image processing - OpenCV Histogram Comparison Methods -


looking @ histogram documentation, there 4(5) different comparison methods:

  1. cv_comp_correl correlation
  2. cv_comp_chisqr chi-square
  3. cv_comp_intersect intersection
  4. cv_comp_bhattacharyya bhattacharyya distance
  5. cv_comp_hellinger synonym for cv_comp_bhattacharyya

they give different outputs read differently shown in compare histogram documentation. can't find states how each method performs compared against each other. surely there pros , cons each method, otherwise why have multiple methods?

even opencv 2 computer vision application programming cookbook has little on differnces:

the call cv::comparehist straightforward. input 2 histograms , function returns measured distance. specific measurement method want use specified using flag. in imagecomparator class, intersection method used (with flag cv_comp_intersect). method compares, each bin, 2 values in each histogram, , keeps minimum one. similarity measure sum of these minimum values. consequently, 2 images having histograms no colors in common intersection value of 0, while 2 identical histograms value equal total number of pixels.

the other methods available chi-square (flag cv_comp_chisqr) sums normalized square difference between bins, correlation method (flag cv_comp_correl) based on normalized cross-correlation operator used in signal processing measure similarity between 2 signals, , bhattacharyya measure (flag cv_comp_bhattacharyya) used in statistics estimate similarity between 2 probabilistic distributions.

there must differences between methods, question they? , under circumstances work best?

cv_comp_intersect fast compute since need minimum value each bin. not tell distribution of differences. other methods try achieve better , more continuous score match, under different assumptions pixel distribution.

you can find formulae used in different methods, at

http://docs.opencv.org/doc/tutorials/imgproc/histograms/histogram_comparison/histogram_comparison.html

some references more details on matching algorithms can found at:

http://siri.lmao.sk/fiit/dso/prednasky/7%20a%20histogram%20based%20methods/7%20a%20histogram%20based%20methods.pdf


Comments

Post a Comment

Popular posts from this blog

c++ - Difference between pre and post decrement in recursive function argument -

i have following sample code used pre-decrement void function(int c) { if(c == 0) { return; } else { cout << "dp" << c << endl; function(--c); cout << c << endl; return; } } this function give output input 4 : dp3 dp2 dp1 dp0 0 1 2 3 but when use post decrement void function(int c) { if(c == 0) { return; } else { cout << "dp" << c << endl; function(c--); cout << c << endl; return; } } output goes in infinite loop dp4 can explain me in detail why happens ? this happens because function(c--) called same value of c , when finishes c decremented. recursively called, hence called same value no chance of return , hit stack overflow error. assume this, int x = 1, y = 0; y = x++ result y == 1 , x == 2. if y = ++x , bot x , y 2.
Read more

php - Nothing but 'run(); ' when browsing to my local project, how do I fix this? -

i added new project. made mistake in projectname.conf file in sites-available apache2, led me reinstalling apache2. after reinstalling , re-enabling projects on every page of every project .. <body> run(); </body> .. i've run composer update, restarted service, restarted pc, checked config files, tried disabling new project. there nothing in error log, , access.log: 127.0.0.1 - - [15/may/2015:01:40:47 +0200] "get / http/1.1" 304 181 "-" "mozilla/5.0 (x11; ubuntu; linux x86_64; rv:38.0) gecko/20100101 firefox/38.0" maybe i'm forgetting apache2 reinstall? don't think did different last time installed it. looks haven't setup php correctly. take @ this great guide , maybe you're forgetting link php config apache2.
Read more

php - How can I echo out this array? -

i don't know how go grabbing data in variable , put foreach loop. class tree{ private $info = array( array('name'=>'jim','state'=>'nu','company'=>'nu','phone'=>array('cell'=>'5615111111','office'=>'5611111111'),'email'=>array('primary'=>'exs@example.com','ex@there.com')), array('name'=>'joe smith','city'=>'phoenix','phone'=>'4805551111','email'=>'jsmith@some_email.com'), array('name'=>'john doe','city'=>'chandler','company'=>'doe co.','email'=>array('jdoe@gmail.com','personal'=>'email@email.com'),'phone'=>'6025550002') ); } if you're inside of class, can access private variable using $this->variablename . example, i...
Read more