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lang=EN-US>7.4</span><span style='font-family:宋体;
"Times New Roman"'>。是不是很象一顶墨西哥草帽？所以，</span><span
lang=EN-US>LOG</span><span style='font-family:宋体;
"Times New Roman"'>又叫墨西哥草帽滤波器。</span></p>
<p class=a style='line-height:18.0pt'><span lang=EN-US> <img width=268 height=148
src="chap07.files/image032.jpg" v:shapes="_x0000_i1047"> </span></p>
<p align=center style='text-align:center;line-height:18.0pt'><b><span
style='font-family:宋体;"Times New Roman"'>图</span>7.4 LOG</b><b><span
style='font-family:宋体;"Times New Roman"'>到中心点的距离与位置加权系数的关系曲线</span><span lang=EN-US></span></b></p>
<p style='line-height:18.0pt'><span style='font-family:宋体;
"Times New Roman"'>图</span><span
lang=EN-US>7.5</span><span style='font-family:宋体;
"Times New Roman"'>为图</span><span lang=EN-US>7.1</span><span
style='font-family:宋体;"Times New Roman"'>用</span><span lang=EN-US>LOG</span><span style='font-family:
宋体;"Times New Roman"'>滤波器处理后的结果。</span></p>
<p class=a style='line-height:18.0pt'><span lang=EN-US> <img width=303 height=192
src="chap07.files/image034.jpg" v:shapes="_x0000_i1048"> </span></p>
<p align=center style='text-align:center;line-height:18.0pt'><b><span
style='font-family:宋体;"Times New Roman"'>图</span>7.5 </b><b><span
style='font-family:宋体;"Times New Roman"'>图</span><span lang=EN-US>7.1</span></b><b><span
style='font-family:宋体;"Times New Roman"'>用</span><span lang=EN-US>LOG</span></b><b><span
style='font-family:宋体;"Times New Roman"'>滤波器处理后的结果图</span><span lang=EN-US></span></b></p>
<p style='line-height:18.0pt'><span lang=EN-US>LOG</span><span
style='font-family:宋体;"Times New Roman"'>的算法和普通模板操作的算法没什么不同，只不过把</span><span lang=EN-US>3</span><span
style='font-family:宋体;"Times New Roman"'>×</span><span lang=EN-US>3</span><span style='font-family:
宋体;"Times New Roman"'>改成了</span><span
lang=EN-US>5</span><span style='font-family:宋体;
"Times New Roman"'>×</span><span lang=EN-US>5</span><span
style='font-family:宋体;"Times New Roman"'>，这里就不再给出了。读者可以参照第</span><span lang=EN-US>3</span><span
style='font-family:宋体;"Times New Roman"'>章的源程序自己来完成。</span></p>
<h2> <span
lang=EN-US>7.2</span> <a name="_Toc486331899"></a><a
name="_Toc486332899"></a><a name="_Toc486339008"></a><a name="_Toc454810873"></a><a
name="_Toc454856647"><span><span>Hough</span></span></a><span><span><span style='font-family:黑体;'>变换</span></span></span></h2>
<p style='line-height:18.0pt'><span
lang=EN-US>Hough</span><span style='font-family:宋体;
"Times New Roman"'>变换用来在图象中查找直线。它的原理很简单：假设有一条与原点距离为</span><span
lang=EN-US>s</span><span style='font-family:宋体;
"Times New Roman"'>，方向角为θ的一条直线，如图</span><span lang=EN-US>7.6</span><span
style='font-family:宋体;"Times New Roman"'>所示。</span></p>
<p align=center style='text-align:center;
line-height:18.0pt'><span lang=EN-US> <img width=232 height=178
src="chap07.files/image036.jpg" v:shapes="_x0000_i1049"> </span></p>
<p align=center style='text-align:center;
line-height:18.0pt'><b><span style='font-family:宋体;
"Times New Roman"'>图</span>7.6 </b><b><span
style='font-family:宋体;"Times New Roman"'>一条与原点距离为</span><span lang=EN-US>s</span></b><b><span
style='font-family:宋体;"Times New Roman"'>，方向角为θ的一条直线</span><span lang=EN-US></span></b></p>
<p style='line-height:18.0pt'><span style='font-family:宋体;
"Times New Roman"'>直线上的每一点都满足方程</span></p>
<p align=center style='text-align:center;line-height:18.0pt'><span
lang=EN-US><sub> <img width=128 height=21
src="chap07.files/image038.gif" v:shapes="_x0000_i1050"> </sub> </span></p>
<p align=right style='text-align:right;line-height:18.0pt'><span
lang=EN-US>(7.1)</span></p>
<p style='line-height:18.0pt'><span style='font-family:宋体;
"Times New Roman"'>利用这个事实，我们可以找出某条直线来。下面将给出一段程序，用来找出图象中最长的直线</span><span
lang=EN-US>(</span><span style='font-family:宋体;
"Times New Roman"'>见图</span><span lang=EN-US>7.7)</span><span
style='font-family:宋体;"Times New Roman"'>。找到直线的两个端点，在它们之间连一条红色的直线。为了看清效果，将结果描成粗线，如图</span><span
lang=EN-US>7.8</span><span style='font-family:宋体;
"Times New Roman"'>所示。</span></p>
<table border=0 cellspacing=0 cellpadding=0>
<tr>
<td width=276 valign=top class="Normal">
<p style='line-height:18.0pt'><span lang=EN-US> <img width=239 height=193
src="chap07.files/image040.gif" v:shapes="_x0000_i1051"> </span></p>
<p align=center style='text-align:center;line-height:18.0pt'><b><span
