// Highlight roll-off in the develop, and the four tonal knobs in the tone pass. // // THE DEVELOP holds the knee: // // L' = L , L < T // L' = T + (L - T) / (1 + 2 S (L - T)) , L >= T // // drawn on the sensor's own levels (T = 0.7, S = 1 / (2 (1 - T)), which puts the // asymptote on 1.0) so the two stops the sensor holds above its white level are // COMPRESSED into the frame instead of being thrown away by the old // fade-to-white — which is also the only reason HIGHLIGHT has detail left at the // top to move. // // THE TONE PASS moves the luma by the four knobs (HIGHLIGHT, SHADOW, WHITE, // BLACK), and each one is the MOVE ITS OWN LIGHTROOM EXPORT MADE, measured: // TONE_KNOBS in toneShader.ts holds, per knob and per side of zero, the knot // table of that move on the encoded luma. They are NOT the doc's four compact // windows any more — the windows were confined to a quarter of the ramp each and // were worth a few hundredths of luma inside it and the exact identity outside, // which is the "sau khi chỉnh sửa 4 thông số này không đúng, không thay đổi" // report: WHITE ±100 was a literal no-op. The reference exports say something // else: WHITE +100 takes everything above luma 0.50 to 1.0 (mean +0.43 over the // frame), BLACK -100 takes everything below 0.21 to 0.0 (mean -0.14), HIGHLIGHT // +100 is a +0.24 lift peaking on luma 0.18 and dead by 0.72. // // The four are applied ONE AFTER THE OTHER (BLACK -> SHADOW -> HIGHLIGHT -> // WHITE), each clamped on the way to the next, so a composition of monotone maps // is monotone by construction and the ramp needs no guard whatever the four // sliders say — and the knot tables are cut so that L + move is non-decreasing on // every segment, which the sweep below measures rather than asserts. // // Both are SkSL, so the SHAPE is pinned on the source; the tables are then // re-run here as a twin and checked against the measurement they were FITTED to // (the nine exports in the repo root), so a table that drifts off the export is a // red check. The frame-through-the-real-shader diff lives in the scratchpad // harness render.mjs, which needs the nine JPEGs. // // node scripts/highlight-knee-check.mjs import assert from 'node:assert/strict'; import { mkdtempSync, readFileSync, writeFileSync } from 'node:fs'; import { tmpdir } from 'node:os'; import { join } from 'node:path'; import { fileURLToPath, pathToFileURL } from 'node:url'; import ts from 'typescript'; const read = (p) => readFileSync(new URL(p, import.meta.url), 'utf8'); const develop = read('../src/engine/rawDevelop.ts'); const tone = read('../shared/utils/toneShader.ts'); // The tone shader is IMPORTED, transpiled, so the numbers below are the ones the // shader is built with and not a regex's reading of them. const transpile = (path) => ts.transpileModule(read(path), { compilerOptions: { module: ts.ModuleKind.ESNext, target: ts.ScriptTarget.ES2022 }, }).outputText; const dir = mkdtempSync(join(tmpdir(), 'highlight-knee-check-')); writeFileSync(join(dir, 'colorUtils.mjs'), transpile('../shared/utils/colorUtils.ts')); writeFileSync( join(dir, 'toneShader.mjs'), transpile('../shared/utils/toneShader.ts').replace( /^import .*from ['"]\.\/colorUtils['"];$/m, 'import { HSL_BANDS, hslBandGaps, isMonochromeBase } from "./colorUtils.mjs";', ), ); const { TONE_SKSL: sksl, TONE_MATH_SKSL: maths, EXPOSURE_SKSL, TONE_KNOBS, TONE_BLACK_EDGE, TONE_BASE_RADIUS, TONE_BASE_SIGMA, toneUniformArray, } = await import(pathToFileURL(join(dir, 'toneShader.mjs')).href); const text = (s) => new RegExp(s.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')); const codeOf = (s) => s.replace(/\/\/[^\n]*/g, ''); // THE FOUR KNOBS, as the source declares them. Each curve is a knot table on the // encoded luma: positions ascending from the floor to the head, values the move // at +100 (the minus side is read with an amount below zero). const KNOBS = ['bl', 'sh', 'hl', 'wh']; for (const k of KNOBS) { for (const side of ['plus', 'minus']) { const c = TONE_KNOBS[k][side]; assert.equal(c.p.length, c.v.length, `${k}.