Schlagwort-Archive: filter

Isolated vertical or horizontal lines in gel images are not jpg compression artifacts

I frequently find the PubPeer excuse of compression artifacts in doctored images.

So lets have a look at that issue using the jpegoptim (manpage) and also jpeginfo (manpage). These are the usual effects

  • Ringing – high contrast areas with waves
  • Contouring, Banding, Pposterisation – extreme brightness changes
  • Staircase noise – along curving edges
  • Blockiness in “busy” regions – may mimick duplications
  • Gibbs phenomenon – small highlighted area of large contrast
  • Alias, Moiré, frequent color/brightness change

Now let’s have a look at the compression artifacts in descending quality (BTW this also good exercise for the upcoming 125kB Content Upload Filter, I am therefore adding  filesize also)

 

original image 893kB

Isolated vertical or horizontal lines in gel images are not jpg compression artifacts weiterlesen