[imager.git] / fileformatdocs / bmp.txt

BITMAPFILEHEADER  [3.0]

Bitmap File Information
The BITMAPFILEHEADER data structure contains information about the type, 
size, and layout of a device-independent bitmap (DIB) file.

typedef struct tagBITMAPFILEHEADER {
        WORD    bfType;
        DWORD   bfSize;
        WORD    bfReserved1;
        WORD    bfReserved2;
        DWORD   bfOffBits;
} BITMAPFILEHEADER;

The BITMAPFILEHEADER data structure contains the following fields:

Field		Description
bfType		Specifies the type of file. It must be BM.
bfSize		Specifies the size in DWORDs of the file. 
bfReserved1	Is reserved and must be set to zero. 
bfReserved2	Is reserved and must be set to zero. 
bfOffBits	Specifies in bytes the offset from the BITMAPFILEHEADER 
		of the actual bitmap in the file. 

Comments	A BITMAPINFO or BITMAPCOREINFO data structure immediately 
follows the BITMAPFILEHEADER structure in the DIB file.


BITMAPINFO  [3.0]

Device-Indpendent Bitmap Information
The BITMAPINFO structure fully defines the dimensions and color 
information for a Windows 3.0 device-independent bitmap.

typedef struct tagBITMAPINFO { 
   BITMAPINFOHEADER    bmiHeader;
   RGBQUAD             bmiColors[1];
} BITMAPINFO;

The BITMAPINFO structure contains the following fields:

Field	Description
bmiHeader	Specifies a BITMAPINFOHEADER data structure that 
		contains information about the dimensions and color 				format of a device-independent bitmap. 
bmiColors	Specifies an array of RGBQUAD data structures that 
		define the colors in the bitmap.  

Comments:	A Windows 3.0 device-independent bitmap consists of two 
distinct parts: a BITMAPINFO data structure that describes the dimensions 
and colors of the bitmap, and an array of bytes that 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 can 
appear anywhere in the bitmap, however. The origin of the bitmap is the 
lower-left corner.

The biBitCount field of the BITMAPINFOHEADER structure determines the 
number of bits which define each pixel and the maximum number of colors 
in the bitmap. This field may be set to any of the following values:

Value	Meaning
1	The bitmap is monochrome, and the bmiColors field 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 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 
	field contains up to 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,  then 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 16th table entry.
8	The bitmap has a maximum of 256 colors, and the bmiColors 
	field contains up to 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 bmiColors 
	field is NULL, and each three bytes in the bitmap array 
	represents the relative intensities of red, green, and blue, 
	respectively, of a pixel.

The biClrUsed field of the BITMAPINFOHEADER structure specifies the number
of color indexes in the color table actually used by the bitmap. If the 
biClrUsed field is set to 0, the bitmap uses the maximum number of colors 
corresponding to the value of the biBitCount field.

The colors in the bmiColors table should appear in order of importance.

Alternatively, for functions that use device-independent bitmaps, the 
bmiColors field 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 
device-independent bitmap functions with the wUsage parameter set to 
DIB_PAL_COLORS.

Note:	The bmiColors field should not contain palette indices 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.

BITMAPINFOHEADER  [3.0]

Device-Independent Bitmap Format Information
The BITMAPINFOHEADER structure contains information about the dimensions 
and color format of a Windows 3.0 device-independent bitmap.

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

The BITMAPINFOHEADER structure has the following fields:

