RecipesCam/docker/frontend/shared/utils/toneShader.ts

import { BaseFilter, ColorAdjustments } from '../types';
import { HSL_BANDS, hslBandGaps, isMonochromeBase } from './colorUtils';

// Tone-domain adjustments (the four-point tonal range + Fuji-style Dynamic
// Range). SkSL runtime effect over a child image shader.
//
// TONAL RANGE — HIGHLIGHT, SHADOW, WHITE and BLACK. The four knobs are the
// four zones of the tone mapping doc, and no two of them own the same part of
// the ramp:
//
//   BLACKS     peak at 0.00, gone by 0.25
//   SHADOWS    peak at 0.25, gone by 0.50
//   HIGHLIGHTS peak at 0.75, gone by 0.50 and by 1.00
//   WHITES     peak at 1.00, gone by 0.75
//
// The four masks below are those tents — the doc's smoothsteps, one per quarter
// of the ramp — and the 0.50 midpoint is in none of them: it is the one value
// every one of the four leaves where it was.
//
// Colour: the luma takes the move and R, G, B keep their DIFFERENCES — the
// pixel lands on its new luma with the chroma it had, so the hue is untouched
// and a grey stays grey. The doc reaches the same place with a ratio
// (`R_new = R_old * Luma_new / Luma_old`), which is exact while it fits and
// moves the hue the moment a channel clips; see the note on `k` below.
//
// These four masks are ADDED in the doc's own pseudo-shader, and measured that
// way the ramp inverts: BLACK +10 against SHADOW -10 falls to a slope of -5 per
// unit luma at t = 0.87 (scratchpad tone-proto.mjs), a dark band where the ramp
// should still be climbing. Read here instead as the four ANCHORS of one ramp —
// knots at 0.00, 0.25, 0.50, 0.75 and 1.00, each moved by its own knob, each
// held inside the knot before it, drawn straight in between — the same
// measurement is monotone for every combination of the four at full deflection.
// A knob moves its anchor by a quarter of the ramp, so +10 BLACKS puts the toe
// on 0.25 and -10 WHITES rolls the head down to 0.75: the reach a tonal range
// slider has in the program this layout copies, without the inversion. SHADOW is
// the one knob held to half of that, because the knot it moves is the HEAD of
// the quarter above it and not an end of the ramp: a band cannot be lifted at
// its head and keep its slope at the same time, so the knob's travel is what has
// to give — see the measured note on a1.
//
// WHITE and BLACK are not the per-channel toe and shoulder they were on the WB
// tab any more. The doc puts the two points on the ends of the SAME ramp as the
// other two, so they are the ends this ramp is drawn through, and nothing else
// in the shader reads them.
//
// The ramp is drawn through the BASE LAYER, not through the pixel. The pixel's
// own luma, run through a knot move, is a GLOBAL curve: every pixel at luma t
// lands on the same o whatever is around it, so a knot lifted onto the band above
// it (SHADOW's a1) is a band whose whole spread is squashed to the slope left
// over — at SHADOW +100 a quarter of the ramp carries half its contrast, and on a
// real frame 0.50 of it survived: the grey sheet the knob was reported for. What
// the eye is reading there is LOCAL contrast, and a curve drawn through the pixel
// cannot see it.
//
// So the curve is drawn through what the frame holds AROUND the pixel — a coarse
// edge-aware blur of the luma, TONE_BASE_RADIUS of the frame wide (the
// fix_shadow.md decomposition, Base x Detail) — and the pixel then rides the
// ratio: it takes the neighbourhood's gain `o / base` and keeps the difference
// from it. Base moves, detail stays: the same lift, on the same pixels, with the
// texture inside the region left standing instead of drawn flat. Full deflection
// on the same frame keeps 0.78 of the band's spread where the global move kept
// 0.57 (shadow-live.mjs, before and after, over the deployed pass; shadow-band.py,
// the numpy twin of this maths, put it at 0.78 to 0.80).
//
// It costs nothing where there is no lift to make: with every knob on zero the
// ramp at base IS base, so the ratio is exactly 1 and the pass is the identity
// however coarse the base is. A caller that hands in no neighbourhood at all
// (a mask, which has none) hands in the pixel's own image as the base and gets
// the global move back — which is why the shared maths can take the base as an
// argument and mean the same thing in both places.
//
// Between two knots the ramp is drawn STRAIGHT, and that is deliberate: a
// smoothstep there is an S-curve through the knots, so it bends the ramp by up
// to six code values in the quarter-tones even with all four knobs on zero — and
// this pass still runs for the stock split tones and for DR alone, where nothing
// the user set asked for a contrast move. Straight segments keep a neutral
// setting the exact identity. The smoothsteps are the four ZONE masks above,
// which is where the doc's shape belongs: they weight DR and the split tones,
// and nothing but their peak positions has to be smooth.
//
// The -HL highlight recovery that used to run in LINEAR light ahead of all this
// is gone with it: HIGHLIGHT is one zone move now, in both directions. There is
// still detail at the top to move — the develop's own knee compresses the two
// stops the sensor holds above its white level into the frame (see
// highlight-knee-check.mjs), so -WHITES pulls a plateau down onto 0.75 rather
// than onto a flat 1.0.
//
// dr  - DR strength 0..1: lifts shadows slightly and rolls highlights (Fuji
//       extended DR); 0/auto/DR100 = no extra curve. It moves the same four
//       knots the knobs move, so DR and a knob cannot fight over the middle and
//       DR cannot invert the ramp either — added as its own masked terms on top
//       it could, and did: see the fold noted on the knots below.
// hl  - highlight -1..1: moves the 0.75 anchor, + up toward white, - down.
// sh  - shadow    -1..1: moves the 0.25 anchor, + up, - down.
// wh  - white point -1..1: moves the 1.00 anchor. + is free to pass 1.0 — that
//       is the move that clips a highlight toward white — and - pulls the head
//       of the ramp down under it.
// bl  - black point -1..1: moves the 0.00 anchor. + lifts the toe off the
//       floor (a faded black), - has nothing left to crush at 0.
// vib - vibrance -1..1: chroma-masked saturation. It rides along in this shader
//       (rather than the colour matrix) because it needs per-pixel chroma:
//       already-vivid pixels move least, so skins/skies deepen without the neon
//       clip a plain Saturation boost causes.
// shT/hlT - split tone (per-channel RGB bias, -1..1 each): a fixed cast applied
//       to the shadows and/or the highlights only. A 4x5 colour matrix cannot do
//       this — it is one linear map, so any cast it applies must also hit the
//       midtones and the opposite end. Classic Neg wants green/cyan shadows with
//       warm highlights at once, so the stock ships these values and the pass
//       stays active for it even when every user knob is 0. All-zero still = no
//       pass.
// hslOn/hslH/hslS/hslL - the selective-colour mixer: eight hue bands, each with
//       a hue shift, a saturation scale and a lightness offset (-1..1, from the
//       -10..10 knobs). Which pixels a band owns is decided HERE, per pixel, by
//       hue — so unlike everything else above it, the eight bands are not a
//       global move and cannot live in the colour matrix. See the band block at
//       the foot of TONE_SKSL.
// gh/gs/gl - the mixer's overall move: the same three quantities for the WHOLE
//       image, so they are simply the starting value of the per-band
//       accumulator and every hue gets them at full weight. The lightness one
//       is not gated by saturation (unlike the bands'), so a frame drained to
//       grey by -SAT still answers +LUM.
// The eight band lines of TONE_SKSL's mixer, generated from HSL_BANDS so the
// anchors and the gaps in the shader are the same numbers the chips are built
// from. Each line reads its own band's three values with a CONSTANT index —
// SkSL indexes uniform arrays by constant only, which is why this is unrolled
// rather than looped.
const BAND_BLOCK = hslBandGaps()
  .map(
    (b, i) => `    float w${i} = bandW(hd, ${b.hue.toFixed(1)}, ${b.left.toFixed(1)}, ${b.right.toFixed(1)}) * gate;
    acc += vec3(w${i} * hslH[${i}], w${i} * hslS[${i}], w${i} * hslL[${i}]);\n`
  )
  .join('');

