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 > <mailto: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 >> <mailto: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 >> > >
