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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<BASE HREF="http://www.oreilly.com/centers/gff/formats/miccur/"><table border=1 width=100%><tr><td><table border=1 bgcolor=#ffffff cellpadding=10 cellspacing=0 width=100% color=#ffffff><tr><td><font face=arial,sans-serif color=black size=-1>This is <b><font color=#0039b6>G</font> <font color=#c41200>o</font> <font color=#f3c518>o</font> <font color=#0039b6>g</font> <font color=#30a72f>l</font> <font color=#c41200>e</font></b>'s <a href="http://www.google.com/help/features.html#cached"><font color=blue>cache</font></a> of <A HREF="http://www.oreilly.com/centers/gff/formats/miccur/"><font color=blue>http://www.oreilly.com/centers/gff/formats/miccur/</font></a>.<br>
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The page may have changed since that time. Click here for the <A HREF="http://www.oreilly.com/centers/gff/formats/miccur/"><font color=blue>current page</font></a> without highlighting.<br>To link to or bookmark this page, use the following url: <code>http://www.google.com/search?q=cache:dgpSCZ8_GJwC:www.oreilly.com/centers/gff/formats/miccur/+windows++icon+transparent&hl=en&ie=UTF-8</code></font><br><br><center><font size=-2><i>Google is not affiliated with the authors of this page nor responsible for its content.</i></font></center></td></tr>
<tr><td>
<table border=0 cellpadding=0 cellspacing=0><tr><td><font face=arial,sans-serif color=black size=-1>These search terms have been highlighted: </font></td><td bgcolor=#ffff66><B><font face=arial,sans-serif color=black size=-1>windows </font></B></td><td bgcolor=#A0FFFF><B><font face=arial,sans-serif color=black size=-1>icon </font></B></td><td bgcolor=#99ff99><B><font face=arial,sans-serif color=black size=-1>transparent </font></B></td></tr></table>
</td></tr></table></td></tr></table>
<hr>
<html>
<head>
<title>GFF Format Summary: Microsoft Windows Cursor and Icon</title>
</head>
<body>
<h1><A NAME="SPEC-MICCUR">Microsoft <B style="color:black;background-color:#ffff66">Windows</B> Cursor and <B style="color:black;background-color:#A0FFFF">Icon</B></A></h1>
<p>
<b>Also Known As:</b> CUR, ICO
<p>
<hr>
<p>
<p>
<table border=0>
<tr valign=top>
<td align=left><b>Type</b></td>
<td align=left>Bitmap</td>
</tr>
<tr valign=top>
<td align=left><b>Colors</b></td>
<td align=left>1-bit and 4-bit</td>
</tr>
<tr valign=top>
<td align=left><b>Compression</b></td>
<td align=left>None</td>
</tr>
<tr valign=top>
<td align=left><b>Maximum Image Size</b></td>
<td align=left>4Gx4G pixels</td>
</tr>
<tr valign=top>
<td align=left><b>Multiple Images Per File</b></td>
<td align=left>Yes</td>
</tr>
<tr valign=top>
<td align=left><b>Numerical Format</b></td>
<td align=left>Little-endian</td>
</tr>
<tr valign=top>
<td align=left><b>Originator</b></td>
<td align=left>Microsoft</td>
</tr>
<tr valign=top>
<td align=left><b>Platform</b></td>
<td align=left>Microsoft <B style="color:black;background-color:#ffff66">Windows</B></td>
</tr>
<tr valign=top>
<td align=left><b>Supporting Applications</b></td>
<td align=left>Microsoft <B style="color:black;background-color:#ffff66">Windows</B></td>
</tr>
<tr valign=top>
<td align=left><b>See Also</b></td>
<td align=left><A HREF="gffse:/format.micbmp">Microsoft Bitmap</A>, <A HREF="gffse:/format.os2bmp">OS/2 Bitmap</A>, <A HREF="gffse:/format.micriff">Microsoft RIFF</A></td>
</tr>
</table>
<p>
<b>Usage</b><br>
The <B style="color:black;background-color:#ffff66">Windows</B> environment uses icons as graphical links to objects
(data files and executable programs). Cursors are used by the pointing device
as graphical indications of the current state of the <B style="color:black;background-color:#ffff66">Windows</B> environment.
<p>
<b>Comments</b><br>
<B style="color:black;background-color:#ffff66">Windows</B> icons and cursors are almost identical in format.
In fact, cursor and <B style="color:black;background-color:#A0FFFF">icon</B> bitmaps can be used interchangeably.