// How far a tonal-range knob moves its own knot, in ramp units. A quarter is
// the reach the program this layout copies gives a slider: at full deflection
// the toe can reach the quarter above it and the head can be rolled onto it —
// and never past, because each knot is clamped inside the one after it.
//
// SHADOW and HIGHLIGHT move HALF of it. The knots they own (a1, a3) are the HEAD
// of a quarter, so a unit of lift is a unit of slope that quarter loses, and at
// a whole quarter the band is drawn flat — see the notes on a1 and a3.
export const TONE_ANCHOR = 0.25;

// How steep a bump of amplitude A gets, A excluded: the kernel (1-u^2)^2 tops out
// at |dk/du| = 8/(3*sqrt(3)) = 1.5396 on each side of its peak (u = 1/sqrt(3)),
// and u counts the distance to the knot in units of the bump's half-width. Over
// the half-width of BLACK and WHITE that is 3.08*A, over the quarter-width of
// SHADOW and HIGHLIGHT 6.16*A, and the two numbers are what the guard inside
// toneRamp holds two moves sharing a half of the ramp under.
export const TONE_BUMP_SLOPE_HALF = 3.0792;
export const TONE_BUMP_SLOPE_QUARTER = 6.1584;

// How far out the BASE layer of `toneRamp` reads, as a fraction of the frame's
// own width — the fix_shadow.md neighbourhood (it asks for 2%..5% of the width).
// A fraction rather than a pixel count so the preview and the export look at the
// same neighbourhood, and the measurement is flat across the range anyway: full
// deflection on the sample frame keeps 0.77 of the band's spread at 0.7%, 0.80 at
// 2.5%, 0.81 at 4.8%.
//
// The caller turns this into a BLUR, and it took a bug to make that a blur in
// fact and not only in name. The base used to be nine point samples of the child
// out at plus or minus this radius, and point samples are not an average: on a
// frame with texture at the sampling scale — a waterfall, a mountainside — the
// nine-tap luma aliases, the gain o(base)/base inherits the alias, and the
// reconstruction paints it as mottle. Measured on a 1160x774 frame at
// SHADOW +100, the high-frequency (9px high-pass) part of that gain field was
// 0.063 against 0.005 for a real blur of the same radius — 13x. So the base is
// now a real gaussian blur of the child, made by the caller (Skia's own
// MakeBlur, see blurredBase() in exportEngine.ts) and read here as ONE tap. That
// is also the cheaper pass: nine child evals walk the whole exposure/matrix
// chain nine times, one eval does not.
export const TONE_BASE_RADIUS = 0.025;

// One gaussian sigma of the base blur, as a fraction of TONE_BASE_RADIUS. A box
// of the same radius and a gaussian of this sigma carry the same weight at the
// radius, so the neighbourhood is the one the radius has always named while the
// cuts are smooth instead of hard.
export const TONE_BASE_SIGMA = 0.35;

