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| -rw-r--r-- | src/tone_mapping.c | 775 |
1 files changed, 775 insertions, 0 deletions
diff --git a/src/tone_mapping.c b/src/tone_mapping.c new file mode 100644 index 0000000..f08bb58 --- /dev/null +++ b/src/tone_mapping.c @@ -0,0 +1,775 @@ +/* + * This file is part of libplacebo. + * + * libplacebo is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * libplacebo 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 Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with libplacebo. If not, see <http://www.gnu.org/licenses/>. + */ + +#include <math.h> + +#include "common.h" + +#include <libplacebo/tone_mapping.h> + +#define fclampf(x, lo, hi) fminf(fmaxf(x, lo), hi) +static void fix_constants(struct pl_tone_map_constants *c) +{ + const float eps = 1e-6f; + c->knee_adaptation = fclampf(c->knee_adaptation, 0.0f, 1.0f); + c->knee_minimum = fclampf(c->knee_minimum, eps, 0.5f - eps); + c->knee_maximum = fclampf(c->knee_maximum, 0.5f + eps, 1.0f - eps); + c->knee_default = fclampf(c->knee_default, c->knee_minimum, c->knee_maximum); + c->knee_offset = fclampf(c->knee_offset, 0.5f, 2.0f); + c->slope_tuning = fclampf(c->slope_tuning, 0.0f, 10.0f); + c->slope_offset = fclampf(c->slope_offset, 0.0f, 1.0f); + c->spline_contrast = fclampf(c->spline_contrast, 0.0f, 1.5f); + c->reinhard_contrast = fclampf(c->reinhard_contrast, eps, 1.0f - eps); + c->linear_knee = fclampf(c->linear_knee, eps, 1.0f - eps); + c->exposure = fclampf(c->exposure, eps, 10.0f); +} + +static inline bool constants_equal(const struct pl_tone_map_constants *a, + const struct pl_tone_map_constants *b) +{ + pl_static_assert(sizeof(*a) % sizeof(float) == 0); + return !memcmp(a, b, sizeof(*a)); +} + +bool pl_tone_map_params_equal(const struct pl_tone_map_params *a, + const struct pl_tone_map_params *b) +{ + return a->function == b->function && + a->param == b->param && + a->input_scaling == b->input_scaling && + a->output_scaling == b->output_scaling && + a->lut_size == b->lut_size && + a->input_min == b->input_min && + a->input_max == b->input_max && + a->input_avg == b->input_avg && + a->output_min == b->output_min && + a->output_max == b->output_max && + constants_equal(&a->constants, &b->constants) && + pl_hdr_metadata_equal(&a->hdr, &b->hdr); +} + +bool pl_tone_map_params_noop(const struct pl_tone_map_params *p) +{ + float in_min = pl_hdr_rescale(p->input_scaling, PL_HDR_NITS, p->input_min); + float in_max = pl_hdr_rescale(p->input_scaling, PL_HDR_NITS, p->input_max); + float out_min = pl_hdr_rescale(p->output_scaling, PL_HDR_NITS, p->output_min); + float out_max = pl_hdr_rescale(p->output_scaling, PL_HDR_NITS, p->output_max); + bool can_inverse = p->function->map_inverse; + + return fabs(in_min - out_min) < 1e-4 && // no BPC + in_max < out_max + 1e-2 && // no range reduction + (out_max < in_max + 1e-2 || !can_inverse); // no inverse tone-mapping +} + +void pl_tone_map_params_infer(struct pl_tone_map_params *par) +{ + if (!par->function) + par->function = &pl_tone_map_clip; + + if (par->param) { + // Backwards compatibility for older API + if (par->function == &pl_tone_map_st2094_40 || par->function == &pl_tone_map_st2094_10) + par->constants.knee_adaptation = par->param; + if (par->function == &pl_tone_map_bt2390) + par->constants.knee_offset = par->param; + if (par->function == &pl_tone_map_spline) + par->constants.spline_contrast = par->param; + if (par->function == &pl_tone_map_reinhard) + par->constants.reinhard_contrast = par->param; + if (par->function == &pl_tone_map_mobius || par->function == &pl_tone_map_gamma) + par->constants.linear_knee = par->param; + if (par->function == &pl_tone_map_linear || par->function == &pl_tone_map_linear_light) + par->constants.exposure = par->param; + } + + fix_constants(&par->constants); + + // Constrain the input peak to be no less than target SDR white + float sdr = pl_hdr_rescale(par->output_scaling, par->input_scaling, par->output_max); + sdr = fminf(sdr, pl_hdr_rescale(PL_HDR_NITS, par->input_scaling, PL_COLOR_SDR_WHITE)); + par->input_max = fmaxf(par->input_max, sdr); + + // Constrain the output peak if function does not support inverse mapping + if (!par->function->map_inverse) + par->output_max = fminf(par->output_max, par->input_max); +} + +// Infer params and rescale to function scaling +static struct pl_tone_map_params fix_params(const struct pl_tone_map_params *params) +{ + struct pl_tone_map_params fixed = *params; + pl_tone_map_params_infer(&fixed); + + const struct pl_tone_map_function *fun = params->function; + fixed.input_scaling = fun->scaling; + fixed.output_scaling = fun->scaling; + fixed.input_min = pl_hdr_rescale(params->input_scaling, fun->scaling, fixed.input_min); + fixed.input_max = pl_hdr_rescale(params->input_scaling, fun->scaling, fixed.input_max); + fixed.input_avg = pl_hdr_rescale(params->input_scaling, fun->scaling, fixed.input_avg); + fixed.output_min = pl_hdr_rescale(params->output_scaling, fun->scaling, fixed.output_min); + fixed.output_max = pl_hdr_rescale(params->output_scaling, fun->scaling, fixed.output_max); + + return fixed; +} + +#define FOREACH_LUT(lut, V) \ + for (float *_iter = lut, *_end = lut + params->lut_size, V; \ + _iter < _end && ( V = *_iter, 1 ); *_iter++ = V) + +static void map_lut(float *lut, const struct pl_tone_map_params *params) +{ + if (params->output_max > params->input_max + 1e-4) { + // Inverse tone-mapping + pl_assert(params->function->map_inverse); + params->function->map_inverse(lut, params); + } else { + // Forward tone-mapping + params->function->map(lut, params); + } +} + +void pl_tone_map_generate(float *out, const struct pl_tone_map_params *params) +{ + struct pl_tone_map_params fixed = fix_params(params); + + // Generate input values evenly spaced in `params->input_scaling` + for (size_t i = 0; i < params->lut_size; i++) { + float x = (float) i / (params->lut_size - 1); + x = PL_MIX(params->input_min, params->input_max, x); + out[i] = pl_hdr_rescale(params->input_scaling, fixed.function->scaling, x); + } + + map_lut(out, &fixed); + + // Sanitize outputs and adapt back to `params->scaling` + for (size_t i = 0; i < params->lut_size; i++) { + float x = PL_CLAMP(out[i], fixed.output_min, fixed.output_max); + out[i] = pl_hdr_rescale(fixed.function->scaling, params->output_scaling, x); + } +} + +float pl_tone_map_sample(float x, const struct pl_tone_map_params *params) +{ + struct pl_tone_map_params fixed = fix_params(params); + fixed.lut_size = 1; + + x = PL_CLAMP(x, params->input_min, params->input_max); + x = pl_hdr_rescale(params->input_scaling, fixed.function->scaling, x); + map_lut(&x, &fixed); + x = PL_CLAMP(x, fixed.output_min, fixed.output_max); + x = pl_hdr_rescale(fixed.function->scaling, params->output_scaling, x); + return x; +} + +// Rescale from input-absolute to input-relative +static inline float rescale_in(float x, const struct pl_tone_map_params *params) +{ + return (x - params->input_min) / (params->input_max - params->input_min); +} + +// Rescale from input-absolute to output-relative +static