style='font-family:宋体;"Times New Roman"'>图</span><span lang=EN-US>7.7 </span></b><b><span
style='font-family:宋体;"Times New Roman"'>原图</span><span lang=EN-US></span></b></p>
</td>
<td width=276 valign=top class="Normal">
<p style='line-height:18.0pt'><span lang=EN-US> <img width=243 height=193
src="chap07.files/image042.jpg" v:shapes="_x0000_i1052"> </span></p>
<p align=center style='text-align:center;line-height:18.0pt'><b><span
style='font-family:宋体;"Times New Roman"'>图</span><span lang=EN-US>7.8 Hough</span></b><b><span
style='font-family:宋体;"Times New Roman"'>变换的结果</span><span lang=EN-US></span></b></p>
</td>
</tr>
</table>
<p style='line-height:18.0pt'><span style='font-family:宋体;
"Times New Roman"'>可以看出，找到的确实是最长的直线。方法是，开一个二维数组做为计数器，第一维是角度，第二维是距离。先计算可能出现的最大距离为</span><span
lang=EN-US><sub> <img width=125 height=29
src="chap07.files/image044.gif" v:shapes="_x0000_i1053"> </sub> </span><span style='font-family:宋体;"Times New Roman";"Times New Roman"'>，用来确定数组第二维的大小。对于每一个黑色点，角度的变化范围从</span><span
lang=EN-US>0<sup>0</sup></span><span style='font-family:宋体;"Times New Roman";"Times New Roman"'>到</span><span
lang=EN-US>178<sup>0</sup>(</span><span style='font-family:宋体;"Times New Roman";"Times New Roman"'>为了减少存储空间和计算时间，角度每次增加</span><span
lang=EN-US>2<sup>0</sup></span><span style='font-family:宋体;"Times New Roman";"Times New Roman"'>而不是</span><span
lang=EN-US>1<sup>0</sup>)</span><span style='font-family:宋体;"Times New Roman";"Times New Roman"'>，按方程</span><span
lang=EN-US>(7.1)</span><span style='font-family:宋体;
"Times New Roman"'>求出对应的距离</span><span lang=EN-US>s</span><span
style='font-family:宋体;"Times New Roman"'>来，相应的数组元素</span><span lang=EN-US>[s][<sub>
<img width=13 height=19
src="chap07.files/image046.gif" v:shapes="_x0000_i1054"> </sub> ]</span><span style='font-family:宋体;"Times New Roman";"Times New Roman"'>加</span><span
lang=EN-US>1</span><span style='font-family:宋体;
"Times New Roman"'>。同时开一个数组</span><span lang=EN-US>Line</span><span
style='font-family:宋体;"Times New Roman"'>，计算每条直线的上下两个端点。所有的象素都算完后，找到数组元素中最大的，就是最长的那条直线。直线的端点可以在</span><span
lang=EN-US>Line</span><span style='font-family:宋体;
"Times New Roman"'>中找到。要注意的是，我们处理的虽然是二值图，但实际上是</span><span
lang=EN-US>256</span><span style='font-family:宋体;
"Times New Roman"'>级灰度图，不过只用到了</span><span lang=EN-US>0</span><span
style='font-family:宋体;"Times New Roman"'>和</span><span lang=EN-US>255</span><span style='font-family:
宋体;"Times New Roman"'>两种颜色。</span></p>
<p style='line-height:18.0pt'><span lang=EN-US>BOOL Hough(HWND hWnd)</span></p>
<p style='line-height:18.0pt'><span lang=EN-US>{</span></p>
<p style='line-height:18.0pt'><span
lang=EN-US>//</span><span style='font-family:宋体;
"Times New Roman"'>定义一个自己的直线结构</span></p>
<p style='line-height:18.0pt'><span> </span>typedef struct{</p>
<p style='line-height:18.0pt'><span> </span>
int topx; //<span
style='font-family:宋体;"Times New Roman"'>最高点的</span><span lang=EN-US>x</span><span style='font-family:
宋体;"Times New Roman"'>坐标</span></p>
<p style='line-height:18.0pt'><span> </span>
int topy; //<span
style='font-family:宋体;"Times New Roman"'>最高点的</span><span lang=EN-US>y</span><span style='font-family:
宋体;"Times New Roman"'>坐标</span></p>
<p style='line-height:18.0pt'><span> </span>
int botx; //<span
style='font-family:宋体;"Times New Roman"'>最低点的</span><span lang=EN-US>x</span><span style='font-family:
宋体;"Times New Roman"'>坐标</span></p>
<p style='line-height:18.0pt'><span> </span>
int boty; //<span
style='font-family:宋体;"Times New Roman"'>最低点的</span><span lang=EN-US>y</span><span style='font-family:
宋体;"Times New Roman"'>坐标</span></p>
<p style='line-height:18.0pt'><span> </span>
}MYLINE;</p>
<p style='line-height:18.0pt'><span> </span>DWORD
OffBits,BufSize;</p>
<p style='line-height:18.0pt'><span> </span> LPBITMAPINFOHEADER
lpImgData;</p>
<p style='line-height:18.0pt'><span> </span>LPSTR
lpPtr;</p>
<p style='line-height:18.0pt'><span> </span>HDC
hDc;</p>
<p style='line-height:18.0pt'>LONG
x,y;</p>
<p style='line-height:18.0pt'><span> </span>long
i,maxd;</p>
<p style='line-height:18.0pt'><span> </span>int
k;</p>
<p style='line-height:18.0pt'><span> </span>int
Dist,Alpha;</p>
<p style='line-height:18.0pt'>HGLOBAL
hDistAlpha,hMyLine;</p>
<p style='line-height:18.0pt'><span> </span> Int
*lpDistAlpha;</p>
<p style='line-height:18.0pt'><span> </span>MYLINE
*lpMyLine,*TempLine,MaxdLine;</p>
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