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Diffstat (limited to 'thirdparty')
| -rw-r--r-- | thirdparty/README.md | 9 | ||||
| -rw-r--r-- | thirdparty/misc/ok_color.h | 688 | ||||
| -rw-r--r-- | thirdparty/misc/ok_color_shader.h | 663 |
3 files changed, 1360 insertions, 0 deletions
diff --git a/thirdparty/README.md b/thirdparty/README.md index 31b19451b3..97ba4bdca4 100644 --- a/thirdparty/README.md +++ b/thirdparty/README.md @@ -432,6 +432,15 @@ Collection of single-file libraries used in Godot components. * Upstream: https://github.com/Auburn/FastNoiseLite * Version: git (6be3d6bf7fb408de341285f9ee8a29b67fd953f1, 2022) + custom changes * License: MIT +- `ok_color.h` + * Upstream: https://github.com/bottosson/bottosson.github.io/blob/master/misc/ok_color.h + * Version: git (d69831edb90ffdcd08b7e64da3c5405acd48ad2c, 2022) + * License: MIT + * Modifications: License included in header. +- `ok_color_shader.h` + * https://www.shadertoy.com/view/7sK3D1 + * Version: 2021-09-13 + * License: MIT - `pcg.{cpp,h}` * Upstream: http://www.pcg-random.org * Version: minimal C implementation, http://www.pcg-random.org/download.html diff --git a/thirdparty/misc/ok_color.h b/thirdparty/misc/ok_color.h new file mode 100644 index 0000000000..dbc7dafc36 --- /dev/null +++ b/thirdparty/misc/ok_color.h @@ -0,0 +1,688 @@ +// Copyright(c) 2021 Björn Ottosson +// +// Permission is hereby granted, free of charge, to any person obtaining a copy of +// this software and associated documentation files(the "Software"), to deal in +// the Software without restriction, including without limitation the rights to +// use, copy, modify, merge, publish, distribute, sublicense, and /or sell copies +// of the Software, and to permit persons to whom the Software is furnished to do +// so, subject to the following conditions : +// The above copyright notice and this permission notice shall be included in all +// copies or substantial portions of the Software. +// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE +// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE +// SOFTWARE. + +#ifndef OK_COLOR_H +#define OK_COLOR_H + +#include <cmath> +#include <cfloat> + +class ok_color +{ +public: + +struct Lab { float L; float a; float b; }; +struct RGB { float r; float g; float b; }; +struct HSV { float h; float s; float v; }; +struct HSL { float h; float s; float l; }; +struct LC { float L; float C; }; + +// Alternative representation of (L_cusp, C_cusp) +// Encoded so S = C_cusp/L_cusp and T = C_cusp/(1-L_cusp) +// The maximum value for C in the triangle is then found as fmin(S*L, T*(1-L)), for a given L +struct ST { float S; float T; }; + +static constexpr float pi = 3.1415926535897932384626433832795028841971693993751058209749445923078164062f; + +float clamp(float x, float min, float max) +{ + if (x < min) + return min; + if (x > max) + return max; + + return x; +} + +float sgn(float x) +{ + return (float)(0.f < x) - (float)(x < 0.f); +} + +float srgb_transfer_function(float a) +{ + return .0031308f >= a ? 12.92f * a : 1.055f * powf(a, .4166666666666667f) - .055f; +} + +float srgb_transfer_function_inv(float a) +{ + return .04045f < a ? powf((a + .055f) / 1.055f, 2.4f) : a / 12.92f; +} + +Lab linear_srgb_to_oklab(RGB c) +{ + float l = 0.4122214708f * c.r + 0.5363325363f * c.g + 0.0514459929f * c.b; + float m = 0.2119034982f * c.r + 0.6806995451f * c.g + 0.1073969566f * c.b; + float s = 0.0883024619f * c.r + 0.2817188376f * c.g + 0.6299787005f * c.b; + + float l_ = cbrtf(l); + float m_ = cbrtf(m); + float s_ = cbrtf(s); + + return { + 0.2104542553f * l_ + 0.7936177850f * m_ - 0.0040720468f * s_, + 1.9779984951f * l_ - 2.4285922050f * m_ + 0.4505937099f * s_, + 0.0259040371f * l_ + 0.7827717662f * m_ - 0.8086757660f * s_, + }; +} + +RGB oklab_to_linear_srgb(Lab c) +{ + float l_ = c.L + 0.3963377774f * c.a + 0.2158037573f * c.b; + float m_ = c.L - 0.1055613458f * c.a - 0.0638541728f * c.b; + float s_ = c.L - 0.0894841775f * c.a - 1.2914855480f * c.b; + + float l = l_ * l_ * l_; + float m = m_ * m_ * m_; + float s = s_ * s_ * s_; + + return { + +4.0767416621f * l - 3.3077115913f * m + 0.2309699292f * s, + -1.2684380046f * l + 2.6097574011f * m - 0.3413193965f * s, + -0.0041960863f * l - 0.7034186147f * m + 1.7076147010f * s, + }; +} + +// Finds the maximum saturation possible for a given hue that fits in sRGB +// Saturation here is defined as S = C/L +// a and b must be normalized so a^2 + b^2 == 1 +float compute_max_saturation(float a, float b) +{ + // Max saturation will be when one of r, g or b goes below zero. + + // Select different coefficients depending on which component goes below zero first + float k0, k1, k2, k3, k4, wl, wm, ws; + + if (-1.88170328f * a - 0.80936493f * b > 1) + { + // Red component + k0 = +1.19086277f; k1 = +1.76576728f; k2 = +0.59662641f; k3 = +0.75515197f; k4 = +0.56771245f; + wl = +4.0767416621f; wm = -3.3077115913f; ws = +0.2309699292f; + } + else if (1.81444104f * a - 1.19445276f * b > 1) + { + // Green component + k0 = +0.73956515f; k1 = -0.45954404f; k2 = +0.08285427f; k3 = +0.12541070f; k4 = +0.14503204f; + wl = -1.2684380046f; wm = +2.6097574011f; ws = -0.3413193965f; + } + else + { + // Blue component + k0 = +1.35733652f; k1 = -0.00915799f; k2 = -1.15130210f; k3 = -0.50559606f; k4 = +0.00692167f; + wl = -0.0041960863f; wm = -0.7034186147f; ws = +1.7076147010f; + } + + // Approximate max saturation using a polynomial: + float S = k0 + k1 * a + k2 * b + k3 * a * a + k4 * a * b; + + // Do one step Halley's method to get closer + // this gives an error less than 10e6, except for some blue hues where the dS/dh is close to infinite + // this should be sufficient for most applications, otherwise do two/three steps + + float k_l = +0.3963377774f * a + 0.2158037573f * b; + float k_m = -0.1055613458f * a - 0.0638541728f * b; + float k_s = -0.0894841775f * a - 1.2914855480f * b; + + { + float l_ = 1.f + S * k_l; + float m_ = 1.f + S * k_m; + float s_ = 1.f + S * k_s; + + float l = l_ * l_ * l_; + float m = m_ * m_ * m_; + float s = s_ * s_ * s_; + + float l_dS = 3.f * k_l * l_ * l_; + float m_dS = 3.f * k_m * m_ * m_; + float s_dS = 3.f * k_s * s_ * s_; + + float l_dS2 = 6.f * k_l * k_l * l_; + float m_dS2 = 6.f * k_m * k_m * m_; + float s_dS2 = 6.f * k_s * k_s * s_; + + float f = wl * l + wm * m + ws * s; + float f1 = wl * l_dS + wm * m_dS + ws * s_dS; + float f2 = wl * l_dS2 + wm * m_dS2 + ws * s_dS2; + + S = S - f * f1 / (f1 * f1 - 0.5f * f * f2); + } + + return S; +} + +// finds L_cusp and C_cusp for a given hue +// a and b must be normalized so a^2 + b^2 == 1 +LC find_cusp(float a, float b) +{ + // First, find the maximum saturation (saturation S = C/L) + float S_cusp = compute_max_saturation(a, b); + + // Convert to linear sRGB to find the first point where at least one of r,g or b >= 1: + RGB rgb_at_max = oklab_to_linear_srgb({ 1, S_cusp * a, S_cusp * b }); + float L_cusp = cbrtf(1.f / fmax(fmax(rgb_at_max.r, rgb_at_max.g), rgb_at_max.b)); + float C_cusp = L_cusp * S_cusp; + + return { L_cusp , C_cusp }; +} + +// Finds intersection of the line defined by +// L = L0 * (1 - t) + t * L1; +// C = t * C1; +// a and b must be normalized so a^2 + b^2 == 1 +float find_gamut_intersection(float a, float b, float L1, float C1, float L0, LC cusp) +{ + // Find the intersection for upper and lower half seprately + float t; + if (((L1 - L0) * cusp.C - (cusp.L - L0) * C1) <= 0.f) + { + // Lower half + + t = cusp.C * L0 / (C1 * cusp.L + cusp.C * (L0 - L1)); + } + else + { + // Upper half + + // First intersect with triangle + t = cusp.C * (L0 - 1.f) / (C1 * (cusp.L - 1.f) + cusp.C * (L0 - L1)); + + // Then one step Halley's method + { + float dL = L1 - L0; + float dC = C1; + + float k_l = +0.3963377774f * a + 0.2158037573f * b; + float k_m = -0.1055613458f * a - 0.0638541728f * b; + float k_s = -0.0894841775f * a - 1.2914855480f * b; + + float l_dt = dL + dC * k_l; + float m_dt = dL + dC * k_m; + float s_dt = dL + dC * k_s; + + + // If higher accuracy is required, 2 or 3 iterations of the following block can be used: + { + float L = L0 * (1.f - t) + t * L1; + float C = t * C1; + + float l_ = L + C * k_l; + float m_ = L + C * k_m; + float s_ = L + C * k_s; + + float l = l_ * l_ * l_; + float m = m_ * m_ * m_; + float s = s_ * s_ * s_; + + float ldt = 3 * l_dt * l_ * l_; + float mdt = 3 * m_dt * m_ * m_; + float sdt = 3 * s_dt * s_ * s_; + + float ldt2 = 6 * l_dt * l_dt * l_; + float mdt2 = 6 * m_dt * m_dt * m_; + float sdt2 = 6 * s_dt * s_dt * s_; + + float r = 4.0767416621f * l - 3.3077115913f * m + 0.2309699292f * s - 1; + float r1 = 4.0767416621f * ldt - 3.3077115913f * mdt + 0.2309699292f * sdt; + float r2 = 4.0767416621f * ldt2 - 3.3077115913f * mdt2 + 0.2309699292f * sdt2; + + float u_r = r1 / (r1 * r1 - 0.5f * r * r2); + float t_r = -r * u_r; + + float g = -1.2684380046f * l + 2.6097574011f * m - 0.3413193965f * s - 1; + float g1 = -1.2684380046f * ldt + 2.6097574011f * mdt - 0.3413193965f * sdt; + float g2 = -1.2684380046f * ldt2 + 2.6097574011f * mdt2 - 0.3413193965f * sdt2; + + float u_g = g1 / (g1 * g1 - 0.5f * g * g2); + float t_g = -g * u_g; + + b = -0.0041960863f * l - 0.7034186147f * m + 1.7076147010f * s - 1; + float b1 = -0.0041960863f * ldt - 0.7034186147f * mdt + 1.7076147010f * sdt; + float b2 = -0.0041960863f * ldt2 - 0.7034186147f * mdt2 + 1.7076147010f * sdt2; + + float u_b = b1 / (b1 * b1 - 0.5f * b * b2); + float t_b = -b * u_b; + + t_r = u_r >= 0.f ? t_r : FLT_MAX; + t_g = u_g >= 0.f ? t_g : FLT_MAX; + t_b = u_b >= 0.f ? t_b : FLT_MAX; + + t += fmin(t_r, fmin(t_g, t_b)); + } + } + } + + return t; +} + +float find_gamut_intersection(float