<p>
<hr>
<p>
<A NAME="MICCUR-DMYID.1"><!-- Overview anchor --></A>
<p>
In an object-oriented graphical user interface--as Microsoft
<B style="color:black;background-color:#ffff66">Windows</B> is sometimes described--icons are small bitmaps containing an
iconographic picture that makes an object accessible to the user. The
"objects" made available by icons are: collections of data (files);
executable programs (more files); and peripheral devices (the toys
you have hooked up to your computer). Rather than typing a file or
program name on a command line, applications are started and files
manipulated by clicking on an <B style="color:black;background-color:#A0FFFF">icon</B>, or "dragging and dropping" an
<B style="color:black;background-color:#A0FFFF">icon</B> on to a window or another <B style="color:black;background-color:#A0FFFF">icon</B>.
<p>
A cursor, or pointer as they are also called, is a special type of
<B style="color:black;background-color:#A0FFFF">icon</B> that is used to track the location of the pointing device on the
user interface. The cursor changes its appearance to indicate the
state of the system and the user interface. Such states include that
a search is in progress, an application is starting or stopping, or a
user-initiated action is being processed. The appearance of the
cursor also indicates what action may be performed based on the
current position of the pointer on the display. For example, actions
such as resizing a window or entering text may only be performed at
specific locations within a window.
<p>
Although a wide variety of physical pointing devices (mouse,
joystick, trackball, touch pad, light pen, pointing stick, etc.) are
typically supported by a user interface, the input received by
<B style="color:black;background-color:#ffff66">Windows</B> is identical from all types of pointing devices.
<p>
<P>
<B>Contents:</B><br>
<A HREF="#MICCUR-DMYID.2">File Organization</A><br>
<A HREF="#MICCUR-DMYID.3">File Details</A><br>
<A HREF="#MICCUR-DMYID.4">For Further Information</A><br>
<p>
Icons and cursors themselves are types of resources available in the
<B style="color:black;background-color:#ffff66">Windows</B> environment. When an application makes a request for <B style="color:black;background-color:#ffff66">Windows</B>
to display an <B style="color:black;background-color:#A0FFFF">icon</B> or cursor, <B style="color:black;background-color:#ffff66">Windows</B> must locate the appropriate
file and choose which of the bitmaps stored in the file best fits the
resolution and color depth of the display.
<p>
The <B style="color:black;background-color:#A0FFFF">icon</B> displayed is chosen based on its size and number of colors.
For example, a two-color <B style="color:black;background-color:#A0FFFF">icon</B> 16x16 pixels in size might look good on
a monochrome display at 640x480 resolution, but the same <B style="color:black;background-color:#A0FFFF">icon</B> bitmap
will probably look terrible on a 256-color, 1024x768 display. For
such a high-resolution display, the choice of the 16-color, 64x64
pixel version of the <B style="color:black;background-color:#A0FFFF">icon</B> would look much better. However, if the
<B style="color:black;background-color:#A0FFFF">icon</B> file only contains one bitmap, then that is the <B style="color:black;background-color:#A0FFFF">icon</B> bitmap that
will be displayed.
<p>
<B style="color:black;background-color:#A0FFFF">Icon</B> and cursor bitmaps are typically very small. Under the 16-bit
<B style="color:black;background-color:#ffff66">Windows</B> environment (Win16) icons are traditionally square (16x16,
32x32, or 64x64 pixels in size) and have 16 or fewer colors. The
32-bit <B style="color:black;background-color:#ffff66">Windows</B> (Win32) environment allows icons to be larger and have
a greater pixel depth, such as 72x72 pixels with 256 colors. Win32 is
also tolerant of rectangular <B style="color:black;background-color:#A0FFFF">icon</B> formats.
<p>
Cursors under <B style="color:black;background-color:#ffff66">Windows</B> 3.<i>x</i> are two-color (1-bit) bitmaps. Under
<B style="color:black;background-color:#ffff66">Windows</B> 4.<i>x</i> cursors with 8, 16, or more colors are possible. Cursors
are also not limited to a specific range of sizes as are icons,
although most cursors are 32x32 pixels in size.
<p>
Both cursor and <B style="color:black;background-color:#A0FFFF">icon</B> data may be stored in separate file formats
(<i>*.ico</i> and <i>*.cur</i>) on disk, or be stored as a <B style="color:black;background-color:#ffff66">Windows</B>
resource file (<i>*.res</i>) and embedded directly into a <B style="color:black;background-color:#ffff66">Windows</B>
executable file (<i>*.exe</i>), Dynamic Link Library (<i>*.dll</i>),
Visual Basic control (<i>*.vbx</i>), or OLE
control (<i>*.ocx</i>). (This article only discusses the ICO and CUR file
formats and will leave the <B style="color:black;background-color:#ffff66">Windows</B> Resource format to a future
article.)
