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{ RCSid $Id$ } |
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{ |
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Mapping of Luminance to Brightness for CRT display. |
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Hand this file to pcomb(1) with the -f option. |
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The picture file should have been run previously through |
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the automatic exposure procedure of pfilt(1), and |
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pcomb should not be given -o option. Like so: |
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|
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pfilt input.pic | pcomb -f tumblin.cal - > output.pic |
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|
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Formulas adapted from Stevens by Tumblin and Rushmeier. |
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|
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29 May 1993 |
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} |
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PI : 3.14159265358979323846; { Hmm, looks familiar... } |
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LAMBERT : 1e4/PI/WE; { Number of watts/sr/m2 in a Lambert } |
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DL : .027; { Maximum display luminance (Lamberts) } |
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AL : .5/le(1)*10^.84/LAMBERT; { Adaptation luminance (from exposure) } |
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|
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sq(x) : x*x; |
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aa(v) : .4*log10(v) + 2.92; |
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bb(v) : -.4*sq(log10(v)) + -2.584*log10(v) + 2.0208; |
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|
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power : aa(AL)/aa(DL); |
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|
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mult = li(1)^(power-1) * |
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( LAMBERT^-power/DL * 10^((bb(AL)-bb(DL))/aa(DL)) / le(1) ); |
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|
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ro = mult*ri(1); |
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go = mult*gi(1); |
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bo = mult*bi(1); |