inline float rescale(float x, const struct pl_tone_map_params *params) +{ + return (x - params->input_min) / (params->output_max - params->output_min); +} + +// Rescale from output-relative to output-absolute +static inline float rescale_out(float x, const struct pl_tone_map_params *params) +{ + return x * (params->output_max - params->output_min) + params->output_min; +} + +static inline float bt1886_eotf(float x, float min, float max) +{ + const float lb = powf(min, 1/2.4f); + const float lw = powf(max, 1/2.4f); + return powf((lw - lb) * x + lb, 2.4f); +} + +static inline float bt1886_oetf(float x, float min, float max) +{ + const float lb = powf(min, 1/2.4f); + const float lw = powf(max, 1/2.4f); + return (powf(x, 1/2.4f) - lb) / (lw - lb); +} + +static void noop(float *lut, const struct pl_tone_map_params *params) +{ + return; +} + +const struct pl_tone_map_function pl_tone_map_clip = { + .name = "clip", + .description = "No tone mapping (clip)", + .map = noop, + .map_inverse = noop, +}; + +// Helper function to pick a knee point (for suitable methods) based on the +// HDR10+ brightness metadata and scene brightness average matching. +// +// Inspired by SMPTE ST2094-10, with some modifications +static void st2094_pick_knee(float *out_src_knee, float *out_dst_knee, + const struct pl_tone_map_params *params) +{ + const float src_min = pl_hdr_rescale(params->input_scaling, PL_HDR_PQ, params->input_min); + const float src_max = pl_hdr_rescale(params->input_scaling, PL_HDR_PQ, params->input_max); + const float src_avg = pl_hdr_rescale(params->input_scaling, PL_HDR_PQ, params->input_avg); + const float dst_min = pl_hdr_rescale(params->output_scaling, PL_HDR_PQ, params->output_min); + const float dst_max = pl_hdr_rescale(params->output_scaling, PL_HDR_PQ, params->output_max); + + const float min_knee = params->constants.knee_minimum; + const float max_knee = params->constants.knee_maximum; + const float def_knee = params->constants.knee_default; + const float src_knee_min = PL_MIX(src_min, src_max, min_knee); + const float src_knee_max = PL_MIX(src_min, src_max, max_knee); + const float dst_knee_min = PL_MIX(dst_min, dst_max, min_knee); + const float dst_knee_max = PL_MIX(dst_min, dst_max, max_knee); + + // Choose source knee based on source scene brightness + float src_knee = PL_DEF(src_avg, PL_MIX(src_min, src_max, def_knee)); + src_knee = fclampf(src_knee, src_knee_min, src_knee_max); + + // Choose target adaptation point based on linearly re-scaling source knee + float target = (src_knee - src_min) / (src_max - src_min); + float adapted = PL_MIX(dst_min, dst_max, target); + + // Choose the destnation knee by picking the perceptual adaptation point + // between the source knee and the desired target. This moves the knee + // point, on the vertical axis, closer to the 1:1 (neutral) line. + // + // Adjust the adaptation strength towards 1 based on how close the knee + // point is to its extreme values (min/max knee) + float tuning = 1.0f - pl_smoothstep(max_knee, def_knee, target) * + pl_smoothstep(min_knee, def_knee, target); + float adaptation = PL_MIX(params->constants.knee_adaptation, 1.0f, tuning); + float dst_knee = PL_MIX(src_knee, adapted, adaptation); + dst_knee = fclampf(dst_knee, dst_knee_min, dst_knee_max); + + *out_src_knee = pl_hdr_rescale(PL_HDR_PQ, params->input_scaling, src_knee); + *out_dst_knee = pl_hdr_rescale(PL_HDR_PQ, params->output_scaling, dst_knee); +} + +// Pascal's triangle +static const uint16_t