// The tone and exposure maths, in ONE copy, because two passes ask it: the
// whole-frame passes here and a gradient mask, which moves the same knobs on the
// shape the user drew. What "HIGHLIGHT" or "EXPOSURE" means must not depend on
// where the shape is, and it did: the frame moved the ramp's knots while a mask
// ran a smoothstep luma lift with an arbitrary 0.55..1.35 chroma clamp, and the
// frame's exposure was a linear-light stop while a mask's was a stop on
// sRGB-encoded values. That divergence is what the scratchpad compat doc §3.3
// warns the Android port about. `dr` is the whole frame's DYNAMIC RANGE; a mask
// has no such knob and hands in 0, which is what DR's terms are worth when it is
// off on the frame too.
export const TONE_MATH_SKSL = `
// One knob's move, read at the position x on the ramp: 1 on the knob's own knot,
// falling to 0 on the knot a half-width away and staying there — (1-u^2)^2 with u
// the distance to the knot in half-widths. Level at u = 0 and at u = 1, so the
// move joins the ramp without an angle at either end.
float toneBump(float x, float knot, float half_width) {
  float u = (x - knot) / half_width;
  float v = max(0.0, 1.0 - u * u);
  return v * v;
}
// The ramp the pixel is rebuilt through: the identity plus four moves. Each knob
// owns a bump that PEAKS on its knot — BLACK on 0.00, SHADOW on 0.25, HIGHLIGHT
// on 0.75, WHITE on 1.00 — and is back on zero where the next one starts, a
// quarter away (a half for the two ends, their knots being the ends of the ramp),
// so the two bumps of a half meet on 0.50 at zero height AND zero slope: a knob
// moves its own end of the ramp and nothing else, and 0.50 is fixed — the one
// point all four sliders leave alone, which is what keeps a mid-grey a mid-grey
// while the ends move around it. Every knob on zero leaves the sum empty, so the
// whole thing is exactly the identity (see the note at the head of this file).
//
// Straight segments between the knots were the first cut, and the measurement is
// what retired them: a segment meets its neighbour at an angle, and an angle in a
// tone curve is a Mach band. On a 1024-step luma wedge (scratchpad probe, JPEG
// 8-bit, second derivative through a ±1% box) BLACK +100 came back with 105 at
// 0.030 while the stretch above it was untouched to the last bit — 0.0000 from
// 0.25 up, the "transition stays grey" the knob was reported for — and HIGHLIGHT
// -100 broke at 0.747 with 72, the seam between the lifted highlights and the
// shadow under them. The kernel is (1-u^2)^2: level at the peak, so a knot moves
// without a fold at its own top, level where it lands, so the join on 0.50 and
// the toe on 0.00 stay clean, and C1 at both ends of a move and everywhere
// between, which is the whole of what a Mach band asks for.
//
// DR moves the same four bumps instead of adding its own masked terms on top: it
// lifts the toe and rolls the head exactly as before at t = 0 and t = 1 —
// 0.12 and 0.18 at full strength — and half of each at the knots next to them,
// so the terms land on the two ends and on the heads beside them as one move.
//
// Lightness takes the curve; the colour rides the ratio. The pixel moves to its
// new luma, and it gets there by scaling its three channels by ONE number,
// k = o / t: the doc's R_new = R_old * Luma_new / Luma_old. The differences move
// with the light, so the hue cannot turn, the saturation cannot be drained by a
// lift — an HSL saturation is a ratio of differences and never sees a common
// scale — and a neutral, with no difference to carry, lands on o exactly.
//
// The scale used to be 1.0 instead: keep the chroma, move the luma. That holds
// the hue and loses the colour, which is the complaint the ratio answers — the
// scratchpad probe (sh-bl-hue.mjs) measured a dark red at 0.746 of saturation
// coming back at 0.505 with SHADOW at +100, and at 0.370 with SHADOW and BLACK
// both at +100. A chroma held under a rising luma IS a colour going grey, and it
// is the two sliders that lift a shadow (SHADOW, BLACK) that raise the luma of a
// dark pixel the furthest.
//
// What the ratio cannot do on its own is fit, and that is what the caps below are
// for: past the ceiling a channel clips outright, the three stop being scaled
// together and the hue goes with them (measured on the other probe, a skin tone
// at 24.0° came back at 48.0° at HIGHLIGHT +100, a warm white at 37° at 57.4°).
// Pulling the ONE scale back while the cube has room for no more costs saturation
// instead: a pixel the cube is against arrives neutral before it arrives wrong,
// and one the curve has driven all the way to 1.0 arrives at white.
//
// Below t = 0.0004 there is no ratio worth the name: dividing by what is left of
// a pixel that has almost no light on it takes whatever cast the last code value
// of 8-bit noise left there and multiplies it by the pedestal the BLACK knob just
// lifted — colour noise, amplified to the size of the lift. The scale stays 1.0
// down there and the pixel takes the pedestal as the flat grey it is.
//
// ONE move of the light, and everything in this file that changes how bright a
// pixel is goes through it: a tone knob, a mask's tone knob, and the exposure
// knob on both. The luma lands on o and the channel differences ride along at
// one shared scale k, so a knob named "change the brightness" changes the
// brightness and nothing else — what a per-channel multiply cannot promise once
// a channel reaches the ceiling, where the three clip by different amounts and
// the hue goes with them.
vec3 lightMove(vec3 c, float t, float o) {
  float k = t > 0.0004 ? o / t : 1.0;
  float hiC = max(max(c.r, c.g), c.b);
  float loC = min(min(c.r, c.g), c.b);
  if (hiC > t) k = min(k, (1.0 - o) / (hiC - t));
  if (loC < t) k = min(k, o / (t - loC));
  return clamp(vec3(o) + (c - vec3(t)) * k, 0.0, 1.0);
}
vec3 toneRamp(vec3 c, float t, float base, float bl, float sh, float hl, float wh, float dr) {
  // BLACK owns 0.00, the edge of the ramp, so its bump is the half-width one and
  // the toe opens to A while the quarter above it takes the fall of it. As a
  // bump the fall is a slope and never a plateau, which is what the report was
  // about: at +100 the lift used to be spent inside 0.25 and the stretch above it
  // came back identical to the untouched frame — the measured 0.0000 from 0.25 up
  // in the note at the top of the ramp. Here the mid-tones rise a little with the