${side}: ${c.p.length} knots against ${c.v.length} values`); assert.equal(c.p[0], 0, `${k}.${side} does not start on the floor`); assert.equal(c.p[c.p.length - 1], 1, `${k}.${side} does not end on the head`); for (let i = 1; i < c.p.length; i++) assert.ok(c.p[i] > c.p[i - 1], `${k}.${side} knot ${i} is not past the one before it`); } } // One knob as the shader gets it: the table drawn STRAIGHT between the knots — a // hinge per segment, written as a sum of clamps because SkSL indexes arrays by // constant only — scaled by the amount, added to the luma it reads and clamped. // The side of zero picks the table, and the clamp is what makes a -- knob's own // clip a plateau instead of a fold. for (const k of KNOBS) assert.match( maths, text(`float tone${k}(float L, float amt) {\n return clamp(L + (amt >= 0.0 ? amt * (`), `${k} is not the measured table read as a polyline` ); assert.match(maths, /: -amt \* \(/); // ...pinned at the SOURCE's own numbers: the hinge from knot 0.045 to knot 0.185 // on BLACK's plus side is worth 0.1155 - 0.0876, over a segment 0.140 wide. assert.match(maths, text(' + (0.0279) * clamp((L - 0.045) / 0.140, 0.0, 1.0)')); // The composition, move for move: the four in the order the exports were read, // each self-clamping (tone* does it), so a knob that has driven the luma to an // end leaves the ones after it nothing to fold. assert.match( maths, text('float toneCurve(float L, float bl, float sh, float hl, float wh) {\n L = tonebl(L, bl);\n L = tonesh(L, sh);\n L = tonehl(L, hl);\n L = tonewh(L, wh);\n return clamp(L, 0.0, 1.0);\n}') ); // ...and the four COMPACT WINDOWS the knobs used to be are gone from the CODE — // they were the "không thay đổi" bug. The prose is not read for these: // TONE_MATH_SKSL still tells the story of what replaced them. assert.doesNotMatch(codeOf(maths), /toneBlackW|toneBlack\(|toneShadowW|toneHighW|toneWhiteW|toneBump|holdLo|holdHi/); assert.doesNotMatch( tone, /export const TONE_WHITE_EDGE|export const TONE_BLACK_LIFT|export const TONE_BLACK_CRUSH|export const TONE_HIGH_GAIN|export const TONE_WHITE_GAIN|export const TONE_ANCHOR|export const TONE_BUMP_SLOPE/, 'a window edge or rate is still declared' ); // The BLACK knob's Hunt chroma mask is the one thing that still reads the doc's // 0.18 — it is a chroma floor, not a knob window. assert.match(maths, new RegExp(text(`float uBl = clamp(1.0 - t / ${TONE_BLACK_EDGE}, 0.0, 1.0);`))); const knobBlock = maths.slice(maths.indexOf('float tonebl'), maths.indexOf('float toneCurve')); assert.ok(knobBlock.includes('float tonewh'), 'the four knob functions are gone'); assert.doesNotMatch( knobBlock, /smoothstep|pow\(|exp\(/, 'a knob is not the measured table any more — it bends again' ); // DR rides the same four moves with a share of each instead of masked terms of // its own, so it cannot fight a knob over a band or invert the ramp. assert.match(maths, text('float blVal = clamp(bl + dr * 0.12, -1.0, 1.0);')); assert.match(maths, text('float shVal = clamp(sh + dr * 0.06, -1.0, 1.0);')); assert.doesNotMatch(maths, /o = clamp\(base/, 'the ramp clamps the base before the curve again — the ends of the ramp are the anchors'); assert.doesNotMatch(codeOf(sksl), /float a4 = /, 'the ramp is back inside the pass — one copy, not two'); // The uniform block: the shader's declarations, arrays expanded and in // declaration order, have to be the numbers `toneUniformArray` writes — a // mismatch is a silent off-by-one down the whole block. const declared = [...sksl.matchAll(/uniform (float2|float) (\w+)(?:\[(\d+)\])?;/g)].reduce( (n, [, kind, , len]) => n + (len ? Number(len) : kind === 'float2' ? 2 : 1), 0 ); const arrayFn = tone.match(/export function toneUniformArray\(u: ToneUniforms\): number\[\] \{\n return \[([\s\S]*?)\n \];/)?.[1]; assert.ok(arrayFn, 'toneUniformArray is gone'); const written = arrayFn .split(',') .map((s) => s.trim()) .filter(Boolean) .reduce((n, s) => n + (s.startsWith('...u.hsl') ? 