📄 第2章 图象的几何变换.htm
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style="FONT-FAMILY: 宋体">分量包含了灰度图的所有信息，只用</SPAN><SPAN lang=EN-US>Y</SPAN><SPAN
style="FONT-FAMILY: 宋体">分量就能完全能够表示出一幅灰度图来。当同时考虑</SPAN><SPAN
lang=EN-US>U</SPAN><SPAN style="FONT-FAMILY: 宋体">，</SPAN><SPAN
lang=EN-US>V</SPAN><SPAN
style="FONT-FAMILY: 宋体">分量时，就能够表示出彩色信息来。这样，用同一种表示方法可以很方便的在灰度和彩色图之间切换，而</SPAN><SPAN
lang=EN-US>RGB</SPAN><SPAN style="FONT-FAMILY: 宋体">表示方法就做不到这一点了。</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN lang=EN-US>(2)<SPAN
style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN><SPAN
style="FONT-FAMILY: 宋体">人眼对于亮度信号非常敏感，而对色差信号的敏感程度相对较弱。也就是说，图象的主要信息包含在</SPAN><SPAN
lang=EN-US>Y</SPAN><SPAN style="FONT-FAMILY: 宋体">分量中。这就提示我们：如果在对</SPAN><SPAN
lang=EN-US>YUV</SPAN><SPAN
style="FONT-FAMILY: 宋体">信号进行量化时，可以“偏心”一点，让</SPAN><SPAN lang=EN-US>Y</SPAN><SPAN
style="FONT-FAMILY: 宋体">的量化级别多一些</SPAN><SPAN lang=EN-US>(</SPAN><SPAN
style="FONT-FAMILY: 宋体">谁让它重要呢？</SPAN><SPAN lang=EN-US>)</SPAN><SPAN
style="FONT-FAMILY: 宋体">而让</SPAN><SPAN lang=EN-US>UV</SPAN><SPAN
style="FONT-FAMILY: 宋体">的量化级别少一些，就可以实现图象信息的压缩。这一点将在第</SPAN><SPAN
lang=EN-US>9</SPAN><SPAN
style="FONT-FAMILY: 宋体">章介绍图象压缩时仔细研究，这里就不深入讨论了。而</SPAN><SPAN
lang=EN-US>RGB</SPAN><SPAN style="FONT-FAMILY: 宋体">的表示方法就做不到这一点，因为</SPAN><SPAN
lang=EN-US>RGB</SPAN><SPAN style="FONT-FAMILY: 宋体">三个分量同等重要，缺了谁也不行。</SPAN><SPAN
lang=EN-US>YUV</SPAN><SPAN style="FONT-FAMILY: 宋体">和</SPAN><SPAN
lang=EN-US>RGB</SPAN><SPAN style="FONT-FAMILY: 宋体">之间有着如下的对应关系</SPAN></P>
<P style="LINE-HEIGHT: 18pt; TEXT-ALIGN: center" align=center><SPAN
lang=EN-US><SUB><IMG height=77 src="第2章 图象的几何变换.files/image014.gif" width=352
v:shapes="_x0000_i1071"> </SUB></SPAN></P>
<P style="LINE-HEIGHT: 18pt; TEXT-ALIGN: right" align=right><SPAN
lang=EN-US>(2.3)</SPAN></P>
<P style="LINE-HEIGHT: 18pt; TEXT-ALIGN: center" align=center><SPAN
lang=EN-US><SUB><IMG height=75 src="第2章 图象的几何变换.files/image016.gif" width=324
v:shapes="_x0000_i1072"> </SUB></SPAN></P>
<P style="LINE-HEIGHT: 18pt; TEXT-ALIGN: right" align=right><SPAN
lang=EN-US>(2.4)</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN style="FONT-FAMILY: 宋体">当</SPAN><SPAN
lang=EN-US>RGB</SPAN><SPAN style="FONT-FAMILY: 宋体">三个分量的大小一样时，假设都是</SPAN><SPAN
lang=EN-US>a</SPAN><SPAN style="FONT-FAMILY: 宋体">，代入公式</SPAN><SPAN
lang=EN-US>(2.3)</SPAN><SPAN style="FONT-FAMILY: 宋体">，得到</SPAN><SPAN
lang=EN-US>Y=a</SPAN><SPAN style="FONT-FAMILY: 宋体">，</SPAN><SPAN
lang=EN-US>U=0</SPAN><SPAN style="FONT-FAMILY: 宋体">，</SPAN><SPAN lang=EN-US>V=0
</SPAN><SPAN style="FONT-FAMILY: 宋体">。你现在该明白我前面所说不是巧合的原因了吧。</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN
style="FONT-FAMILY: 宋体">使用灰度图有一个好处，那就是方便。首先</SPAN><SPAN
