When Windows draws an icon, it uses the AND and XOR masks to combine the icon
image with the pixels already on the display surface. Windows first applies
the AND mask by using a bitwise AND operation; this preserves or removes
existing pixel color.  Windows then applies the XOR mask by using a bitwise
XOR operation. This sets the final color for each pixel.

The following illustration shows the XOR and AND masks that create a
monochrome icon (measuring 8 pixels by 8 pixels) in the form of an uppercase
K:

Windows Icon Selection

Windows detects the resolution of the current display and matches it against
the width and height specified for each version of the icon image. If Windows
determines that there is an exact match between an icon image and the current
device, it uses the matching image. Otherwise, it selects the closest match
and stretches the image to the proper size.

If an icon-resource file contains more than one image for a particular
resolution, Windows uses the icon image that most closely matches the color
capabilities of the current display. If no image matches the device
capabilities exactly, Windows selects the image that has the greatest number
of colors without exceeding the number of display colors. If all images
exceed the color capabilities of the current display, Windows uses the icon
image with the least number of colors.



Cursor-Resource File Format

A cursor-resource file contains image data for cursors used by Windows
applications. The file consists of a cursor directory identifying the number
and types of cursor images in the file, plus one or more cursor images. The
default filename extension for a cursor-resource file is .CUR.

Cursor Directory

Each cursor-resource file starts with a cursor directory. The cursor
directory, defined as a CURSORDIR structure, specifies the number of cursors
in the file and the dimensions and color format of each cursor image. The
CURSORDIR structure has the following form:


typedef struct _CURSORDIR {
    WORD           cdReserved;
    WORD           cdType;
    WORD           cdCount;
    CURSORDIRENTRY cdEntries[];
} CURSORDIR;

Following are the members in the CURSORDIR structure: 

cdReserved	Reserved; must be zero. 
cdType		Specifies the resource type. This member must be set to 2. 
cdCount		Specifies the number of cursors in the file. 
cdEntries	Specifies an array of CURSORDIRENTRY structures containing
information about individual cursors. The cdCount member specifies the number
of structures in the array.

A CURSORDIRENTRY structure specifies the dimensions and color format of a
cursor image. The structure has the following form:



typedef struct _CURSORDIRENTRY {
    BYTE  bWidth;
    BYTE  bHeight;
    BYTE  bColorCount;
    BYTE  bReserved;
    WORD  wXHotspot;
    WORD  wYHotspot;
    DWORD lBytesInRes;
    DWORD dwImageOffset;
} CURSORDIRENTRY;

Following are the members in the CURSORDIRENTRY structure: 

bWidth		Specifies the width of the cursor, in pixels. 
bHeight		Specifies the height of the cursor, in pixels. 
bColorCount	Reserved; must be zero. 
bReserved	Reserved; must be zero. 
wXHotspot	Specifies the x-coordinate, in pixels, of the hot spot. 
wYHotspot	Specifies the y-coordinate, in pixels, of the hot spot. 
lBytesInRes	Specifies the size of the resource, in bytes. 
dwImageOffset	Specifies the offset, in bytes, from the start of the file to
the cursor image.

Cursor Image

Each cursor-resource file contains one cursor image for each image identified
in the cursor directory. A cursor image consists of a cursor-image header, a
color table, an XOR mask, and an AND mask. The cursor image has the following
form:



BITMAPINFOHEADER    crHeader;
RGBQUAD             crColors[];
BYTE                crXOR[];
BYTE                crAND[];

The cursor hot spot is a single pixel in the cursor bitmap that Windows uses
to track the cursor. The crXHotspot and crYHotspot members specify the x- and
y-coordinates of the cursor hot spot. These coordinates are 16-bit integers.

The cursor-image header, defined as a BITMAPINFOHEADER structure, specifies
the dimensions and color format of the cursor bitmap. Only the biSize through
biBitCount members and the biSizeImage member are used. The biHeight member
specifies the combined height of the XOR and AND masks for the cursor. This
value is twice the height of the XOR mask. The biPlanes and biBitCount
members must be 1. All other members (such as biCompression and
biClrImportant) must be set to zero.

