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<HEAD><TITLE>CS 664: Problem Set 2</TITLE></HEAD><BODY><h1> CS 664: Problem Set 2 : Motion and Snakes </h1>A postscript copy of the <a href="ps2/ps2.ps">assignment</a>.<p> <dt><b>New Test Images.</b> Here is another set of <ahref="ps2/test2.tgz">images</a>, with corresponding squared-gradient magnitudeimage. Be sure to read mini-FAQ below. I've also recomputed the coke-canimage, there seemed to be problems with its sg image. These images are alsoavailable in ~jmiller/test2 on the cs and sunlab machines. I would prefer thatyou just create symbolic links to the images if you can, since they exceed3MB. "ln -s ~jmiller/test2 ."<p><dt><b>Test Images.</b> Here is the first set of images, available ina <a href="ps2/test.tar.gz">tar file</a>. There are two sets ofstereo images that you can use to test your motion calculations.There is a sequence called dots that is a moving box on a randombackground. There is also the coke-can images along with the dx,dy,and squared gradient magnitude images for the coke can. You can usethe squared gradient magnitude image as a simple external energy fieldfor snakes that are attracted to edges.<p>For you Sun users on the cs filesystems, feel free to use ~robotlab/bin/drawsnake or markpoints to draw your initial snakes. (Also available on the sunlab in ~jmiller/664/ps2).<h3>Problem Set 2: MINI-FAQ</h3><UL> <li> <em>Mask for census transform.</em> <br><pre>/* ShortImage census_transform(GrayImage inim) * * Performs the census_transform using the following 7x7 mask * approximation. * - - x - - - - (2,0) * - x - x - x - (1,1) (3,1) (5,1) * - - x - x - x (2,2) (4,2) (6,2) * x - x P - x - (0,3) (2,3) (5,3) * - x - x - x - (1,4) (3,4) (5,4) * - - x - x - - (2,5) (4,5) * - - - x - - - (3,6) * * Input: a pgm image * Output: a ShortInt image containing the census transform of the * input, representing each comparison using on bit.*/</pre><li> There are a few typos in the Chandran et al. paper. In algorithm II, theline "if(temp < Si(<em>j</em>)" should be "if(temp < Si(<em>k</em>)". Theyalso get the order of growth for the algorithm wrong.<li> There is no need to "perturb" the point as described in Algorithm III,step 3. The correct approach is to take a set of point positions , run algorithm II,and using the output set of point positions from alg. II, feed it into alg. IIagain. Do this until the energy stops decreasing.<li> I've just been shown the error of my ways. There is a way to dynamicallyprogram normalized correlation. The solution is very cute, I'm not going togive any hints. This goes beyond just precomputing the means and averagesusing sliding-sums.<li> The squared gradient images I have given you are images smoothed with agaussian mask (sigma = 2.0). Note that the squared gradient is highest atedges, your energy function needs to be lowest at edges for the snake to beattracted to edges. Simply negating the image will work.</UL><h3>Using the ADT image libraries</h3> The following versions of the library are available<ul><li> SunOS<ul> <li>available on the cs dept machines as ~robotlab/new/lib/libadt.a, with the appropriate header files in ~robotlab/new/include/adt/ . <b>USE -DSUNOS on your command line</b>.<li>Sunlab: located in ~jmiller/664/libadt.a, with header files in ~jmiller/664/include. <li>Other locations: <a href="ps1/libadt.a">library</a> and <a href="ps1/adt-include.tgz">header files</a>.</ul><li> Solaris<ul><li>available on the cs dept machines as~robotlab/new/lib/libadt-svr4.a, with the appropriate header files in~robotlab/new/include/adt/ , <b>be sure to include -DSVR4 on your commandline</b>.<li>Sunlab: you won't need the Solaris version.<li>Other locations: <a href="ps1/libadt-svr4.a">library</a> and <a href="ps1/adt-include.tgz">header files</a>.</ul><li>Linux: Here is the (ELF) <a href="ps1/libadt-linux.a">library</a>and a tarfile containing the <a href="ps1/includes.tgz">header files</a>.<li> <a href="http://www.tc.cornell.edu/~ckline/lib-adt-aix3.2.5.tar.gz">AIX 3.2.5</a> (thanks to Christoper Kline), here is a <a href="ps1/ckline.txt">copy</a> of the email he sent me.</ul>⌨️ 快捷键说明
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