Changes

[[File:lighterstill.jpg]][[File:Superimposition.jpg|right|frame]]

[[File:lighterstill.jpg]][[File:Superimposition.jpg|right|frame]]

*Date: [http://www.wikipedia.org/wiki/18th_Century 1794]

*Date: [https://www.wikipedia.org/wiki/18th_Century 1794]

==Definition==

==Definition==

*to place or lay over or above something <superimposed images>

*to place or lay over or above something <superimposed images>

In graphics, '''superimposition''' is the placement of an image or video on top of an already-existing image or video, usually to add to the overall image [[effect]], but also sometimes to conceal something (such as when a [[different]] face is superimposed over the [[original]] face in a photograph).

In graphics, '''superimposition''' is the placement of an image or video on top of an already-existing image or video, usually to add to the overall image [[effect]], but also sometimes to conceal something (such as when a [[different]] face is superimposed over the [[original]] face in a photograph).

This [[technique]] is used in [http://www.wikipedia.org/wiki/Cartography cartography] to produce photomaps by superimposing grid lines, contour lines and other [[linear]] or [[textual]] mapping features over aerial photographs.

This [[technique]] is used in [https://www.wikipedia.org/wiki/Cartography cartography] to produce photomaps by superimposing grid lines, contour lines and other [[linear]] or [[textual]] mapping features over aerial photographs.

Superimposition of 2D images containing correlated periodic grid structures may produce [http://en.wikipedia.org/wiki/Moir%C3%A9_pattern moiré patterns]. Superimposition of two correlated layers comprising [[parallel]] lines or curves may give rise [http://en.wikipedia.org/wiki/Line_moir%C3%A9 line moiré] patterns. The movement of one of the layers results in a faster movement of the line moiré superimposition image. Such optical acceleration is known as [http://en.wikipedia.org/wiki/Moir%C3%A9_speedup moiré speedup] (check for the [[formula]]s of optical speedup for curved patterns). When superimposing two identical layers comprising [[random]]ly spaced [[parallel]] lines, at a small angle or with a small scaling [[difference]] [http://switzernet.com/people/emin-gabrielyan/070227-random-line-moire/ random line moiré] patterns, namely line Glass patterns (after Leon Glass, 1969) appear. Similarly, when superimposing two identical layers of randomly scattered dots at a small angle or with a small scaling difference random dot Glass patterns, namely [http://switzernet.com/people/emin-gabrielyan/070212-random-moire/ random dot moiré], appears. When one of the layers embeds [[complex]] shapes, such as [[sequences]] of [[symbols]] forming a [[text]], and another layer contains parallel lines or curves, the superimposition image may give rise to magnified shapes, called [http://en.wikipedia.org/wiki/Shape_moir%C3%A9 shape moiré patterns].

Superimposition of 2D images containing correlated periodic grid structures may produce [https://en.wikipedia.org/wiki/Moir%C3%A9_pattern moiré patterns]. Superimposition of two correlated layers comprising [[parallel]] lines or curves may give rise [https://en.wikipedia.org/wiki/Line_moir%C3%A9 line moiré] patterns. The movement of one of the layers results in a faster movement of the line moiré superimposition image. Such optical acceleration is known as [https://en.wikipedia.org/wiki/Moir%C3%A9_speedup moiré speedup] (check for the [[formula]]s of optical speedup for curved patterns). When superimposing two identical layers comprising [[random]]ly spaced [[parallel]] lines, at a small angle or with a small scaling [[difference]] [https://switzernet.com/people/emin-gabrielyan/070227-random-line-moire/ random line moiré] patterns, namely line Glass patterns (after Leon Glass, 1969) appear. Similarly, when superimposing two identical layers of randomly scattered dots at a small angle or with a small scaling difference random dot Glass patterns, namely [https://switzernet.com/people/emin-gabrielyan/070212-random-moire/ random dot moiré], appears. When one of the layers embeds [[complex]] shapes, such as [[sequences]] of [[symbols]] forming a [[text]], and another layer contains parallel lines or curves, the superimposition image may give rise to magnified shapes, called [https://en.wikipedia.org/wiki/Shape_moir%C3%A9 shape moiré patterns].

[[Category: The Arts]]

[[Category: The Arts]]