I downloaded the file and asked vlc what's the resolution. I can still see the jaggies on the lines. That's probably all I know about your problem. Maybe by looking at two adjacent frames in PostScript, one could learn more.
Bradley C Kuszmaul - via snartphone On Jan 23, 2018 4:53 PM, "Paul Wessel" <pwes...@hawaii.edu> wrote: > Quicktime says it is 2000x1250 and that is indeed the frame PNG dimensions > - perhaps you are viewing it in a browser which shows it to be smaller. in > my browser it looks much smaller as well. > Anyway, we are trying to quantify if indeed it is -/+1 pixel which makes > sense in terms of rounding. I thought the anti-aliasing settings would add > the gray to nearby pixels to simulate the sub-pixeling but that does not > seem to happen on the projected tex [it does happen on other text that we > have examined]. > > Paul > > > On Jan 23, 2018, at 2:00 PM, Bradley C. Kuszmaul <kuszm...@gmail.com> > wrote: > > This video is only 800x500, and the jitter's amplitude appears to be one > pixel. > > On Tue, Jan 23, 2018 at 3:52 PM, Paul Wessel <pwes...@hawaii.edu> wrote: > >> 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> wrote: >> >>> Hi developers- >>> >>> GMT (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. 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. >>> >>> 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 >>> >>> >> > >