Field		Description
biSize		Specifies the number of bytes required by the 
		BITMAPINFOHEADER structure. 
biWidth		Specifies the width of the bitmap in pixels. 
biHeight	Specifies the height of the bitmap in pixels. 
biPlanes	Specifies the number of planes for the target device and
 		must be set to 1. 
biBitCount	Specifies the number of bits per pixel. This value must 
		be 1, 4, 8, or 24. 
biCompression	Specifies the type of compression for a compressed 	
		bitmap. It can be one of the following values:.
		Value		Meaning
		BI_RGB		Specifies that the bitmap is not 
				compressed.
		BI_RLE8		Specifies a run-length encoded format 
				for bitmaps with 8 bits per pixel. The 
				compression format is a two-byte 
				format consisting of a count byte 
				followed by a byte containing a color 
				index. See the following 'Comments' 
				section for more information.
		BI_RLE4		Specifies a run-length encoded format 
				for bitmaps with 4 bits per pixel. The 
				compression format is a two-byte 
				format consisting of a count byte 
				followed by two word-length color 
				indexes. See the following 'Comments' 
				section for more information.
biSizeImage	Specifies the size in bytes of the image. 
biXPelsPerMeter	Specifies the horizontal resolution in pixels per meter 			of the target device for the bitmap. An application can 			use this value to select a bitmap from a resource group 			that best matches the characteristics of the current 				device. biYPelsPerMeter	Specifies the vertical 					resolution in pixels per meter of the target device for 			the bitmap. 
biClrUsed	Specifies the number of color indexes in the color table 
		actually used by the bitmap. If this value is 0, the 	
		bitmap uses the maximum number of colors corresponding 	
		to the value of the biBitCount field. See the 		
		description of the BITMAPINFO data structure earlier in 	
		this chapter for more information on the maximum sizes 
		of the color table. If biClrUsed is nonzero, then the 
		biClrUsed field specifies the actual number of colors 
		which the graphics engine or device driver will access 
		if the biBitCount field is less than 24. If the 	
		biBitCount field is set to 24, the biClrUsed field 	
		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 field must be set to 0 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 0, 	
		then all colors are important. 

Comments:	The BITMAPINFO data structure combines the 
BITMAPINFOHEADER structure and a color table to provide a complete 
definition of the dimensions and colors of a Windows 3.0 
device-independent bitmap. See the description of the BITMAPINFO data 
structure for more information about specifying a Windows 3.0 
device-independent bitmap.

An application should use the information stored in the biSize field to 
locate the color table in a BITMAPINFO data structure with a method such 
as the following:

pColor = ((LPSTR) pBitmapInfo + (WORD) (pBitmapInfo -> biSize))

Bitmap Compression Formats	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.

When the biCompression field 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:

7	Encoded
7	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:

Second Byte
Of Escape	
		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 signalled by the first byte set to zero and the second 
byte set to a value between 03H and FFH. In absolute mode, the second 
byte represents the number of bytes which 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

When the biCompression field is set to BI_RLE4, the bitmap is compressed 
using a run-length encoding 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

RGBQUAD  [3.0]

RGB Color Structure
The RGBQUAD data structure describes a color consisting of relative 
intensities of red, green, and blue. The bmiColors field of the 
BITMAPINFO data structure consists of an array of RGBQUAD data structures.

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

The RGBQUAD structure contains the following fields:

Field		Description
rgbBlue		Specifies the intensity of blue in the color. 
rgbGreen	Specifies the intensity of green in the color. 
rgbRed		Specifies the intensity of red in the color. 
rgbReserved	Is not used and must be set to zero. 


#define BI_RGB      0L
#define BI_RLE8     1L
#define BI_RLE4     2L

BITMAPCOREINFO  [3.0]

Device-Indpendent Bitmap Information
The BITMAPCOREINFO structure fully defines the dimensions and color 
information for a device-independent bitmap that is compatible with 
Microsoft OS/2 Presentation Manager versions 1.1 and 1.2 bitmaps.

typedef struct _BITMAPCOREINFO {
        BITMAPCOREHEADER  bmciHeader;
        RGBTRIPLE         bmciColors[];
} BITMAPCOREINFO;

The BITMAPCOREINFO structure contains the following fields:

Field	Description
bmciHeader	Specifies a BITMAPCOREHEADER data structure that 
		contains information about the dimensions and color 
		format of a device-independent bitmap. 
bmciColors	Specifies an array of RGBTRIPLE data structures that 
		define the colors in the bitmap.  

Comments	An OS/2 Presentation Manager device-independent bitmap 
consists of two distinct parts:  a BITMAPCOREINFO data structure that 
describes the dimensions and colors of the bitmap, and 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 can appear anywhere in the bitmap, however. 
The origin of the bitmap is the lower-left corner.

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

Value	Meaning
1	The bitmap is monochrome, and the bmciColors field 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 
	field 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,  then 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 16th table entry.
8	The bitmap has a maximum of 256 colors, and the bmciColors 
	field 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 
	field is NULL, and each three bytes 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 device-independent bitmaps, the 
bmciColors field 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 device-independent bitmap functions with the wUsage parameter 
set to DIB_PAL_COLORS.

Note	The bmciColors field 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.