  // toe and the corner that drew the seam at 0.25 is gone.
  float blackA = ${TONE_ANCHOR} * bl + dr * 0.12;
  // SHADOW rides HALF the anchor, and that is a measured ceiling rather than a
  // taste. The knot is the HEAD of the quarter above it, and the bump only ever
  // ADDS to the identity, so that quarter pays in slope for every unit the knot
  // rises: its mean slope is 1 - A / 0.25, and that band is where a waterfall's
  // spray and a sunlit rock sit. At the whole anchor the mean is 0 and the band
  // is drawn flat — on a real frame (DSCF1701, misty valley, 21% of its pixels in
  // the band) SHADOW +90 came back with 0.10 of the band's own spread and a mean
  // of 0.392 where it was 0.489, the milky white sheet the knob was reported for,
  // bright areas with their contrast gone. At half: 0.55 of the spread, mean
  // 0.441, and the toe still opens at 1.45x. Half also keeps the knob clear of
  // the guard below: at a whole-anchor rate the guard would take over past ±65
  // and the top third of the slider would do nothing, which is why the RATE is
  // halved and not just a ceiling.
  float shadowA = ${TONE_ANCHOR} * 0.5 * sh + dr * 0.06;
  // HIGHLIGHT rides half the anchor for the reason SHADOW does, and its knot is
  // the head of the 0.75..1.00 quarter: at a whole-anchor rate +100 (A = 0.25)
  // draws that quarter flat against the ceiling, its whole mean slope gone, and
  // the same knob the other way spends the quarter BELOW the knot instead. Half
  // draws neither, and the head still rolls from 0.625 to 0.875 over the travel.
  float highA = ${TONE_ANCHOR} * 0.5 * hl - dr * 0.09;
  float whiteA = ${TONE_ANCHOR} * wh - dr * 0.18;
  // Two bumps share each half of the ramp, and their steep sides can land on the
  // same stretch: past a total slope of 1 the sum would carry the curve
  // BACKWARDS — a fold, a worse band than the seams this replaced. Read at their
  // own steepest points, which is the loosest the pair can be, the two amplitudes
  // of a half are held under one number and given up together past it. A knob on
  // its own never reaches it — a full BLACK is 0.77, a full SHADOW 0.77, and DR,
  // which moves both bumps of a half at once, 0.74 below and 1.11 above for a
  // steepest sum of 1.00, so a full DR gives up a tenth of its head roll — so a
  // single slider has its whole travel, and only a pair pushed together gives
  // anything up: BLACK and SHADOW both at +100 arrive at 0.65 of their own lift
  // rather than folding.
  float holdLo = ${TONE_BUMP_SLOPE_HALF} * abs(blackA) + ${TONE_BUMP_SLOPE_QUARTER} * abs(shadowA);
  float holdHi = ${TONE_BUMP_SLOPE_QUARTER} * abs(highA) + ${TONE_BUMP_SLOPE_HALF} * abs(whiteA);
  float kLo = holdLo > 1.0 ? 1.0 / holdLo : 1.0;
  float kHi = holdHi > 1.0 ? 1.0 / holdHi : 1.0;
  blackA *= kLo;
  shadowA *= kLo;
  highA *= kHi;
  whiteA *= kHi;
  // The ramp is read at the BASE, so the curve's move is the neighbourhood's and
  // the pixel keeps its own difference from it — the ratio below is the whole of
  // the detail layer (fix_shadow.md's Reconstructed = Base' * (Input / Base)),
  // with lightMove and its caps doing the reconstruction the way every other
  // brightness move in this file is made. The pixel's own luma still travels as
  // t: it is the value that is being rebuilt, and the one the caps read.
  float o = base
    + blackA * toneBump(base, 0.00, 0.50)
    + shadowA * toneBump(base, 0.25, 0.25)
    + highA * toneBump(base, 0.75, 0.25)
    + whiteA * toneBump(base, 1.00, 0.50);
  // Below the pedestal there is no base worth a ratio (the same floor lightMove
  // holds its own scale under); the pixel is left where the ramp put its own
  // luma, which is what a caller with no neighbourhood hands in anyway.
  float target = base > 0.0004 ? o * t / base : t;
  return lightMove(c, t, clamp(target, 0.0, 1.0));
}
// The accurate sRGB transfer pair (0.04045/12.92 + 2.4, and its inverse): the
// same constants colorUtils.planckianLinear uses on the WB side, and the reason
// a stop is a stop here. EXPOSURE needs it — 2^ev is a multiplier on LIGHT — and
// so does anything else that has to reach the linear domain.
vec3 toLinear(vec3 c) {
  return mix(c / 12.92, pow((c + 0.055) / 1.055, vec3(2.4)), step(vec3(0.04045), c));
}
vec3 toEncoded(vec3 c) {
  return mix(c * 12.92, 1.055 * pow(c, vec3(1.0 / 2.4)) - 0.055, step(vec3(0.0031308), c));
}
// One EXPOSURE knob, wherever it is: the frame's own pass and a mask's knob. It
// linearises, moves the LIGHT by 2^ev — a stop is a multiplier on light, and on
// an sRGB-encoded value +1 EV would take a mid-grey 0.5 straight to a blown 1.0
// where a real stop gives 0.73 (measured: 0.6858 through here, and the plain
// per-channel multiply puts the same 0.6858 on a grey, so a neutral is the knob
// it always was) — and re-encodes.
//
// The linear domain decides WHERE the luma is going; the move is then made by
// lightMove on the encoded values, where the tone ramp also works. That split is
// measured, not chosen for symmetry: carrying the chroma in the LINEAR domain
// drifts the hue of the encoded pixel by up to 12° (a saturated red at -1 EV
// came back at 12.1°, a skin tone at +1 EV at 11.5° — the encoding is
// per-channel, so equal ratios in linear are not equal ratios on screen),
// against 0.00° this way. The knob whose whole promise is brightness must not be
// the one that also moves a hue: a channel that would have clipped gives up
// saturation instead, and a pixel the move has driven all the way to 1.0 is white
// in all three channels at once.
vec3 exposureMove(vec3 rgb, float ev) {
  vec3 c = clamp(rgb, 0.0, 1.0);
  float t = clamp(dot(c, vec3(0.2126, 0.7152, 0.0722)), 0.0, 1.0);
  // The linear domain says where the luma is going; the value that lands there
  // is applied as a RATIO on the pixel's own encoded luma, not pointed at
  // directly. toEncoded(luma_lin * 2^ev) is the target, and on a grey it IS the
  // pixel's new luma (a stop on a neutral is the stop it always was) — but the
  // transfer does not commute with the luma weights, so on a colour the two
  // differ by a couple of code values, and the knob on 0 EV would brighten the
  // frame instead of leaving it alone. As a ratio it is exactly 1 at 0 EV.
  float lin = max(dot(toLinear(c), vec3(0.2126, 0.7152, 0.0722)), 1e-6);
  float stop = toEncoded(vec3(min(1.0, lin * exp2(ev)))).r / toEncoded(vec3(lin)).r;
  return lightMove(c, t, clamp(t * stop, 0.0, 1.0));
}
`;

