title: OpenCV - imread(), imwrite() increases the size of png?
body: <p>I wanted to try out some simple operations on files and I started with opening and saving files (I use Python)</p>
  
  <pre><code>image = cv2.imread("image.png")
  cv2.imwrite("image_processed.png", image)
  </code></pre>
  
  <p>After this operation my original <code>image</code> from 33kB transforms into the same looking 144kB image. </p>
  
  <p>I have tried doing something like this : <a href="http://opencv.itseez.com/modules/highgui/doc/reading_and_writing_images_and_video.html?highlight=imwrite#imwrite" rel="noreferrer">http://opencv.itseez.com/modules/highgui/doc/reading_and_writing_images_and_video.html?highlight=imwrite#imwrite</a></p>
  
  <pre><code>    params = list()
      params.append(cv.CV_IMWRITE_PNG_COMPRESSION)
      params.append(8)
  
      image = cv2.imread("image.png")
      cv2.imwrite("image_processed.png",image,params)
  </code></pre>
  
  <p>But this does not change much ( size decreased to 132kB )</p>
  
  <p>This is the image which I am working with:</p>
  
  <p><img src="https://i.stack.imgur.com/e4oLa.jpg" alt="enter image description here"></p>