<p>
Simple animations may be created by the sequential display of several
<B style="color:black;background-color:#A0FFFF">icon</B> or cursor bitmaps in a continuous loop. These "flipbook"
animations are not directly supported by the Win16 environment, but
they do appear in some <B style="color:black;background-color:#ffff66">Windows</B> applications.
<p>
A true animated cursor format was defined by Microsoft in 1992 as part
of the RIFF multimedia specification. Animated cursors are the
<i>*.ani</i> files you might have noticed on your hard drive if you
use <B style="color:black;background-color:#ffff66">Windows</B> 95 or <B style="color:black;background-color:#ffff66">Windows</B> NT. They are actually little more than a
collection of ICO files stored in a single ANI file. For more
information on the format of <B style="color:black;background-color:#ffff66">Windows</B> animated icons, see the
<a href="gffse:/format.micriff">Microsoft RIFF</a> article.
<p>
If you are interested in the <B style="color:black;background-color:#A0FFFF">icon</B> and pointer file formats used by
OS/2, then have a look at the <a href="gffse:/format.os2bmp">OS/2
Bitmap</a> article. OS/2 uses its own flavor of the BMP format to
store <B style="color:black;background-color:#A0FFFF">icon</B> and pointer data.
<p>
It should also be noted that there is no formal specification for
either the <B style="color:black;background-color:#ffff66">Windows </B><B style="color:black;background-color:#A0FFFF">icon</B> or cursor file formats. In fact, there are no
definitions for these file formats in the <B style="color:black;background-color:#ffff66">Windows</B> Software Development
Kit (SDK) header files. What information that can be found must be
scraped up from <B style="color:black;background-color:#ffff66">Windows</B> SDK manuals, Knowledge Base articles, and
several sample applications. See the <a href="#MICCUR-DMYID.4">For
Further Information</a> section in this article for more details on
additional reference material for <B style="color:black;background-color:#ffff66">Windows</B> icons and cursors.
<p>
<h2><A NAME="MICCUR-DMYID.2">File Organization</A></h2>
<p>
The <B style="color:black;background-color:#ffff66">Windows </B><B style="color:black;background-color:#A0FFFF">icon</B> (ICO) and cursor (CUR) file formats are identical.
Only the interpretation of the file data differs slightly. In fact,
<B style="color:black;background-color:#A0FFFF">icon</B> and cursor files may be used interchangeably by applications that
realize this fact.
<p>
Every ICO and CUR file contains a header, a directory of bitmap
entries, and one or more bitmaps that describes the appearance of an
<B style="color:black;background-color:#A0FFFF">icon</B> or cursor (shown below).
<p>
<table border=1>
<tr valign=center>
<td align=center>Header</td>
</tr>
<tr valign=center>
<td align=center>Bitmap Directory</td>
</tr>
<tr valign=center>
<td align=center>Bitmap 1</td>
</tr>
<tr valign=center>
<td align=center>Bitmap 2</td>
</tr>
<tr valign=center>
<td align=center>...</td>
</tr>
<tr valign=center>
<td align=center>Bitmap N</td>
</tr>
</table>
<p>
The header stores information that is used to determine how many
bitmaps are in the file. ICO and CUR files will contain one or more
uncompressed bitmaps. Each entry in the bitmap directory will contain
information that describes one of the bitmaps stored in the file. The
directory will contain one entry per bitmap.
<p>
<h3><A NAME="MICCUR-DMYID.3">File Details</A></h3>
<p>
As <B style="color:black;background-color:#ffff66">Windows</B> ICO and CUR files are nearly identical, we will first look
at the ICO format and then discuss the differences between the ICO
and CUR formats.
<p>
The ICO header contains only a <B style="color:black;background-color:#ffff66">Windows</B> resource identification value
and the count of the number of icons stored in the file. The header
is immediately followed by a directory that contains information for
all the icons stored in the ICO file. The directory is followed by
the <B style="color:black;background-color:#A0FFFF">icon</B> bitmaps themselves.