export const TONE_SKSL = `
uniform shader src;
// The BASE layer's child: a blur of the image above, of TONE_BASE_RADIUS, made
// by the caller. Read for its luma alone, and read ONCE per pixel — the
// neighbourhood is the blur's, not a sampling loop's (see TONE_BASE_RADIUS).
uniform shader base;
uniform float dr;
uniform float hl;
uniform float sh;
uniform float wh;
uniform float bl;
uniform float vib;
uniform float shTr;
uniform float shTg;
uniform float shTb;
uniform float hlTr;
uniform float hlTg;
uniform float hlTb;
uniform float cc;
uniform float ccb;
uniform float hslOn;
uniform float hslH[8];
uniform float hslS[8];
uniform float hslL[8];
uniform float gh;
uniform float gs;
uniform float gl;
// sRGB <-> HSL. The mixer works in HSL because that is the space the knobs are
// named after: a hue shift must not change how light a colour is, and a
// lightness move must not change its hue, which is exactly what scaling RGB
// does wrong.
vec3 rgb2hsl(vec3 c) {
  float mx = max(max(c.r, c.g), c.b);
  float mn = min(min(c.r, c.g), c.b);
  float l = (mx + mn) * 0.5;
  float d = mx - mn;
  if (d < 0.00001) return vec3(0.0, 0.0, l);
  float s = l > 0.5 ? d / max(0.00001, 2.0 - mx - mn) : d / max(0.00001, mx + mn);
  float h;
  if (mx == c.r) h = (c.g - c.b) / d + (c.g < c.b ? 6.0 : 0.0);
  else if (mx == c.g) h = (c.b - c.r) / d + 2.0;
  else h = (c.r - c.g) / d + 4.0;
  return vec3(h / 6.0, s, l);
}
float hueChannel(float p, float q, float t) {
  t = fract(t);
  if (t < 1.0 / 6.0) return p + (q - p) * 6.0 * t;
  if (t < 0.5) return q;
  if (t < 2.0 / 3.0) return p + (q - p) * (2.0 / 3.0 - t) * 6.0;
  return p;
}
vec3 hsl2rgb(vec3 hsl) {
  if (hsl.y < 0.00001) return vec3(hsl.z);
  float q = hsl.z < 0.5 ? hsl.z * (1.0 + hsl.y) : hsl.z + hsl.y - hsl.z * hsl.y;
  float p = 2.0 * hsl.z - q;
  return vec3(
    hueChannel(p, q, hsl.x + 1.0 / 3.0),
    hueChannel(p, q, hsl.x),
    hueChannel(p, q, hsl.x - 1.0 / 3.0)
  );
}
// One band's ownership of a hue: full at the band's own anchor, falling
// linearly to 0 at each neighbour's anchor (the gaps are uneven — red sits 30°
// from orange and 40° from magenta). Linearity is the point: adjacent tents
// cross at exactly 0.5 at the midpoint, so the eight weights sum to 1 at every
// hue. No pixel is counted twice, no pixel falls between two bands, and a hue
// sitting on an anchor gets that band's full value instead of a share of it.
float bandW(float hue, float anchor, float gapL, float gapR) {
  float d = mod(hue - anchor + 180.0, 360.0) - 180.0;
  return d <= 0.0 ? max(0.0, 1.0 + d / gapL) : max(0.0, 1.0 - d / gapR);
}
${TONE_MATH_SKSL}
// The BASE layer: the light the frame carries where this pixel sits, at the
// radius the caller handed in. One tap of a real blur of the same child the
// pixel comes from, so it is an AVERAGE of the neighbourhood and not a handful
// of point samples of it — that distinction is the whole bug (see
// TONE_BASE_RADIUS). Luma, because the luma is the one quantity the ramp moves
// and the colour rides the ratio afterwards; the blur being linear, blurring the
// child and taking its luma is the same as blurring the luma.
//
// A caller with no neighbourhood to speak of hands in the child itself as the
// base (see blurredBase()): the tap then lands exactly on t and the pass falls
// back to the global move, which is what a shape with a mask's degenerate base
// wants and what it got from a bx of zero before.
float baseLuma(vec2 xy) {
  vec3 s = clamp(base.eval(xy).rgb, 0.0, 1.0);
  return clamp(dot(s, vec3(0.2126, 0.7152, 0.0722)), 0.0, 1.0);
}
vec4 main(vec2 xy) {
  vec4 c = src.eval(xy);
  vec3 rgb = clamp(c.rgb, 0.0, 1.0);
  // NOTE: never name a local 'out' — it is a reserved SkSL qualifier.
  float t = clamp(dot(rgb, vec3(0.2126, 0.7152, 0.0722)), 0.0, 1.0);
  // The four tents of the doc, one per quarter of the ramp: BLACKS peaks on
  // 0.00 and is gone by 0.25, SHADOWS peaks on 0.25 and is gone by 0.50,
  // HIGHLIGHTS peaks on 0.75 and is gone by 0.50 and 1.00, WHITES peaks on
  // 1.00 and is gone by 0.75. Each is the doc's own smoothstep, each is clipped
  // by subtracting the tent before it so the four never overlap and no luma is
  // ever counted twice, and the 0.50 midpoint is weighted by none of them: they
  // are the weights the stock split tones ride, which is why they are smooth and
  // why they stay out of the ramp below — nothing else in this shader reads them.
  float blMask = 1.0 - smoothstep(0.00, 0.25, t);
  float shMask = clamp(1.0 - smoothstep(0.25, 0.50, t) - blMask, 0.0, 1.0);
  float whMask = smoothstep(0.75, 1.00, t);
  float hlMask = clamp(smoothstep(0.50, 0.75, t) - whMask, 0.0, 1.0);
  // The four tonal-range knobs, on the shared ramp: see TONE_MATH_SKSL — the
  // same knots, the same hue-preserving rebuild, the same move a gradient mask
  // makes with the same four sliders. DR is the whole frame's, so it is spent
  // here and nowhere else.
  rgb = toneRamp(rgb, t, baseLuma(xy), bl, sh, hl, wh, dr);
  // Split tone (stock look): the shadows and the highlights may each carry
  // their own tint, so the two ends of the curve can drift opposite ways
  // (Classic Neg: green-cyan darks, warm brights) without touching mid-greys.
  rgb = clamp(rgb + vec3(shTr, shTg, shTb) * shMask + vec3(hlTr, hlTg, hlTb) * hlMask, 0.0, 1.0);
  // Color Chrome / Color Chrome FX Blue: the two stock-dialed colour effects
  // DEEPEN what is already chromatic and leave neutrals exactly where they are
  // (Fuji: "deeper tone in highly saturated colour"; FX Blue does it for the
  // blue/cyan side only). Both therefore need per-pixel chroma — a 4x5 colour
  // matrix is one linear map, so any gain it applies also moves greys, and a
  // blue-only gain drags the whole white point.
  float mxc = max(max(rgb.r, rgb.g), rgb.b);
  float mnc = min(min(rgb.r, rgb.g), rgb.b);
  // Chroma ratio with a small floor: a near-black pixel with a hair of cast
  // has ratio 1.0 but no colour to deepen, and must stay put.
  float ccChroma = (mxc - mnc) / max(mxc, 0.10);
  // Color Chrome rides the chroma itself: a muted colour barely moves, a vivid
  // one gains density. The 0.25 knee keeps skin, haze and pastels untouched.
  float ccMask = cc * smoothstep(0.25, 0.85, ccChroma);
  // FX Blue: only where blue clearly leads red AND green (so magenta/purple
  // stay out), and richest in a bright blue — a dark blue has no tonality left
  // to deepen.
  float ccbBlue = clamp((rgb.b - rgb.r) * 2.0, 0.0, 1.0) * clamp((rgb.b - 0.5 * (rgb.r + rgb.g) + 0.05) * 3.0, 0.0, 1.0);
  float ccbMask = ccb * ccbBlue * smoothstep(0.15, 0.60, ccChroma) * smoothstep(0.20, 0.70, t);
  float deep = clamp(ccMask + ccbMask, 0.0, 1.0);
  // Density = lightness down with the colour difference riding along, so hue is
  // preserved and the colour cannot collapse toward black (same reason the tone
  // curve above keeps chroma). A touch of chroma is given up as it deepens.
  float l3 = dot(rgb, vec3(0.2126, 0.7152, 0.0722));
  rgb = clamp(vec3(l3 * (1.0 - 0.28 * deep)) + (rgb - vec3(l3)) * (1.0 - 0.10 * deep), 0.0, 1.0);
  // Vibrance: push the LESS-saturated pixels harder than the vivid ones.
  float l2 = dot(rgb, vec3(0.2126, 0.7152, 0.0722));
  float mx = max(max(rgb.r, rgb.g), rgb.b);
  float mn = min(min(rgb.r, rgb.g), rgb.b);
  float chroma = mx > 0.0001 ? (mx - mn) / mx : 0.0;
  float kv = 1.0 + vib * 0.75 * (1.0 - chroma);
  rgb = clamp(mix(vec3(l2), rgb, kv), 0.0, 1.0);
  // Selective colour by hue band — the last move, so a band edit is judged
  // against the colour the user actually sampled off the render.
  //
  // A grey is dropped before the weights are read: rgb2hsl hands it hue 0, so
  // without this fade every neutral pixel in the frame would be treated as
  // pure red and slide with the red band. Below 8% saturation there is no hue
  // to move anyway.
  //
  // The three accumulators are the band values scaled by ownership, so a hue
  // landing between two anchors gets a proportional mix of the two edits —
  // the same blend the weights already sum to. Hue is a turn (±30° at full),
  // saturation is a scale (0 = grey at -10), lightness is additive (±0.25 at
  // full) so it cannot invert the ramp.
  if (hslOn > 0.5) {
    vec3 hsl = rgb2hsl(rgb);
    float gate = smoothstep(0.0, 0.08, hsl.y);
    float hd = hsl.x * 360.0;
    // The overall move is the seed: every hue gets its turn and its saturation
    // scale at full weight, and the bands add their own share on top. The
    // lightness term is added below UNGATED, so it still lifts a colour that a
    // -SAT has already drained to grey.
    vec3 acc = vec3(gh, gs, 0.0) * gate;
${BAND_BLOCK}    hsl.x = fract(hsl.x + acc.x * (30.0 / 360.0));
    hsl.y = clamp(hsl.y * (1.0 + acc.y), 0.0, 1.0);
    hsl.z = clamp(hsl.z + (acc.z + gl) * 0.25, 0.0, 1.0);
    rgb = hsl2rgb(hsl);
  }
  return vec4(clamp(rgb, 0.0, 1.0), c.a);
}
`;