8 : 1), 0); assert.equal(written, declared, `toneUniformArray writes ${written} floats, the pass declares ${declared}`); // The develop: knee on the sensor's max channel, the channel ratios kept, so the // hue and the saturation of a blown area survive the pull-down. const dev = develop.match(/if \(mx > 0\.7\) \{[\s\S]*?\n \}/)?.[0]; assert.ok(dev, 'the develop knee is gone — a blown sky is flat 1.0 again'); assert.match(dev, /float over = mx - 0\.7;/); assert.match(dev, /rgb \*= \(0\.7 \+ over \/ \(1\.0 \+ over \* 3\.3333\)\) \/ mx;/); assert.doesNotMatch(develop, /mix\(rgb \/ mx, float3\(1\.0\)/, 'the fade-to-white is back'); const mask = readFileSync(new URL('../shared/utils/gradientMask.ts', import.meta.url), 'utf8'); assert.ok(mask.includes('${TONE_MATH_SKSL}'), 'the mask pass does not read the shared maths'); assert.match(mask, /c = half3\(exposureMove\(vec3\(c\), a\.x\)\);/); // The mask hands the ramp its OWN pixel as the base, twice over: a shape has no // neighbourhood of its own, and base == t is a ratio of exactly 1, so what a mask // does with SHADOW is what it always did. The knob means the same thing on both // sides of the call; what differs is the neighbourhood, and a mask has none. assert.match(mask, /c = half3\(toneRamp\(vec3\(c\), lf, lf, tone\.w, tone\.y, tone\.x, tone\.z, 0\.0\)\);/); assert.doesNotMatch(mask, /0\.55, 1\.35/, 'the mask kept its own arbitrary saturation clamp'); assert.doesNotMatch(mask, /cg = clamp\(lifted/, 'the mask is back on its own tone formula'); // The four tents, one per quarter of the ramp, each clipped by its neighbour so // no luma is counted by two of them. These weight the stock SPLIT TONES now — the // four knobs no longer ride them, they ride their own measured curves (TONE_KNOBS). assert.match(sksl, /float blMask = 1\.0 - smoothstep\(0\.00, 0\.25, t\);/); assert.match(sksl, /float shMask = clamp\(1\.0 - smoothstep\(0\.25, 0\.50, t\) - blMask, 0\.0, 1\.0\);/); assert.match(sksl, /float whMask = smoothstep\(0\.75, 1\.00, t\);/); assert.match(sksl, /float hlMask = clamp\(smoothstep\(0\.50, 0\.75, t\) - whMask, 0\.0, 1\.0\);/); // The composition, and NOT a sum of bumps on the identity: the four MEASURED // curves are applied one after the other, each self-clamping via its own tone*() // helper, which is what makes one knob's travel independent of another's (the // shared ceiling used to take 0.663 of BLACK's travel off on the monochrome // stock) and the ramp monotone by construction rather than by a guard. No // linear-light knee runs ahead of them either — CURVE_SKSL is a different pass. assert.doesNotMatch(sksl, /float blackA = |float whiteA = /, 'the amplitudes are summed again — the moves must be sequential'); assert.doesNotMatch(sksl, /o \+= dr \* 0\.12/, 'DR is an additive term again — it folds the flat stretch at 0.238'); assert.doesNotMatch(sksl, /float lin\(/, 'the linear-light knee ahead of the knobs came back'); assert.doesNotMatch(sksl, /clamp\(0\.25 \+ 0\.25/, 'a knob is clamped against a neighbour knot again'); assert.match(sksl, /float target = clamp\(o, 0\.0, 1\.0\);/); assert.doesNotMatch(sksl, /float target = base > 0\.0004 \? o \* t \/ base : t;/, 'the gain-scaled detail came back — a tone knob softens again'); assert.match(sksl, /vec3 res = lightMove\(c, t, target\);/); assert.doesNotMatch(sksl, /float target = base > 0\.0004 \? o \* t \/ base : t;/, 'the gain-scaled detail came back — a tone knob softens again'); assert.match(sksl, /vec3 res = lightMove\(c, t, target\);/); assert.doesNotMatch(sksl, /lightMove\(c, t, clamp\(o, 0\.0, 1\.0\)\)/, 'the ramp is read at the pixel again — a global curve'); assert.doesNotMatch(sksl, /mix\(a0, a1, smoothstep/, 'the ramp is smoothstepped again'); // The linear-light knee that used to run ahead of all this is GONE from the tone // pass: HIGHLIGHT is one zone move in both directions now, and a second pass over // the same knob would double-count it. assert.doesNotMatch(tone, /if \(hl < 0\.0\) \{/, 'the linear-light recovery