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POAn integer [0,4095] 12bits to a tuble{A,B,C} the fastest way in c++
 

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  1. POAn integer [0,4095] 12bits to a tuble{A,B,C} the fastest way in c++
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    <p>Intput: An integer [0,4095] 12bits.<br> Output: A tuble of {A,B,C} all [0,255]</p> <p>The A,B,C are given as 0 to 255, where 255 maps to 15 in the 4 bits. Reason are that I want to construct a Color struct having RGB defined from 0 to 255.</p> <p>I assume the solution to be something like bit shifting the input to extract the 3 sets of 4bits and then multiply by 17 as (255/15 | 15 = 1111(binary)).</p> <p>How would you compute this fastest?</p> <p>my own solution:</p> <pre><code>QColor mycolor(int value) { if(value &gt; 0xFFF) value = 0xFFF; int a=0,b=0,c=0; a = (value &amp; 0xF) * 17; b = ((value&amp;(0xF&lt;&lt;4))&gt;&gt;4) *17; c = ((value&amp;(0xF&lt;&lt;8))&gt;&gt;8) *17; return QColor(c,b,a); } cv::Mat cv_image(10,10,CV_16U,cv::Scalar::all(1)); QImage image(cv_image.data, 10,10,QImage::Format_RGB444); QPainter p(&amp;image); p.setPen(mycolor(255)); p.drawLine(0,0,9,0); p.setPen(mycolor(4095)); p.drawLine(0,1,9,1); p.setPen(mycolor(0)); p.drawLine(0,2,9,2); p.setPen(mycolor(10000)); p.drawLine(0,3,9,3); ********* Start testing of Test1 ********* Config: Using QTest library 4.7.4, Qt 4.7.4 PASS : Test1::initTestCase() [255, 255, 255, 255, 255, 255, 255, 255, 255, 255; 4095, 4095, 4095, 4095, 4095, 4095, 4095, 4095, 4095, 4095; 0, 0, 0, 0, 0, 0, 0, 0, 0, 0; 4095, 4095, 4095, 4095, 4095, 4095, 4095, 4095, 4095, 4095; 1, 1, 1, 1, 1, 1, 1, 1, 1, 1; 1, 1, 1, 1, 1, 1, 1, 1, 1, 1; 1, 1, 1, 1, 1, 1, 1, 1, 1, 1; 1, 1, 1, 1, 1, 1, 1, 1, 1, 1; 1, 1, 1, 1, 1, 1, 1, 1, 1, 1; 1, 1, 1, 1, 1, 1, 1, 1, 1, 1] PASS : Test1::test1() </code></pre>
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    1. USPoul K. Sørensen
    1. USPoul K. Sørensen
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    1. CO12 bits and not 16.
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      1. POAn integer [0,4095] 12bits to a tuble{A,B,C} the fastest way in c++
      1. USPoul K. Sørensen
 

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