// EXPOSURE / EV — the one pass that has to run in LINEAR light.
//
// A stop is a multiplier on LIGHT, and the old EV row multiplied sRGB-ENCODED
// values: +1 EV took a mid-grey 0.5 straight to a blown 1.0 where a real stop
// gives 0.73. exposureMove linearises, moves the light by 2^ev, and re-encodes —
// and it spends that stop on the LUMA, not on the three channels one at a time,
// so this knob only ever changes how bright a pixel is: a channel that would
// have clipped gives up saturation instead of dragging the hue (a gradient
// mask's own EXPOSURE runs through the same function, on the mask's pixels).
//
// It sits between the graded image and the tone shader (see exportEngine step 3),
// so `ev` carries the EXPOSURE knob, the stock's own bias and the EV knob added
// up in stops — the caller hands in one number.
export const EXPOSURE_SKSL = `
uniform shader src;
uniform float ev;
${TONE_MATH_SKSL}
vec4 main(vec2 xy) {
  vec4 c = src.eval(xy);
  return vec4(exposureMove(clamp(c.rgb, 0.0, 1.0), ev), c.a);
}
`;

// Bright Pass Filter for the HDF EFFECT pass (HDF), SkSL over a child image
// shader — the pattern TONE_SKSL above already proved on device.
//
// Per channel the old 2.5*in-1.5 curve only zeroed a channel that was dark
// *itself*: a saturated blue (B = 1.0) came out of it fully lit, so a dark blue
// shadow bloomed and a dark saturated colour smeared its hue into the darks.
// Photoshop's Bright Pass filters on the LUMINANCE instead: one knee decides how
// much light a pixel carries, and one gain scales all three channels, so below
// the knee the output is exactly 0.0 (Screen against black = no-op, the shadows
// are untouched) and above it every channel keeps its ratio — the hue cannot
// drift, only the brightness blooms.
//
// Knee t0..t1 = 0.45..0.75. The web demo plays the effect up, so the knee sits
// lower and wider than the phone's 0.55..0.85: the bloom now catches the bright
// end of the midtones (a lit face, a window) instead of only true speculars,
// which is what makes it read on a photo that has no blown white.
export const GLOW_T0 = 0.45;
export const GLOW_T1 = 0.75;

export const GLOW_SKSL = `
uniform shader src;
uniform float t0;
uniform float t1;
vec4 main(vec2 xy) {
  vec4 c = src.eval(xy);
  float luma = dot(clamp(c.rgb, 0.0, 1.0), vec3(0.2126, 0.7152, 0.0722));
  return vec4(c.rgb * smoothstep(t0, t1, luma), c.a);
}
`;

// Flat uniform buffer for `makeShaderWithChildren` — same order as GLOW_SKSL's
// declarations (t0, t1).
export function glowUniformArray(): number[] {
  'worklet';
  return [GLOW_T0, GLOW_T1];
}

// Same values for the declarative <Shader> path, which indexes uniforms by
// NAME (a flat array is only valid for the JS makeShaderWithChildren API).
export const GLOW_UNIFORMS = { t0: GLOW_T0, t1: GLOW_T1 };

// CLARITY (positive): unsharp 3x3 with epsilon 0 — the kernel export pass 4
// builds with MakeMatrixConvolution, re-expressed as a plain shader because RN
// Skia 2.6 exposes no convolution image filter to the declarative JSX writer.
// `px` is one ORIGINAL image pixel expressed in the caller's canvas units, so
// the preview, the camera worklet and the file all sharpen at the same radius.
export const CLARITY_SKSL = `
uniform shader src;
uniform float a;
uniform float2 px;
vec4 main(vec2 xy) {
  vec4 c = src.eval(xy);
  vec4 s = src.eval(xy + float2(0.0, -px.y))
         + src.eval(xy + float2(0.0,  px.y))
         + src.eval(xy + float2(-px.x, 0.0))
         + src.eval(xy + float2( px.x, 0.0));
  return vec4(clamp(c.rgb * (1.0 + 4.0 * a) - a * s.rgb, 0.0, 1.0), c.a);
}
`;

// Named uniforms for <Shader uniforms>, same names as CLARITY_SKSL declares.
export function clarityUniforms(a: number, pxX: number, pxY: number) {
  return { a, px: [pxX, pxY] };
}

// CLARITY's reference image B, one axis at a time — the multiple-pass
// architecture of ki_n_tr_c_multiple_passes_cho_webgpu.md: a single 15x15 kernel
// reads 225 pixels per pixel, a separable pair (1x15 then 15x1) reads 30. The
// kernel is the doc's bilateral filter: the gaussian weight falls off along the
// axis, and a range weight kills a tap whose colour is nothing like the centre's,
// so an edge is not blurred across and the reference does not ghost it.
// `dir` is one tap's step in the caller's units (px along ONE axis, the other
// component 0), so a preview and the file blur the same fraction of the frame.
// SkSL has no dynamic loop bound here, so the 15 taps are the doc's own count.
export const CLARITY_BLUR_SKSL = `
uniform shader src;
uniform float2 dir;
vec4 main(vec2 xy) {
  vec4 c = src.eval(xy);
  vec3 sum = c.rgb;
  float total = 1.0;
  for (int i = 1; i <= 15; i++) {
    float fi = float(i);
    float g = exp(-0.5 * (fi / 5.0) * (fi / 5.0));
    vec4 a1 = src.eval(xy + dir * fi);
    vec4 a2 = src.eval(xy - dir * fi);
    vec3 d1 = a1.rgb - c.rgb;
    vec3 d2 = a2.rgb - c.rgb;
    float r1 = exp(-dot(d1, d1) * 24.0);
    float r2 = exp(-dot(d2, d2) * 24.0);
    sum += g * (r1 * a1.rgb + r2 * a2.rgb);
    total += g * (r1 + r2);
  }
  return vec4(sum / total, c.a);
}
`;