lang=EN-US>RGB</SPAN><SPAN
style="FONT-FAMILY: 宋体">的值都一样；其次，图象数据即调色板索引值，也就是实际的</SPAN><SPAN
lang=EN-US>RGB</SPAN><SPAN style="FONT-FAMILY: 宋体">值，也就是亮度值；另外，因为是</SPAN><SPAN
lang=EN-US>256</SPAN><SPAN
style="FONT-FAMILY: 宋体">色调色板，所以图象数据中一个字节代表一个象素，很整齐。如果是</SPAN><SPAN
lang=EN-US>2</SPAN><SPAN style="FONT-FAMILY: 宋体">色图或</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体">色图，还要拼凑字节，很麻烦。如果是彩色的</SPAN><SPAN
lang=EN-US>256</SPAN><SPAN
style="FONT-FAMILY: 宋体">色图，由于图象处理后有可能会产生不属于这</SPAN><SPAN
lang=EN-US>256</SPAN><SPAN
style="FONT-FAMILY: 宋体">种颜色的新颜色，就更麻烦了；这一点，今后你就会有深刻体会的。所以，做图象处理时，一般采用灰度图。为了将重点放在算法本身上，</SPAN><B><SPAN
style="FONT-FAMILY: 黑体">今后给出的程序如不做特殊说明，都是针对<SPAN
lang=EN-US>256级灰度图的。</SPAN></SPAN></B><SPAN
style="FONT-FAMILY: 宋体">其它颜色的情况，你可以自己想一想，把算法补全。</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN
style="FONT-FAMILY: 宋体">如果想得到一幅灰度图，可以使用</SPAN><SPAN lang=EN-US>Sea</SPAN><SPAN
style="FONT-FAMILY: 宋体">或者</SPAN><SPAN lang=EN-US>PhotoShop</SPAN><SPAN
style="FONT-FAMILY: 宋体">等软件提供的颜色转换功能将彩色图转换成灰度图。</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN
style="FONT-FAMILY: 宋体">好了，言归正传，下面给出</SPAN><SPAN
lang=EN-US>Translation</SPAN><SPAN
style="FONT-FAMILY: 宋体">的源代码。算法的思想是先将所有区域填成白色，然后找平移后显示区域的左上角点</SPAN><SPAN
lang=EN-US>(x<SUB>0</SUB>,y<SUB>0</SUB>) </SPAN><SPAN
style="FONT-FAMILY: 宋体">和右下角点</SPAN><SPAN
lang=EN-US>(x<SUB>1</SUB>,y<SUB>1</SUB>) </SPAN><SPAN
style="FONT-FAMILY: 宋体">，分几种情况进行处理。</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN style="FONT-FAMILY: 宋体">先看</SPAN><SPAN
lang=EN-US>x</SPAN><SPAN style="FONT-FAMILY: 宋体">方向</SPAN><SPAN
lang=EN-US>(width</SPAN><SPAN style="FONT-FAMILY: 宋体">指图象的宽度</SPAN><SPAN
lang=EN-US>)</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN lang=EN-US>(1)<SPAN
style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN><SPAN
lang=EN-US>t<SUB>x</SUB></SPAN><SPAN style="FONT-FAMILY: 宋体">≤</SPAN><SPAN
lang=EN-US>-width</SPAN><SPAN
style="FONT-FAMILY: 宋体">：很显然，图象完全移出了屏幕，不用做任何处理；</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN lang=EN-US>(2)<SPAN
style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN><SPAN
lang=EN-US>-width<tx</SPAN><SPAN style="FONT-FAMILY: 宋体">≤</SPAN><SPAN
lang=EN-US>0</SPAN><SPAN style="FONT-FAMILY: 宋体">：如图</SPAN><SPAN
lang=EN-US>2.5</SPAN><SPAN style="FONT-FAMILY: 宋体">所示。容易看出，图象区域的</SPAN><SPAN
lang=EN-US>x</SPAN><SPAN style="FONT-FAMILY: 宋体">范围从</SPAN><SPAN
lang=EN-US>0</SPAN><SPAN style="FONT-FAMILY: 宋体">到</SPAN><SPAN
lang=EN-US>width-|tx|,</SPAN><SPAN style="FONT-FAMILY: 宋体">对应原图的范围从</SPAN><SPAN
lang=EN-US>|tx|</SPAN><SPAN style="FONT-FAMILY: 宋体">到</SPAN><SPAN
lang=EN-US>width</SPAN><SPAN style="FONT-FAMILY: 宋体">；</SPAN></P>
