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Edge detect code gives different outputs

Posted 9 months ago
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I have often noticed that examples of the past when done in newer versions of Mathematica generate inconsistent results. A prime example related to the following post (Character edge finding):

pic = Thinning@Binarize[GradientFilter[Rasterize[Style["\[Euro]", 
FontFamily -> "Times"], ImageSize -> 200] // Image, 1]]; 
pdata = Position[ImageData[pic], 1];
lcp = ListCurvePathPlot[pdata];

This simple piece of code gives different results in Mathematica 9.0, 10.4 and 11.2 with default options. I have posted the results on StackExchange (click the link to see).

Note: this is not the only example where I have seen differences.

To the WRI quality assurance department: Can you kindly check why similar functions do not behave the same across different versions ?? I think it is more crucial to establish whether the built-in functions are working properly rather than releasing more and more functions without appropriate checks.

2 Replies

I would guess that Rasterize would be the culprit here… try applying your functions on the same image…


My guess is that the function FindCurvePath and friends never has been very satisfying. This has been reported for earlier versions, and maybe WR is working on it - which might explain the difference in behavior. I would rather use FindShortestTour instead:

pic = Thinning@Binarize[EdgeDetect[Rasterize@Style["\[Euro]", FontFamily -> "Times", 500]]];

Or much better (and without discrepancy to earlier versions! - because there was no ImageMesh ...):

rEur = ColorNegate@Rasterize@Style["\[Euro]", FontFamily -> "Times", 500];
eurLines = MeshPrimitives[ImageMesh[rEur], 1];

In general I think that WR must have the chance of improving things - which will necessarily result in changes of behavior depending on versions.

Regards -- Henrik

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