95 lines
3.6 KiB
HTML
95 lines
3.6 KiB
HTML
<html>
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<title>Merging</title>
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<style type="text/css">
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TABLE.ba { max-width: 678; text-align: center; padding-bottom: 15; padding-top: 5}
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TABLE.inline { padding-right: 300; clear: left}
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TD.text_table {padding-left: 2; padding-right: 2; border-width: 1}
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P.header {max-width: none; width: auto; padding-left: 0}
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HR.main {max-width: 640; clear: left; padding-left: 0; margin-left: 0}
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HR.footer {clear: both}
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</style>
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</head><body>
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<table align=right valign=top width=160>
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<td valign=top height=600 width=160>
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<a href="http://auricle.dyndns.org/ALE/">
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<big>ALE</big>
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<br>
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Image Processing Software
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<br>
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<br>
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<small>Deblurring, Anti-aliasing, and Superresolution.</small></a>
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<br><br>
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<big>
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Local Operation
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</big>
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<hr>
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localhost<br>
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5393119533<br>
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</table>
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<p><b>[ <a href="../">Up</a> ]</b></p>
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<h1>Merging</h1>
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Merging uses bilinear interpolation to determine each frame's contribution to
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the accumulated image, with each contribution assigned equal weight. Where
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bilinear interpolation does not define a value, the accumulated image pixel is
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not updated. Sections below outline the properties of this approach.
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<h2>Properties</h2>
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<h3>Convolution with the Bartlett (triangle) filter as the limiting case</h3>
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<p>Assuming predicates for translation and point sampling, bilinear
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interpolation is equivalent to convolution with a Bartlett filter. Combined
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with the box filter approximation, jittering assumptions, and Bartlett filter
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approximation, the result of merging should be an acceptable approximation of
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<b>T</b>. This should be proven at some point. Until then, this result should
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be considered unreliable.
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<h3>Density and false local minima</h3>
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<p>Informally, the merging method outlined above always updates a dense set
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of pixels in the accumulated image. In particular, any accumulated image pixel
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whose center falls on a line between updated pixels is also an updated pixel.
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<p>It is conceivable that this property reduces the likelihood of alignment
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failure due to entrapment in local minima; hence, the merging renderer is
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always used as a reference for the <a href="../alignment/">alignment</a>
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algorithm. Except in cases where a large radius is used, <a
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href="../drizzling/">drizzling</a> does not share these properties.</p>
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<!--
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<p>Define a dense update method to be one that
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<p>The merging method outlined above has the property of always updating a
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dense set of pixels in the accumulated image (i.e. any accumulated image pixel
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whose center falls on a line between updated pixels is also an updated pixel,
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and all updated pixels are connected by a path consisting of only updated
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pixels), even when the accumulated image is of finer resolution than the new
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frame. This ensures that the area of defined pixels in the accumulated image
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is dense and that any uniform change in intensity between frames is reflected
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uniformly over a dense area. The absence of these properties may cause
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alignment to fail due to entrapment in local minima, and so merging is always
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used internally to create the renderings used by the alignment algorithm.
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Except in the case of a large pixel footprint, <a
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href="../drizzling">drizzling</a> does not share these properties.
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-->
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<br><br>
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<hr>
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<i>Copyright 2002, 2003, 2004 <a href="mailto:dhilvert@auricle.dyndns.org">David Hilvert</a></i>
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<p>Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved.
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</body>
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</html>
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