clipRect 介绍

    <span lang="EN-US">android</span>的<span lang="EN-US">clip</span>有以下两点疑问：


<p class="MsoListParagraph"><span><span lang="EN-US">Clip</span>中的<span lang="EN-US">Op</span>的参数的意思。</span>

<p class="MsoNormal"><span>通常咱们理解的<span lang="EN-US">clip(</span>剪切<span lang="EN-US">)</span>，是对已经存在的图形进行<span lang="EN-US">clip</span>的。但是，在<span lang="EN-US">android</span>上是对<span lang="EN-US">canvas</span>（画布）上进行<span lang="EN-US">clip</span>的，要在画图之前对<span lang="EN-US">canvas</span>进行<span lang="EN-US">clip</span>，如果画图之后再对<span lang="EN-US">canvas</span>进行<span lang="EN-US">clip</span>不会影响到已经画好的图形。一定要记住<span lang="EN-US">clip</span>是针对<span lang="EN-US">canvas</span>而非图形。</span>

<p class="MsoNormal"><span>接下来通过<span lang="EN-US">android</span>自带的<span lang="EN-US">APIdemo Clipping</span>例子详细讲述<span lang="EN-US">Clip</span>中的<span lang="EN-US">Op</span>的参数的意思。<span lang="EN-US">Android</span>提供<span lang="EN-US">clipRect</span>、<span lang="EN-US">clipPath</span>和<span lang="EN-US">clipRegion</span>剪切区域的<span lang="EN-US">API</span>。</span>

DIFFERENCE,INTERSECT,UNION,XOR, REVERSE_DIFFERENCE, REPLACE</span>六种选择。</span>[/b]

<p class="MsoNormal"><span>例子<span lang="EN-US">:</span></span>

<p class="MsoListParagraph"><span>在<span lang="EN-US">canvas</span>上剪切从<span lang="EN-US">(40,40)</span>到<span lang="EN-US">(100,100)</span>的方块。下图橄榄色区域加紫色区域。</span>


<br><img src="http://dl.iteye.com/upload/attachment/598940/ef58b990-9ff0-3c74-836f-743595ba4879.bmp" alt=""><br>?<span><br></span>

<p class="MsoNormal"><span>先在第二方块上加上<span lang="EN-US">Op</span>参数例如：<span lang="EN-US">canvas.clipRect(40, 40, 100, 100, Region.Op. DIFFERENCE);</span></span>

<p class="MsoNormal"><span><span lang="EN-US">Op</span>参数针对的对象是之前剪切的区域以及当前要剪切的区域。</span>

<p class="MsoNormal"><span>那有哪些含义呢？就是表示当前要剪切的区域与之前剪切过的之间的关系。</span>

<p class="MsoNormal"><span><span lang="EN-US">DIFFERENCE</span>：之前剪切过除去当前要剪切的区域（蓝色区域）。</span>

<p class="MsoNormal"><span><span lang="EN-US">UNION</span>：当前要剪切的区域加上之前剪切过内部的部分（蓝色区域<span lang="EN-US">+</span>紫色区域<span lang="EN-US">+</span>橄榄色区域）。</span>

<p class="MsoNormal"><span><span lang="EN-US">REVERSE_DIFFERENCE</span>：与<span lang="EN-US">DIFFERENCE</span>相反，以当前要剪切的区域为参照物，当前要剪切的区域除去之前剪切过的区域<span lang="EN-US">(</span>橄榄色区域<span lang="EN-US">);</span></span>

<p class="MsoNormal"><span>没带<span lang="EN-US">Op</span>参数效果与<span lang="EN-US">INTERSECT</span>的效果一样，两个区域的交集。</span>
 
   
     
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