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<title>第1章 Windows位图和调色板</title>
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<h1><a name="_Toc486331863"></a><a name="_Toc486332863"></a><a
name="_Toc486338972"></a><a name="_Toc454810837"></a><a name="_Toc454856611"><span><span>第<span
lang=EN-US>1</span></span></span></a><span><span><span style='font-family:黑体;"Times New Roman"'>章</span><span
lang=EN-US> Windows</span></span></span><span><span><span style='font-family:黑体;"Times New Roman"'>位图和调色板</span></span></span></h1>
<h2> <span
lang=EN-US>1.1</span> <span lang=EN-US> </span><a name="_Toc486331864"></a><a
name="_Toc486332864"></a><a name="_Toc486338973"></a><a name="_Toc454810838"></a><a
name="_Toc454856612"><span><span>位图和调色板的概念</span></span></a></h2>
<p style='line-height:18.0pt'><span
style='font-family:宋体;"Times New Roman"'>如今</span><span lang=EN-US>Windows(3.x</span><span
style='font-family:宋体;"Times New Roman"'>以及</span><span lang=EN-US>95</span><span style='font-family:
宋体;"Times New Roman"'>，</span><span
lang=EN-US>98</span><span style='font-family:宋体;
"Times New Roman"'>，</span><span lang=EN-US>NT)</span><span
style='font-family:宋体;"Times New Roman"'>系列已经成为绝大多数用户使用的操作系统，它比</span><span lang=EN-US>DOS</span><span
style='font-family:宋体;"Times New Roman"'>成功的一个重要因素是它可视化的漂亮界面。那么</span><span lang=EN-US>Windows</span><span
style='font-family:宋体;"Times New Roman"'>是如何显示图象的呢？这就要谈到位图</span><span lang=EN-US>(bitmap)</span><span
style='font-family:宋体;"Times New Roman"'>。</span></p>
<p style='line-height:18.0pt'><span
style='font-family:宋体;"Times New Roman"'>我们知道，普通的显示器屏幕是由许许多多点构成的，我们称之为象素。显示时采用扫描的方法：电子枪每次从左到右扫描一行，为每个象素着色，然后从上到下这样扫描若干行，就扫过了一屏。为了防止闪烁，每秒要重复上述过程几十次。例如我们常说的屏幕分辨率为</span><span
lang=EN-US>640×480</span><span style='font-family:宋体;"Times New Roman";"Times New Roman"'>，刷新频率为</span><span
lang=EN-US>70Hz</span><span style='font-family:宋体;
"Times New Roman"'>，意思是说每行要扫描</span><span lang=EN-US>640</span><span
style='font-family:宋体;"Times New Roman"'>个象素，一共有</span><span lang=EN-US>480</span><span
style='font-family:宋体;"Times New Roman"'>行，每秒重复扫描屏幕</span><span lang=EN-US>70</span><span
style='font-family:宋体;"Times New Roman"'>次。</span></p>
<p style='line-height:18.0pt'><span
style='font-family:宋体;"Times New Roman"'>我们称这种显示器为位映象设备。所谓位映象，就是指一个二维的象素矩阵，而位图就是采用位映象方法显示和存储的图象。举个例子，图</span><span
lang=EN-US>1.1</span><span style='font-family:宋体;
"Times New Roman"'>是一幅普通的黑白位图，图</span><span lang=EN-US>1.2</span><span
style='font-family:宋体;"Times New Roman"'>是被放大后的图，图中每个方格代表了一个象素。我们可以看到：整个骷髅就是由这样一些黑点和白点组成的。</span></p>
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<p class=a style='line-height:18.0pt'><span lang=EN-US> <img width=48 height=48
src="chap01.files/image001.gif" v:shapes="_x0000_i1026"> </span></p>
<p class=a style='line-height:18.0pt'><b><span style='font-family:宋体;
"Times New Roman"'>图</span>1.1 </b><b><span
style='font-family:宋体;"Times New Roman"'>骷髅</span></b></p>
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<td width=276 valign=bottom class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><b><span
lang=EN-US> <img width=157 height=177
src="chap01.files/image003.jpg" v:shapes="_x0000_i1025"> </span></b></p>
<p align=center style='text-align:center;line-height:18.0pt'><b><span
style='font-family:宋体;"Times New Roman"'>图</span>1.2
</b><b><span style='font-family:
宋体;"Times New Roman"'>放大后的骷髅位图</span></b></p>
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<p style='line-height:18.0pt'><span
style='font-family:宋体;"Times New Roman"'>那么，彩色图是怎么回事呢？</span></p>
<p style='line-height:18.0pt'><span
style='font-family:宋体;"Times New Roman"'>我们先来说说三元色</span><span lang=EN-US>RGB</span><span
style='font-family:宋体;"Times New Roman"'>概念。</span></p>
<p style='line-height:18.0pt'><span
style='font-family:宋体;"Times New Roman"'>我们知道，自然界中的所有颜色都可以由红、绿、蓝</span><span lang=EN-US>(R</span><span