came back'); assert.doesNotMatch(sksl, /max\(hl, 0\.0\)/, 'the additive lift came back'); assert.doesNotMatch(sksl, /bl \* 0\.18 \* dk|wh \* 0\.18 \* rgb/, 'WHITE/BLACK are per-channel again'); // The rebuild after the ramp: the doc's ratio (R_new = R_old * Luma_new / // Luma_old), as ONE shared scale o / t, so the differences move with the light // and neither the hue nor the saturation goes with them. The caps are what make // it fit — applying the ratio past the ceiling clips a channel outright and the // hue goes with it (a skin tone at 24.0° came back at 48.0° at HIGHLIGHT +100, // scratchpad hl-variants.mjs) — and the scale is held at 1.0 only below // t = 0.0004, where the ratio would multiply a near-black pixel's cast by // whatever pedestal BLACK has just lifted. assert.match(maths, /float safeT = max\(t, 0\.005\);/); assert.match(maths, /float k = t > 0\.0004 \? min\(o \/ safeT, 3\.5\) : 1\.0;/); assert.match(maths, /if \(hiC > t\) k = min\(k, \(1\.0 - o\) \/ max\(hiC - t, 0\.0001\)\);/); assert.match(maths, /if \(loC < t\) k = min\(k, o \/ max\(t - loC, 0\.0001\)\);/); assert.match(maths, /return clamp\(vec3\(o\) \+ \(c - vec3\(t\)\) \* k, 0\.0, 1\.0\);/); assert.match(maths, /vec3 res = lightMove\(c, t, target\);/); assert.doesNotMatch(tone, /0\.55, 1\.35/, 'the arbitrary saturation clamp came back'); assert.doesNotMatch(maths, /float k = 1\.0;/, 'the chroma-constant scale came back — a shadow lift drains the colour'); // The transfer pair has to be the accurate one where it is still used (the // exposure pass), or that pass is drawn in a space that is not linear at all. assert.match(tone, /return mix\(c \/ 12\.92, pow\(\(c \+ 0\.055\) \/ 1\.055, vec3\(2\.4\)\), step\(vec3\(0\.04045\), c\)\);/); // The develop's arithmetic. T = 0.7 / S = 1 / (2 (1 - T)) is its pair (S is what // puts the asymptote on 1.0: T + 1/(2S) = 1). const knee = (l, T, S) => (l < T ? l : T + (l - T) / (1 + 2 * S * (l - T))); const T = 0.7; const S = 1 / (2 * (1 - T)); // Below the knee the frame is untouched, and the curve is continuous and C1 at T // — slope 1 on both sides — so there is no seam for a later pass to mask. assert.equal(knee(T - 0.2, T, S), T - 0.2); assert.equal(knee(T, T, S), T); const slope = (x) => (knee(x + 1e-6, T, S) - knee(x, T, S)) / 1e-6; assert.ok(Math.abs(slope(T) - 1) < 1e-3, `seam at T=${T}: slope ${slope(T)}`); // Monotone, and never a brightening: an inverted pair of pixels is a visible edge. let prev = -Infinity; for (let l = 0; l <= 2; l += 1 / 512) { assert.ok(slope(l) > 0, `inverted at ${l}`); assert.ok(knee(l, T, S) <= l + 1e-9, `brightened ${l} -> ${knee(l, T, S)}`); assert.ok(knee(l, T, S) >= prev); prev = knee(l, T, S); } // The asymptote: everything the sensor held above the knee lands under it, on // exactly 1.0. assert.ok(Math.abs(knee(1e6, T, S) - (T + 1 / (2 * S))) < 1e-4); assert.ok(Math.abs(T + 1 / (2 * S) - 1) < 1e-9, 'the develop plateau left 1.0'); // ...and the same pair in the encoded domain, which is the domain the develop // hands over: mx = 1.0 (the white level) lands on 237, the sensor's own plateau // (1.93) on 248 — a ramp of a dozen code values where the old fade-to-white left // nothing above 250 at all. This is the headroom the four tone knobs move. const enc = (x) => (x <= 0.0031308 ? x * 12.92 : 1.055 * x ** (1 / 2.4) - 0.055); assert.equal(Math.round(enc(knee(1.0, T, S)) * 255), 237); assert.equal(Math.round(enc(knee(1.93, T, S)) * 255), 248); // The ramp as arithmetic — the same four windows, the same rates and the same // sequential composition the SkSL above carries, so the shape is measured and // not described. Each move is monotone for any amount in [-1, 1] and lands on 0 // and 1 without moving either, so the composition is monotone by construction // and the two ends of the ramp are FIXED POINTS whatever the sliders say. const clamp01 = (x) => Math.min(1, Math.max(0, x)); const clamp = (x, lo, hi) => Math.min(hi, Math.max(lo, x)); // Float-exact comparisons are a trap once a value