels to be drawn using the color index contained in the second
 byte. In addition, the first byte of the pair can be set to zero to indicate
 an escape that denotes an end of line, end of bitmap, or a delta. The
 interpretation of the escape depends on the value of the second byte of the
 pair. The following list shows the meaning of the second byte:

 Value   Meaning

 0       End of line.
 1       End of bitmap.
 2       Delta. The two bytes following the escape contain unsigned values
 indicating the horizontal and vertical offset of the next pixel from the
 current position.

 Absolute mode is signaled by the first byte set to zero and the second byte
 set to a value between 0x03 and 0xFF. In absolute mode, the second byte
 represents the number of bytes that follow, each of which contains the color
 index of a single pixel. When the second byte is set to 2 or less, the escape
 has the same meaning as in encoded mode. In absolute mode, each run must be
 aligned on a word boundary.  The following example shows the hexadecimal
 values of an 8-bit compressed bitmap:

 03 04 05 06 00 03 45 56 67 00 02 78 00 02 05 01
 02 78 00 00 09 1E 00 01

 This bitmap would expand as follows (two-digit values represent a color index
 for a single pixel):

 04 04 04
 06 06 06 06 06
 45 56 67
 78 78
 move current position 5 right and 1 down
 78 78
 end of line
 1E 1E 1E 1E 1E 1E 1E 1E 1E
 end of RLE bitmap

 BI_RLE4

 When the biCompression member is set to BI_RLE4, the bitmap is compressed
 using a run-length encoding (RLE) format for a 4-bit bitmap, which also uses
 encoded and absolute modes. In encoded mode, the first byte of the pair
 contains the number of pixels to be drawn using the color indexes in the
 second byte. The second byte contains two color indexes, one in its
 high-order nibble (that is, its low-order four bits) and one in its low-order
 nibble. The first of the pixels is drawn using the color specified by the
 high-order nibble, the second is drawn using the color in the low-order
 nibble, the third is drawn with the color in the high-order nibble, and so
 on, until all the pixels specified by the first byte have been drawn.  In
 absolute mode, the first byte contains zero, the second byte contains the
 number of color indexes that follow, and subsequent bytes contain color
 indexes in their high- and low-order nibbles, one color index for each pixel.
 In absolute mode, each run must be aligned on a word boundary. The
 end-of-line, end-of-bitmap, and delta escapes also apply to BI_RLE4.

 The following example shows the hexadecimal values of a 4-bit compressed
 bitmap:

 03 04 05 06 00 06 45 56 67 00 04 78 00 02 05 01
 04 78 00 00 09 1E 00 01

 This bitmap would expand as follows (single-digit values represent a color
 index for a single pixel):

 0 4 0
 0 6 0 6 0
 4 5 5 6 6 7
 7 8 7 8
 move current position 5 right and 1 down
 7 8 7 8
 end of line
 1 E 1 E 1 E 1 E 1
 end of RLE bitmap

 See Also

 BITMAPINFO

 ==============================================================================
 RGBQUAD (3.0)

 typedef struct tagRGBQUAD {     /* rgbq */
     BYTE    rgbBlue;
     BYTE    rgbGreen;
     BYTE    rgbRed;
     BYTE    rgbReserved;
 } RGBQUAD;

 The RGBQUAD structure describes a color consisting of relative intensities of
 red, green, and blue. The bmiColors member of the BITMAPINFO structure
 consists of an array of RGBQUAD structures.

 Member          Description

 rgbBlue         Specifies the intensity of blue in the color.
 rgbGreenSpecifies the intensity of green in the color.
 rgbRed          Specifies the intensity of red in the color.
 rgbReserved     Not used; must be set to zero.

 See Also

 BITMAPINFO

 ==============================================================================
 RGB (2.x)

 COLORREF RGB(cRed, cGreen, cBlue)

 BYTE cRed;      /* red component of color       */
 BYTE cGreen;    /* green component of color     */
 BYTE cBlue;     /* blue component of color      */

 The RGB macro selects an RGB color based on the parameters supplied and the
 color capabilities of the output device.

 Parameter       Description

 cRed    Specifies the intensity of the red color field.
 cGreen  Specifies the intensity of the green color field.
 cBlue   Specifies the intensity of the blue color field.

 Returns

 The return value specifies the resultant RGB color.

 Comments

 The intensity for each argument can range from 0 through 255. If all three
 intensities are specified as zero, the result is black. If all three
 intensities are specified as 255, the result is white.

 Comments

 The RGB macro is defined in WINDOWS.H as follows:

 #define RGB(r,g,b)   ((COLORREF)(((BYTE)(r)|((WORD)(g)<<8))| \
     (((DWORD)(BYTE)(b))<<16)))

 See Also

 GetBValue, GetGValue, GetRValue, PALETTEINDEX, PALETTERGB

 ==============================================================================
 BITMAPCOREINFO (3.0)

 typedef struct tagBITMAPCOREINFO {  /* bmci */
     BITMAPCOREHEADER bmciHeader;
     RGBTRIPLE        bmciColors[1];
 } BITMAPCOREINFO;

 The BITMAPCOREINFO structure fully defines the dimensions and color
 information for a device-independent bitmap (DIB).  Windows applications
 should use the BITMAPINFO structure instead of BITMAPCOREINFO whenever
 possible.

