Sorry, should probably state what our final gs command is. Here is one (building a tif):
gs -q -dSAFER -dNOPAUSE -dBATCH -dPDFSETTINGS=/prepress -dDownsampleColorImages=false -dDownsampleGrayImages=false -dDownsampleMonoImages=false -dUseFlateCompression=true -dEmbedAllFonts=true -dSubsetFonts=true -dMonoImageFilter=/FlateEncode -dAutoFilterGrayImages=false -dGrayImageFilter=/FlateEncode -dAutoFilterColorImages=false -dColorImageFilter=/FlateEncode -dSCANCONVERTERTYPE=2 -dMaxBitmap=2147483647 -dUseFastColor=true -dTextAlphaBits=4 -sDEVICE=tiff24nc -sCompression=lzw -g800x500 -r200 -sOutputFile='bug_163.tif' -f'./psconvert_22623d.eps' > On Jan 22, 2018, at 8:06 PM, Paul Wessel <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 >