a, float b, float L1, float C1, float L0) +{ + // Find the cusp of the gamut triangle + LC cusp = find_cusp(a, b); + + return find_gamut_intersection(a, b, L1, C1, L0, cusp); +} + +RGB gamut_clip_preserve_chroma(RGB rgb) +{ + if (rgb.r < 1 && rgb.g < 1 && rgb.b < 1 && rgb.r > 0 && rgb.g > 0 && rgb.b > 0) + return rgb; + + Lab lab = linear_srgb_to_oklab(rgb); + + float L = lab.L; + float eps = 0.00001f; + float C = fmax(eps, sqrtf(lab.a * lab.a + lab.b * lab.b)); + float a_ = lab.a / C; + float b_ = lab.b / C; + + float L0 = clamp(L, 0, 1); + + float t = find_gamut_intersection(a_, b_, L, C, L0); + float L_clipped = L0 * (1 - t) + t * L; + float C_clipped = t * C; + + return oklab_to_linear_srgb({ L_clipped, C_clipped * a_, C_clipped * b_ }); +} + +RGB gamut_clip_project_to_0_5(RGB rgb) +{ + if (rgb.r < 1 && rgb.g < 1 && rgb.b < 1 && rgb.r > 0 && rgb.g > 0 && rgb.b > 0) + return rgb; + + Lab lab = linear_srgb_to_oklab(rgb); + + float L = lab.L; + float eps = 0.00001f; + float C = fmax(eps, sqrtf(lab.a * lab.a + lab.b * lab.b)); + float a_ = lab.a / C; + float b_ = lab.b / C; + + float L0 = 0.5; + + float t = find_gamut_intersection(a_, b_, L, C, L0); + float L_clipped = L0 * (1 - t) + t * L; + float C_clipped = t * C; + + return oklab_to_linear_srgb({ L_clipped, C_clipped * a_, C_clipped * b_ }); +} + +RGB gamut_clip_project_to_L_cusp(RGB rgb) +{ + if (rgb.r < 1 && rgb.g < 1 && rgb.b < 1 && rgb.r > 0 && rgb.g > 0 && rgb.b > 0) + return rgb; + + Lab lab = linear_srgb_to_oklab(rgb); + + float L = lab.L; + float eps = 0.00001f; + float C = fmax(eps, sqrtf(lab.a * lab.a + lab.b * lab.b)); + float a_ = lab.a / C; + float b_ = lab.b / C; + + // The cusp is computed here and in find_gamut_intersection, an optimized solution would only compute it once. + LC cusp = find_cusp(a_, b_); + + float L0 = cusp.L; + + float t = find_gamut_intersection(a_, b_, L, C, L0); + + float L_clipped = L0 * (1 - t) + t * L; + float C_clipped = t * C; + + return oklab_to_linear_srgb({ L_clipped, C_clipped * a_, C_clipped * b_ }); +} + +RGB gamut_clip_adaptive_L0_0_5(RGB rgb, float alpha = 0.05f) +{ + if (rgb.r < 1 && rgb.g < 1 && rgb.b < 1 && rgb.r > 0 && rgb.g > 0 && rgb.b > 0) + return rgb; + + Lab lab = linear_srgb_to_oklab(rgb); + + float L = lab.L; + float eps = 0.00001f; + float C = fmax(eps, sqrtf(lab.a * lab.a + lab.b * lab.b)); + float a_ = lab.a / C; + float b_ = lab.b / C; + + float Ld = L - 0.5f; + float e1 = 0.5f + fabs(Ld) + alpha * C; + float L0 = 0.5f * (1.f + sgn(Ld) * (e1 - sqrtf(e1 * e1 - 2.f * fabs(Ld)))); + + float t = find_gamut_intersection(a_, b_, L, C, L0); + float L_clipped = L0 * (1.f - t) + t * L; + float C_clipped = t * C; + + return oklab_to_linear_srgb({ L_clipped, C_clipped * a_, C_clipped * b_ }); +} + +RGB gamut_clip_adaptive_L0_L_cusp(RGB rgb, float alpha = 0.05f) +{ + if (rgb.r < 1 && rgb.g < 1 && rgb.b < 1 && rgb.r > 0 && rgb.g > 0 && rgb.b > 0) + return rgb; + + Lab lab = linear_srgb_to_oklab(rgb); + + float L = lab.L; + float eps = 0.00001f; + float C = fmax(eps, sqrtf(lab.a * lab.a + lab.b * lab.b)); + float a_ = lab.a / C; + float b_ = lab.b / C; + + // The cusp is computed here and in find_gamut_intersection, an optimized solution would only compute it once. + LC cusp = find_cusp(a_, b_); + + float Ld = L - cusp.L; + float k = 2.f * (Ld > 0 ? 1.f - cusp.L : cusp.L); + + float e1 = 0.5f * k + fabs(Ld) + alpha * C / k; + float L0 = cusp.L + 0.5f * (sgn(Ld) * (e1 - sqrtf(e1 * e1 - 2.f * k * fabs(Ld)))); + + float t = find_gamut_intersection(a_, b_, L, C, L0); + float L_clipped = L0 * (1.f - t) + t * L; + float C_clipped = t * C; + + return oklab_to_linear_srgb({ L_clipped, C_clipped * a_, C_clipped * b_ }); +} + +float toe(float x) +{ + constexpr float k_1 = 0.206f; + constexpr float k_2 = 0.03f; + constexpr float k_3 = (1.f + k_1) / (1.f + k_2); + return 0.5f * (k_3 * x - k_1 + sqrtf((k_3 * x - k_1) * (k_3 * x - k_1) + 4 * k_2 * k_3 * x)); +} + +float toe_inv(float x) +{ + constexpr float k_1 = 0.206f; + constexpr float k_2 = 0.03f; + constexpr float k_3 = (1.f + k_1) / (1.f + k_2); + return (x * x + k_1 * x) / (k_3 * (x + k_2)); +} + +ST to_ST(LC cusp) +{ + float L = cusp.L; + float C = cusp.C; + return { C / L, C / (1 - L) }; +} + +// Returns a smooth approximation of the location of the cusp +// This polynomial was created by an optimization process +// It has been designed so that S_mid < S_max and T_mid < T_max +ST get_ST_mid(float a_, float b_) +{ + float S = 0.11516993f + 1.f / ( + +7.44778970f + 4.15901240f * b_ + + a_ * (-2.19557347f + 1.75198401f * b_ + + a_ * (-2.13704948f - 10.02301043f * b_ + + a_ * (-4.24894561f + 5.38770819f * b_ + 4.69891013f * a_ + ))) + ); + + float T = 0.11239642f + 1.f / ( + +1.61320320f - 0.68124379f * b_ + + a_ * (+0.40370612f + 0.90148123f * b_ + + a_ * (-0.27087943f + 