binom[17][17] = { + {1}, + {1,1}, + {1,2,1}, + {1,3,3,1}, + {1,4,6,4,1}, + {1,5,10,10,5,1}, + {1,6,15,20,15,6,1}, + {1,7,21,35,35,21,7,1}, + {1,8,28,56,70,56,28,8,1}, + {1,9,36,84,126,126,84,36,9,1}, + {1,10,45,120,210,252,210,120,45,10,1}, + {1,11,55,165,330,462,462,330,165,55,11,1}, + {1,12,66,220,495,792,924,792,495,220,66,12,1}, + {1,13,78,286,715,1287,1716,1716,1287,715,286,78,13,1}, + {1,14,91,364,1001,2002,3003,3432,3003,2002,1001,364,91,14,1}, + {1,15,105,455,1365,3003,5005,6435,6435,5005,3003,1365,455,105,15,1}, + {1,16,120,560,1820,4368,8008,11440,12870,11440,8008,4368,1820,560,120,16,1}, +}; + +static inline float st2094_intercept(uint8_t N, float Kx, float Ky) +{ + if (Kx <= 0 || Ky >= 1) + return 1.0f / N; + + const float slope = Ky / Kx * (1 - Kx) / (1 - Ky); + return fminf(slope / N, 1.0f); +} + +static void st2094_40(float *lut, const struct pl_tone_map_params *params) +{ + const float D = params->output_max; + + // Allocate space for the adjusted bezier control points, plus endpoints + float P[17], Kx, Ky, T; + uint8_t N; + + if (params->hdr.ootf.num_anchors) { + + // Use bezier curve from metadata + Kx = PL_CLAMP(params->hdr.ootf.knee_x, 0, 1); + Ky = PL_CLAMP(params->hdr.ootf.knee_y, 0, 1); + T = PL_CLAMP(params->hdr.ootf.target_luma, params->input_min, params->input_max); + N = params->hdr.ootf.num_anchors + 1; + pl_assert(N < PL_ARRAY_SIZE(P)); + memcpy(P + 1, params->hdr.ootf.anchors, (N - 1) * sizeof(*P)); + P[0] = 0.0f; + P[N] = 1.0f; + + } else { + + // Missing metadata, default to simple brightness matching + float src_knee, dst_knee; + st2094_pick_knee(&src_knee, &dst_knee, params); + Kx = src_knee / params->input_max; + Ky = dst_knee / params->output_max; + + // Solve spline to match slope at knee intercept + const float slope = Ky / Kx * (1 - Kx) / (1 - Ky); + N = PL_CLAMP((int) ceilf(slope), 2, PL_ARRAY_SIZE(P) - 1); + P[0] = 0.0f; + P[1] = st2094_intercept(N, Kx, Ky); + for (int i = 2; i <= N; i++) + P[i] = 1.0f; + T = D; + + } + + if (D < T) { + + // Output display darker than OOTF target, make brighter + const float Dmin = 0.0f, u = fmaxf(0.0f, (D - Dmin) / (T - Dmin)); + + // Scale down the knee point to make more room for the OOTF + Kx *= u; + Ky *= u; + + // Make the slope of the knee more closely approximate a clip(), + // constrained to avoid exploding P[1] + const float beta = N * Kx / (1 - Kx); + const float Kxy = fminf(Kx * params->input_max / D, beta / (beta + 1)); + Ky = PL_MIX(Kxy, Ky, u); + + for (int p = 2; p <= N; p++) + P[p] = PL_MIX(1.0f, P[p], u); + + // Make the OOTF intercept linear as D -> Dmin + P[1] = PL_MIX(st2094_intercept(N, Kx, Ky), P[1], u); + + } else if (D > T) { + + // Output display brighter than OOTF target, make more linear + pl_assert(params->input_max > T); + const float w = powf(1 - (D - T) / (params->input_max - T), 1.4f); + + // Constrain the slope of the input knee to prevent it from + // exploding and making the picture way too bright + Ky *= T / D; + + // Make the slope of the knee more linear by solving for f(Kx) = Kx + float Kxy = Kx * D / params->input_max; + Ky = PL_MIX(Kxy, Ky, w); + + for (int p = 2; p < N; p++) { + float anchor_lin = (float) p / N; + P[p] = PL_MIX(anchor_lin, P[p], w); + } + + // Make the OOTF intercept linear as D -> input_max + P[1] = PL_MIX(st2094_intercept(N, Kx, Ky), P[1], w); + + } + + pl_assert(Kx >= 0 && Kx <= 1); + pl_assert(Ky >= 0 && Ky <= 1); + + FOREACH_LUT(lut, x) { + x = bt1886_oetf(x, params->input_min, params->input_max); + x = bt1886_eotf(x, 0.0f, 1.0f); + + if (x <= Kx && Kx) { + // Linear section + x *= Ky / Kx; + } else { + // Bezier section + const float t = (x - Kx) / (1 - Kx); + + x = 0; // Bn + for (uint8_t p = 0; p <= N; p++) + x += binom[N][p] * powf(t, p) * powf(1 - t, N - p) * P[p]; + + x = Ky + (1 - Ky) * x; + } + + x = bt1886_oetf(x, 0.0f, 1.0f); + x = bt1886_eotf(x, params->output_min, params->output_max); + } +} + +const struct pl_tone_map_function pl_tone_map_st2094_40 = { + .name = "st2094-40", + .description = "SMPTE ST 2094-40 Annex B", + .param_desc = "Knee point target", + .param_min = 0.00f, + .param_def = 0.70f, + .param_max = 1.00f, + .scaling = PL_HDR_NITS, + .map = st2094_40, +}; + +static void st2094_10(float *lut, const struct pl_tone_map_params *params) +{ + float src_knee, dst_knee; + st2094_pick_knee(&src_knee, &dst_knee, params); + + const float x1 = params->input_min; + const float x3 = params->input_max; + const float x2 = src_knee; + + const float y1 = params->output_min; + const float y3 = params->output_max; + const float y2 = dst_knee; + + const pl_matrix3x3 cmat = {{ + { x2*x3*(y2 - y3), x1*x3*(y3 - y1), x1*x2*(y1 - y2) }, + { x3*y3 - x2*y2, x1*y1 - x3*y3, x2*y2 - x1*y1 }, + { x3 - x2, x1 - x3, x2 - x1 }, + }}; + + float coeffs[3] = { y1, y2, y3 }; + pl_matrix3x3_apply(&cmat, coeffs); + + const float k = 1.0 / (x3*y3*(x1 - x2) + x2*y2*(x3 - x1) + x1*y1*(x2 - x3)); + const float c1 = k * coeffs[0]; + const float c2 = k * coeffs[1]; + const float c3 = k * coeffs[2]; + + FOREACH_LUT(lut, x) + x = (c1 + c2 * x) / (1 + c3 * x); +} + +const struct pl_tone_map_function pl_tone_map_st2094_10 = { + .name = "st2094-10", + .description = "SMPTE ST 2094-10 Annex B.2", + .param_desc = "Knee point target", + .param_min = 0.00f, + .param_def = 0.70f, + .param_max = 1.00f, + .scaling = PL_HDR_NITS, + .map = st2094_10, +}; + +static void bt2390(float *lut, const struct pl_tone_map_params *params) +{ + const float minLum = rescale_in(params->output_min, params); + const float maxLum = rescale_in(params->output_max, params); + const float offset = params->constants.knee_offset; + const float ks = (1 + offset) * maxLum - offset; + const float bp = minLum > 0 ? fminf(1 / minLum, 4) : 4; + const float gain_inv = 1 + minLum / maxLum * powf(1 - maxLum, bp); + const float gain = maxLum < 1 ? 1 / gain_inv : 1; + + FOREACH_LUT(lut, x) { + x = rescale_in(x, params); + + // Piece-wise hermite spline + if (ks < 1) { + float tb = (x - ks) / (1 - ks); + float tb2 = tb * tb; + float tb3 = tb2 * tb; + float pb = (2 * tb3 - 3 * tb2 + 1) * ks + + (tb3 - 2 * tb2 + tb) * (1 - ks) + + (-2 * tb3 + 3 * tb2) * maxLum; + x = x < ks ? x : pb; + } + + // Black point adaptation + if (x < 1) { + x += minLum * powf(1 - x, bp); + x = gain * (x - minLum) + minLum; + } + + x = x * (params->input_max - params->input_min) + params->input_min; + } +} + +const struct pl_tone_map_function pl_tone_map_bt2390 = { + .name = "bt2390", + .description = "ITU-R BT.2390 EETF", + .scaling = PL_HDR_PQ, + .param_desc = "Knee offset", + .param_min = 0.50, + .param_def = 1.00, + .param_max = 2.00, + .map = bt2390, +}; + +static void bt2446a(float *lut, const struct pl_tone_map_params *params) +{ + const float phdr = 1 + 32 * powf(params->input_max / 10000, 1/2.4f); + const float psdr = 1 + 32 * powf(params->output_max / 10000, 1/2.4f); + + FOREACH_LUT(lut, x) { + x = powf(rescale_in(x, params), 1/2.4f); + x = logf(1 + (phdr - 1) * x) / logf(phdr); + + if (x <= 0.7399f) { + x = 1.0770f * x; + } else if (x < 0.9909f) { + x = (-1.1510f * x + 2.7811f) * x - 0.6302f; + } else { + x = 0.5f * x + 0.5f; + } + + x = (powf(psdr, x) - 1) / (psdr - 1); + x = bt1886_eotf(x, params->output_min, params->output_max); + } +} + +static void bt2446a_inv(float *lut, const struct pl_tone_map_params *params) +{ + FOREACH_LUT(lut, x) { + x = bt1886_oetf(x, params->input_min, params->input_max); + x *= 255.0; + if (x > 70) { + x = powf(x, (2.8305e-6f * x - 7.4622e-4f) * x + 1.2528f); + } else { + x = powf(x, (1.8712e-5f * x - 2.7334e-3f) * x + 1.3141f); + } + x = powf(x / 1000, 2.4f); + x = rescale_out(x, params); + } +} + +const struct pl_tone_map_function pl_tone_map_bt2446a = { + .name = "bt2446a", + .description = "ITU-R BT.2446 Method A", + .scaling = PL_HDR_NITS, + .map = bt2446a, + .map_inverse = bt2446a_inv, +}; + +static void spline(float *lut, const struct pl_tone_map_params *params) +{ + float src_pivot, dst_pivot; + st2094_pick_knee(&src_pivot, &dst_pivot, params); + + // Solve for linear knee (Pa = 0) + float slope = (dst_pivot - params->output_min) / + (src_pivot - params->input_min); + + // Tune the slope at the knee point slightly: raise it to a user-provided + // gamma exponent, multiplied by an extra tuning coefficient designed to + // make the slope closer to 1.0 when the difference in peaks is low, and + // closer to linear when the difference between peaks is high. + float ratio = params->input_max / params->output_max - 1.0f; + ratio = fclampf(params->constants.slope_tuning * ratio, + params->constants.slope_offset, + 1.0f + params->constants.slope_offset); + slope = powf(slope, (1.0f - params->constants.spline_contrast) * ratio); + + // Normalize everything the pivot to make the math easier + const float in_min = params->input_min - src_pivot; + const float in_max = params->input_max - src_pivot; + const float out_min = params->output_min - dst_pivot; + const float out_max = params->output_max - dst_pivot; + + // Solve P of order 2 for: + // P(in_min) = out_min + // P'(0.0) = slope + // P(0.0) = 0.0 + const float Pa = (out_min - slope * in_min) / (in_min * in_min); + const float Pb = slope; + + // Solve Q of order 3 for: + // Q(in_max) = out_max + // Q''(in_max) = 0.0 + // Q(0.0) = 0.0 + // Q'(0.0) = slope + const float t = 2 * in_max * in_max; + const float Qa = (slope * in_max - out_max) / (in_max * t); + const float Qb = -3 * (slope * in_max - out_max) / t; + const float Qc = slope; + + FOREACH_LUT(lut, x) { + x -= src_pivot; + x = x > 0 ? ((Qa * x + Qb) * x + Qc) * x : (Pa * x + Pb) * x; + x += dst_pivot; + } +} + +const struct pl_tone_map_function pl_tone_map_spline = { + .name = "spline", + .description = "Single-pivot polynomial spline", + .param_desc = "Contrast", + .param_min = 0.00f, + .param_def = 0.50f, + .param_max = 1.50f, + .scaling = PL_HDR_PQ, + .map = spline, + .map_inverse = spline, +}; + +static void reinhard(float *lut, const struct pl_tone_map_params *params) +{ + const float peak = rescale(params->input_max, params), + contrast = params->constants.reinhard_contrast, + offset = (1.0 - contrast) / contrast, + scale = (peak + offset) / peak; + + FOREACH_LUT(lut, x) { + x = rescale(x, params); + x = x / (x + offset); + x *= scale; + x = rescale_out(x, params); + } +} + +const struct pl_tone_map_function pl_tone_map_reinhard = { + .name = "reinhard", + .description = "Reinhard", + .param_desc = "Contrast", + .param_min = 0.001, + .param_def = 0.50, + .param_max = 0.99, + .map = reinhard, +}; + +static void mobius(float *lut, const struct pl_tone_map_params *params) +{ + const float peak = rescale(params->input_max, params), + j = params->constants.linear_knee; + + // Solve