<p>
The following structure illustrates the entire format of an ICO
(or CUR) file:
<pre>
typedef struct _IconFile
{
WORD Reserved; /* Reserved (always 0) */
WORD ResourceType; /* Resource ID (always 1) */
WORD IconCount; /* Number of <B style="color:black;background-color:#A0FFFF">icon</B> bitmaps in file */
ICONENTRY IconDir[]; /* Directory of <B style="color:black;background-color:#A0FFFF">icon</B> entries */
ICONDATA IconData[]; /* Listing of ICO bitmaps */
} ICONFILE;
</pre>
<p>
Reserved is a two-byte value that is always zero in all ICO files.
<p>
ResourceType is the <B style="color:black;background-color:#ffff66">Windows</B> resource identifier type value. For icons
this value is always 1.
<p>
IconCount is the number of icons stored in the ICO file. It is also
the number of elements in the Icons array.
<p>
IconDir is an array of directory entries that describe the icons stored
in the ICO file. There will be one entry per <B style="color:black;background-color:#A0FFFF">icon</B> stored. The number
of entries will also equal the value of the IconCount field. Each
ICONENTRY element has the following format:
<pre>
typedef struct _IconEntry
{
BYTE Width; /* Width of <B style="color:black;background-color:#A0FFFF">icon</B> in pixels */
BYTE Height; /* Height of <B style="color:black;background-color:#A0FFFF">icon</B> in pixels */
BYTE NumColors; /* Maximum number of colors */
BYTE Reserved; /* Not used (always 0) */
WORD NumPlanes; /* Not used (always 0) */
WORD BitsPerPixel; /* Not used (always 0) */
DWORD DataSize; /* Length of <B style="color:black;background-color:#A0FFFF">icon</B> bitmap in bytes */
DWORD DataOffset; /* Offset position of <B style="color:black;background-color:#A0FFFF">icon</B> bitmap in file */
} ICONENTRY;
</pre>
<p>
Width and Height are the size of the <B style="color:black;background-color:#A0FFFF">icon</B> in pixels. Only the values
of 16, 32, and 64 for these fields are accepted by Win16. Other
values are also accepted by Win32. And as square icons are the most
common, both of these fields will typically store the same value
(although 32x16 icons were commonly used for the now antiquated
300x200 CGA display mode).
<p>
NumColors is the maximum number of colors that may appear in the
<B style="color:black;background-color:#A0FFFF">icon</B>. The values 2, 8, and 16 are the only values accepted by Win16.
Other values are accepted by Win32. If the bitmap contains 256 or
more colors the value of NumColors will be 0.
<p>
Reserved is not used and is always zero. This field was probably
included as an element-alignment padding structure.
<p>
NumPlanes and BitsPerPixel are not used and are always 0. Earlier
revisions of the ICO format may have used these fields, but in the
current revision of ICO this information is now stored in the <B style="color:black;background-color:#A0FFFF">icon</B>
data itself.
<p>
DataSize is the length of the <B style="color:black;background-color:#A0FFFF">icon</B> data in bytes for this entry.
This value is the total size of both bitmaps used to render
the <B style="color:black;background-color:#A0FFFF">icon</B> (explained below).
<p>
DataOffset is the location of the <B style="color:black;background-color:#A0FFFF">icon</B> data for this entry. The
offset is measured in bytes from the start of the ICO file.
<p>
Following the <B style="color:black;background-color:#A0FFFF">icon</B> directory is the data for the <B style="color:black;background-color:#A0FFFF">icon</B>(s) themselves
(the IconData array in the ICONFILE structure). Each <B style="color:black;background-color:#A0FFFF">icon</B> stored in
an ICO file is actually an independent file format in itself, and
contains a header, a color palette, <B style="color:black;background-color:#A0FFFF">icon</B> bitmap data, and a display
bit mask.
<p>
The start of each section of <B style="color:black;background-color:#A0FFFF">icon</B> data is specified by the IconOffset
field in each <B style="color:black;background-color:#A0FFFF">icon</B> directory entry. Each section of <B style="color:black;background-color:#A0FFFF">icon</B> data has the
following format:
<pre>
typedef struct _IconData
{
WIN3XBITMAPHEADER Header; /* Bitmap header data */
WIN3XPALETTEELEMENT Palette[]; /* Color palette */
BYTE XorMap[]; /* <B style="color:black;background-color:#A0FFFF">Icon</B> bitmap */
BYTE AndMap[]; /* Display bit mask */
} ICONDATA;
</pre>
<p>
Header is a 40-byte <B style="color:black;background-color:#ffff66">Windows</B> 3.<i>x</i> BMP file header structure. Only the
Size, Width, Height, Planes, BitsPerPixel, and SizeOfBitmap fields of
this header are actually used. All other fields in this structure
(Compression, SizeOfBitmap, HorzResolution, VertResolution,
ColorsUsed, and ColorsImportant) are set to zero. Refer to the
<a href="gffse:/format.micbmp">Microsoft <B style="color:black;background-color:#ffff66">Windows</B> Bitmap</a> article
for more information on this header structure.