0.61223990f * b_ + + a_ * (+0.00299215f - 0.45399568f * b_ - 0.14661872f * a_ + ))) + ); + + return { S, T }; +} + +struct Cs { float C_0; float C_mid; float C_max; }; +Cs get_Cs(float L, float a_, float b_) +{ + LC cusp = find_cusp(a_, b_); + + float C_max = find_gamut_intersection(a_, b_, L, 1, L, cusp); + ST ST_max = to_ST(cusp); + + // Scale factor to compensate for the curved part of gamut shape: + float k = C_max / fmin((L * ST_max.S), (1 - L) * ST_max.T); + + float C_mid; + { + ST ST_mid = get_ST_mid(a_, b_); + + // Use a soft minimum function, instead of a sharp triangle shape to get a smooth value for chroma. + float C_a = L * ST_mid.S; + float C_b = (1.f - L) * ST_mid.T; + C_mid = 0.9f * k * sqrtf(sqrtf(1.f / (1.f / (C_a * C_a * C_a * C_a) + 1.f / (C_b * C_b * C_b * C_b)))); + } + + float C_0; + { + // for C_0, the shape is independent of hue, so ST are constant. Values picked to roughly be the average values of ST. + float C_a = L * 0.4f; + float C_b = (1.f - L) * 0.8f; + + // Use a soft minimum function, instead of a sharp triangle shape to get a smooth value for chroma. + C_0 = sqrtf(1.f / (1.f / (C_a * C_a) + 1.f / (C_b * C_b))); + } + + return { C_0, C_mid, C_max }; +} + +RGB okhsl_to_srgb(HSL hsl) +{ + float h = hsl.h; + float s = hsl.s; + float l = hsl.l; + + if (l == 1.0f) + { + return { 1.f, 1.f, 1.f }; + } + + else if (l == 0.f) + { + return { 0.f, 0.f, 0.f }; + } + + float a_ = cosf(2.f * pi * h); + float b_ = sinf(2.f * pi * h); + float L = toe_inv(l); + + Cs cs = get_Cs(L, a_, b_); + float C_0 = cs.C_0; + float C_mid = cs.C_mid; + float C_max = cs.C_max; + + float mid = 0.8f; + float mid_inv = 1.25f; + + float C, t, k_0, k_1, k_2; + + if (s < mid) + { + t = mid_inv * s; + + k_1 = mid * C_0; + k_2 = (1.f - k_1 / C_mid); + + C = t * k_1 / (1.f - k_2 * t); + } + else + { + t = (s - mid)/ (1 - mid); + + k_0 = C_mid; + k_1 = (1.f - mid) * C_mid * C_mid * mid_inv * mid_inv / C_0; + k_2 = (1.f - (k_1) / (C_max - C_mid)); + + C = k_0 + t * k_1 / (1.f - k_2 * t); + } + + RGB rgb = oklab_to_linear_srgb({ L, C * a_, C * b_ }); + return { + srgb_transfer_function(rgb.r), + srgb_transfer_function(rgb.g), + srgb_transfer_function(rgb.b), + }; +} + +HSL srgb_to_okhsl(RGB rgb) +{ + Lab lab = linear_srgb_to_oklab({ + srgb_transfer_function_inv(rgb.r), + srgb_transfer_function_inv(rgb.g), + srgb_transfer_function_inv(rgb.b) + }); + + float C = sqrtf(lab.a * lab.a + lab.b * lab.b); + float a_ = lab.a / C; + float b_ = lab.b / C; + + float L = lab.L; + float h = 0.5f + 0.5f * atan2f(-lab.b, -lab.a) / pi; + + Cs cs = get_Cs(L, a_, b_); + float C_0 = cs.C_0; + float C_mid = cs.C_mid; + float C_max = cs.C_max; + + // Inverse of the interpolation in okhsl_to_srgb: + + float mid = 0.8f; + float mid_inv = 1.25f; + + float s; + if (C < C_mid) + { + float k_1 = mid * C_0; + float k_2 = (1.f - k_1 / C_mid); + + float t = C / (k_1 + k_2 * C); + s = t * mid; + } + else + { + float k_0 = C_mid; + float k_1 = (1.f - mid) * C_mid * C_mid * mid_inv * mid_inv / C_0; + float k_2 = (1.f - (k_1) / (C_max - C_mid)); + + float t = (C - k_0) / (k_1 + k_2 * (C - k_0)); + s = mid + (1.f - mid) * t; + } + + float l = toe(L); + return { h, s, l }; +} + + +RGB okhsv_to_srgb(HSV hsv) +{ + float h = hsv.h; + float s = hsv.s; + float v = hsv.v; + + float a_ = cosf(2.f * pi * h); + float b_ = sinf(2.f * pi * h); + + LC cusp = find_cusp(a_, b_); + ST ST_max = to_ST(cusp); + float S_max = ST_max.S; + float T_max = ST_max.T; + float S_0 = 0.5f; + float k = 1 - S_0 / S_max; + + // first we compute L and V as if the gamut is a perfect triangle: + + // L, C when v==1: + float L_v = 1 - s * S_0 / (S_0 + T_max - T_max * k * s); + float C_v = s * T_max * S_0 / (S_0 + T_max - T_max * k * s); + + float L = v * L_v; + float C = v * C_v; + + // then we compensate for both toe and the curved top part of the triangle: + float L_vt = toe_inv(L_v); + float C_vt = C_v * L_vt / L_v; + + float L_new = toe_inv(L); + C = C * L_new / L; + L = L_new; + + RGB rgb_scale = oklab_to_linear_srgb({ L_vt, a_ * C_vt, b_ * C_vt }); + float scale_L = cbrtf(1.f / fmax(fmax(rgb_scale.r, rgb_scale.g), fmax(rgb_scale.b, 0.f))); + + L = L * scale_L; + C = C * scale_L; + + RGB rgb = oklab_to_linear_srgb({ L, C * a_, C * b_ }); + return { + srgb_transfer_function(rgb.r), + srgb_transfer_function(rgb.g), + srgb_transfer_function(rgb.b), + }; +} + +HSV srgb_to_okhsv(RGB rgb) +{ + Lab lab = linear_srgb_to_oklab({ + srgb_transfer_function_inv(rgb.r), + srgb_transfer_function_inv(rgb.g), + srgb_transfer_function_inv(rgb.b) + }); + + float C = sqrtf(lab.a * lab.a + lab.b * lab.b); + float a_ = lab.a / C; + float b_ = lab.b / C; + + float L = lab.L; + float h = 0.5f + 0.5f * atan2f(-lab.b, -lab.a) / pi; + + LC cusp = find_cusp(a_, b_); + ST ST_max = to_ST(cusp); + float S_max = ST_max.S; + float