has been through a division // and a multiply (x / 0.25 * 0.25 is not x) — assert to within a code value. const close = (a, b, msg) => assert.ok(Math.abs(a - b) < 1e-12, `${msg ?? ''} ${a} != ${b}`); // The readings below come out of this same arithmetic to five decimals, so the // tolerance is the rounding of the number written down, well inside the code // value the cube can see. const near4 = (a, b, msg) => assert.ok(Math.abs(a - b) < 1e-4, `${msg ?? ''} ${a} != ${b}`); // Exact to the last digit where it matters: a window of zero is not "nearly" // zero, and that is the claim the independence checks rest on. const exact = (a, b, msg) => assert.equal(a, b, `${msg ?? ''} ${a} != ${b}`); const smoothstep = (e0, e1, x) => { const u = clamp01((x - e0) / (e1 - e0)); return u * u * (3 - 2 * u); }; // --------------------------------------------------------------------------- // The ramp as arithmetic — the same tables, the same order and the same clamps // the SkSL above carries, so the shape is measured and not described. // // ONE knob's curve, as KNOB_SKSL emits it: the table drawn straight between the // knots, scaled by the amount, added to the luma it reads and clamped. const poly = (c, L) => { let v = c.v[0]; for (let i = 1; i < c.p.length; i++) v += (c.v[i] - c.v[i - 1]) * clamp((L - c.p[i - 1]) / (c.p[i] - c.p[i - 1]), 0, 1); return v; }; const knob = (L, k, amt) => clamp01(L + (amt >= 0 ? amt * poly(TONE_KNOBS[k].plus, L) : -amt * poly(TONE_KNOBS[k].minus, L))); // toneCurve, move for move, with the clamp the shader puts after each one: // BLACK, then SHADOW, then HIGHLIGHT, then WHITE. `afterBlack` is the luma the // SHADOW move reads — the value a stock's own SHADOW cannot drag, because BLACK // runs before it. function ramp(t, k = {}) { const { dr = 0, hl = 0, sh = 0, wh = 0, bl = 0 } = k; const afterBlack = knob(t, 'bl', clamp(bl + dr * 0.12, -1, 1)); const o = knob( knob(knob(afterBlack, 'sh', clamp(sh + dr * 0.06, -1, 1)), 'hl', clamp(hl - dr * 0.09, -1, 1)), 'wh', clamp(wh - dr * 0.18, -1, 1) ); return { o, afterBlack }; } // THE MEASUREMENT THE TABLES WERE FITTED TO. Nine genuine Lightroom Classic // 14.2 exports of Main.jpg — the frame at the repo root — each knob at +100 and // at -100, the per-pixel luma difference against Main.jpg binned by base luma and // averaged. The row is that move at nine luma positions, off the dense grid the // tables were cut from (0.008 of luma is the worst the fit is allowed anywhere); // the tolerance below is 0.01, a little over a code value at ±100. const MEASURED_L = [0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7]; const MEASURED = { 'hl+': [0.0419, 0.1116, 0.1814, 0.2323, 0.1607, 0.1011, 0.078, 0.0452, 0.0108], 'hl-': [-0.0201, -0.0363, -0.0475, -0.0589, -0.0701, -0.0808, -0.1298, -0.1627, -0.1461], 'sh+': [0.1971, 0.24, 0.2467, 0.2533, 0.25, 0.23, 0.205, 0.175, 0.1333], 'sh-': [-0.0434, -0.0874, -0.1285, -0.1583, -0.1359, -0.0912, -0.0734, -0.0473, -0.012], 'wh+': [0.2036, 0.2901, 0.3714, 0.4422, 0.51, 0.5623, 0.4998, 0.3999, 0.3022], 'wh-': [-0.0019, -0.0038, -0.0058, -0.0085, -0.0123, -0.0203, -0.03, -0.0461, -0.0609], 'bl+': [0.0905, 0.1049, 0.1132, 0.1151, 0.099, 0.0843, 0.0702, 0.052, 0.0328], 'bl-': [-0.0501, -0.0997, -0.1498, -0.1983, -0.2429, -0.2247, -0.1574, -0.1141, -0.0773], }; for (const [name, want] of Object.entries(MEASURED)) { const k = name.slice(0, 2); const amt = name.endsWith('+') ? 1 : -1; want.forEach((move, i) => { const got = knob(MEASURED_L[i], k, amt); assert.ok( Math.abs(got - clamp01(MEASURED_L[i] + move)) <= 0.01, `${name} at luma ${MEASURED_L[i]}: the table moves to ${got.toFixed(4)}, the export to ${(clamp01(MEASURED_L[i] + move)).toFixed(4)}` ); }); } // The film stocks ride these same curves, so their numbers are their own. const filmTone = tone.match(/const FILM_TONE[\s\S]*?\n};/)?.