202 lines
7.0 KiB
HTML
202 lines
7.0 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>ALE User Manual: Rendering</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</h1>
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<p>Rendering determines how an output image is constructed from a series of
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aligned input frames, and occurs in two stages: incremental rendering and
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Irani-Peleg rendering. Additional rendering options include exposure
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registration, certainty-weighted rendering, spatial extension, range extension,
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scaling, and bayer pattern specification. Experimental options for video
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stream processing are also available.
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<h2>Incremental Rendering</h2>
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<p>The incremental renderer uses configurable <a href="chains/">rendering
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chains</a> to determine the output image. It can increase resolution and
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reduce aliasing, but it cannot reduce blur.
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<h2>Irani-Peleg Rendering</h2>
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<p>The Irani-Peleg renderer uses configurable <a href="psf/">point-spread
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functions</a> to model blur, which is then reduced by an iterative
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backprojection technique. For iteration defaults, see the <a
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href="../defaults/"> default settings</a> page.
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<pre>
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--ips <i> Run <i> iterations.
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</pre>
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<h2>Exposure Registration</h2>
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<p>By default, ALE adjusts an exposure model to minimize differences in tone
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between frames. The option <code>--exp-noregister</code> indicates that
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exposure should be assumed uniform across all frames. In this case, no
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adjustment is performed.</p>
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<pre>
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--exp-register Register exposure between frames. [default]
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--exp-noregister Assume uniform exposure across all frames.
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</pre>
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<h2>Certainty-weighted Rendering</h2>
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<p>The exposure model in ALE includes an associated certainty function, which
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quantifies the reliability of sensor measurements. By default, this function
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is raised to the zeroth power, to obtain uniform certainty for all measurements.
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To specify a different certainty exponent, the option <code>--cx</code> can be
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used. This option is best used in combination with <code>--exp-extend</code>
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(see below) and <code>--ips</code>. For defaults, see the <a href="../defaults/">
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default settings</a> page.
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<pre>
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--cx <x> Render with certainty exponent <x>
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--no-cx Render with uniform certainty.
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</pre>
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<h2>Scale factor</h2>
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<p>Rendering with a larger scale factor results in image output of the specified
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larger scale. Larger scales can improve alignment precision and output image
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quality, but can also increase alignment and rendering times.
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<pre>
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--scale=x Scale images by the factor x (where x is at least 1.0)
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</pre>
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<h2>Image extents</h2>
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<p>The --extend option records pixel data that falls outside of the region of the
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first frame in the sequence. This can be useful for providing additional
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alignment constraints or creating panoramic image mosaics. (For mosaics, see
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also the description of the --follow option in the <a
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href="../alignment">alignment</a> section.)
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<pre>
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--extend Increase image extents to accommodate all pixel data.
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--no-extend Don't increase extents; crop to original frame. [default]
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</pre>
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<h2>Exposure extents</h2>
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<p>By default, ALE restricts the output range to that of the original frame.
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To adjust the output range to accommodate the ranges of all input frames,
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specify <code>--exp-extend</code>. For defaults, see the <a href="../defaults/">
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default settings</a> page.
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<pre>
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--exp-extend Extend range to include all calculated values.
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--exp-noextend Restrict to the original frame's range.
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</pre>
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<h2>Bayer pattern specification</h2>
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<p>Many cameras sample only one color channel per output pixel. To ignore the
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other channels, a bayer pattern can be specified. In versions prior to 0.7.3,
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device-specific bayer patterns override the command-line specification. In
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version 0.7.3 and later, the reverse holds.
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<pre>
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--bayer <b> Set default bayer pattern to <b>, one of:
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(clockwise from top left pixel)
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rgbg Red-green-blue-green
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gbgr Green-blue-green-red
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grgb Green-red-green-blue
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bgrg Blue-green-red-green
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none RGB-RGB-RGB-RGB
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Default is none or device-specific.
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</pre>
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<h2>Video stream processing (Experimental)</h2>
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<p>If a sequence of frames represents a video stream, then, in addition to
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producing a single output image, ALE can also produce one or more sequences of
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processed frames, corresponding to one or more occurrences of the
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<code>--visp</code> option. This option has its own associated scaling option,
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as well as an option to show excluded regions as dimmed wherever possible.</p>
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<pre>
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--visp <args> Process a video sequence.
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<args> are:
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<chain> <stabilization-type> <prefix> <suffix>
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<chain> is an incremental rendering chain.
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<stabilization-type> is one of:
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ma:<x> Moving average over 2*<x> + 1 frames
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sf:<x> Stabilize to single frame number <x>
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identity Same as ma:0
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<prefix> is an output file prefix
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<suffix> is an output file suffix
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--visp-scale=<x> Use scale <x> for VISP output. (default is 1.0)
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--exshow For single-invariant chains, show --ex regions dimmed.
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</pre>
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<h3>Video stream processing example</h3>
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<p>To mimic the behavior of repeated applications of the 0.6.0
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<code>--replace</code> option over a sequence of frames, the following
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<code>--visp</code> option could be used.
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<pre>
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--visp last:nex:triangle:2 sf:0 frame .jpg
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</pre>
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<p>For better filtering, the following option could be used instead:
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<pre>
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--visp last:nex:sinc*lanc:6 sf:0 frame .jpg
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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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