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POHow to implement a part of histogram equalization in matlab without using for loops and influencing speed and performance
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copied!<p>Suppose that I have these Three variables in matlab <a href="http://www.4shared.com/rar/xUDqy8up/variables.html" rel="nofollow">Variables</a><br> I want to extract diverse values in NewGrayLevels and sum rows of OldHistogram that are in the same rows as one diverse value is.<br> For example you see in NewGrayLevels that the six first rows are equal to zero. It means that 0 in the NewGrayLevels has taken its value from (0 1 2 3 4 5) of OldGrayLevels. So the corresponding rows in OldHistogram should be summed.<br> So 0+2+12+38+113+163=328 would be the frequency of the gray level 0 in the equalized histogram and so on.<br> Those who are familiar with image processing know that it's part of the histogram equalization algorithm.<br> Note that I don't want to use built-in function "histeq" available in image processing toolbox and I want to implement it myself.<br> I know how to write the algorithm with for loops. I'm seeking if there is a faster way without using for loops.<br> The code using for loops: </p> <pre><code> for k=0:255 Condition = NewGrayLevels==k; ConditionMultiplied = Condition.*OldHistogram; NewHistogram(k+1,1) = sum(ConditionMultiplied); end </code></pre> <p>I'm afraid if this code gets slow for high resolution big images.Because the variables that I have uploaded are for a small image downloaded from the internet but my code may be used for sattellite images. </p>

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