[0]; assert.ok(filmTone, 'FILM_TONE is gone — the stocks no longer shape the ramp at all'); // The keys are quoted or not depending on whether they are identifiers, so the // quotes come off before the lookup. const filmFlat = filmTone.replace(/['"]/g, ''); for (const [name, src, kn, toe, head] of [ ['classic-chrome', 'sh: -0.47', { sh: -0.47 }, 0.1791844], ['classic-vivid', 'sh: -0.47', { sh: -0.47 }, 0.1791844], ['monochrome', 'sh: -0.20, hl: -0.1143', { sh: -0.2, hl: -0.1143 }, 0.2126235, 0.7396688], ['mono-high-contrast', 'sh: -1.0, wh: 0.26', { sh: -1.0, wh: 0.26 }, 0.1734727, 0.8150685], ]) { assert.ok( filmFlat.includes(`${name}: { ${src} }`), `${name} is not on the ${src} its ends were solved at` ); near4(ramp(0.25, kn).o, toe, `${name}'s shadow knot moved`); if (head) near4(ramp(0.75, kn).o, head, `${name}'s highlight knot moved`); } // Non-decreasing on EVERY segment, for every amount in [-1, 1] — not just at the // ±100 the exports were sampled at. A fold in a tone curve is a band the eye // reads, and a knob's own shape is what has to rule it out: the tables are cut so // L + move never turns back. for (const k of KNOBS) for (let amt = -1; amt <= 1.0001; amt += 1 / 64) { let prev = -Infinity; for (let i = 0; i <= 4000; i++) { const o = knob(i / 4000, k, amt); assert.ok(o >= prev - 1e-12, `${k} at ${amt.toFixed(4)} folds the ramp at luma ${i / 4000}`); prev = o; } } // Every knob on zero is EXACTLY the identity — the pass also runs for the stock // split tones and for DR alone, so a neutral setting must not curve the frame. for (let i = 0; i <= 2000; i++) exact(ramp(i / 2000, {}).o, i / 2000, `identity broke at ${i / 2000}`); // The ends of the ramp are where the MEASUREMENT put them, and nowhere else. The // floor is the one that surprises: HIGHLIGHT +100 lifts a true black by 0.084 — // the biggest move any knob makes on luma 0 — while BLACK +100, the knob named // for it, is worth 0.0042 there; and the head moves under WHITES -100 alone // (-0.10 on a true white, which is why its table does not tail off to zero). // Nothing may drag an end further than the export did. for (const k of KNOBS) for (const side of ['plus', 'minus']) { const c = TONE_KNOBS[k][side]; const amt = side === 'plus' ? 1 : -1; near4(knob(0, k, amt), clamp01(c.v[0]), `${k}.${side} floor travel`); near4(knob(1, k, amt), clamp01(1 + c.v[c.v.length - 1]), `${k}.${side} head travel`); } for (const k of KNOBS) for (const side of ['plus', 'minus']) { const c = TONE_KNOBS[k][side]; assert.ok(Math.abs(c.v[0]) <= 0.15, `${k}.${side} drags the floor by ${c.v[0]} — past what any export did`); assert.ok(Math.abs(c.v[c.v.length - 1]) <= 0.1, `${k}.${side} drags the head by ${c.v[c.v.length - 1]} — past what any export did`); } // The two landmarks the whole change is measured by, read at the export's own // numbers: WHITES +100 puts everything above luma 0.50 on 1.0 — it rounds to the // ceiling from there up, which is the "+0.43 mean" a user sees as the frame // opening — and BLACKS -100 puts everything below 0.21 on 0.0 (under a code // value), the crushed toe. for (let L = 0.5; L <= 1.0001; L += 1 / 512) assert.equal(Math.round(knob(L, 'wh', 1) * 255), 255, `WHITES +100 leaves luma ${L} short of the ceiling`); for (let L = 0; L <= 0.2; L += 1 / 512) assert.ok(knob(L, 'bl', -1) < 0.006, `BLACKS -100 leaves luma ${L} above the floor`); // On a mid-grey the four are all live — the old windows left the 0.50 midpoint to // nothing but the two ends, which is the "không thay đổi" the report is about. for (const k of KNOBS) { assert.ok(Math.abs(knob(0.5, k, 1) - 0.5) > 0.01, `${k} +100 does nothing on a mid-grey`); assert.ok(Math.abs(knob(0.5, k, -1) - 0.5) > 0.001, `${k} -100 does nothing on a mid-grey`); } // ...and no combination of the four at full deflection can drive an end of the // ramp off the cube, fold the ramp back on itself, or cross the toe over the // head — the composition is monotone by construction, and this is that // construction run over all 162 combinations. const combos = []; for (const bl of [-1, 0, 1]) for (const sh of [-1, 0, 1]) for (const hl of [-1, 0, 1]) for (const wh of [-1, 0, 1]) for (const dr