BITMAPCOREHEADER  [3.0]

Device-Independent Bitmap Format Information
The BITMAPCOREHEADER structure contains information about the dimensions 
and color format of a device-independent bitmap that is compatible with 
Microsoft OS/2 Presentation Manager versions 1.1 and 1.2 bitmaps.

typedef struct tagBITMAPCOREHEADER {
        DWORD   bcSize;
        WORD    bcWidth;
        WORD    bcHeight;
        WORD    bcPlanes;
        WORD    bcBitCount;
} BITMAPCOREHEADER;

The BITMAPCOREHEADER structure has the following fields:

Field		Description
bcSize		Specifies the number of bytes required by the BITMAPCOREHEADER 
		structure. 
bcWidth		Specifies the width of the bitmap in pixels. 
bcHeight	Specifies the height of the bitmap in pixels. 
bcPlanes	Specifies the number of planes for the target device and 
		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 data structure combines the 
BITMAPCOREHEADER structure and a color table to provide a complete 
definition of the dimensions and colors of a device-independent bitmap. 
See the description of the BITMAPCOREINFO data structure for more 
information about specifying a device-independent bitmap.

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

pColor = ((LPSTR) pBitmapCoreInfo + (WORD) (pBitmapCoreInfo -> bcSize))


RGBTRIPLE  [3.0]

RGB Color Structure
The RGBTRIPLE data structure describes a color consisting of relative 
intensities of red, green, and blue. The bmciColors field of the 
BITMAPCOREINFO data structure consists of an array of RGBTRIPLE data 
structures.

typedef struct tagRGBTRIPLE {
        BYTE    rgbtBlue;
        BYTE    rgbtGreen;
        BYTE    rgbtRed;
} RGBTRIPLE;

The RGBTRIPLE structure contains the following fields:

Field		Description
rgbtBlue	Specifies 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. 


-----------------------------------------------------------------------

	Non official comments

How to distinguish between BITMAPINFO and BITMAPCOREINFO when reading
in a BMP file.