<p>
Palette is the color palette for the data in the XorMap array. The
BitsPerPixel field of the Header is used to determine the number of
elements in the Palette array (BitsPerPixel >= 1). For two-color
icons there will be two palette entries; for 8- and 16-color icons
there will be 16 entries. Each palette element is a four-byte RGB
structure as described in the <a href="gffse:/format.micbmp">Microsoft
<B style="color:black;background-color:#ffff66">Windows</B> Bitmap</a> article.
<p>
XorMap contains the <B style="color:black;background-color:#A0FFFF">icon's</B> foreground bitmap. The size of the pixels
is indicated by the BitsPerPixel values in the header. Two-color
(monochrome) bitmaps are stored as one bit per pixel; 8- and 16-color
bitmap data is stored as 4 bits per pixel. Each pixel value is
actually an index into the Palette color map.
<p>
AndMap is the <B style="color:black;background-color:#A0FFFF">icon's</B> background bit mask. This is a 1-bit-per-pixel
mask that is the same size (in pixels) as the XorMap. This mask is
used to map the visible area of the <B style="color:black;background-color:#A0FFFF">icon</B> on the screen before the
<B style="color:black;background-color:#A0FFFF">icon</B> is actually displayed.
<p>
At first it may seem redundant to have Height and Width fields in
both the <B style="color:black;background-color:#A0FFFF">icon</B> entry (ICONENTRY) and the <B style="color:black;background-color:#A0FFFF">icon</B> header
(WIN3XBITMAPHEADER) structures. In fact, the Height and Width values
stored in the <B style="color:black;background-color:#A0FFFF">icon</B> header are the combined size of the XorMap and
AndMap bitmaps. The Width values in the two structures will be the
same, but the Height value in the <B style="color:black;background-color:#A0FFFF">icon</B> header will be double that of
the Height value in the <B style="color:black;background-color:#A0FFFF">icon</B> directory entry. The <B style="color:black;background-color:#A0FFFF">icon</B> directory
specifies the actual size of the <B style="color:black;background-color:#A0FFFF">icon</B> as it appears on the display,
and the <B style="color:black;background-color:#A0FFFF">icon</B> header specifies the size of the data used to create the
<B style="color:black;background-color:#A0FFFF">icon</B>.
<p>
Under the <B style="color:black;background-color:#ffff66">Windows</B> environment an <B style="color:black;background-color:#A0FFFF">icon</B> is displayed by first looking
through an ICO file and determining which <B style="color:black;background-color:#A0FFFF">icon</B> bitmap best matches
the number of colors and resolution of the display. The AND bit mask
for the chosen <B style="color:black;background-color:#A0FFFF">icon</B> is bitwise ANDed with the pixels on the display
where the <B style="color:black;background-color:#A0FFFF">icon</B> will appear. This removes the pixels from the display
and leaves a virtual "hole" in the display where the non-<B style="color:black;background-color:#99ff99">transparent</B>
parts of the <B style="color:black;background-color:#A0FFFF">icon</B> will appear. Finally, the XOR map is bitwise XORed
to the same pixels on the display. This operation adds the <B style="color:black;background-color:#A0FFFF">icon's</B>
color to the display.
<p>
Let's look at this process in more detail. Assume we have an ICO
file that contains several "happy face" <B style="color:black;background-color:#A0FFFF">icon</B> bitmaps. The ICO file
actually stores four different bitmap variations of the same happy
face:
<p>
<table border=0>
<tr>
<th align=left>Width</th>
<th align=left>Height</th>
<th align=left>Number of Colors</th>
<th align=left>BitsPerPixel</th>
</tr>
<tr>
<td align=left>8</td>
<td align=left>8</td>
<td align=left>16</td>
<td align=left>4</td>
</tr>
<tr>
<td align=left>16</td>
<td align=left>16</td>
<td align=left>16</td>
<td align=left>4</td>
</tr>
<tr>
<td align=left>32</td>
<td align=left>32</td>
<td align=left>16</td>
<td align=left>4</td>
</tr>
<tr>
<td align=left>48</td>
<td align=left>48</td>
<td align=left>64</td>
<td align=left>8</td>
</tr>
</table>
<p>
When <i>happyfac.ico</i> is loaded, one of the <B style="color:black;background-color:#A0FFFF">icon</B> bitmaps must be chosen
that matches resolution of the display. The ICO reader searches each
ICO directory entry for a "best fit" <B style="color:black;background-color:#A0FFFF">icon</B> bitmap. For a 320x240x16
display the 8x8, 16-color "happy face" <B style="color:black;background-color:#A0FFFF">icon</B> would probably look best.
