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closed curved path without doubling start/end point

Forum|Forum|4 years ago
August 12, 2021
2 replies
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Is it possible to make a closed path (curved, no straight lines) in pure PostScript without having two equal points at start/end? I can contruct this easily in Illustrator clicking the last point onto the start point and dragging the handles, but I didn't find a way to realize it in code.

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Correct answer Brad @ Roaring Mouse

Ahh, okay.. so here's the thing:

There's always 3 points involved; Your starting location, your second location, then the third location. It doesn't matter if it's the same position, it's still a third position.

In the simple Postscript you are using, it doesn't KNOW you want to join the first and third position as a common control point; a closepath will ALWAYS add a line segment between the first and last positions.

Even the Illustrator shape is technically 3 points, but Illustrator (and Illustrator's procset dictionary) is defining what to do with that common point, so it requires the dictionary to decode it in the program.

When the postscript is sent to a printer, it's still 3 positions with an implied closepath which you don't see.

Brad @ Roaring Mouse

Community Expert

Where are you seeing the result as 3 points?

Basically, it should be as simple as:

starting Point A (x1,y1) (move to)

Point B x2,y2 (curve to)

Point A x1,y1 (curve to)

then close it (close path)

gengAuthor

Participant

After moveto, curveto, curveto there a three points, regardless of a closepath, last point sitting on top of the first one.

Open this text (file) in Illustrator

%!PS-Adobe-2.0 EPSF-1.2
%%BoundingBox: 0 0 400 400
100 200 moveto
120 280 240 260 280 160 curveto 
320 60 80 120 100 200 curveto closepath stroke

Select left point, drag it away, and you can see it: three points.

T

Test Screen Name

Legend

SO you are trying to test how PostScript works by importing it to Illustrator? Seems to me you could be seeing a limitation of Illustrator's import.

T

Test Screen Name

Legend

To close a path in PostScript use "closepath". Just returning to the starting point does not close the path, however, for filling operations closure is assumed.

gengAuthor

Participant

Without returning to the starting point (last point some distance away from start point), closepath will connect the last point with the start point by a straight line (not what I want).

What I need is a curveto to the same location as the starting point. In that case, closepath connects these points (end on top of start) with a straight line (lenght zero), leaving two same points. Doing the same in Illustrator, I get one less point:

The picture shows the result in Illustrator: A closed curved path with only two points.

My question is how to achieve this with pure PostScript code. But after the second curveto, followed by a closepath I get a path with three points.

Brad @ Roaring Mouse

Correct answer

Community Expert

Ahh, okay.. so here's the thing:

There's always 3 points involved; Your starting location, your second location, then the third location. It doesn't matter if it's the same position, it's still a third position.

In the simple Postscript you are using, it doesn't KNOW you want to join the first and third position as a common control point; a closepath will ALWAYS add a line segment between the first and last positions.

Even the Illustrator shape is technically 3 points, but Illustrator (and Illustrator's procset dictionary) is defining what to do with that common point, so it requires the dictionary to decode it in the program.

When the postscript is sent to a printer, it's still 3 positions with an implied closepath which you don't see.

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