After reading the BITMAPFILEHEADER read the next DWORD from the file. 
If it is 12 you are reading a BITMAPCOREHEADER, if it is 40 you are
reading a BITMAPINFOHEADER.
Commit	Line	Data
66614d6e TC	1	BITMAPFILEHEADER [3.0]
	2
	3	Bitmap File Information
	4	The BITMAPFILEHEADER data structure contains information about the type,
	5	size, and layout of a device-independent bitmap (DIB) file.
	6
	7	typedef struct tagBITMAPFILEHEADER {
	8	WORD bfType;
	9	DWORD bfSize;
	10	WORD bfReserved1;
	11	WORD bfReserved2;
	12	DWORD bfOffBits;
	13	} BITMAPFILEHEADER;
	14
	15	The BITMAPFILEHEADER data structure contains the following fields:
	16
	17	Field Description
	18	bfType Specifies the type of file. It must be BM.
	19	bfSize Specifies the size in DWORDs of the file.
	20	bfReserved1 Is reserved and must be set to zero.
	21	bfReserved2 Is reserved and must be set to zero.
	22	bfOffBits Specifies in bytes the offset from the BITMAPFILEHEADER
	23	of the actual bitmap in the file.
	24
	25	Comments A BITMAPINFO or BITMAPCOREINFO data structure immediately
	26	follows the BITMAPFILEHEADER structure in the DIB file.
	27
	28
	29	BITMAPINFO [3.0]
	30
	31	Device-Indpendent Bitmap Information
	32	The BITMAPINFO structure fully defines the dimensions and color
	33	information for a Windows 3.0 device-independent bitmap.
	34
	35	typedef struct tagBITMAPINFO {
	36	BITMAPINFOHEADER bmiHeader;
	37	RGBQUAD bmiColors[1];
	38	} BITMAPINFO;
	39
	40	The BITMAPINFO structure contains the following fields:
	41
	42	Field Description
	43	bmiHeader Specifies a BITMAPINFOHEADER data structure that
	44	contains information about the dimensions and color format of a device-independent bitmap.
	45	bmiColors Specifies an array of RGBQUAD data structures that
	46	define the colors in the bitmap.
	47
	48	Comments: A Windows 3.0 device-independent bitmap consists of two
	49	distinct parts: a BITMAPINFO data structure that describes the dimensions
	50	and colors of the bitmap, and an array of bytes that define the pixels of
	51	the bitmap. The bits in the array are packed together, but each scan line
	52	must be zero-padded to end on a LONG boundary. Segment boundaries can
	53	appear anywhere in the bitmap, however. The origin of the bitmap is the
	54	lower-left corner.
	55
	56	The biBitCount field of the BITMAPINFOHEADER structure determines the
	57	number of bits which define each pixel and the maximum number of colors
	58	in the bitmap. This field may be set to any of the following values:
	59
	60	Value Meaning
	61	1 The bitmap is monochrome, and the bmiColors field must
	62	contain two entries. Each bit in the bitmap array represents a
	63	pixel. If the bit is clear, the pixel is displayed with the
	64	color of the first entry in the bmiColors table; if the bit is
65	set, the pixel has the color of the second entry in the table.
66	4 The bitmap has a maximum of 16 colors, and the bmiColors
67	field contains up to 16 entries. Each pixel in the bitmap is
68	represented by a four-bit index into the color table.
69	For example, if the first byte in the bitmap is 0x1F, then the
70	byte represents two pixels. The first pixel contains the color
71	in the second table entry, and the second pixel contains the
72	color in the 16th table entry.
73	8 The bitmap has a maximum of 256 colors, and the bmiColors
74	field contains up to 256 entries. In this case, each byte in the
75	array represents a single pixel.
76	24 The bitmap has a maximum of 2^24 colors. The bmiColors
77	field is NULL, and each three bytes in the bitmap array
78	represents the relative intensities of red, green, and blue,
79	respectively, of a pixel.
80
81	The biClrUsed field of the BITMAPINFOHEADER structure specifies the number
82	of color indexes in the color table actually used by the bitmap. If the
83	biClrUsed field is set to 0, the bitmap uses the maximum number of colors
84	corresponding to the value of the biBitCount field.
85
86	The colors in the bmiColors table should appear in order of importance.
87
88	Alternatively, for functions that use device-independent bitmaps, the
89	bmiColors field can be an array of 16-bit unsigned integers that specify
90	an index into the currently realized logical palette instead of explicit
91	RGB values. In this case, an application using the bitmap must call
92	device-independent bitmap functions with the wUsage parameter set to
93	DIB_PAL_COLORS.
94
95	Note: The bmiColors field should not contain palette indices if the
96	bitmap is to be stored in a file or transferred to another application.
97	Unless the application uses the bitmap exclusively and under its complete
98	control, the bitmap color table should contain explicit RGB values.
99
100	BITMAPINFOHEADER [3.0]
101
102	Device-Independent Bitmap Format Information
103	The BITMAPINFOHEADER structure contains information about the dimensions