The reader then seeks to the offset of the selected <B style="color:black;background-color:#A0FFFF">icon</B> data.
<p>
Next, the AndMap bitmap must be loaded and ANDed to proper location
on the display. The AndMap data follows the XorMap data, so the ICO
reader must skip past the XorMap data to read the AndMap data. It is
important to note that the scan lines of data in the AndMap and
XorMap bitmaps are stored from the bottom up (the origin is in the
lower left-hand corner). That is, the first scan line of the bitmap
is actually the last scan line of the <B style="color:black;background-color:#A0FFFF">icon</B>.
<p>
In the 8x8x16 bitmap chosen, the AndMap contains only eight bytes
of data (8 rows x 8 columns):
<pre>
FF 99 99 E7 66 BD C3 FF
</pre>
<p>
In this form the data looks meaningless. Looking at the AndMap as an
array of bits we can see our happy face more clearly:
<pre>
1 1 1 1 1 1 1 1
1 0 0 1 1 0 0 1
1 0 0 1 1 0 0 1
1 1 1 0 0 1 1 1
0 1 1 0 0 1 1 0
1 0 1 1 1 1 0 1
1 1 0 0 0 0 1 1
1 1 1 1 1 1 1 1
</pre>
<p>
If we ANDed this bitmap to a location on the display that was all the
same color we would see this result:
<pre>
C C C C C C C C 1 1 1 1 1 1 1 1 C C C C C C C C
C C C C C C C C 1 0 0 1 1 0 0 1 C 0 0 C C 0 0 C
C C C C C C C C 1 0 0 1 1 0 0 1 C 0 0 C C 0 0 C
C C C C C C C C + 1 1 1 0 0 1 1 1 = C C C 0 0 C C C
C C C C C C C C 0 1 1 0 0 1 1 0 0 C C 0 0 C C 0
C C C C C C C C 1 0 1 1 1 1 0 1 C 0 C C C C 0 C
C C C C C C C C 1 1 0 0 0 0 1 1 C C 0 0 0 0 C C
C C C C C C C C 1 1 1 1 1 1 1 1 C C C C C C C C
Display AndMap ANDed Display
</pre>
<p>
Each 1 bit in the AndMap preserved a display pixel (the <B style="color:black;background-color:#99ff99">transparent</B>
portion of the <B style="color:black;background-color:#A0FFFF">icon</B>) and each 0 bit removed a display pixel (the
opaque portion of the <B style="color:black;background-color:#A0FFFF">icon</B>).
<p>
Finally, we need to XOR the XorMap <B style="color:black;background-color:#A0FFFF">icon</B> pixel values into the hole we
punched into the display. Remember that the actual pixel color values
are stored in the color palette, and the bitmap data is only an index
map that indicates where the pixel colors should be written.
<p>
In our happy face <B style="color:black;background-color:#A0FFFF">icon</B> each pixel in the bitmap is four bits in size
and packed two pixels per byte. The XorMap bitmap data appears as
such:
<pre>
00 00 00 00
04 40 04 40
04 40 04 40
00 0F F0 00
90 0F F0 09
09 00 00 90
00 99 99 00
00 00 00 00
</pre>
<p>
In case you can't see the happy face, the eyes are the value 0x4,
the nose 0xF, and the smile 0x9. We now need to map the bitmap
index values to color values in the palette. Let's assume that
index 0x04 maps to color value 0x1, 0xF to 0xF, and 0x9 to 0x07.
