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{ RCSid $Id$ } |
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{ |
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Tone Mapping Operator due to Ferwerda, Pattanaik, Shirley and Greenberg |
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(Siggraph 1996, pp. 249-258). Equilibrium adaptation version. |
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|
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Greg Ward August 30, 1996 |
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|
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We assume that the input picture has already been adjusted with |
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a reasonable exposure value, which gives the adaptation level |
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implicitly. The visual acuity function should also be applied |
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if desired separately prior to applying this mapping. We're |
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also assuming that the picture is in standard RGB Radiance format, |
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not CIE XYZ format. |
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|
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Don't use the -o option of pcomb, just execute like so: |
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|
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% pcomb -f ferwerda.cal exposed.pic > mapped.pic |
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} |
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|
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sL(r,g,b) = .062*r + .608*g + .330*b; { approx. scotopic brightness } |
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Lwa : WE*.5/le(1); { world adaptation luminance } |
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lLwa : log10(Lwa); |
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Ldmax : 100; { maximum display luminance (cd/m^2) } |
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Lda : Ldmax/2; { display adaptation luminance } |
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lLda : log10(Lda); |
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|
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{ log10 of cone threshold luminance } |
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ltp(lLa) : if(-2.6 - lLa, -.72, if(lLa - 1.9, lLa - 1.255, |
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(.249*lLa + .65)^2.7 - .72)); |
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|
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{ log10 of rod threshold luminance } |
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lts(lLa) : if(-3.94 - lLa, -2.86, if(lLa - -1.44, lLa - .395, |
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(.405*lLa + 1.6)^2.18 - 2.86)); |
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|
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{ photopic multiplier } |
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mp : 10^(ltp(lLda) - ltp(lLwa)); |
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|
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{ scotopic multiplier } |
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ms : 10^(lts(lLda) - lts(lLwa)) * |
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if(-2.5 - lLwa, 1, if(lLwa - .8, 0, (.8 - lLwa)/(.8 - -2.5))); |
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|
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{ display calibration factor } |
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df : WE/Ldmax/le(1); |
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{ adjusted scotopic luminance } |
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msl = ms*df * sL(ri(1),gi(1),bi(1)); |
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{ compute output pixel } |
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ro = msl + mp*df * ri(1); |
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go = msl + mp*df * gi(1); |
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bo = msl + mp*df * bi(1); |