104	and color format of a Windows 3.0 device-independent bitmap.
105
106	typedef struct tagBITMAPINFOHEADER{
107	DWORD biSize;
108	DWORD biWidth;
109	DWORD biHeight;
110	WORD biPlanes;
111	WORD biBitCount
112	DWORD biCompression;
113	DWORD biSizeImage;
114	DWORD biXPelsPerMeter;
115	DWORD biYPelsPerMeter;
116	DWORD biClrUsed;
117	DWORD biClrImportant;
118	} BITMAPINFOHEADER;
119
120	The BITMAPINFOHEADER structure has the following fields:
121
122	Field Description
123	biSize Specifies the number of bytes required by the
124	BITMAPINFOHEADER structure.
125	biWidth Specifies the width of the bitmap in pixels.
126	biHeight Specifies the height of the bitmap in pixels.
127	biPlanes Specifies the number of planes for the target device and
128	must be set to 1.
129	biBitCount Specifies the number of bits per pixel. This value must
130	be 1, 4, 8, or 24.
131	biCompression Specifies the type of compression for a compressed
132	bitmap. It can be one of the following values:.
133	Value Meaning
134	BI_RGB Specifies that the bitmap is not
135	compressed.
136	BI_RLE8 Specifies a run-length encoded format
137	for bitmaps with 8 bits per pixel. The
138	compression format is a two-byte
139	format consisting of a count byte
140	followed by a byte containing a color
141	index. See the following 'Comments'
142	section for more information.
143	BI_RLE4 Specifies a run-length encoded format
144	for bitmaps with 4 bits per pixel. The
145	compression format is a two-byte
146	format consisting of a count byte
147	followed by two word-length color
148	indexes. See the following 'Comments'
149	section for more information.
150	biSizeImage Specifies the size in bytes of the image.
151	biXPelsPerMeter Specifies the horizontal resolution in pixels per meter of the target device for the bitmap. An application can use this value to select a bitmap from a resource group that best matches the characteristics of the current device. biYPelsPerMeter Specifies the vertical resolution in pixels per meter of the target device for the bitmap.
152	biClrUsed Specifies the number of color indexes in the color table
153	actually used by the bitmap. If this value is 0, the
154	bitmap uses the maximum number of colors corresponding
155	to the value of the biBitCount field. See the
156	description of the BITMAPINFO data structure earlier in
157	this chapter for more information on the maximum sizes
158	of the color table. If biClrUsed is nonzero, then the
159	biClrUsed field specifies the actual number of colors
160	which the graphics engine or device driver will access
161	if the biBitCount field is less than 24. If the
162	biBitCount field is set to 24, the biClrUsed field
163	specifies the size of the reference color table used to
164	optimize performance of Windows color palettes.
165	If the bitmap is a 'packed' bitmap (that is, a bitmap in
166	which the bitmap array immediately follows the
167	BITMAPINFO header and which is referenced by a single
168	pointer), the biClrUsed field must be set to 0 or to the
169	actual size of the color table.
170	biClrImportant Specifies the number of color indexes that are considered
171	important for displaying the bitmap. If this value is 0,
172	then all colors are important.
173
174	Comments: The BITMAPINFO data structure combines the
175	BITMAPINFOHEADER structure and a color table to provide a complete
176	definition of the dimensions and colors of a Windows 3.0
177	device-independent bitmap. See the description of the BITMAPINFO data
178	structure for more information about specifying a Windows 3.0
179	device-independent bitmap.
180
181	An application should use the information stored in the biSize field to
182	locate the color table in a BITMAPINFO data structure with a method such
183	as the following:
184
185	pColor = ((LPSTR) pBitmapInfo + (WORD) (pBitmapInfo -> biSize))
186
187	Bitmap Compression Formats Windows supports formats for compressing
188	bitmaps that define their colors with 8 bits per pixel and with 4 bits
189	per pixel. Compression reduces the disk and memory storage required for
190	the bitmap. The following paragraphs describe these formats.
191
192	When the biCompression field is set to BI_RLE8, the bitmap is compressed
193	using a run-length encoding format for an 8-bit bitmap. This format may
194	be compressed in either of two modes:
195
196	7 Encoded
197	7 Absolute
198
199
200	Both modes can occur anywhere throughout a single bitmap.
201
202	Encoded mode consists of two bytes: the first byte specifies the number
203	of consecutive pixels to be drawn using the color index contained in the
204	second byte. In addition, the first byte of the pair can be set to zero
205	to indicate an escape that denotes an end of line, end of bitmap, or a
206	delta. The interpretation of the escape depends on the value of the
207	second byte of the pair. The following list shows the meaning of the