for M(j) = j; M(peak) = 1.0; M'(j) = 1.0 + // where M(x) = scale * (x+a)/(x+b) + const float a = -j*j * (peak - 1.0f) / (j*j - 2.0f * j + peak); + const float b = (j*j - 2.0f * j * peak + peak) / + fmaxf(1e-6f, peak - 1.0f); + const float scale = (b*b + 2.0f * b*j + j*j) / (b - a); + + FOREACH_LUT(lut, x) { + x = rescale(x, params); + x = x <= j ? x : scale * (x + a) / (x + b); + x = rescale_out(x, params); + } +} + +const struct pl_tone_map_function pl_tone_map_mobius = { + .name = "mobius", + .description = "Mobius", + .param_desc = "Knee point", + .param_min = 0.00, + .param_def = 0.30, + .param_max = 0.99, + .map = mobius, +}; + +static inline float hable(float x) +{ + const float A = 0.15, B = 0.50, C = 0.10, D = 0.20, E = 0.02, F = 0.30; + return ((x * (A*x + C*B) + D*E) / (x * (A*x + B) + D*F)) - E/F; +} + +static void hable_map(float *lut, const struct pl_tone_map_params *params) +{ + const float peak = params->input_max / params->output_max, + scale = 1.0f / hable(peak); + + FOREACH_LUT(lut, x) { + x = bt1886_oetf(x, params->input_min, params->input_max); + x = bt1886_eotf(x, 0, peak); + x = scale * hable(x); + x = bt1886_oetf(x, 0, 1); + x = bt1886_eotf(x, params->output_min, params->output_max); + } +} + +const struct pl_tone_map_function pl_tone_map_hable = { + .name = "hable", + .description = "Filmic tone-mapping (Hable)", + .map = hable_map, +}; + +static void gamma_map(float *lut, const struct pl_tone_map_params *params) +{ + const float peak = rescale(params->input_max, params), + cutoff = params->constants.linear_knee, + gamma = logf(cutoff) / logf(cutoff / peak); + + FOREACH_LUT(lut, x) { + x = rescale(x, params); + x = x > cutoff ? powf(x / peak, gamma) : x; + x = rescale_out(x, params); + } +} + +const struct pl_tone_map_function pl_tone_map_gamma = { + .name = "gamma", + .description = "Gamma function with knee", + .param_desc = "Knee point", + .param_min = 0.001, + .param_def = 0.30, + .param_max = 1.00, + .map = gamma_map, +}; + +static void linear(float *lut, const struct pl_tone_map_params *params) +{ + const float gain = params->constants.exposure; + + FOREACH_LUT(lut, x) { + x = rescale_in(x, params); + x *= gain; + x = rescale_out(x, params); + } +} + +const struct pl_tone_map_function pl_tone_map_linear = { + .name = "linear", + .description = "Perceptually linear stretch", + .param_desc = "Exposure", + .param_min = 0.001, + .param_def = 1.00, + .param_max = 10.0, + .scaling = PL_HDR_PQ, + .map = linear, + .map_inverse = linear, +}; + +const struct pl_tone_map_function pl_tone_map_linear_light = { + .name = "linearlight", + .description = "Linear light stretch", + .param_desc = "Exposure", + .param_min = 0.001, + .param_def = 1.00, + .param_max = 10.0, + .scaling = PL_HDR_NORM, + .map = linear, + .map_inverse = linear, +}; + +const struct pl_tone_map_function * const pl_tone_map_functions[] = { + &pl_tone_map_clip, + &pl_tone_map_st2094_40, + &pl_tone_map_st2094_10, + &pl_tone_map_bt2390, + &pl_tone_map_bt2446a, + &pl_tone_map_spline, + &pl_tone_map_reinhard, + &pl_tone_map_mobius, + &pl_tone_map_hable, + &pl_tone_map_gamma, + &pl_tone_map_linear, + &pl_tone_map_linear_light, + NULL +}; + +const int pl_num_tone_map_functions = PL_ARRAY_SIZE(pl_tone_map_functions) - 1; + +const struct pl_tone_map_function *pl_find_tone_map_function(const char *name) +{ + for (int i = 0; i < pl_num_tone_map_functions; i++) { + if (strcmp(name, pl_tone_map_functions[i]->name) == 0) + return pl_tone_map_functions[i]; + } + + return NULL; +} |