style='font-family:宋体;"Times New Roman"'>，</span><span lang=EN-US>G</span><span style='font-family:
宋体;"Times New Roman"'>，</span><span
lang=EN-US>B)</span><span style='font-family:宋体;
"Times New Roman"'>组合而成。有的颜色含有红色成分多一些，如深红；有的含有红色成分少一些，如浅红。针对含有红色成分的多少，可以分成</span><span
lang=EN-US>0</span><span style='font-family:宋体;
"Times New Roman"'>到</span><span lang=EN-US>255</span><span
style='font-family:宋体;"Times New Roman"'>共</span><span lang=EN-US>256</span><span style='font-family:
宋体;"Times New Roman"'>个等级，</span><span
lang=EN-US>0</span><span style='font-family:宋体;
"Times New Roman"'>级表示不含红色成分；</span><span lang=EN-US>255</span><span
style='font-family:宋体;"Times New Roman"'>级表示含有</span><span lang=EN-US>100%</span><span
style='font-family:宋体;"Times New Roman"'>的红色成分。同样，绿色和蓝色也被分成</span><span lang=EN-US>256</span><span
style='font-family:宋体;"Times New Roman"'>级。这种分级概念称为量化。</span></p>
<p style='line-height:18.0pt'><span
style='font-family:宋体;"Times New Roman"'>这样，根据红、绿、蓝各种不同的组合我们就能表示出</span><span lang=EN-US>256×256×256</span><span
style='font-family:宋体;"Times New Roman"'>，约</span><span lang=EN-US>1600</span><span style='font-family:
宋体;"Times New Roman"'>万种颜色。这么多颜色对于我们人眼来说已经足够丰富了。</span></p>
<p align=center style='text-align:center;line-height:18.0pt'><b><span
style='font-family:宋体;"Times New Roman"'>表</span>1.1 </b><b><span
style='font-family:宋体;"Times New Roman"'>常见颜色的</span><span lang=EN-US>RGB</span></b><b><span
style='font-family:宋体;"Times New Roman"'>组合值</span><span lang=EN-US></span></b></p>
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<p class=a style='line-height:18.0pt'><span style='font-family:宋体;"Times New Roman";"Times New Roman"'>颜色</span></p>
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<p class=a style='line-height:18.0pt'><span lang=EN-US>R</span></p>
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<td width="25%" class="Normal">
<p class=a style='line-height:18.0pt'><span lang=EN-US>G</span></p>
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<td width="25%" class="Normal">
<p class=a style='line-height:18.0pt'><span lang=EN-US>B</span></p>
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</tr>
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<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
style='font-family:宋体;"Times New Roman"'>红</span></p>
</td>
<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
lang=EN-US>255</span></p>
</td>
<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
lang=EN-US>0</span></p>
</td>
<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
lang=EN-US>0</span></p>
</td>
</tr>
<tr>
<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
style='font-family:宋体;"Times New Roman"'>蓝</span></p>
</td>
<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
lang=EN-US>0</span></p>
</td>
<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
lang=EN-US>255</span></p>
</td>
<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
lang=EN-US>0</span></p>
</td>
</tr>
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<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
style='font-family:宋体;"Times New Roman"'>绿</span></p>
</td>
<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
lang=EN-US>0</span></p>
</td>
<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
lang=EN-US>0</span></p>
</td>
<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
lang=EN-US>255</span></p>
</td>
</tr>
<tr>
<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
style='font-family:宋体;"Times New Roman"'>黄</span></p>
</td>
<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
lang=EN-US>255</span></p>
</td>
<td width="25%" class="Normal">
<p align=center style='text-align:center;line-height:18.0pt'><span
lang=EN-US>255</span></p>
</td>
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