title: Is there any reverse operation to (image) gradient?
body: <p>Suppose I have calculated gradient (of a grayscale image). </p>
  
  <p>Gradient is a difference between neighboring pixels in X and Y directions.</p>
  
  <p>Can I calculate image back, having this gradient information? </p>
  
  <p>Can I filter gradient data somehow so that reverse operation give some reasonable results?</p>