In pdfToolbox v11, callas introduced a new preflight technology called “Context aware object detection”. It’s special because it doesn’t just examine individual objects (“Is the resolution of this image high enough”, “Is this black text set to overprint”) but it checks relationships between objects.
Because of that, it can answer questions such as: “Is this object hidden by any other objects?” or, “Does this text come too close to the cut line?”. Very powerful and ideal to weed out the majority of false positives (things reported as errors while they’re actually fine) preflight engines tend to find.
However pdfToolbox 11 could not tell you whether an object came to close to another object. Why not? Because it would take too long!
In pdfToolbox 12, callas does introduce a proximity test, but there is a precaution built-in…
You can read more about this in an article by David van Driessche in the Callas blog.