<P class=a style="LINE-HEIGHT: 18pt"><SPAN lang=EN-US><IMG height=364
src="第2章 图象的几何变换.files/image018.jpg" width=397 v:shapes="_x0000_i1026">
</SPAN></P>
<P style="LINE-HEIGHT: 18pt; TEXT-ALIGN: center" align=center><B><SPAN
style="FONT-FAMILY: 宋体">图</SPAN>2.5 tx</B><B><SPAN
style="FONT-FAMILY: 宋体">≤</SPAN><SPAN lang=EN-US>0</SPAN></B><B><SPAN
style="FONT-FAMILY: 宋体">，</SPAN><SPAN lang=EN-US>ty</SPAN></B><B><SPAN
style="FONT-FAMILY: 宋体">≤</SPAN><SPAN lang=EN-US>0</SPAN></B><B><SPAN
style="FONT-FAMILY: 宋体">的情况</SPAN><SPAN lang=EN-US></SPAN></B></P>
<P style="LINE-HEIGHT: 18pt"><SPAN lang=EN-US>(3)<SPAN
style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN><SPAN
lang=EN-US>0< t<SUB>x</SUB> <width</SPAN><SPAN
style="FONT-FAMILY: 宋体">：如图</SPAN><SPAN lang=EN-US>2.6</SPAN><SPAN
style="FONT-FAMILY: 宋体">所示。容易看出，图象区域的</SPAN><SPAN lang=EN-US>x</SPAN><SPAN
style="FONT-FAMILY: 宋体">范围从</SPAN><SPAN lang=EN-US>t<SUB>x</SUB> </SPAN><SPAN
style="FONT-FAMILY: 宋体">到</SPAN><SPAN lang=EN-US>width</SPAN><SPAN
style="FONT-FAMILY: 宋体">，对应原图的范围从</SPAN><SPAN lang=EN-US>0</SPAN><SPAN
style="FONT-FAMILY: 宋体">到</SPAN><SPAN lang=EN-US>width - t<SUB>x
</SUB></SPAN><SPAN style="FONT-FAMILY: 宋体">；</SPAN></P>
<P class=a style="LINE-HEIGHT: 18pt"><SPAN lang=EN-US><IMG height=342
src="第2章 图象的几何变换.files/image020.jpg" width=417 v:shapes="_x0000_i1039">
</SPAN></P>
<P style="LINE-HEIGHT: 18pt; TEXT-ALIGN: center" align=center><B><SPAN
style="FONT-FAMILY: 宋体">图</SPAN>2.6 0<
tx<width</B><B><SPAN style="FONT-FAMILY: 宋体">，</SPAN><SPAN
lang=EN-US>0<ty<height</SPAN></B><B><SPAN
style="FONT-FAMILY: 宋体">的情况</SPAN><SPAN lang=EN-US></SPAN></B></P>
<P style="LINE-HEIGHT: 18pt"><SPAN lang=EN-US>(4)<SPAN
style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN><SPAN
lang=EN-US>t<SUB>x</SUB> </SPAN><SPAN style="FONT-FAMILY: 宋体">≥</SPAN><SPAN
lang=EN-US>width</SPAN><SPAN
style="FONT-FAMILY: 宋体">：很显然，图象完全移出了屏幕，不用做任何处理。</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN lang=EN-US>y</SPAN><SPAN
style="FONT-FAMILY: 宋体">方向是对应的</SPAN><SPAN lang=EN-US>(height</SPAN><SPAN
style="FONT-FAMILY: 宋体">表示图象的高度</SPAN><SPAN lang=EN-US>)</SPAN><SPAN
style="FONT-FAMILY: 宋体">：</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN lang=EN-US>(1)<SPAN
style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN><SPAN
lang=EN-US>t<SUB>y</SUB></SPAN><SPAN style="FONT-FAMILY: 宋体">≤</SPAN><SPAN
lang=EN-US>-height</SPAN><SPAN
style="FONT-FAMILY: 宋体">，图象完全移出了屏幕，不用做任何处理；</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN lang=EN-US>(2)<SPAN
style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN><SPAN
lang=EN-US>-height<t<SUB>y</SUB></SPAN><SPAN
