Need the correct word for a shape transformation
May 24, 2024 5:28 AM Subscribe
If I draw an outline around a shape and delete the original shape, what have I achieved? I’ve been saying “embiggened” but I’m pretty sure that’s not right.
(To head off any confusion, this is different from scaling. Any concave parts of the shape are going to end up smaller, not bigger.)
(To head off any confusion, this is different from scaling. Any concave parts of the shape are going to end up smaller, not bigger.)
Best answer: The computational geometry / geospatial jargon for this operation is "buffer". E.g. "buffer the polygon by a radius of 10 meters". you can also use a negative buffer radius.
Buffering a shape by a radius of +10 and then buffering the result by a radius of -10 may not produce the original shape. E.g. buffering a "pretzel" with 1m radius pretzel holes using a buffer radius of +2m will fill in the holes. Then buffering the result by -2m will give you something pretzel-ish (perhaps a little rounded) with no holes.
In practical geospatial/geometry processing applications this can be quite a handy trick to fill in holes or eliminate fine hairline cracks between 2d polygons that you want to be joined together as hole-free solids.
The PostGIS documentation page for ST_Buffer has some examples -- this is 2D computational geometry so it is focused on polygons, but theoretically you could buffer any shape described by any set of points in N dimensional space.
If you want a precise mathematical definition
> The buffer of a geometry is defined as the Minkowski sum (or difference, for negative distance) of the geometry with a circle with radius equal to the absolute value of the buffer distance.
c/o- the python shapely library documentation for the buffer operation
posted by are-coral-made at 5:38 AM on May 24, 2024 [10 favorites]
Buffering a shape by a radius of +10 and then buffering the result by a radius of -10 may not produce the original shape. E.g. buffering a "pretzel" with 1m radius pretzel holes using a buffer radius of +2m will fill in the holes. Then buffering the result by -2m will give you something pretzel-ish (perhaps a little rounded) with no holes.
In practical geospatial/geometry processing applications this can be quite a handy trick to fill in holes or eliminate fine hairline cracks between 2d polygons that you want to be joined together as hole-free solids.
The PostGIS documentation page for ST_Buffer has some examples -- this is 2D computational geometry so it is focused on polygons, but theoretically you could buffer any shape described by any set of points in N dimensional space.
If you want a precise mathematical definition
> The buffer of a geometry is defined as the Minkowski sum (or difference, for negative distance) of the geometry with a circle with radius equal to the absolute value of the buffer distance.
c/o- the python shapely library documentation for the buffer operation
posted by are-coral-made at 5:38 AM on May 24, 2024 [10 favorites]
Best answer: In image processing this is called dilation.
In typography it's called a stroke.
posted by AzraelBrown at 6:41 AM on May 24, 2024 [3 favorites]
In typography it's called a stroke.
posted by AzraelBrown at 6:41 AM on May 24, 2024 [3 favorites]
I’m not familiar with any of the technical terms people have quoted. As a native English speaker I would just say you “enlarged” the shape, or maybe that “”expanded” it.
(On preview, it’s kind of cool how similar “enlarged” is to “embiggened”.)
posted by Winnie the Proust at 6:51 AM on May 24, 2024 [1 favorite]
(On preview, it’s kind of cool how similar “enlarged” is to “embiggened”.)
posted by Winnie the Proust at 6:51 AM on May 24, 2024 [1 favorite]
buffer of a geometry is defined as the Minkowski sum
"Voronoi diagram is a partition of a plane into regions"
posted by HearHere at 7:17 AM on May 24, 2024
"Voronoi diagram is a partition of a plane into regions"
posted by HearHere at 7:17 AM on May 24, 2024
On preview, it’s kind of cool how similar “enlarged” is to “embiggened”
"Embiggened" is a made-up word from The Simpsons, meant to sound like a weird local slang variant.
I would be tempted to say "extrapolated" but that's me being poetic and not technical.
posted by praemunire at 7:27 AM on May 24, 2024 [1 favorite]
"Embiggened" is a made-up word from The Simpsons, meant to sound like a weird local slang variant.
I would be tempted to say "extrapolated" but that's me being poetic and not technical.
posted by praemunire at 7:27 AM on May 24, 2024 [1 favorite]
In Photoshop, the feather option - part of “refine edges” - is a little similar. It embiggens fuzzily.
posted by rongorongo at 9:23 AM on May 24, 2024
posted by rongorongo at 9:23 AM on May 24, 2024
Best answer: In print design, that's a stroke and then a knockout.
posted by wenestvedt at 10:03 AM on May 24, 2024
posted by wenestvedt at 10:03 AM on May 24, 2024
I'd also call it "adding padding" to the outside shape.
posted by hydra77 at 11:40 AM on May 24, 2024
posted by hydra77 at 11:40 AM on May 24, 2024
Best answer: "Expansion" is used for this in spatial data processing while also making sense to the non-specialist.
posted by away for regrooving at 12:58 PM on May 24, 2024 [1 favorite]
posted by away for regrooving at 12:58 PM on May 24, 2024 [1 favorite]
In case you want to see a mathematician's musings on this operation: The Mathematics of Doodling by Ravi Vakil
posted by aws17576 at 10:13 PM on May 24, 2024
posted by aws17576 at 10:13 PM on May 24, 2024
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