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73 lines
2.7 KiB
C++
73 lines
2.7 KiB
C++
// SPDX-License-Identifier: MIT
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#include "gfx/rgba.hpp"
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#include <algorithm>
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#include <math.h>
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#include <stdint.h>
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#include "helpers.hpp" // assume
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#include "gfx/main.hpp" // options
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// Based on inverting the "Modern - Accurate" formula used by SameBoy
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// since commit b5a611c5db46d6a0649d04d24d8d6339200f9ca1 (Dec 2020),
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// with gaps in the scale curve filled by polynomial interpolation.
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// clang-format off: vertically align columns of values
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static std::array<uint8_t, 256> reverse_curve{
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3,
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3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5,
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5, 5, 5, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7,
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7, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 10, 10, 10, 10,
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10, 10, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 13, 13, 13,
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13, 13, 14, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 16, 16, 16,
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16, 16, 16, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 18, 19, 19,
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19, 19, 19, 20, 20, 20, 20, 20, 20, 21, 21, 21, 21, 21, 21, 22,
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22, 22, 22, 22, 22, 22, 23, 23, 23, 23, 23, 23, 24, 24, 24, 24,
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24, 24, 24, 25, 25, 25, 25, 25, 25, 25, 25, 26, 26, 26, 26, 26,
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26, 26, 26, 27, 27, 27, 27, 27, 27, 27, 27, 27, 28, 28, 28, 28,
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28, 28, 28, 28, 28, 28, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
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29, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30,
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31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31,
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31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31,
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};
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// clang-format on
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uint16_t Rgba::cgbColor() const {
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if (isTransparent()) {
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return transparent;
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}
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assume(isOpaque());
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uint8_t r = red, g = green, b = blue;
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if (options.useColorCurve) {
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double g_linear = pow(g / 255.0, 2.2), b_linear = pow(b / 255.0, 2.2);
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double g_adjusted = std::clamp((g_linear * 4 - b_linear) / 3, 0.0, 1.0);
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g = round(pow(g_adjusted, 1 / 2.2) * 255);
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r = reverse_curve[r];
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g = reverse_curve[g];
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b = reverse_curve[b];
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} else {
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r >>= 3;
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g >>= 3;
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b >>= 3;
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}
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return r | g << 5 | b << 10;
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}
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uint8_t Rgba::grayIndex() const {
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assume(isGray());
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// 2bpp shades are inverted from RGB PNG; %00 = white, %11 = black
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uint8_t gray = 255 - red;
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if (options.palSpecType == Options::DMG) {
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assume(!options.hasTransparentPixels);
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// Reduce gray shade from 0..<256 to 0..<4, then map to color index,
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// then reduce to 0..<nbColorsPerPal
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return options.dmgColors[gray * 4 / 256] * options.nbColorsPerPal / 4;
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}
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// Reduce gray shade from 0..<256 to hasTransparentPixels..<nbColorsPerPal
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// Note that `maxOpaqueColors()` already takes `hasTransparentPixels` into account
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return gray * options.maxOpaqueColors() / 256 + options.hasTransparentPixels;
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}
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