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