Display Bug

*To*: mathgroup at smc.vnet.net*Subject*: [mg22383] Display Bug*From*: me at talmanl1.mscd.edu*Date*: Sat, 26 Feb 2000 22:05:12 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Readers of this list may be interested in the fact that Mathematica's v3/4 Display operator is buggy. When the operator is used to write a graphics object to non-vector graphics formats (GIF in particular) it does not treat the Thickness directive correctly. This can be seen by first using SetDirectory to define a convenient file path and then executing Show[Graphics[{Thickness[0.03], Map[Line, Table[{{0,0},{Cos[t],Sin[t]}}, {t, 0, 15 Pi/8, Pi/8}]]}], AspectRatio->Automatic, DisplayFunction -> ((Display["MyFile.GIF", #, "GIF"]; #)&)] Import["Myfile.GIF"] Show[%] The appearance of the resulting "spoked wheel" seems to suffer from a peculiar kind of astigmatism. That the defect is in the Display operator is evident from two circumstances: 1.) The same distortion is evident in the GIF if we view it using some piece of software other than Mathematica 2.) Version 4.0's Export operator does not exhibit this behavior. When I informed WRI of this anomaly, their response was that, indeed, "Export" is the preferred manner of exporting graphics. It should be noted that Export is considerably slower than Display, and that Display does not seem to malfunction when applied to a graphic whose construction does not involve the Thickness directive. I discovered this behavior while preparing some of the QuickTime animations that now reside at http://clem.mscd.edu/~talmanl/MathAnim.html and which may be of interest to some of the readers of this list. --Lou Talman Department of Mathematical & Computer Sciences Metropolitan State College of Denver Campus Box 38 PO Box 173362 Denver CO 80217-3362 http://clem.mscd.edu/~talmanl