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Update the reverse color curve (#1241)

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Based on SameBoy's "accurate modern" colour mapping.

Special thanks to @Rangi42 for her patience throughout development, @LIJI32 for researching the colour curve and helping with the creation of the reverse mapping (colour spaces are *fun*!), and @coffeevalenbat for testing :)
This commit is contained in:
Rangi
2023-11-21 13:41:18 -05:00
committed by GitHub
parent f5ae6a80f0
commit c7b39f094c
1 changed files with 24 additions and 20 deletions
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44
src/gfx/rgba.cpp
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@@ -2,33 +2,35 @@
#include "gfx/rgba.hpp" #include "gfx/rgba.hpp"
#include <algorithm>
#include <assert.h> #include <assert.h>
#include <math.h>
#include <stdint.h> #include <stdint.h>
#include "gfx/main.hpp" // options #include "gfx/main.hpp" // options
/* /*
* based on the Gaussian-like curve used by SameBoy since commit * Based on inverting the "Modern - Accurate" formula used by SameBoy
* 65dd02cc52f531dbbd3a7e6014e99d5b24e71a4c (Oct 2017) * since commit b5a611c5db46d6a0649d04d24d8d6339200f9ca1 (Dec 2020),
* with ties resolved by comparing the difference of the squares. * with gaps in the scale curve filled by polynomial interpolation.
*/ */
static std::array<uint8_t, 256> reverse_curve{ static std::array<uint8_t, 256> reverse_curve{
0, 0, 1, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, // These 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, // These
5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, // comments 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, // comments
7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, // prevent 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, // prevent
9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, // clang-format 5, 5, 5, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, // clang-format
10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, // from 7, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 10, 10, 10, 10, // from
12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, // reflowing 10, 10, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 13, 13, 13, // reflowing
13, 13, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 14, // these 13, 13, 14, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 16, 16, 16, // these
14, 14, 14, 14, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, // sixteen 16, 16, 16, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 18, 19, 19, // sixteen
16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, // 16-item 19, 19, 19, 20, 20, 20, 20, 20, 20, 21, 21, 21, 21, 21, 21, 22, // 16-item
17, 17, 17, 17, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 18, 18, // lines, 22, 22, 22, 22, 22, 22, 23, 23, 23, 23, 23, 23, 24, 24, 24, 24, // lines,
18, 18, 18, 18, 18, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, // which, 24, 24, 24, 25, 25, 25, 25, 25, 25, 25, 25, 26, 26, 26, 26, 26, // which,
19, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 21, 21, 21, 21, // in 26, 26, 26, 27, 27, 27, 27, 27, 27, 27, 27, 27, 28, 28, 28, 28, // in
21, 21, 21, 21, 21, 21, 21, 22, 22, 22, 22, 22, 22, 22, 22, 22, // my 28, 28, 28, 28, 28, 28, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, // my
22, 23, 23, 23, 23, 23, 23, 23, 23, 23, 24, 24, 24, 24, 24, 24, // opinion, 29, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, // opinion,
24, 24, 25, 25, 25, 25, 25, 25, 25, 25, 26, 26, 26, 26, 26, 26, // help 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, // help
26, 27, 27, 27, 27, 27, 28, 28, 28, 28, 29, 29, 29, 30, 30, 31, // visualization! 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, // visualization!
}; };
uint16_t Rgba::cgbColor() const { uint16_t Rgba::cgbColor() const {
@@ -39,7 +41,9 @@ uint16_t Rgba::cgbColor() const {
uint8_t r = red, g = green, b = blue; uint8_t r = red, g = green, b = blue;
if (options.useColorCurve) { if (options.useColorCurve) {
g = g * 4 < b ? 0 : (g * 4 - b) / 3; double g_linear = pow(g / 255.0, 2.2), b_linear = pow(b / 255.0, 2.2);
double g_adjusted = std::clamp((g_linear * 4 - b_linear) / 3, 0.0, 1.0);
g = round(pow(g_adjusted, 1 / 2.2) * 255);
r = reverse_curve[r]; r = reverse_curve[r];
g = reverse_curve[g]; g = reverse_curve[g];
b = reverse_curve[b]; b = reverse_curve[b];