<p>
With the color values determined, we XOR the pixel values to the same
region we applied the AndMap mask. The 0 bits on the display (the
black regions) indicate the non-<B style="color:black;background-color:#99ff99">transparent</B> pixels of the <B style="color:black;background-color:#A0FFFF">icon</B>. It is
the pixel represented by the 0 bits that will have their color
changed to that of the <B style="color:black;background-color:#A0FFFF">icon</B>. The <B style="color:black;background-color:#99ff99">transparent</B> pixels will retain the
original color of the display:
<pre>
C C C C C C C C 0 0 0 0 0 0 0 0 C C C C C C C C
C 0 0 C C 0 0 C 0 1 1 0 0 1 1 0 C 1 1 C C 1 1 C
C 0 0 C C 0 0 C 0 1 1 0 0 1 1 0 C 1 1 C C 1 1 C
C C C 0 0 C C C + 0 0 0 F F 0 0 0 = C C C F F C C C
0 C C 0 0 C C 0 7 0 0 F F 0 0 7 7 C C F F C C 7
C 0 C C C C 0 C 0 7 0 0 0 0 7 0 C 7 C C C C 7 C
C C 0 0 0 0 C C 0 0 7 7 7 7 0 0 C C 7 7 7 7 C C
C C C C C C C C 0 0 0 0 0 0 0 0 C C C C C C C C
ANDed Display XORed values <B style="color:black;background-color:#A0FFFF">Icon</B> on Display
</pre>
<p>
A monochrome (1-bit) <B style="color:black;background-color:#A0FFFF">icon</B> or cursor will contain only four possible
pixels values: black, white, <B style="color:black;background-color:#99ff99">transparent</B>, and inverted. A <B style="color:black;background-color:#99ff99">transparent</B>
or inverted pixel may be either black or white in color. The color
palette will contain only two colors, which are black (entry zero)
and white (entry one). The <B style="color:black;background-color:#99ff99">transparent</B> color is the original color of
the display pixels. Inverted is the inverse color of the display
pixels. Inverted pixels are responsible for the shadowy or shimmering
effect you may have noticed when some cursors are moved across the
display.
<p>
The possible combined bitmaps values are shown in Table Microsoft
<B style="color:black;background-color:#ffff66">Windows</B> Cursor and <B style="color:black;background-color:#A0FFFF">Icon</B>-1.
<p>
<table border=0>
<caption>Table Microsoft <B style="color:black;background-color:#ffff66">Windows</B> and Cursor <B style="color:black;background-color:#A0FFFF">Icon</B>-1. Monochrome <B style="color:black;background-color:#A0FFFF">icon</B> and cursor mask value combinations</caption>
<tr valign=center>
<th></th>
<th align=left>AndMap Value</th>
<th align=left>XorMap Value</th>
<th align=left>Display Pixel Value</th>
<th align=left>Resulting Color</th>
</tr>
<tr>
<td align=left>Black</td>
<td align=left>0</td>
<td align=left>0</td>
<td align=left>0 or 1</td>
<td align=left>0</td>
</tr>
<tr>
<td align=left>White</td>
<td align=left>0</td>
<td align=left>1</td>
<td align=left>0 or 1</td>
<td align=left>1</td>
</tr>
<tr>
<td align=left><B style="color:black;background-color:#99ff99">Transparent</B></td>
<td align=left>1</td>
<td align=left>0</td>
<td align=left>0</td>
<td align=left>0</td>
</tr>
<tr>
<td></td>
<td align=left>1</td>
<td align=left>0</td>
<td align=left>1</td>
<td align=left>1</td>
</tr>
<tr>
<td align=left>Inverted</td>
<td align=left>1</td>
<td align=left>1</td>
<td align=left>0</td>
<td align=left>1</td>
</tr>
<tr>
<td></td>
<td align=left>1</td>
<td align=left>1</td>
<td align=left>1</td>
<td align=left>0</td>
</tr>
</table>
<p>
<h3><A NAME="MICCUR-DMYID.3.1">CUR File Format</A></h3>
<p>
Everything we have covered for the ICO format also applies to the
CUR format with only a few exceptions:
<p>
The value of the ResourceType field in the header (ICONFILE) is 2,
indicating the file contains cursor bitmap data.
<p>
The cursor directory entry redefines two unused fields to store hot
spot information and modifies the possible values of two additional
fields:
<pre>
typedef struct _IconEntry
{
BYTE Width; /* Width of cursor in pixels */
BYTE Height; /* Height of cursor in pixels */
BYTE NumColors; /* Maximum number of colors */
BYTE Reserved; /* Not used (always 0) */
WORD XHotSpot; /* X location of cursor's hot spot */
WORD YHotSpot; /* Y location of cursor's hot spot */
DWORD DataSize; /* Length of cursor bitmap in bytes */
DWORD DataOffset; /* Offset position of cursor bitmap in file */
} ICONENTRY;
</pre>
<p>
Width and Height values in the <B style="color:black;background-color:#A0FFFF">icon</B> directory may be any size,
although 32x32 pixels is the most common size for <B style="color:black;background-color:#ffff66">Windows</B> cursors.