208	second byte:
209
210	Second Byte
211	Of Escape
212	Meaning
213	0 End of line.
214	1 End of bitmap.
215	2 Delta. The two bytes following the escape contain
216	unsigned values indicating the horizontal and vertical
217	offset of the next pixel from the current position.
218
219	Absolute mode is signalled by the first byte set to zero and the second
220	byte set to a value between 03H and FFH. In absolute mode, the second
221	byte represents the number of bytes which follow, each of which contains
222	the color index of a single pixel. When the second byte is set to 2 or
223	less, the escape has the same meaning as in encoded mode.
224	In absolute mode, each run must be aligned on a word boundary.
225
226	The following example shows the hexadecimal values of an 8-bit compressed
227	bitmap:
228
229	03 04 05 06 00 03 45 56 67 00 02 78 00 02 05 01
230	02 78 00 00 09 1E 00 01
231
232	This bitmap would expand as follows (two-digit values represent a color
233	index for a single pixel):
234
235	04 04 04
236	06 06 06 06 06
237	45 56 67
238	78 78
239	move current position 5 right and 1 down
240	78 78
241	end of line
242	1E 1E 1E 1E 1E 1E 1E 1E 1E
243	end of RLE bitmap
244
245	When the biCompression field is set to BI_RLE4, the bitmap is compressed
246	using a run-length encoding format for a 4-bit bitmap, which also uses
247	encoded and absolute modes. In encoded mode, the first byte of the pair
248	contains the number of pixels to be drawn using the color indexes in the
249	second byte. The second byte contains two color indexes, one in its
250	high-order nibble (that is, its low-order four bits) and one in its
251	low-order nibble. The first of the pixels is drawn using the color
252	specified by the high-order nibble, the second is drawn using the color
253	in the low-order nibble, the third is drawn with the color in the
254	high-order nibble, and so on, until all the pixels specified by the
255	first byte have been drawn.
256
257	In absolute mode, the first byte contains zero, the second byte contains
258	the number of color indexes that follow, and subsequent bytes contain
259	color indexes in their high- and low-order nibbles, one color index for
260	each pixel. In absolute mode, each run must be aligned on a word boundary.
261	The end-of-line, end-of-bitmap, and delta escapes also apply to BI_RLE4.
262
263	The following example shows the hexadecimal values of a 4-bit compressed
264	bitmap:
265
266	03 04 05 06 00 06 45 56 67 00 04 78 00 02 05 01
267	04 78 00 00 09 1E 00 01
268
269	This bitmap would expand as follows (single-digit values represent a
270	color index for a single pixel):
271
272	0 4 0
273	0 6 0 6 0
274	4 5 5 6 6 7
275	7 8 7 8
276	move current position 5 right and 1 down
277	7 8 7 8
278	end of line
279	1 E 1 E 1 E 1 E 1
280	end of RLE bitmap
281
282	RGBQUAD [3.0]
283
284	RGB Color Structure
285	The RGBQUAD data structure describes a color consisting of relative
286	intensities of red, green, and blue. The bmiColors field of the
287	BITMAPINFO data structure consists of an array of RGBQUAD data structures.
288
289	typedef struct tagRGBQUAD {
290	BYTE rgbBlue;
291	BYTE rgbGreen;
292	BYTE rgbRed;
293	BYTE rgbReserved;
294	} RGBQUAD;
295
296	The RGBQUAD structure contains the following fields:
297
298	Field Description
299	rgbBlue Specifies the intensity of blue in the color.
300	rgbGreen Specifies the intensity of green in the color.
301	rgbRed Specifies the intensity of red in the color.
302	rgbReserved Is not used and must be set to zero.
303
304
305
306	#define BI_RGB 0L
307	#define BI_RLE8 1L
308	#define BI_RLE4 2L
309
310	BITMAPCOREINFO [3.0]
311
312	Device-Indpendent Bitmap Information
313	The BITMAPCOREINFO structure fully defines the dimensions and color
314	information for a device-independent bitmap that is compatible with
315	Microsoft OS/2 Presentation Manager versions 1.1 and 1.2 bitmaps.
316
317	typedef struct _BITMAPCOREINFO {
318	BITMAPCOREHEADER bmciHeader;
319	RGBTRIPLE bmciColors[];
320	} BITMAPCOREINFO;
321
322	The BITMAPCOREINFO structure contains the following fields:
323
324	Field Description
325	bmciHeader Specifies a BITMAPCOREHEADER data structure that
326	contains information about the dimensions and color
327	format of a device-independent bitmap.
328	bmciColors Specifies an array of RGBTRIPLE data structures that
329	define the colors in the bitmap.
330
331	Comments An OS/2 Presentation Manager device-independent bitmap
332	consists of two distinct parts: a BITMAPCOREINFO data structure that
333	describes the dimensions and colors of the bitmap, and an array of bytes
334	which define the pixels of the bitmap. The bits in the array are packed
335	together, but each scan line must be zero-padded to end on a LONG
336	boundary. Segment boundaries can appear anywhere in the bitmap, however.
