46 lines
1.9 KiB
XML
46 lines
1.9 KiB
XML
<?xml version="1.0"?>
|
|
|
|
<!DOCTYPE book PUBLIC "-//Norman Walsh//DTD DocBk XML V3.1.4//EN"
|
|
"file:///usr/share/xml/docbook/schema/dtd/4.4/docbookx.dtd">
|
|
|
|
<chapter id="user-psf"><title>Point Spread Functions</title>
|
|
<p>The ALE Irani-Peleg renderer uses a point-spread function to model the optical
|
|
and electronic properties of the capture device used. The PSF can be specified
|
|
in terms of one linear and one non-linear component.</p>
|
|
|
|
<s><t>PSF specification</t>
|
|
|
|
<p>The PSF can be explicitly specified by using one or both of the psf options.</p>
|
|
|
|
<ll>--lpsf <p> Set linear colorspace point-spread function to <p>
|
|
--nlpsf <p> Set non-linear colorspace point-spread function to <p>
|
|
</ll>
|
|
|
|
<p>Available explicit point-spread functions are as follows:</p>
|
|
|
|
<ll>box=<d> Set the PSF to a box filter with diameter <d>.
|
|
circle=<d> Set the PSF to a circular filter with diameter <d>.
|
|
stdin Specify a custom filter at runtime.
|
|
stdin_vg stdin with vertically-oriented gaps after every 8th pixel.
|
|
<p>+<p> Summation of two functions
|
|
<p>^<p> Convolution of two functions.
|
|
<n>*<p> Multiplication by a scalar <n>.
|
|
</ll>
|
|
|
|
<p>If a device is known to ALE, then its PSF can be implicitly set with the
|
|
<l>--device</l> option. (See the <a href="../../device/">device</a> page
|
|
for more information.) If a device is not specified, then the default linear
|
|
PSF component is <l>box=1</l>. The non-linear PSF component is disabled
|
|
by default.</p>
|
|
|
|
</s><s><t>Determining the PSF</t>
|
|
|
|
<p>The PSF can be approximated based on images of known scenes. The ALE source
|
|
distribution includes an experimental script that numerically approximates the
|
|
PSF in this way (<l>d2/render/psf/ale-psf-calibrate</l>). Other, more
|
|
efficient methods for approximating the PSF are likely possible, however.</p>
|
|
|
|
</s>
|
|
|
|
</chapter>
|