173 lines
5.7 KiB
HTML
173 lines
5.7 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>ALE User Manual: Rendering Chains</title>
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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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2684415918<br>
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</table>
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<p><b>[ <a href="../">Up</a> ]</b></p>
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<h1>ALE Rendering Chains</h1>
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<p>The ALE incremental renderer is configured using rendering chains. Rendering chains are
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constructed hierarchically from: invariants, SSFEs (scaled sampling filters
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with exclusion), SSFs (scaled sampling filters), and sampling filters. Each of
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these components is described in a section below. Defaults are outlined in the
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final section.
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<h2>Chains</h2>
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<p>The chain is the top level of the rendering chain hierarchy, and is composed of a
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sequence of invariants. Syntactically, a chain is specified as a number of
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invariants separated by commas:
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<blockquote>
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<code>invariant<sub>1</sub>,invariant<sub>2</sub>,invariant<sub>3</sub>,...,invariant<sub>n</sub></code>
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</blockquote>
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<p>Each rendered pixel is assigned a value at the first invariant whose weight
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exceeds the weight threshold, or otherwise at the last invariant in the sequence.
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<h3>Chain Options</h3>
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<pre>
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--wt <w> Set weight threshold for defined pixels (default is 0.8).
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--dchain <g> Use chain <g> to render the default output.
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--ochain <g> <o> Use chain <g> to render output file <o>.
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--achain <g> Use chain <g> to render the alignment reference image.
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</pre>
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<h3>Chain Examples</h3>
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<pre>
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triangle:2 ALE 0.6.0 merging (roughly)
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fine:box:1 Drizzling (roughly)
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fine:sinc*lanc:8 High-frequency preservation
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last:nex:sinc*lanc:8 Useful for video stabilization
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fine:box:1,triangle:2 Multi-resolution rendering
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fine:sinc*lanc:8,sinc*lanc:8 Multi-resolution rendering
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</pre>
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<h2>Invariants</h2>
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<p>Invariants determine whether the rendered pixel value should be taken from a
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single frame, or from an average of all frames. If from a single frame, it can
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be the first, last, minimal, or maximal pixel value. By default, the average
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is used. The syntax is as follows:
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<blockquote>
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<table>
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<tr><th align=left>Syntax</th><th><pre> </pre></th><th align=left>Description</th></tr>
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<tr><td>avg:<SSFE><td><td>Average value
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<tr><td>max:<SSFE><td><td>Maximum value
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<tr><td>min:<SSFE><td><td>Minimum value
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<tr><td>first:<SSFE><td><td>First value
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<tr><td>last:<SSFE><td><td>Last value
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<tr><td><SSFE><td><td>Same as avg:<SSFE>
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</table>
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</blockquote>
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<h2>Scaled Sampling Filter with Exclusion (SSFE)</h2>
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<p>SSFEs qualify SSFs, indicating whether exclusion regions should be honored.
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<blockquote>
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<table>
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<tr><th align=left>Syntax</th><th><pre> </pre></th><th align=left>Description</th></tr>
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<tr><td>ex:<SSF><td><td>Honor exclusion regions
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<tr><td>nex:<SSF><td><td>Don't honor exclusion regions
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<tr><td><SSF><td><td>Same as ex:<SSF>
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</table>
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</blockquote>
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<h2>Scaled Sampling Filter (SSF)</h2>
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<p>SSFs indicate whether filtering should occur at the resolution of the output
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image, or at the minimum of input and output image resolutions. The former prevents loss
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of details; the latter prevents aliasing.
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<blockquote>
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<table>
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<tr><th align=left>Syntax</th><th><pre> </pre></th><th align=left>Description</th></tr>
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<tr><td>fine:<SF><td><td>Filter at full output image resolution
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<tr><td>coarse:<SF><td><td>Filter at minimum resolution
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<tr><td><SF><td><td>Same as coarse:<SF>
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</table>
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</blockquote>
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<h3>SSF Options</h3>
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<pre>
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--afilter <s> Use SSF <s> to interpolate points in alignment.
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</pre>
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<h2>Sampling Filter (SF)</h2>
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<p>SFs are used to limit bandwidth. Primitive functions and pointwise multiplication of these
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functions (windowing) are available.
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<blockquote>
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<table>
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<tr><th align=left>Syntax</th><th><pre> </pre></th><th align=left>Description</th></tr>
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<tr><td>sinc<td><td>Sinc filter: (sin πx) / (πx)</td>
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<tr><td>lanc:<x><td><td>Lanczos, diameter x.
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<tr><td>triangle:<x><td><td>Triangle, diameter x.
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<tr><td>box:<x><td><td>Box, diameter x.
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<tr><td>zero<td><td>Zero function
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<tr><td><f>*<f><td><td>Pointwise multiplication (windowing)
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</table>
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</blockquote>
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<h2>Defaults</h2>
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<p>ALE defaults are as follows:</p>
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<pre>
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dchain Varies by <a href="../../defaults/">default setting</a>
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achain Varies by <a href="../../defaults/">default setting</a>
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afilter internal (approximates triangle:2)
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</pre>
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<br>
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<hr>
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<i>Copyright 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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