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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>The Be Book - System Overview - The Interface Kit</title><link rel="stylesheet" href="be_book.css" type="text/css" media="all" /><link rel="shortcut icon" type="image/vnd.microsoft.icon" href="./images/favicon.ico" /><!--[if IE]>
<link rel="stylesheet" type="text/css" href="be_book_ie.css" />
<![endif]--><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /><meta name="keywords" content="Access, BeOS, BeBook, API" /><link rel="start" href="index.html" title="The Be Book" /><link rel="up" href="TheInterfaceKit_Overview.html" title="The Interface Kit" /><link rel="prev" href="BAlert_Overview.html" title="BAlert" /><link rel="next" href="BBox_Overview.html" title="BBox" /></head><body><div id="header"><div id="headerT"><div id="headerTL"><a accesskey="p" href="BAlert_Overview.html" title="BAlert"><img src="./images/navigation/prev.png" alt="Prev" /></a> <a accesskey="u" href="TheInterfaceKit_Overview.html" title="The Interface Kit"><img src="./images/navigation/up.png" alt="Up" /></a> <a accesskey="n" href="BBox_Overview.html" title="BBox"><img src="./images/navigation/next.png" alt="Next" /></a></div><div id="headerTR"><div id="navigpeople"><a href="http://www.haiku-os.org"><img src="./images/People_24.png" alt="haiku-os.org" title="Visit The Haiku Website" /></a></div><div class="navighome" title="Home"><a accesskey="h" href="index.html"><img src="./images/navigation/home.png" alt="Home" /></a></div><div class="navigboxed" id="navigindex"><a accesskey="i" href="ClassIndex.html" title="Index">I</a></div><div class="navigboxed" id="naviglang" title="English">en</div></div><div id="headerTC">The Be Book - System Overview - The Interface Kit</div></div><div id="headerB">Prev: <a href="BAlert_Overview.html">BAlert</a>  Up: <a href="TheInterfaceKit_Overview.html">The Interface Kit</a>  Next: <a href="BBox_Overview.html">BBox</a></div><hr /></div><div class="section"><div xmlns="" xmlns:d="http://docbook.org/ns/docbook" class="titlepage"><div><div xmlns:d="http://docbook.org/ns/docbook"><h2 xmlns="http://www.w3.org/1999/xhtml" class="title"><a id="BBitmap_Overview"></a>BBitmap</h2></div></div></div><a id="id546631" class="indexterm"></a><p>
A <a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a>
describes a rectangular image as a two-dimensional array of
pixel data (or bitmap). The <a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a>
class lets you create a bitmap by
specifying raw pixel data (through the
<a class="link" href="BBitmap.html#BBitmap_Bits" title="Bits()"><code class="methodname">Bits()</code></a> and
<a class="link" href="BBitmap.html#BBitmap_SetBits" title="SetBits()"><code class="methodname">SetBits()</code></a> functions),
or you can add a
<a class="link" href="BView.html" title="BView"><code class="classname">BView</code></a> to your
<a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a> and use the view's drawing
operations (
<a class="link" href="BView.html#BView_FillRect"><code class="methodname">FillRect()</code></a>,
<a class="link" href="BView.html#BView_StrokeLine" title="StrokeLine()"><code class="methodname">StrokeLine()</code></a>, etc) to draw into the
<a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a>
object (see
"<a class="link" href="BBitmap_Overview.html#BBitmap_Overview_Using_A_View" title="Using a View to Draw into a Bitmap">Using a View to Draw into a Bitmap</a>", below).
</p><p>
The <a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a>
class doesn't provide a way to actually display bitmap data.
Displaying a bitmap is the task of
<a class="link" href="BView.html" title="BView"><code class="classname">BView</code></a> functions such as
<a class="link" href="BView.html#BView_DrawBitmap" title="DrawBitmap(), DrawBitmapAsync()"><code class="methodname">DrawBitmap()</code></a>.
</p><div class="section"><div xmlns="" xmlns:d="http://docbook.org/ns/docbook" class="titlepage"><div><hr /><div xmlns:d="http://docbook.org/ns/docbook"><h3 xmlns="http://www.w3.org/1999/xhtml" class="title"><a id="BBitmap_Overview_Bitmap_Data"></a>Bitmap Data</h3></div></div></div><p>
A bitmap records the color values of every pixel within a rectangular
area. The data is specified in rows, beginning with the top row of pixels
in the image and working downward to the bottom row. Each row is aligned
on a long word boundary.
</p><p>
When you construct a <a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a>
object, you give it a bounds rectangle
(integer coordinates only!) and a color space. For example, this code
</p><pre class="programlisting example cpp"><span class="type">BBitmap*</span> <code class="varname">image</code> = new <code class="classname">BBitmap</code>(<code class="classname">BRect</code>(0.0, 0.0, 79.0, 39.0),
<code class="constant">B_CMAP8</code>);</pre><p>
constructs a 40 x 80 bitmap of 8-bit color data.
</p><p>
The data in a <a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a>
object isn't initialized—a <a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a> has no
default background color. When you set the bitmap's data (however you set
it) you must "paint" every pixel within the bitmap's bounds rectangle.