of [0, 1]) combos.push({ bl, sh, hl, wh, dr }); for (const k of combos) { const lo = ramp(0, k).o; const hi = ramp(1, k).o; assert.ok(lo >= 0 && hi <= 1, `the ramp left the cube at ${JSON.stringify(k)}`); assert.ok(lo <= hi, `the toe ${lo} climbed over the head ${hi} at ${JSON.stringify(k)}`); let prev = -Infinity; for (let i = 0; i <= 2000; i++) { const o = ramp(i / 2000, k).o; assert.ok(o >= prev - 1e-12, `the ramp folds at ${i / 2000} with ${JSON.stringify(k)}`); prev = o; } } // The colour rebuild, as the shader emits it: the ramp's luma, the pixel's own // chroma difference, and the one scale o / t the cube then gets to pull back. const lumaOf = (c) => clamp01(0.2126 * c[0] + 0.7152 * c[1] + 0.0722 * c[2]); // lightMove, as TONE_MATH_SKSL emits it — the one move every brightness change in // the pass goes through (a tone knob, a mask's tone knob, the exposure knob). // NOT clamped on the way out here: the check below wants to see that the scale // alone already landed the pixel inside the cube, and a silent clamp would hide // the case where it did not. function lightMove(rgb, t, o) { let k = t > 0.0004 ? Math.min(o / Math.max(t, 0.005), 3.5) : 1; const hiC = Math.max(...rgb); const loC = Math.min(...rgb); if (hiC > t) k = Math.min(k, (1 - o) / (hiC - t)); if (loC < t) k = Math.min(k, o / Math.max(t - loC, 0.0001)); return rgb.map((c) => o + (c - t) * k); } // The rebuild, with the base layer the shader now draws the ramp through. `base` // defaults to the pixel itself — the degenerate call, and the one a mask makes — // which lands `target` back on `o` and is the move this function had before there // was a base at all. Away from that the pixel's own DIFFERENCE from the base is // ADDED to the neighbourhood's new luma (Base' + Detail), never scaled by it. function rebuild(rgb, k, base) { const t = lumaOf(rgb); const b = base ?? t; const o = ramp(t, k).o; const target = clamp01(o); const out = lightMove(rgb, t, target); return { out, clamped: out.map((c) => clamp01(c)), o, t, base: b, target }; } // The transfer pair the exposure pass crosses into linear light with, and back. const srgbToLin = (c) => (c <= 0.04045 ? c / 12.92 : ((c + 0.055) / 1.055) ** 2.4); const linToSrgb = (c) => (c <= 0.0031308 ? c * 12.92 : 1.055 * c ** (1 / 2.4) - 0.055); // exposureMove, as TONE_MATH_SKSL emits it: the linear sensor moves by the stops, // and the encoded value that lands there is the luma the pixel is rebuilt onto. // The light moves by exp2(ev) in LINEAR light; the colour moves by the one shared // scale of lightMove. A per-channel multiply does neither — it clips the three // channels by three different amounts and takes the hue with it (29.2° at +1 EV // on the scratchpad probe, exp-variant.mjs; this variant measures 0.00°). function exposureMove(rgb, ev) { const c = rgb.map(clamp01); const t = lumaOf(c); // The stop as a RATIO on the pixel's own encoded luma, which is what makes the // knob the identity at 0 EV: pointing the luma straight at the encoded linear // target brightens a colour by a couple of code values even on zero. const lin = Math.max(lumaOf(c.map(srgbToLin)), 1e-6); const stop = linToSrgb(Math.min(1, lin * 2 ** ev)) / linToSrgb(lin); return lightMove(c, t, clamp01(t * stop)).map(clamp01); } function hueOf(c) { const mx = Math.max(...c), mn = Math.min(...c), d = mx - mn; if (d < 1e-9) return NaN; let h; if (mx === c[0]) h = (c[1] - c[2]) / d + (c[1] < c[2] ? 