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62 lines
1.9 KiB
C
62 lines
1.9 KiB
C
/* spek-palette.c
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*
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* Copyright (C) 2010-2012 Alexander Kojevnikov <alexander@kojevnikov.com>
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*
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* Spek 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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*
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* Spek 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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*
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* You should have received a copy of the GNU General Public License
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* along with Spek. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "spek-palette.h"
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// Modified version of Dan Bruton's algorithm:
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// http://www.physics.sfasu.edu/astro/color/spectra.html
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uint32_t spek_palette_spectrum(double level)
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{
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level *= 0.6625;
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double r = 0.0, g = 0.0, b = 0.0;
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if (level >= 0 && level < 0.15) {
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r = (0.15 - level) / (0.15 + 0.075);
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g = 0.0;
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b = 1.0;
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} else if (level >= 0.15 && level < 0.275) {
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r = 0.0;
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g = (level - 0.15) / (0.275 - 0.15);
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b = 1.0;
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} else if (level >= 0.275 && level < 0.325) {
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r = 0.0;
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g = 1.0;
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b = (0.325 - level) / (0.325 - 0.275);
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} else if (level >= 0.325 && level < 0.5) {
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r = (level - 0.325) / (0.5 - 0.325);
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g = 1.0;
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b = 0.0;
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} else if (level >= 0.5 && level < 0.6625) {
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r = 1.0;
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g = (0.6625 - level) / (0.6625 - 0.5f);
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b = 0.0;
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}
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// Intensity correction.
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double cf = 1.0;
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if (level >= 0.0 && level < 0.1) {
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cf = level / 0.1;
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}
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cf *= 255.0;
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// Pack RGB values into a 32-bit uint.
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uint32_t rr = (uint32_t) (r * cf + 0.5);
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uint32_t gg = (uint32_t) (g * cf + 0.5);
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uint32_t bb = (uint32_t) (b * cf + 0.5);
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return (rr << 16) + (gg << 8) + bb;
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}
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