337	The origin of the bitmap is the lower-left corner.
338
339	The bcBitCount field of the BITMAPCOREHEADER structure determines the
340	number of bits which define each pixel and the maximum number of colors
341	in the bitmap. This field may be set to any of the following values:
342
343	Value Meaning
344	1 The bitmap is monochrome, and the bmciColors field must
345	contain two entries. Each bit in the bitmap array represents a
346	pixel. If the bit is clear, the pixel is displayed with the
347	color of the first entry in the bmciColors table; if the bit is
348	set, the pixel has the color of the second entry in the table.
349	4 The bitmap has a maximum of 16 colors, and the bmciColors
350	field contains 16 entries. Each pixel in the bitmap is represented
351	by a four-bit index into the color table.
352	For example, if the first byte in the bitmap is 0x1F, then the
353	byte represents two pixels. The first pixel contains the color in
354	the second table entry, and the second pixel contains the color
355	in the 16th table entry.
356	8 The bitmap has a maximum of 256 colors, and the bmciColors
357	field contains 256 entries. In this case, each byte in the array
358	represents a single pixel.
359	24 The bitmap has a maximum of 2^24 colors. The bmciColors
360	field is NULL, and each three bytes in the bitmap array
361	represents the relative intensities of red, green, and blue,
362	respectively, of a pixel.
363
364	The colors in the bmciColors table should appear in order of importance.
365
366	Alternatively, for functions that use device-independent bitmaps, the
367	bmciColors field can be an array of 16-bit unsigned integers that
368	specify an index into the currently realized logical palette instead of
369	explicit RGB values. In this case, an application using the bitmap must
370	call device-independent bitmap functions with the wUsage parameter
371	set to DIB_PAL_COLORS.
372
373	Note The bmciColors field should not contain palette indexes if the
374	bitmap is to be stored in a file or transferred to another application.
375	Unless the application uses the bitmap exclusively and under its
376	complete control, the bitmap color table should contain explicit
377	RGB values.
378
379
380
381	BITMAPCOREHEADER [3.0]
382
383	Device-Independent Bitmap Format Information
384	The BITMAPCOREHEADER structure contains information about the dimensions
385	and color format of a device-independent bitmap that is compatible with
386	Microsoft OS/2 Presentation Manager versions 1.1 and 1.2 bitmaps.
387
388	typedef struct tagBITMAPCOREHEADER {
389	DWORD bcSize;
390	WORD bcWidth;
391	WORD bcHeight;
392	WORD bcPlanes;
393	WORD bcBitCount;
394	} BITMAPCOREHEADER;
395
396	The BITMAPCOREHEADER structure has the following fields:
397
398	Field Description
399	bcSize Specifies the number of bytes required by the BITMAPCOREHEADER
400	structure.
401	bcWidth Specifies the width of the bitmap in pixels.
402	bcHeight Specifies the height of the bitmap in pixels.
403	bcPlanes Specifies the number of planes for the target device and
404	must be set to 1.
405	bcBitCount Specifies the number of bits per pixel. This value must
406	be 1, 4, 8, or 24.
407
408	Comments The BITMAPCOREINFO data structure combines the
409	BITMAPCOREHEADER structure and a color table to provide a complete
410	definition of the dimensions and colors of a device-independent bitmap.
411	See the description of the BITMAPCOREINFO data structure for more
412	information about specifying a device-independent bitmap.
413
414	An application should use the information stored in the bcSize field to
415	locate the color table in a BITMAPCOREINFO data structure with a method
416	such as the following:
417
418	pColor = ((LPSTR) pBitmapCoreInfo + (WORD) (pBitmapCoreInfo -> bcSize))
419
420
421
422	RGBTRIPLE [3.0]
423
424	RGB Color Structure
425	The RGBTRIPLE data structure describes a color consisting of relative
426	intensities of red, green, and blue. The bmciColors field of the
427	BITMAPCOREINFO data structure consists of an array of RGBTRIPLE data
428	structures.
429
430	typedef struct tagRGBTRIPLE {
431	BYTE rgbtBlue;
432	BYTE rgbtGreen;
433	BYTE rgbtRed;
434	} RGBTRIPLE;
435
436	The RGBTRIPLE structure contains the following fields:
437
438	Field Description
439	rgbtBlue Specifies the intensity of blue in the color.
440	rgbtGreen Specifies the intensity of green in the color.
441	rgbtRed Specifies the intensity of red in the color.
442
443
444
445	-----------------------------------------------------------------------
446
447	Non official comments
448
449	How to distinguish between BITMAPINFO and BITMAPCOREINFO when reading
450	in a BMP file.
451
452	After reading the BITMAPFILEHEADER read the next DWORD from the file.
453	If it is 12 you are reading a BITMAPCOREHEADER, if it is 40 you are
454	reading a BITMAPINFOHEADER.