T_max = ST_max.T; + float S_0 = 0.5f; + float k = 1 - S_0 / S_max; + + // first we find L_v, C_v, L_vt and C_vt + + float t = T_max / (C + L * T_max); + float L_v = t * L; + float C_v = t * C; + + float L_vt = toe_inv(L_v); + float C_vt = C_v * L_vt / L_v; + + // we can then use these to invert the step that compensates for the toe and the curved top part of the triangle: + RGB rgb_scale = oklab_to_linear_srgb({ L_vt, a_ * C_vt, b_ * C_vt }); + float scale_L = cbrtf(1.f / fmax(fmax(rgb_scale.r, rgb_scale.g), fmax(rgb_scale.b, 0.f))); + + L = L / scale_L; + C = C / scale_L; + + C = C * toe(L) / L; + L = toe(L); + + // we can now compute v and s: + + float v = L / L_v; + float s = (S_0 + T_max) * C_v / ((T_max * S_0) + T_max * k * C_v); + + return { h, s, v }; +} + +}; +#endif // OK_COLOR_H diff --git a/thirdparty/misc/ok_color_shader.h b/thirdparty/misc/ok_color_shader.h new file mode 100644 index 0000000000..40d83366ee --- /dev/null +++ b/thirdparty/misc/ok_color_shader.h @@ -0,0 +1,663 @@ +// Copyright(c) 2021 Björn Ottosson +// +// Permission is hereby granted, free of charge, to any person obtaining a copy of +// this software and associated documentation files(the "Software"), to deal in +// the Software without restriction, including without limitation the rights to +// use, copy, modify, merge, publish, distribute, sublicense, and /or sell copies +// of the Software, and to permit persons to whom the Software is furnished to do +// so, subject to the following conditions : +// The above copyright notice and this permission notice shall be included in all +// copies or substantial portions of the Software. +// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE +// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE +// SOFTWARE. + +#ifndef OK_COLOR_SHADER_H +#define OK_COLOR_SHADER_H + +#include "core/string/ustring.h" + +static String OK_COLOR_SHADER = R"(shader_type canvas_item; + +const float M_PI = 3.1415926535897932384626433832795; + +float cbrt( float x ) +{ + return sign(x)*pow(abs(x),1.0f/3.0f); +} + +float srgb_transfer_function(float a) +{ + return .0031308f >= a ? 12.92f * a : 1.055f * pow(a, .4166666666666667f) - .055f; +} + +float srgb_transfer_function_inv(float a) +{ + return .04045f < a ? pow((a + .055f) / 1.055f, 2.4f) : a / 12.92f; +} + +vec3 linear_srgb_to_oklab(vec3 c) +{ + float l = 0.4122214708f * c.r + 0.5363325363f * c.g + 0.0514459929f * c.b; + float m = 0.2119034982f * c.r + 0.6806995451f * c.g + 0.1073969566f * c.b; + float s = 0.0883024619f * c.r + 0.2817188376f * c.g + 0.6299787005f * c.b; + + float l_ = cbrt(l); + float m_ = cbrt(m); + float s_ = cbrt(s); + + return vec3( + 0.2104542553f * l_ + 0.7936177850f * m_ - 0.0040720468f * s_, + 1.9779984951f * l_ - 2.4285922050f * m_ + 0.4505937099f * s_, + 0.0259040371f * l_ + 0.7827717662f * m_ - 0.8086757660f * s_ + ); +} + +vec3 oklab_to_linear_srgb(vec3 c) +{ + float l_ = c.x + 0.3963377774f * c.y + 0.2158037573f * c.z; + float m_ = c.x - 0.1055613458f * c.y - 0.0638541728f * c.z; + float s_ = c.x - 0.0894841775f * c.y - 1.2914855480f * c.z; + + float l = l_ * l_ * l_; + float m = m_ * m_ * m_; + float s = s_ * s_ * s_; + + return vec3( + +4.0767416621f * l - 3.3077115913f * m + 0.2309699292f * s, + -1.2684380046f * l + 2.6097574011f * m - 0.3413193965f * s, + -0.0041960863f * l - 0.7034186147f * m + 1.7076147010f * s + ); +} + +// Finds the maximum saturation possible for a given hue that fits in sRGB +// Saturation here is defined as S = C/L +// a and b must be normalized so a^2 + b^2 == 1 +float compute_max_saturation(float a, float b) +{ + // Max saturation will be when one of r, g or b goes below zero. + + // Select different coefficients depending on which component goes below zero first + float k0, k1, k2, k3, k4, wl, wm, ws; + + if (-1.88170328f * a - 0.80936493f * b > 1.f) + { + // Red component + k0 = +1.19086277f; k1 = +1.76576728f; k2 = +0.59662641f; k3 = +0.75515197f; k4 = +0.56771245f; + wl = +4.0767416621f; wm = -3.3077115913f; ws = +0.2309699292f; + } + else if (1.81444104f * a - 1.19445276f * b > 1.f) + { + // Green component + k0 = +0.73956515f; k1 = -0.45954404f; k2 = +0.08285427f; k3 = +0.12541070f; k4 = +0.14503204f; + wl = -1.2684380046f; wm = +2.6097574011f; ws = -0.3413193965f; + } + else + { + // Blue component + k0 = +1.35733652f; k1 = -0.00915799f; k2 = -1.15130210f; k3 = -0.50559606f; k4 = +0.00692167f; + wl = -0.0041960863f; wm = -0.7034186147f; ws = +1.7076147010f; + } + + // Approximate max saturation using a polynomial: + float S = k0 + k1 * a + k2 * b + k3 * a * a + k4 * a * b; + + // Do one step Halley's method to get closer + // this gives an error less than 10e6, except for some blue hues where the dS/dh is close to infinite + // this should be sufficient for most applications, otherwise do two/three steps + + float k_l = +0.3963377774f * a + 0.2158037573f * b; + float k_m = -0.1055613458f * a - 0.0638541728f * b; + float k_s = -0.0894841775f * a - 1.2914855480f * b; + + { + float l_ = 1.f + S * k_l; + float m_ = 1.f + S * k_m; + float s_ = 1.f + S * k_s; + + float l = l_ * l_ * l_; + float m = m_ * m_ * m_; + float s = s_ * s_ * s_; + + float l_dS = 3.f * k_l * l_ * l_; + float m_dS = 3.f * k_m * m_ * m_; + float s_dS = 3.f * k_s * s_ * s_; + + float l_dS2 = 6.f * k_l * k_l * l_; + float m_dS2 = 6.f * k_m * k_m * m_; + float s_dS2 = 6.f * k_s * k_s * s_; + + float f = wl * l + wm * m + ws * s; + float f1 = wl * l_dS + wm * m_dS + ws * s_dS; + float f2 = wl * l_dS2 + wm * m_dS2 + ws * s_dS2; + + S = S - f * f1 / (f1 * f1 - 0.5f * f * f2); + } + + return S; +} + +// finds L_cusp and C_cusp for a given hue +// a and b must be normalized so a^2 + b^2 == 1 +vec2 find_cusp(float a, float b) +{ + // First, find the maximum saturation (saturation S = C/L) + float S_cusp = compute_max_saturation(a, b); + + // Convert to linear sRGB to find the first point where at least one of r,g or b >= 1: + vec3 rgb_at_max = oklab_to_linear_srgb(vec3( 1, S_cusp * a, S_cusp * b )); + float L_cusp = cbrt(1.f / max(max(rgb_at_max.r, rgb_at_max.g), rgb_at_max.b)); + float C_cusp = L_cusp * S_cusp; + + return vec2( L_cusp , C_cusp ); +} )" +R"(// Finds intersection of the line defined by +// L = L0 * (1 - t) + t * L1; +// C = t * C1; +// a and b must be normalized so a^2 + b^2 == 1 +float find_gamut_intersection(float a, float b, float L1, float C1, float L0, vec2 cusp) +{ + // Find the intersection for upper and lower half seprately + float t; + if (((L1 - L0) * cusp.y - (cusp.x - L0) * C1) <= 0.f) + { + // Lower half + + t = cusp.y * L0 / (C1 * cusp.x + cusp.y * (L0 - L1)); + } + else + { + // Upper half + + // First intersect with triangle + t = cusp.y * (L0 - 1.f) / (C1 * (cusp.x - 1.f) + cusp.y * (L0 - L1)); + + // Then one step Halley's method + { + float dL = L1 - L0; + float dC = C1; + + float k_l = +0.3963377774f * a + 0.2158037573f * b; + float k_m = -0.1055613458f * a - 0.0638541728f * b; + float k_s = -0.0894841775f * a - 1.2914855480f * b; + + float l_dt = dL + dC * k_l; + float m_dt = dL + dC * k_m; + float s_dt = dL + dC * k_s; + + + // If higher accuracy is required, 2 or 3 iterations of the following block can be used: + { + float L = L0 * (1.f - t) + t * L1; + float C = t * C1; + + float l_ = L + C * k_l; + float m_ = L + C * k_m; + float s_ = L + C * k_s; + + float l = l_ * l_ * l_; + float m = m_ * m_ * m_; + float s = s_ * s_ * s_; + + float ldt = 3.f * l_dt * l_ * l_; + float mdt = 3.f * m_dt * m_ * m_; + float sdt = 3.f * s_dt * s_ * s_; + + float ldt2 = 6.f * l_dt * l_dt * l_; + float mdt2 = 6.f * m_dt * m_dt * m_; + float sdt2 = 6.f * s_dt * s_dt * s_; + + float r = 4.0767416621f * l - 3.3077115913f * m + 0.2309699292f * s - 1.f; + float r1 = 4.0767416621f * ldt - 3.3077115913f * mdt + 0.2309699292f * sdt; + float r2 = 4.0767416621f * ldt2 - 3.3077115913f * mdt2 + 0.2309699292f * sdt2; + + float u_r = r1 / (r1 * r1 - 0.5f * r * r2); + float t_r = -r * u_r; + + float g = -1.2684380046f * l + 2.6097574011f * m - 0.3413193965f * s - 1.f; + float g1 = -1.2684380046f * ldt + 2.6097574011f * mdt - 0.3413193965f * sdt; + float g2 = -1.2684380046f * ldt2 + 2.6097574011f * mdt2 - 0.3413193965f * sdt2; + + float u_g = g1 / (g1 * g1 - 0.5f * g * g2); + float t_g = -g * u_g; + + float b = -0.0041960863f * l - 0.7034186147f * m + 1.7076147010f * s - 1.f; + float b1 = -0.0041960863f * ldt - 0.7034186147f * mdt + 1.7076147010f * sdt; + float b2 = -0.0041960863f * ldt2 - 0.7034186147f * mdt2 + 1.7076147010f * sdt2; + + float u_b = b1 / (b1 * b1 - 0.5f * b * b2); + float t_b = -b * u_b; + + t_r = u_r >= 0.f ? t_r : 10000.f; + t_g = u_g >= 0.f ? t_g : 10000.f; + t_b = u_b >= 0.f ? t_b : 10000.f; + + t += min(t_r, min(t_g, t_b)); + } + } + } + + return t; +} + +float find_gamut_intersection_5(float a, float b, float L1, float C1, float L0) +{ + // Find the cusp of the gamut triangle + vec2 cusp = find_cusp(a, b); + + return find_gamut_intersection(a, b, L1, C1, L0, cusp); +})" +R"( + +vec3 gamut_clip_preserve_chroma(vec3 rgb) +{ + if (rgb.r < 1.f && rgb.g < 1.f && rgb.b < 1.f && rgb.r > 0.f && rgb.g > 0.f && rgb.b > 0.f) + return rgb; + + vec3 lab = linear_srgb_to_oklab(rgb); + + float L = lab.x; + float eps = 0.00001f; + float C = max(eps, sqrt(lab.y * lab.y + lab.z * lab.z)); + float a_ = lab.y / C; + float b_ = lab.z / C; + + float L0 = clamp(L, 0.f, 1.f); + + float t = find_gamut_intersection_5(a_, b_, L, C, L0); + float L_clipped = L0 * (1.f - t) + t * L; + float C_clipped = t * C; + + return oklab_to_linear_srgb(vec3( L_clipped, C_clipped * a_, C_clipped * b_ )); +} + +vec3 gamut_clip_project_to_0_5(vec3 rgb) +{ + if (rgb.r < 1.f && rgb.g < 1.f && rgb.b < 1.f && rgb.r > 0.f && rgb.g > 0.f && rgb.b > 0.f) + return rgb; + + vec3 lab = linear_srgb_to_oklab(rgb); + + float L = lab.x; + float eps = 0.00001f; + float C = max(eps, sqrt(lab.y * lab.y + lab.z * lab.z)); + float a_ = lab.y / C; + float b_ = lab.z / C; + + float L0 = 0.5; + + float t = find_gamut_intersection_5(a_, b_, L, C, L0); + float L_clipped = L0 * (1.f - t) + t * L; + float C_clipped = t * C; + + return oklab_to_linear_srgb(vec3( L_clipped, C_clipped * a_, C_clipped * b_ )); +} + +vec3 gamut_clip_project_to_L_cusp(vec3 rgb) +{ + if (rgb.r < 1.f && rgb.g < 1.f && rgb.b < 1.f && rgb.r > 0.f && rgb.g > 0.f && rgb.b > 0.f) + return rgb; + + vec3 lab = linear_srgb_to_oklab(rgb); + + float L = lab.x; + float eps = 0.00001f; + float C = max(eps, sqrt(lab.y * lab.y + lab.z * lab.z)); + float a_ = lab.y / C; + float b_ = lab.z / C; + + // The cusp is computed here and in find_gamut_intersection, an optimized solution would only compute it once. + vec2 cusp = find_cusp(a_, b_); + + float L0 = cusp.x; + + float t = find_gamut_intersection_5(a_, b_, L, C, L0); + + float L_clipped = L0 * (1.f - t) + t * L; + float C_clipped = t * C; + + return oklab_to_linear_srgb(vec3( L_clipped, C_clipped * a_, C_clipped * b_ )); +} + +vec3 gamut_clip_adaptive_L0_0_5(vec3 rgb, float alpha) +{ + if (rgb.r < 1.f && rgb.g < 1.f && rgb.b < 1.f && rgb.r > 0.f && rgb.g > 0.f && rgb.b > 0.f) + return rgb; + + vec3 lab = linear_srgb_to_oklab(rgb); + + float L = lab.x; + float eps = 0.00001f; + float C = max(eps, sqrt(lab.y * lab.y + lab.z * lab.z)); + float a_ = lab.y / C; + float b_ = lab.z / C; + + float Ld = L - 0.5f; + float e1 = 0.5f + abs(Ld) + alpha * C; + float L0 = 0.5f * (1.f + sign(Ld) * (e1 - sqrt(e1 * e1 - 2.f * abs(Ld)))); + + float t = find_gamut_intersection_5(a_, b_, L, C, L0); + float L_clipped = L0 * (1.f - t) + t * L; + float C_clipped = t * C; + + return oklab_to_linear_srgb(vec3( L_clipped, C_clipped * a_, C_clipped * b_ )); +} + +vec3 gamut_clip_adaptive_L0_L_cusp(vec3 rgb, float alpha) +{ + if (rgb.r < 1.f && rgb.g < 1.f && rgb.b < 1.f && rgb.r > 0.f && rgb.g > 0.f && rgb.b > 0.f) + return rgb; + + vec3 lab = linear_srgb_to_oklab(rgb); + + float L = lab.x; + float eps = 0.00001f; + float C = max(eps, sqrt(lab.y * lab.y + lab.z * lab.z)); + float a_ = lab.y / C; + float b_ = lab.z / C; + + // The cusp is computed here and in find_gamut_intersection, an optimized solution would only compute it once. + vec2 cusp = find_cusp(a_, b_); + + float Ld = L - cusp.x; + float k = 2.f * (Ld > 0.f ? 1.f - cusp.x : cusp.x); + + float e1 = 0.5f * k + abs(Ld) + alpha * C / k; + float L0 = cusp.x + 0.5f * (sign(Ld) * (e1 - sqrt(e1 * e1 - 2.f * k * abs(Ld)))); + + float t = find_gamut_intersection_5(a_, b_, L, C, L0); + float L_clipped = L0 * (1.f - t) + t * L; + float C_clipped = t * C; + + return oklab_to_linear_srgb(vec3( L_clipped, C_clipped * a_, C_clipped * b_ )); +} + +float toe(float x) +{ + float k_1 = 0.206f; + float k_2 = 0.03f; + float k_3 = (1.f + k_1) / (1.f + k_2); + return 0.5f * (k_3 * x - k_1 + sqrt((k_3 * x - k_1) * (k_3 * x - k_1) + 4.f * k_2 * k_3 * x)); +} + +float toe_inv(float x) +{ + float k_1 = 0.206f; + float k_2 = 0.03f; + float k_3 = (1.f + k_1) / (1.f + k_2); + return (x * x + k_1 * x) / (k_3 * (x + k_2)); +} +)" +R"(vec2 to_ST(vec2 cusp) +{ + float L = cusp.x; + float C = cusp.y; + return vec2( C / L, C / (1.f - L) ); +} + +// Returns a smooth approximation of the location of the cusp +// This polynomial was created by an optimization process +// It has been designed so that S_mid < S_max and T_mid < T_max +vec2 get_ST_mid(float a_, float b_) +{ + float S = 0.11516993f + 1.f / ( + +7.44778970f + 4.15901240f * b_ + + a_ * (-2.19557347f + 1.75198401f * b_ + + a_ * (-2.13704948f - 10.02301043f * b_ + + a_ * (-4.24894561f + 5.38770819f * b_ + 4.69891013f * a_ + ))) + ); + + float T = 0.11239642f + 1.f / ( + +1.61320320f - 0.68124379f * b_ + + a_ * (+0.40370612f + 0.90148123f * b_ + + a_ * (-0.27087943f + 0.61223990f * b_ + + a_ * (+0.00299215f - 0.45399568f * b_ - 0.14661872f * a_ + ))) + ); + + return vec2( S, T ); +} + +vec3 get_Cs(float L, float a_, float b_) +{ + vec2 cusp = find_cusp(a_, b_); + + float C_max = find_gamut_intersection(a_, b_, L, 1.f, L, cusp); + vec2 ST_max = to_ST(cusp); + + // Scale factor to compensate for the curved part of gamut shape: + float k = C_max / min((L * ST_max.x), (1.f - L) * ST_max.y); + + float C_mid; + { + vec2 ST_mid = get_ST_mid(a_, b_); + + // Use a soft minimum function, instead of a sharp triangle shape to get a smooth value for chroma. + float C_a = L * ST_mid.x; + float C_b = (1.f - L) * ST_mid.y; + C_mid = 0.9f * k * sqrt(sqrt(1.f / (1.f / (C_a * C_a * C_a * C_a) + 1.f / (C_b * C_b * C_b * C_b)))); + } + + float C_0; + { + // for C_0, the shape is