 Member          Description

 bmciHeader      Specifies a BITMAPCOREHEADER structure that contains
 information about the dimensions and color format of a DIB.

 bmciColors      Specifies an array of RGBTRIPLE structures that define the
 colors in the bitmap.

 Comments

 The BITMAPCOREINFO structure describes the dimensions and colors of a bitmap.
 It is followed immediately in memory by an array of bytes which define the
 pixels of the bitmap. The bits in the array are packed together, but each
 scan line must be zero-padded to end on a LONG boundary. Segment boundaries,
 however, can appear anywhere in the bitmap. The origin of the bitmap is the
 lower-left corner.

 The bcBitCount member of the BITMAPCOREHEADER structure determines the number
 of bits that define each pixel and the maximum number of colors in the
 bitmap. This member may be set to any of the following values:

 Value   Meaning

 1       The bitmap is monochrome, and the bmciColors member must contain 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
 bmciColors 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 bmciColors member
 contains 16 entries. Each pixel in the bitmap is represented by a four-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 bmciColors member
 contains 256 entries. In this case, each byte in the array represents a
 single pixel.

 24      The bitmap has a maximum of 2^24 colors. The bmciColors member is
 NULL, and each 3-byte sequence in the bitmap array represents the relative
 intensities of red, green, and blue, respectively, of a pixel.

 The colors in the bmciColors table should appear in order of importance.
 Alternatively, for functions that use DIBs, the bmciColors member can be an
 array of 16-bit unsigned integers that specify an index into the currently
 realized logical palette instead of explicit RGB values. In this case, an
 application using the bitmap must call DIB functions with the wUsage
 parameter set to DIB_PAL_COLORS.

 Note:   The bmciColors member should not contain palette indexes if the
 bitmap is to be stored in a file or transferred to another application.
 Unless the application uses the bitmap exclusively and under its complete
 control, the bitmap color table should contain explicit RGB values.

 See Also

 BITMAPINFO, BITMAPCOREHEADER, RGBTRIPLE

 ==============================================================================
 BITMAPCOREHEADER (3.0)

 typedef struct tagBITMAPCOREHEADER {    /* bmch */
     DWORD   bcSize;
     short   bcWidth;
     short   bcHeight;
     WORD    bcPlanes;
     WORD    bcBitCount;
 } BITMAPCOREHEADER;

 The BITMAPCOREHEADER structure contains information about the dimensions and
 color format of a device-independent bitmap (DIB). Windows applications
 should use the BITMAPINFOHEADER structure instead of BITMAPCOREHEADER
 whenever possible.

 Member          Description

 bcSize          Specifies the number of bytes required by the
 BITMAPCOREHEADER structure.

 bcWidth         Specifies the width of the bitmap, in pixels.
 bcHeightSpecifies the height of the bitmap, in pixels.

 bcPlanesSpecifies the number of planes for the target device. This
 member must be set to 1.

 bcBitCount      Specifies the number of bits per pixel. This value must be 1,
 4, 8, or 24.

 Comments

 The BITMAPCOREINFO structure combines the BITMAPCOREHEADER structure and a
 color table to provide a complete definition of the dimensions and colors of
 a DIB. See the description of the BITMAPCOREINFO structure for more
 information about specifying a DIB.

 An application should use the information stored in the bcSize member to
 locate the color table in a BITMAPCOREINFO structure with a method such as
 the following:

 lpColor = ((LPSTR) pBitmapCoreInfo + (UINT) (pBitmapCoreInfo->bcSize))

 See Also

 BITMAPCOREINFO, BITMAPINFOHEADER, BITMAPINFOHEADER

 =============================================================================
 RGBTRIPLE (3.0)

 typedef struct tagRGBTRIPLE {   /* rgbt */
     BYTE    rgbtBlue;
     BYTE    rgbtGreen;
     BYTE    rgbtRed;
 } RGBTRIPLE;

 The RGBTRIPLE structure describes a color consisting of relative intensities
 of red, green, and blue. The bmciColors member of the BITMAPCOREINFO
 structure consists of an array of RGBTRIPLE structures.  Windows applications
 should use the BITMAPINFO structure instead of BITMAPCOREINFO whenever
 possible. The BITMAPINFO structure uses an RGBQUAD structure instead of the
 RGBTRIPLE structure.

 Member  Description

 rgbtBlueSpecifies the intensity of blue in the color.
 rgbtGreen       Specifies the intensity of green in the color.
 rgbtRed         Specifies the intensity of red in the color.

 See Also

 BITMAPCOREINFO, BITMAPINFO, RGBQUAD

 ==============================================================================

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