The color table, defined as an array of RGBQUAD structures, specifies the
colors used in the XOR mask. For a cursor image, the table contains exactly
two structures, since the biBitCount member in the cursor-image header is
always 1.

The XOR mask, immediately following the color table, is an array of BYTE
values representing consecutive rows of a bitmap. The bitmap defines the
basic shape and color of the cursor image. As with the bitmap bits in a
bitmap file, the bitmap data in a cursor-resource file is organized in scan
lines, with each byte representing one or more pixels, as defined by the
color format. For more information about these bitmap bits, see Section 1.1,
"Bitmap-File Formats."

The AND mask, immediately following the XOR mask, is an array of BYTE values
representing a monochrome bitmap with the same width and height as the XOR
mask. The array is organized in scan lines, with each byte representing 8
pixels.

When Windows draws a cursor, it uses the AND and XOR masks to combine the
cursor image with the pixels already on the display surface. Windows first
applies the AND mask by using a bitwise AND operation; this preserves or
removes existing pixel color.  Window then applies the XOR mask by using a
bitwise XOR operation. This sets the final color for each pixel.

The following illustration shows the XOR and the AND masks that create a
cursor (measuring 8 pixels by 8 pixels) in the form of an arrow:

Following are the bit-mask values necessary to produce black, white,
inverted, and transparent results:

Pixel result	AND mask	XOR mask

Black		0		0 
White		0		1 
Transparent	1		0 
Inverted	1		1 

Windows Cursor Selection

If a cursor-resource file contains more than one cursor image, Windows
determines the best match for a particular display by examining the width and
height of the cursor images.


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


BITMAPFILEHEADER (3.0)



typedef struct tagBITMAPFILEHEADER {    /* bmfh */
    UINT    bfType;
    DWORD   bfSize;
    UINT    bfReserved1;
    UINT    bfReserved2;
    DWORD   bfOffBits;
} BITMAPFILEHEADER;

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

Member		Description

bfType		Specifies the type of file. This member must be BM. 
bfSize		Specifies the size of the file, in bytes. 
bfReserved1	Reserved; must be set to zero. 
bfReserved2	Reserved; must be set to zero. 
bfOffBits	Specifies the byte offset from the BITMAPFILEHEADER structure
to the actual bitmap data in the file.

Comments

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

See Also

BITMAPCOREINFO, BITMAPINFO 


==============================================================================
BITMAPINFO (3.0)



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

The BITMAPINFO structure fully defines the dimensions and color information
for a Windows 3.0 or later device-independent bitmap (DIB).

Member		Description

bmiHeader	Specifies a BITMAPINFOHEADER structure that contains
information about the dimensions and color format of a DIB.

bmiColors	Specifies an array of RGBQUAD structures that define the
colors in the bitmap.

Comments

A Windows 3.0 or later DIB consists of two distinct parts: a BITMAPINFO
structure, which describes the dimensions and colors of the bitmap, and an
array of bytes defining 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 biBitCount member of the BITMAPINFOHEADER structure determines the number
of bits which 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 biClrUsed member of the BITMAPINFOHEADER structure specifies the number
of color indexes in the color table actually used by the bitmap. If the
biClrUsed member is set to zero, the bitmap uses the maximum number of colors
corresponding to the value of the biBitCount member.

The colors in the bmiColors table should appear in order of importance.
Alternatively, for functions that use DIBs, the bmiColors 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 bmiColors 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

BITMAPINFOHEADER, RGBQUAD 

==============================================================================
BITMAPINFOHEADER (3.0)



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;

The BITMAPINFOHEADER structure contains information about the dimensions and
color format of a Windows 3.0 or later device-independent bitmap (DIB).

Member		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. This
member 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 2-byte format consisting of a count
byte followed by a byte containing a color index.  For more information, see
the following Comments section.

BI_RLE4		Specifies a run-length encoded 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
the following Comments section.

biSizeImage	Specifies the size, in bytes, of the image. It is valid to
set this member to zero if the bitmap is in the BI_RGB format.

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 zero, the bitmap uses the
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