</p></div><div class="section"><div xmlns="" xmlns:d="http://docbook.org/ns/docbook" class="titlepage"><div><hr /><div xmlns:d="http://docbook.org/ns/docbook"><h3 xmlns="http://www.w3.org/1999/xhtml" class="title"><a id="BBitmap_Overview_Using_A_View"></a>Using a View to Draw into a Bitmap</h3></div></div></div><p>
If you're going to use a view to draw into your bitmap, you must tell the
<a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a>
constructor by setting the third argument to <code class="constant">true</code>:
</p><pre class="programlisting example cpp"><span class="type">BBitmap *</span><code class="varname">image</code> = new <code class="classname">BBitmap</code>(<code class="classname">BRect</code>(...), <code class="constant">B_CMAP8</code>, <code class="constant">true</code>);</pre><p>
You then add the view to the bitmap (you don't have to do anything
special when constructing the <a class="link" href="BView.html" title="BView"><code class="classname">BView</code></a>):
</p><pre class="programlisting example cpp"><code class="varname">bitmap</code>-&gt;<code class="methodname">AddChild</code>(<code class="varname">view</code>);</pre><p>
When the view draws, the drawing operations are rendered into the bitmap.
Note that you must explicitly tell the <a class="link" href="BView.html" title="BView"><code class="classname">BView</code></a>):
to draw—the <a class="link" href="BView.html" title="BView"><code class="classname">BView</code></a>s
that you use to draw into a <a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a> aren't part of the user interface, so
they won't receive user event messages. When you're done drawing, you
should call <a class="link" href="BView.html" title="BView"><code class="classname">BView</code></a>'s
<a class="link" href="BView.html#BView_Sync"><code class="methodname">Sync()</code></a> function to make sure the drawing has all
been performed. If the bitmap that you've created is static—if it
doesn't need to change after you've drawn into it—you can throw
away the <a class="link" href="BView.html" title="BView"><code class="classname">BView</code></a> that you used create the bitmap data.
</p><p>
A <a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a>
can contain more than one <a class="link" href="BView.html" title="BView"><code class="classname">BView</code></a>—it
can act as the root of an entire view hierarchy. The
<a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a>
class defines a number of
<a class="link" href="BWindow.html" title="BWindow"><code class="classname">BWindow</code></a>-like
functions—<a class="link" href="BBitmap.html#BBitmap_AddChild" title="AddChild()"><code class="methodname">AddChild()</code></a>,
<a class="link" href="BBitmap.html#BBitmap_FindView" title="FindView()"><code class="methodname">FindView()</code></a>,
<a class="link" href="BBitmap.html#BBitmap_ChildAt" title="ChildAt(), CountChildren()"><code class="methodname">ChildAt()</code></a>, and so
on—to help you create and manage the hierarchy.
</p></div><div class="section"><div xmlns="" xmlns:d="http://docbook.org/ns/docbook" class="titlepage"><div><hr /><div xmlns:d="http://docbook.org/ns/docbook"><h3 xmlns="http://www.w3.org/1999/xhtml" class="title"><a id="BBitmap_Overview_Transparency"></a>Transparency</h3></div></div></div><p>
Color bitmaps can have transparent pixels. When the bitmap is imaged in a
drawing mode other than <code class="constant">B_OP_COPY</code>, its transparent pixels won't be
transferred to the destination view. The destination image will show
through wherever the bitmap is transparent.
</p><p>
To introduce transparency into a <code class="constant">B_CMAP8</code> bitmap, a pixel can be assigned
one of the following values, as appropriate for the bitmap's color space.
</p><table class="variablelist constants"><thead><tr><th>Constant</th><th>Description</th></tr></thead><tbody><tr><td><p><span class="term"><code class="constant">B_TRANSPARENT_MAGIC_CMAP8</code></span></p></td><td><p>8-bit indexed color transparent pixel.</p></td></tr><tr><td><p><span class="term"><code class="constant">B_TRANSPARENT_MAGIC_RGBA15</code></span></p></td><td><p>15-bit transparent pixel.</p></td></tr><tr><td><p><span class="term"><code class="constant">B_TRANSPARENT_MAGIC_RGBA15_BIG</code></span></p></td><td><p>15-bit transparent pixel, big-endian.</p></td></tr><tr><td><p><span class="term"><code class="constant">B_TRANSPARENT_MAGIC_RGBA32</code></span></p></td><td><p>32-bit transparent pixel.</p></td></tr><tr><td><p><span class="term"><code class="constant">B_TRANSPARENT_MAGIC_RGBA32_BIG</code></span></p></td><td><p>32-bit transparent pixel, big-endian.</p></td></tr></tbody></table><p>
Opaque pixels should have an alpha value of 255 for 8-bit alpha channels
or 1 for 1-bit alpha channels; values of 0 indicate 100% transparent
pixels. Values in between (for 8-bit alpha channels) represent varying
degrees of transparency.
</p><p>
Transparency is covered in more detail under
"<a class="link" href="TheInterfaceKit_Drawing.html#TheInterfaceKit_Drawing_Drawing_Modes" title="Drawing Modes">Drawing Modes</a>".
</p><p>
See also:
<a class="link" href="TheInterfaceKit_Functions.html#system_colors" title="system_colors()"><code class="function">system_colors()</code></a>
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