<p>
NumColors is always 2 (1-bit, black and white) in a Win16 cursor
file. Win32 cursors have the same color ranges as icons.
<p>
XHotSpot and YHotSpot store the coordinates of the cursor's hot spot.
The X coordinate is relative to the cursor bitmap's left edge; the Y
coordinate is relative to the cursor's top edge. Both coordinates are
measured in pixels.
<p>
The hot spot is a single pixel in size. When the user clicks the
pointing device, the coordinates of the hot spot are sent to <B style="color:black;background-color:#ffff66">Windows</B>.
<B style="color:black;background-color:#ffff66">Windows</B> then performs an action based on where the hot spot is on the
display and on the current state of <B style="color:black;background-color:#ffff66">Windows</B> itself.
<p>
And finally, ICO and CUR files do not contain any type of
identification signature or "magic number". A file reader may assume
that all <i>.ico</i> files are <B style="color:black;background-color:#ffff66">Windows</B> icons and all <i>.cur</i>
files are <B style="color:black;background-color:#ffff66">Windows</B>
cursors, but it would haphazard to do so. If we assume instead that
all ICO files will never contain more than 256 bitmaps (a very safe
assumption) then an ICO file will begin with the byte sequence 00 00
01 00 XX 00, where XX may be any byte value. Making the same
assumption for cursors, all CUR files will begin with the byte
sequence 00 00 02 00 XX 00.
<p>
<h2><A NAME="MICCUR-DMYID.4">For Further Information</A></h2>
<p>
The primary sources of ICO and CUR information are the Microsoft
Win16 and Win32 Software Development Kits (SDK) and the Microsoft
Developer Network Library (MSDN) CD-ROMs.
<p>
The Win16 and Win32 SDKs are distributed with the Microsoft Visual
C++ compiler and the MSDN CD-ROMs. The following SDK references and
Knowledge Base articles discuss the ICO, CUR, and DIB bitmap formats:
<p>
<blockquote>
<p>
<i>Microsoft <B style="color:black;background-color:#ffff66">Windows</B> Software Development Kit, Programmers'
Reference, Volume 4: Resources</i>
<p>
Win32 SDK on-line help for the BITMAPINFO structure
<p>
Q81498 SAMPLE: DIBs and Their Uses
<p>
Q94326 SAMPLE: 16 and 32 Bits-Per-Pel Bitmap Formats
<p>
Specs: Icons in Win32
<p>
Technical Articles: Win32 Binary Resource Formats
<p>
</blockquote>
<p>
You can find the SDK documents on the MSDN Library CD-ROMs. The MSDN
Library is only available by subscription. However, Microsoft has made
the October 1995 MSDN library available at:
<p>
<blockquote>
<p>
<i>ftp://ftp.microsoft.com/developr/MSDN/OctCD/</i>
</blockquote>
<p>
One other MSDN Library file of interest is:
<p>
<blockquote>
MSDN Frequently Asked Questions (FAQ)<br>
PSS ID Number: Q116437, 02-16-1996<br>
<i>ftp://ftp.microsoft.com/developr/MSDN/kb/Q116/4/37.txt</i><br>
<i>http://www.microsoft.com/msdn/msdnfaq.htm</i>
</blockquote>
<p>
The Win32 SDK also contains two sample applications that are necessary
for understanding icons and cursors. They are <i>IconPro</i> and
<i>imagedit</i> (an <B style="color:black;background-color:#A0FFFF">icon</B> and cursor bitmap editor). Both of these
sample applications are distributed with complete source code, but no
compiled binaries. The binaries are only distributed with the <B style="color:black;background-color:#ffff66">Windows</B>
95 and <B style="color:black;background-color:#ffff66">Windows</B> NT Resource Kits.
<p>
You can contact the Microsoft MSDN group at:
<p>
<blockquote>
Microsoft Developers Network<br>
Voice: 206-936-2490<br>
Email: <i>msdn@microsoft.com</i><br>
WWW: <i>http://www.microsoft.com/msdn/</i>
</blockquote>
<p>
And here's the addresses of Microsoft. Try getting what you need from
their FTP and web sites first:
<p>
<blockquote>
Microsoft Corporation<br>
One Microsoft Way<br>
Redmond, WA 98052-6399<br>
FTP: <i>ftp://ftp.microsoft.com/</i><br>
WWW: <i>http://www.microsoft.com/</i><br>
CIS: WINSDK and MSWIN32 forums
</blockquote>
<p>
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