I smoothed a grayscale image using a size 10 gaussian filter and display it in Octave (imshow) which resulted in ripples which appears to be contours for image intensity.


Yet if I save the image (imwrite), I get a proper smoothed image.(The ripple image above was taken as a screenshot.)

saved image

  • $\begingroup$ If what format are you saving the image? $\endgroup$
    – hotpaw2
    Jun 12, 2016 at 22:15
  • $\begingroup$ bmp, jpg produces the same result. $\endgroup$
    – Quevun
    Jun 12, 2016 at 22:23

1 Answer 1


My guess is that imshow, for some reason, has a lower color depth at which it displays greyscale images than your image viewer.

The contours are actually just the quantization steps of the lower number of shades displayable.


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