independent of hue, so vec2 are constant. Values picked to roughly be the average values of vec2. + float C_a = L * 0.4f; + float C_b = (1.f - L) * 0.8f; + + // Use a soft minimum function, instead of a sharp triangle shape to get a smooth value for chroma. + C_0 = sqrt(1.f / (1.f / (C_a * C_a) + 1.f / (C_b * C_b))); + } + + return vec3( C_0, C_mid, C_max ); +} + +vec3 okhsl_to_srgb(vec3 hsl) +{ + float h = hsl.x; + float s = hsl.y; + float l = hsl.z; + + if (l == 1.0f) + { + return vec3( 1.f, 1.f, 1.f ); + } + + else if (l == 0.f) + { + return vec3( 0.f, 0.f, 0.f ); + } + + float a_ = cos(2.f * M_PI * h); + float b_ = sin(2.f * M_PI * h); + float L = toe_inv(l); + + vec3 cs = get_Cs(L, a_, b_); + float C_0 = cs.x; + float C_mid = cs.y; + float C_max = cs.z; + + float mid = 0.8f; + float mid_inv = 1.25f; + + float C, t, k_0, k_1, k_2; + + if (s < mid) + { + t = mid_inv * s; + + k_1 = mid * C_0; + k_2 = (1.f - k_1 / C_mid); + + C = t * k_1 / (1.f - k_2 * t); + } + else + { + t = (s - mid)/ (1.f - mid); + + k_0 = C_mid; + k_1 = (1.f - mid) * C_mid * C_mid * mid_inv * mid_inv / C_0; + k_2 = (1.f - (k_1) / (C_max - C_mid)); + + C = k_0 + t * k_1 / (1.f - k_2 * t); + } + + vec3 rgb = oklab_to_linear_srgb(vec3( L, C * a_, C * b_ )); + return vec3( + srgb_transfer_function(rgb.r), + srgb_transfer_function(rgb.g), + srgb_transfer_function(rgb.b) + ); +} + +vec3 srgb_to_okhsl(vec3 rgb) +{ + vec3 lab = linear_srgb_to_oklab(vec3( + srgb_transfer_function_inv(rgb.r), + srgb_transfer_function_inv(rgb.g), + srgb_transfer_function_inv(rgb.b) + )); + + float C = sqrt(lab.y * lab.y + lab.z * lab.z); + float a_ = lab.y / C; + float b_ = lab.z / C; + + float L = lab.x; + float h = 0.5f + 0.5f * atan(-lab.z, -lab.y) / M_PI; + + vec3 cs = get_Cs(L, a_, b_); + float C_0 = cs.x; + float C_mid = cs.y; + float C_max = cs.z; + + // Inverse of the interpolation in okhsl_to_srgb: + + float mid = 0.8f; + float mid_inv = 1.25f; + + float s; + if (C < C_mid) + { + float k_1 = mid * C_0; + float k_2 = (1.f - k_1 / C_mid); + + float t = C / (k_1 + k_2 * C); + s = t * mid; + } + else + { + float k_0 = C_mid; + float k_1 = (1.f - mid) * C_mid * C_mid * mid_inv * mid_inv / C_0; + float k_2 = (1.f - (k_1) / (C_max - C_mid)); + + float t = (C - k_0) / (k_1 + k_2 * (C - k_0)); + s = mid + (1.f - mid) * t; + } + + float l = toe(L); + return vec3( h, s, l ); +} + + +vec3 okhsv_to_srgb(vec3 hsv) +{ + float h = hsv.x; + float s = hsv.y; + float v = hsv.z; + + float a_ = cos(2.f * M_PI * h); + float b_ = sin(2.f * M_PI * h); + + vec2 cusp = find_cusp(a_, b_); + vec2 ST_max = to_ST(cusp); + float S_max = ST_max.x; + float T_max = ST_max.y; + float S_0 = 0.5f; + float k = 1.f- S_0 / S_max; + + // first we compute L and V as if the gamut is a perfect triangle: + + // L, C when v==1: + float L_v = 1.f - s * S_0 / (S_0 + T_max - T_max * k * s); + float C_v = s * T_max * S_0 / (S_0 + T_max - T_max * k * s); + + float L = v * L_v; + float C = v * C_v; + + // then we compensate for both toe and the curved top part of the triangle: + float L_vt = toe_inv(L_v); + float C_vt = C_v * L_vt / L_v; + + float L_new = toe_inv(L); + C = C * L_new / L; + L = L_new; + + vec3 rgb_scale = oklab_to_linear_srgb(vec3( L_vt, a_ * C_vt, b_ * C_vt )); + float scale_L = cbrt(1.f / max(max(rgb_scale.r, rgb_scale.g), max(rgb_scale.b, 0.f))); + + L = L * scale_L; + C = C * scale_L; + + vec3 rgb = oklab_to_linear_srgb(vec3( L, C * a_, C * b_ )); + return vec3( + srgb_transfer_function(rgb.r), + srgb_transfer_function(rgb.g), + srgb_transfer_function(rgb.b) + ); +} +)" +R"( +vec3 srgb_to_okhsv(vec3 rgb) +{ + vec3 lab = linear_srgb_to_oklab(vec3( + srgb_transfer_function_inv(rgb.r), + srgb_transfer_function_inv(rgb.g), + srgb_transfer_function_inv(rgb.b) + )); + + float C = sqrt(lab.y * lab.y + lab.z * lab.z); + float a_ = lab.y / C; + float b_ = lab.z / C; + + float L = lab.x; + float h = 0.5f + 0.5f * atan(-lab.z, -lab.y) / M_PI; + + vec2 cusp = find_cusp(a_, b_); + vec2 ST_max = to_ST(cusp); + float S_max = ST_max.x; + float T_max = ST_max.y; + float S_0 = 0.5f; + float k = 1.f - S_0 / S_max; + + // first we find L_v, C_v, L_vt and C_vt + + float t = T_max / (C + L * T_max); + float L_v = t * L; + float C_v = t * C; + + float L_vt = toe_inv(L_v); + float C_vt = C_v * L_vt / L_v; + + // we can then use these to invert the step that compensates for the toe and the curved top part of the triangle: + vec3 rgb_scale = oklab_to_linear_srgb(vec3( L_vt, a_ * C_vt, b_ * C_vt )); + float scale_L = cbrt(1.f / max(max(rgb_scale.r, rgb_scale.g), max(rgb_scale.b, 0.f))); + + L = L / scale_L; + C = C / scale_L; + + C = C * toe(L) / L; + L = toe(L); + + // we can now compute v and s: + + float v = L / L_v; + float s = (S_0 + T_max) * C_v / ((T_max * S_0) + T_max * k * C_v); + + return vec3 (h, s, v ); +})"; + +#endif |