54 lines
2.0 KiB
Markdown
54 lines
2.0 KiB
Markdown
/*
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This file is part of darktable,
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Copyright (C) 2020 darktable developers.
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darktable is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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darktable is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with darktable. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "common.h"
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kernel void
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negadoctor (read_only image2d_t in, write_only image2d_t out, int width, int height,
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const float4 Dmin, const float4 wb_high, const float4 offset,
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const float exposure, const float black, const float gamma, const float soft_clip, const float soft_clip_comp)
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{
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const unsigned int x = get_global_id(0);
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const unsigned int y = get_global_id(1);
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if(x >= width || y >= height) return;
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float4 i = read_imagef(in, sampleri, (int2)(x, y));
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float4 o;
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// Convert transmission to density using Dmin as a fulcrum
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o = -native_log10(Dmin / fmax(i, (float4)2.3283064365386963e-10f)); // threshold to -32 EV
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// Correct density in log space
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o = wb_high * o + offset;
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// Print density on paper : ((1 - 10^corrected_de + black) * exposure)^gamma rewritten for FMA
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o = -((float4)exposure * native_exp10(o) + (float4)black);
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o = dtcl_pow(fmax(o, (float4)0.0f), gamma); // note : this is always > 0
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// Compress highlights and clip negatives. from https://lists.gnu.org/archive/html/openexr-devel/2005-03/msg00009.html
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o = (o > (float4)soft_clip) ? soft_clip + ((float4)1.0f - native_exp(-(o - (float4)soft_clip) / (float4)soft_clip_comp)) * (float4)soft_clip_comp
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: o;
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// Copy alpha
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o.w = i.w;
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write_imagef(out, (int2)(x, y), o);
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}
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