style="FONT-FAMILY: 宋体">≤</SPAN><SPAN lang=EN-US>0</SPAN><SPAN
style="FONT-FAMILY: 宋体">，图象区域的</SPAN><SPAN lang=EN-US>y</SPAN><SPAN
style="FONT-FAMILY: 宋体">范围从</SPAN><SPAN lang=EN-US>0</SPAN><SPAN
style="FONT-FAMILY: 宋体">到</SPAN><SPAN
lang=EN-US>height-|t<SUB>y</SUB>|,</SPAN><SPAN
style="FONT-FAMILY: 宋体">对应原图的范围从</SPAN><SPAN
lang=EN-US>|t<SUB>y</SUB>|</SPAN><SPAN style="FONT-FAMILY: 宋体">到</SPAN><SPAN
lang=EN-US>height</SPAN><SPAN style="FONT-FAMILY: 宋体">；</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN lang=EN-US>(3)<SPAN
style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN><SPAN
lang=EN-US>0<t<SUB>y</SUB><height </SPAN><SPAN
style="FONT-FAMILY: 宋体">，图象区域的</SPAN><SPAN lang=EN-US>y</SPAN><SPAN
style="FONT-FAMILY: 宋体">范围从</SPAN><SPAN lang=EN-US>t<SUB>y</SUB></SPAN><SPAN
style="FONT-FAMILY: 宋体">到</SPAN><SPAN lang=EN-US>height,</SPAN><SPAN
style="FONT-FAMILY: 宋体">对应原图的范围从</SPAN><SPAN lang=EN-US>0</SPAN><SPAN
style="FONT-FAMILY: 宋体">到</SPAN><SPAN
lang=EN-US>height-t<SUB>y</SUB></SPAN><SPAN style="FONT-FAMILY: 宋体">；</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN lang=EN-US>(4)<SPAN
style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN><SPAN
lang=EN-US>t<SUB>y</SUB></SPAN><SPAN style="FONT-FAMILY: 宋体">≥</SPAN><SPAN
lang=EN-US>height</SPAN><SPAN
style="FONT-FAMILY: 宋体">，图象完全移出了屏幕，不用做任何处理。</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN
style="FONT-FAMILY: 宋体">这种做法利用了位图存储的连续性，即同一行的象素在内存中是相邻的。利用</SPAN><SPAN
lang=EN-US>memcpy</SPAN><SPAN style="FONT-FAMILY: 宋体">函数，从</SPAN><SPAN
lang=EN-US>(x<SUB>0</SUB>,y<SUB>0</SUB>)</SPAN><SPAN
style="FONT-FAMILY: 宋体">点开始，一次可以拷贝一整行</SPAN><SPAN lang=EN-US>(</SPAN><SPAN
style="FONT-FAMILY: 宋体">宽度为</SPAN><SPAN lang=EN-US>x<SUB>1</SUB></SPAN><SPAN
style="FONT-FAMILY: 宋体">－</SPAN><SPAN lang=EN-US>x<SUB>0</SUB>)</SPAN><SPAN
style="FONT-FAMILY: 宋体">，然后将内存指针移到</SPAN><SPAN
lang=EN-US>(x<SUB>0</SUB>,y<SUB>0</SUB>+1)</SPAN><SPAN
style="FONT-FAMILY: 宋体">处，拷贝下一行。这样拷贝</SPAN><SPAN
lang=EN-US>(y<SUB>1</SUB>-y<SUB>0</SUB>)</SPAN><SPAN
style="FONT-FAMILY: 宋体">行就完成了全部操作，避免了一个一个象素的计算，提高了效率。</SPAN><SPAN
lang=EN-US>Translation</SPAN><SPAN style="FONT-FAMILY: 宋体">的源代码如下：</SPAN></P>
<P style="LINE-HEIGHT: 18pt">int xOffset=0,yOffset=0;</P>
<P style="LINE-HEIGHT: 18pt"><SPAN lang=EN-US>BOOL Translation(HWND
hWnd)</SPAN></P>
<P style="LINE-HEIGHT: 18pt"><SPAN lang=EN-US>{</SPAN></P>
<P
style="LINE-HEIGHT: 18pt">DLGPROC
dlgInputBox = NULL;</P>
<P
style="LINE-HEIGHT: 18pt">DWORD
OffBits,BufSize;</P>
<P style="LINE-HEIGHT: 18pt">LPBITMAPINFOHEADER lpImgData;</P>
<P
style="LINE-HEIGHT: 18pt">LPSTR
lpPtr;</P>
<P
style="LINE-HEIGHT: 18pt">HLOCAL
hTempImgData;</P>
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