title: Android OpenCV optimization - line detection is slow Hough Lines
body: <p>in my project I need to detect lines in image. I actually have to detect rows and columns inside rectangle. I use OpenCV to accomplish this. I have done it succesfuly but it's kinda slow. I use many functions to preprocess the image - e.g. thresholding, canny, dilation, gaussian blur etc.</p>
  
  <p>I use HoughLines like this </p>
  
  <pre><code>Imgproc.HoughLines(image, lines, 1, Math.PI/90 , threshold, minLineSize, maxGap);
  </code></pre>
  
  <p>It takes about 2.5 s to complete my program which has ~ 600 lines. But on this one line it takes 2.2 s. As you can see I use Java interface for OpenCV. Is it possible to optimize it someway? Would rewriting my program to NDK make it faster? If I understand OpenCV4Android, than it's just wrapper for functions written in NDK, so I don't think it would be faster. Or is there better and faster approach to detect lines in image? Thanks for any advice. </p>