title: OpenCV from Python shows different results for JPG and PNG images?
body: <p>I have been working to create an OMR bubble sheet scanner using OpenCV from Python.</p>
  
  <p>I have created the bubble-sheets (using OpenCV) in PNG format. </p>
  
  <p>Then I am using OpenCV to read those files. <strong>OpenCV does a perfect job on PNG images, it works perfectly.... but when I use this on JPG files, <em>it simply doesn't! Lists running out of indexes because it cannot detect all the proper contours.</em></strong></p>
  
  <p>I know this doesn't make sense, but I tried saving the same PNG image directly into JPG (using Paint), and the same results. It works on PNG version, but doesn't work on JPG version. It also shows a different number of contours in the images even the images are exact same.</p>
  
  <p>Any help regarding this would be greatly appreciated, thanks!</p>