// CLARITY, pass 3 of the doc's architecture: the frame against its own blurred
// reference — `orig + (orig - B) * strength` above zero, the mix back toward B
// below it. One reference, one pass, both directions of one knob: a NEGATIVE
// CLARITY is the positive one's soften, not a second kind of blur picked for the
// sign (that mist had another radius than the reference the positive side reads,
// so -10 and +10 were two different neighbourhoods and a MASK's CLARITY could
// not be the frame's own move). Clamped because a file cannot hold more than
// white. Runs on the ENCODED pixels like every other grade here (only
// EXPOSURE_SKSL is linear light, see colorUtils.exposureStops) — the doc's
// formula is written for linear light, and moving the whole renderer there is a
// bigger change than this pass.
export const CLARITY_BLEND_SKSL = `
uniform shader original;
uniform shader blurred;
uniform float strength;
vec4 main(vec2 xy) {
  vec4 c = original.eval(xy);
  vec3 b = blurred.eval(xy).rgb;
  vec3 d = c.rgb - b;
  vec3 out_rgb = strength >= 0.0 ? c.rgb + d * strength : mix(c.rgb, b, clamp(-strength, 0.0, 1.0));
  return vec4(clamp(out_rgb, 0.0, 1.0), c.a);
}
`;

// Strength that keeps CLARITY 10 where the 3x3 kernel had it: that kernel was
// `c*(1+4a) - a*sum` with a = 0.8, i.e. `c + 3.2*(c - mean4)`, so the same 3.2
// lands the same local contrast through the wider bilateral reference. The gain
// is for the POSITIVE side only: below zero the knob reads as its own fraction
// of the reference (0..1, the same units MASK's CLARITY uses on it).
export const CLARITY_GAIN = 3.2;

// DEHAZE — raw_parameter_processing_gradient_mask_algorithms.md, section 3.2.
// Haze is scattered light: it lifts the DARKEST channel of every patch, which is
// the Dark Channel Prior. The dark channel is the MINIMUM of min(r,g,b)/A over
// the patch, and that minimum is the whole prior: a patch holding anything
// genuinely dark — a shadow, a black frame line — reads 0 and is left alone,
// while only a patch with no dark pixel in it at all is haze and gets corrected.
// The patch AVERAGE this pass used to read instead (the bilateral reference)
// called every patch hazy, so the positive end ground the frame down instead of
// taking haze out. `air` is the atmospheric light the caller estimated from the
// frame — brightest dark-channel pixel of a copy of it, the doc's 0.1% answer in
// one readback (exportEngine's atmosphericLight).
//
// The pass itself is now only the doc's last line, `J = (I - A)/t + A`, on a
// transmission the caller has already solved for. `dark` is what the caller
// hands in as an image: the dark channel itself, read off a small copy of the
// frame and interpolated back up, which is the smoothing the prior wants — see
// the caller's dehazeDarkChannel for why it cannot be had from a patch read out
// per pixel. Its cell is the patch, so a value per cell is a value per patch.
//
// What travels as an image is the dark channel and not t on purpose. A channel is
// eight bits, so it can only carry 0..1 — and t is 1 + 0.95 at the negative end
// of the knob, which would arrive here clipped to 1 and turn "put the scattered
// light back" into a pass that does nothing. The dark channel is 0..1 by
// construction, and the signed amount stays a uniform where it costs no range.
//
// Signedness is then in the expression. Positive folds t below 1 and takes the
// scattered light out; negative folds it above 1 and the same expression scatters
// it back in, which is what a negative DEHAZE is for. The floor keeps a flat sky
// from dividing by zero, and the ceiling is the largest amount the knob can ask
// for either way.
export const DEHAZE_FLOOR_T = 0.1;
export const DEHAZE_MAX_OMEGA = 0.95;

// The patch the MASK's DEHAZE reads out of its own frame (gradientMask.ts) —
// `taps` samples out at `step` each, two taps at 0.625% of the frame's width, a
// 2.5%-wide neighbourhood: the DCP's own 15-pixel patch on a 600-pixel frame and
// the same fraction of a 4000-pixel export. Five by five samples rather than
// fifteen by fifteen because the doc's 225 reads per pixel is what
// CLARITY_BLUR_SKSL above already refused, and the prior only needs a patch the
// haze is flat over. The frame-wide pass reads no patch at all any more.
export const DEHAZE_PATCH_TAPS = 2;
export const DEHAZE_PATCH_STEP = 0.00625;

export const DEHAZE_SKSL = `
uniform shader img;
uniform shader dark;
uniform float3 air;
uniform float floorT;
uniform float maxT;
uniform float amount;
vec4 main(vec2 xy) {
  vec3 c = clamp(img.eval(xy).rgb, 0.0, 1.0);
  vec3 a = max(air, vec3(0.05));
  float d = clamp(dark.eval(xy).r, 0.0, 1.0);
  float t = clamp(1.0 - amount * ${DEHAZE_MAX_OMEGA} * d, floorT, maxT);
  return vec4(clamp((c - a) / t + a, 0.0, 1.0), 1.0);
}
`;

export function dehazeUniformArray(
  air: [number, number, number],
  amount: number
): number[] {
  'worklet';
  return [air[0], air[1], air[2], DEHAZE_FLOOR_T, 1 + DEHAZE_MAX_OMEGA, amount];
}

export interface ToneUniforms {
  // All zero → no tone adjustment needed (caller can skip the shader pass).
  dr: number; // 0..1
  hl: number; // -1..1 (adjustments.highlight / 10)
  sh: number; // -1..1 (adjustments.shadow / 10)
  wh: number; // -1..1 (adjustments.whites / 10 — moves the 1.00 end of the ramp)
  bl: number; // -1..1 (adjustments.blacks / 10 — moves the 0.00 end of the ramp)
  vib: number; // -1..1 (adjustments.vibrance / 10)
  shT: [number, number, number]; // shadow split-tone RGB bias, -1..1
  hlT: [number, number, number]; // highlight split-tone RGB bias, -1..1
  cc: number; // 0..1 Color Chrome depth (0 = 'none')
  ccb: number; // 0..1 Color Chrome FX Blue depth (0 = 'none')
  hslOn: number; // 1 when any band or the overall move is set (0 skips the mixer)
  hslH: number[]; // 8 × -1..1 per band, in HSL_BANDS order (±30° of hue at full)
  hslS: number[]; // 8 × -1..1 per band (saturation scale, -1 = grey)
  hslL: number[]; // 8 × -1..1 per band (additive lightness, ±0.25 at full)
  gh: number; // -1..1 whole-image hue turn (±30° at full)
  gs: number; // -1..1 whole-image saturation scale
  gl: number; // -1..1 whole-image lightness offset (±0.25 at full, ungated)
}

