Seems resolution independent; I've tried up to 4K. Here is a 2000x1250 MP4 movie, just showing the text HELL. It is especially noticeable for angles 20-30.
www.soest.hawaii.edu/pwessel/bug.mp4 <http://www.soest.hawaii.edu/pwessel/bug_200.mp4> > On Jan 23, 2018, at 5:59 AM, Bradley C. Kuszmaul <kuszm...@gmail.com> wrote: > > It looks like even the straight lines and circles have jaggies, and your > jittering looks like it's just jaggies spread across the time domain. I > don't think you can expect it to look good at such low resolution without > taking a lot more care about anti-aliasing. Can you increase the resolution? > > Bradley C Kuszmaul - via snartphone > > On Jan 22, 2018 10:06 PM, "Paul Wessel" <pwes...@hawaii.edu > <mailto:pwes...@hawaii.edu>> wrote: > Hi developers- > > GMT (gmt.soest.hawaii.edu <http://gmt.soest.hawaii.edu/>) is using PostScript > to make plots and one application builds an animation from sequences of > PostScript plots converted to PNG with ghostscript (9.22) and then to MP4 > with ffmpeg. We have found a problem that may be a ghostscript bug, or > alternatively we are doing something wrong. When using a perspective view > (i.e., using a matrix concatenation to simulate perspective), the resulting > oblique text strings "jitter" when viewed as a movie. For an example, see > www.soest.hawaii.edu/pwessel/bug_200.mp4 > <http://www.soest.hawaii.edu/pwessel/bug_200.mp4>. As the movie plays, you > will see the INDIVIDUAL letters in the word HELL jitter relative to each > other, despite being set via a single show command (here just a snippet of > our code; setting currentpoint, font etc are omitted here) > > (HELL) dup dup stringwidth pop -2 div exch sh -2 div rmoveto show > > where sh is defined as > > /sh {gsave matrix setmatrix 0 0 moveto true charpath flattenpath pathbbox > newpath 4 1 roll pop pop pop grestore} bind def > > [a complete PS example of a single frame can be found here: > www.soest.hawaii.edu/pwessel/bug.ps > <http://www.soest.hawaii.edu/pwessel/bug.ps>. > > At first we suspected flattenpath but HELL (using Helvetica) has no curved > segments (?). We also tried to override the flattening with 0.2 setflat, but > no difference. We suspect some sort of roundoff but it affects the different > letters in the word differently, and that is not under our control. Could > any of the operators above be subject to round-off that affect individual > letters? > > Perhaps developers know where this may happen and if there is anything we can > do on our side to remedy the problem. As you can see there is no jittering > for plotting a circle or lines. The map frame annotations show the same > jittering so it affects all text. > > Thanks for any insight! We can provide more details, all individual PS > files, etc upon request. FYI, we have tried both tif and jpg instead of png > but no difference. We also made PDFs and used OS X Automator to build PNGs > and made a movie using QuickTime Pro; same jittering (not sure if OS X High > Sierra uses ghostscript in Preview etc). > > Paul Wessel > Lead developer > The Generic Mapping Tools >
