Best way to apply a function to each element of Mat (Android)

asked 2018-03-03 13:58:37 -0600

oralb
31 ●4

updated 2018-03-04 10:57:58 -0600

Hello,

I've seen the thread here with the same request but the two main answers were to use pointers and to use parallel methods. Neither are really available on the Android implementation of OpenCV.

What would be the fastest way to apply a function like sin(pi/k * element^2) on Android OpenCV and then insert that value into another matrix?

edit: related question: is it faster to collect elements in a Java array first and then insert all of them at once as a row instead of individually with .put()

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" is it faster to collect elements in a Java array first and then insert all of them at once " -- definitely !

berak ( 2018-03-04 10:59:20 -0600 )edit

@berak, confirming that you mean collect as a row right? Or can I collect all elements in some kind of multi-dimensional array and then do only one operation to stick it in to the matrix?

oralb ( 2018-03-04 11:40:14 -0600 )edit

I've just seen this answer which answers some of my questions

oralb ( 2018-03-04 11:43:45 -0600 )edit

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Is this get operation retrieving an entire row/column or just one element? Would I stick the .get() in a loop that iterates over each element, do my operation, and then stick back in? Additionally, how comes pixels is a byte array, is that what I should use or is it an example (because I thought my pixels matrix is just in doubles)? Sorry for so many questions

oralb ( 2018-03-04 11:39:19 -0600 )edit

"Is this get operation retrieving an entire row/column or just one element?" -- the whole image.

berak ( 2018-03-04 12:23:24 -0600 )edit

I've got it now, it gets the whole image starting from 0,0 and sticks it in the array. For my case I needed a double[] and was able to get and put. It's roughly 3x faster on a small matrix. Thanks!

oralb ( 2018-03-04 12:26:58 -0600 )edit

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Best way to apply a function to each element of Mat (Android)

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