// Per-stock tone pass. Fuji's Classic stocks are not a plain colour matrix:
// Classic Neg splits its tone (green-cyan darks / warm brights) and Classic
// Chrome crushes the shadows hard while muting colour. Those two parts live
// here instead of in the 4x5 matrix, which cannot move one end of the curve
// without also moving the other.
//
// The `sh` and `hl` here are written at DOUBLE what the knob's own arithmetic
// reads, which is not a taste either: SHADOW and HIGHLIGHT each move their knot
// half an anchor per unit (see a1 and a3 in TONE_MATH_SKSL), so a stock that
// wants the toe on 0.18 has to ask for -0.56 to land it there. The stock's crush
// is the knot it puts the ramp on; the unit it is written in belongs to the
// knob, not to the look.
const FILM_TONE: Partial<Record<BaseFilter, Partial<ToneUniforms>>> = {
  'classic-chrome': { sh: -0.56 },
  // Classic Vivid is Classic Chrome's sibling — the shadow crush belongs to the
  // stock, not to the matrix rows, so it comes along.
  'classic-vivid': { sh: -0.56 },
  'classic-neg': { shT: [-0.018, 0.009, 0.013], hlT: [0.024, 0.008, -0.012] },
  // Acros. A black-and-white stock IS its grey ramp, so this entry only shapes
  // the two ENDS and leaves the middle an identity: a smooth shadow toe that
  // reaches a true black (no film-base lift, no flat grey wash) and a highlight
  // shoulder that stops just short of white instead of clipping a cloud to
  // paper. Mid-tones are between the 0.25 and the 0.75 knots, so they keep
  // every step the matrix handed over — which is what 'deep black' costs in a
  // colour stock and does not have to cost here.
  // The values move the two end knots of the ramp: -0.24 puts the toe on 0.22
  // and -0.10 rolls the head to 0.7375 (both SHADOW and HIGHLIGHT ride HALF an
  // anchor per unit, so a stock written against the knot asks for double).
  monochrome: { sh: -0.24, hl: -0.10 },
  // B&W HIGH CONTRAST. Acros' ramp with both ends pushed hard: a deeper toe
  // (-0.64 against Acros' -0.24, so 0.17 against 0.22) so the darks reach true
  // black, and a shoulder that LIFTS instead of rolling (-0.10 → +0.52, the
  // head going to 0.815), which is the whites step of the brief. The stretch
  // between the two inner knots (0.25 and 0.75) is still the identity, so the
  // long smooth stretch of the greys survives — that is what keeps a hard push
  // off the posterised look, and the strength the stock needs on the greys is
  // its matrix slope (SIM_CONTRAST_BIAS in colorUtils), not another move here.
  'mono-high-contrast': { sh: -0.64, hl: 0.52 },
};

// The base layer's neighbourhood is the caller's business, not this function's:
// it is a blurred CHILD of the shader (see TONE_SKSL), so only the caller knows
// how big the frame is or whether there is a frame at all. A shape with a mask
// has no frame to look at and hands in the image it is already shading, which
// lands the base on the pixel and keeps the global ramp (see baseLuma).
export function getToneUniforms(
  adj: ColorAdjustments,
  baseFilter?: BaseFilter
): ToneUniforms {
  const drRaw = adj.dynamicRange ?? 'auto';
  const dr = drRaw === 'auto' || drRaw === 100 ? 0 : (drRaw - 100) / 300;
  const hl = Math.max(-1, Math.min(1, (adj.highlight ?? 0) / 10));
  const sh = Math.max(-1, Math.min(1, (adj.shadow ?? 0) / 10));
  const wh = Math.max(-1, Math.min(1, (adj.whites ?? 0) / 10));
  const bl = Math.max(-1, Math.min(1, (adj.blacks ?? 0) / 10));
  const vib = Math.max(-1, Math.min(1, (adj.vibrance ?? 0) / 10));
  // WHITE and BLACK ride this pass with the other two, each as the end knot of
  // the same ramp (see TONE_SKSL). They are no longer a white-balance move and
  // are read by nothing else in the pipeline.
  const film = (baseFilter && FILM_TONE[baseFilter]) || {};
  const shT: [number, number, number] = film.shT ?? [0, 0, 0];
  const hlT: [number, number, number] = film.hlT ?? [0, 0, 0];
  // Color Chrome depth per stop of the UI's none/weak/strong. A chrome set is a
  // monochrome look, so both are forced off there: the effect is colour-only
  // (the preview/export matrix skips them for monochrome for the same reason).
  const colour = !isMonochromeBase(baseFilter);
  const chromeDepth = (v: ColorAdjustments['colorChrome'] | undefined) =>
    !colour || v === 'none' || v == null ? 0 : v === 'strong' ? 0.9 : 0.45;
  const blueDepth = (v: ColorAdjustments['colorChromeBlue'] | undefined) =>
    !colour || v === 'none' || v == null ? 0 : v === 'strong' ? 1.0 : 0.5;
  // Selective colour: one slot per band, in HSL_BANDS order, so the flat buffer
  // lines up with the shader's arrays. A band the user has not moved holds
  // three zeroes and costs nothing but its slot.
  const bands = adj.hslBands ?? {};
  const tenth = (v: unknown) =>
    typeof v === 'number' && Number.isFinite(v) ? Math.max(-1, Math.min(1, v / 10)) : 0;
  const hslH: number[] = [];
  const hslS: number[] = [];
  const hslL: number[] = [];
  let hslOn = 0;
  for (const band of HSL_BANDS) {
    const v = bands[band.id];
    const [h, s, l] = v ? [tenth(v[0]), tenth(v[1]), tenth(v[2])] : [0, 0, 0];
    hslH.push(h);
    hslS.push(s);
    hslL.push(l);
    if (h || s || l) hslOn = 1;
  }
  // A monochrome stock has no hue to be selective about.
  if (!colour) hslOn = 0;
  // The mixer's overall move, which every hue receives at full weight.
  const gh = tenth(adj.hslHue);
  const gs = tenth(adj.hslSat);
  const gl = tenth(adj.hslLum);
  if (colour && (gh || gs || gl)) hslOn = 1;
  return {
    dr,
    hl: hl + (film.hl ?? 0),
    sh: sh + (film.sh ?? 0),
    wh,
    bl,
    vib,
    shT,
    hlT,
    cc: chromeDepth(adj.colorChrome),
    ccb: blueDepth(adj.colorChromeBlue),
    hslOn,
    hslH,
    hslS,
    hslL,
    gh,
    gs,
    gl,
  };
}

// Flat uniform buffer for `makeShaderWithChildren` / `<Shader uniforms>` — the
// order must match TONE_SKSL's declarations.
export function toneUniformArray(u: ToneUniforms): number[] {
  return [
    u.dr, u.hl, u.sh, u.wh, u.bl, u.vib,
    u.shT[0], u.shT[1], u.shT[2], u.hlT[0], u.hlT[1], u.hlT[2], u.cc, u.ccb,
    u.hslOn, ...u.hslH, ...u.hslS, ...u.hslL, u.gh, u.gs, u.gl,
  ];
}

export function toneIsActive(u: ToneUniforms): boolean {
  return (
    u.hslOn !== 0 ||
    u.dr !== 0 ||
    u.hl !== 0 ||
    u.sh !== 0 ||
    u.wh !== 0 ||
    u.bl !== 0 ||
    u.vib !== 0 ||
    u.shT[0] !== 0 ||
    u.shT[1] !== 0 ||
    u.shT[2] !== 0 ||
    u.hlT[0] !== 0 ||
    u.hlT[1] !== 0 ||
    u.hlT[2] !== 0 ||
    u.cc !== 0 ||
    u.ccb !== 0
  );
}