64 lines
2.5 KiB
HTML
64 lines
2.5 KiB
HTML
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<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<title>Luminance HDR User Manual — Tonemapping operators reference — Fattal</title>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<link href="style.css" rel="stylesheet" type="text/css" />
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</head>
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<body>
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<h2>Fattal</h2>
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The implementation of a tone mapping operator as described in:
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<P>
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Gradient Domain High Dynamic Range Compression
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R. Fattal, D. Lischinski, and M. Werman
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In ACM Transactions on Graphics (3), p. 249, 2002.
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<P>
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With respect to the original paper, this program provides additional parameter
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which limits the amplification of noise. The noise is often starkly amplified
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because of division by zero in one of the equations in the paper. Extension
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contributed by Przemyslaw Bazarnik.
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<P>
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At the core of the programme is a Poisson PDE which as suggested in
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the original paper is solved using a Full Multigrid
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Algorithm. However, this is an iterative solver which seems to lose
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accuracy when applied to higher resolution images resulting in halo
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effects and surreal looking images. For that reason a second solver
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has been implemented using the discrete cosine transform as the
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underlying method and is considerably more accurate mainly because it
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is a direct solver. This solver is the preferred method and is used by
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default. The old multigrid solver can be selected unchecking the <b>Version 2.3.0</b> checkbox.
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<A NAME="lbAE"> </A>
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<p>Please note that resulted LDR image always requires gamma correction which you can do using Levels tool.</p>
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<H3>OPTIONS</H3>
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<DL COMPACT>
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<DT><B>Alpha</B><DD>
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<P>
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Set alpha parameter. This parameter is depreciated as setting a value other
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than 1.0 has only the effect of a global gamma adjustment of the luminance
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channel.
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See the paper for the definition of alpha.
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<DT><B>Beta</B><DD>
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<P>
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Set beta parameter. It sets the strength of gradient (local contrast) modification.
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Suggested range is 0.8 to 0.96, default is 0.9 (see paper for details).
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Value of 1 does not change contrasts, values above 1 reverse the effect:
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local contrast is stretched and details are attenuated.
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Values below 0.5 lead to very strong amplification of small contrast, so
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consider using <b>Noise Reduction</b> parameter to prevent noise.
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<DT><B>Color Saturation</B><DD>
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<P>
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Amount of color saturation. Suggested range is 0.4 to 0.8. Default
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value: 0.8.
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<DT><B>Noise Reduction</B><DD>
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<P>
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Amount of noise reduction.
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</body>
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</html>
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