6 : 0); else if (mx === c[1]) h = (c[2] - c[0]) / d + 2; else h = (c[0] - c[1]) / d + 4; return ((h * 60) % 360 + 360) % 360; } const colourCases = [ [0.9, 0.72, 0.6], // skin — the case that moved 24° under the ratio [1, 0.97, 0.92], // a warm white at the very top of the ramp [0.45, 0.65, 0.9], // sky [1, 0.6, 0.2], // orange, one channel already on the ceiling [0.45, 0.85, 0.4], // green [0.05, 0.03, 0.02], // a shadow with a cast [0.01, 0.008, 0.006],// and the same cast with almost no light on it at all ]; const greyCases = [[0.1, 0.1, 0.1], [0.5, 0.5, 0.5], [0.7, 0.7, 0.7], [0.9, 0.9, 0.9], [0.97, 0.97, 0.97]]; const knobSets = []; for (const hl of [-1, -0.5, 0, 0.5, 1]) for (const wh of [-1, 0, 1]) for (const sh of [-1, 0, 1]) for (const bl of [-1, 0, 1]) knobSets.push({ hl, wh, sh, bl }); for (const k of knobSets) { for (const rgb of colourCases) { const { out, clamped, o } = rebuild(rgb, k); // The clamp is never what saves the pixel: the scale already landed the // result inside the cube, which is the whole point of it. for (let i = 0; i < 3; i++) assert.ok(Math.abs(out[i] - clamped[i]) < 1e-12, `the cube clipped ${i} of ${rgb} at ${JSON.stringify(k)}`); // Hue cannot move: every channel difference is scaled by the same number. const dh = hueOf(clamped) - hueOf(rgb); assert.ok(Number.isNaN(dh) || Math.abs(dh) < 1e-9, `hue moved ${dh} for ${rgb} at ${JSON.stringify(k)}`); // ...and the new luma is the ramp's, exactly (the differences sum to zero // in this weighting, so the scale drops out of the luma). close(lumaOf(clamped), o, `luma ${rgb} at ${JSON.stringify(k)}`); } // A grey is a grey: no difference to carry, so it lands on the ramp value and // picks up no cast on the way. for (const rgb of greyCases) { const { clamped, o } = rebuild(rgb, k); for (const c of clamped) close(c, o, `grey drifted at ${JSON.stringify(k)}`); } } // Every knob on zero is the identity for the colour too, not just the luma. for (const rgb of [...colourCases, ...greyCases]) { const { clamped } = rebuild(rgb, {}); for (let i = 0; i < 3; i++) close(clamped[i], rgb[i], 'the colour rebuild is not the identity at zero'); } // The chroma RIDES THE RATIO: where the cube has room the channel differences // come out multiplied by the one scale o / t. That is what keeps the saturation — // an HSL saturation is a ratio of differences and a common scale never touches it // — and the hue along with it, which is the report behind this move: held at // k = 1.0 (the chroma carried unchanged) a dark red came back at 0.505 of // saturation from 0.746 with SHADOW at +100, and at 0.370 with SHADOW and BLACK // both, which is a colour going grey under a lift. for (const [rgb, knobs] of [ [[0.7, 0.55, 0.45], { hl: 0.5 }], [[0.25, 0.12, 0.08], { sh: 0.5, bl: 0.5 }], ]) { const lifted = rebuild(rgb, knobs); const grew = (lifted.clamped[0] - lifted.clamped[1]) / (rgb[0] - rgb[1]); assert.ok(Math.abs(lifted.target / lifted.t - 1) > 1e-3, `the lift left the ramp alone on ${rgb} — the case proves nothing`); close(grew, lifted.target / lifted.t, `the chroma did not ride the ratio on ${rgb} at ${JSON.stringify(knobs)}`); } // THE BASE LAYER. A band with texture in it — SHADOW's own quarter, 0.26 to // 0.50, at the deflection this was reported at (the full +100, which is +1 here): // // read at the pixel every pixel lands on its own o, so the band's spread // comes out multiplied by whatever slope the curve has // over it — 1.2347 of its own spread at this deflection, // the SHADOW +100 table steepening through 0.26..0.50. // read at the base every pixel of ONE neighbourhood takes the same move, // o(base) - base, and its own difference from the base is // added to it, so the texture inside the region comes out // at ITS OWN size and the same lift lands on the pixels // either way. // // The base is the whole point of the second reading: what SHADOW does to a // frame's texture is a property of the neighbourhood, not of the pixel. (The // spread here is kept WHOLE because this twin's band sits on ONE base, where the // reconstruction is exact by construction; on a real frame the band spans many // neighbourhoods and the live number is the one to read.) const band = Array.from({ length: 32 }, (_, i) => 0.26 + 0.24 * (i / 31)); const spread = (xs) => Math.max(...xs) - Math.min(...xs); const bandBase = band.reduce((a, b) => a + b, 0) / band.length; const movedGlobally = band.map((t) => rebuild([t, t, t], { sh: 1 }).clamped[0]); // Every knob on zero is the identity, whatever base is handed in for (const b of [0.01, 0.1, 0.35, 0.7, 0.99]) for (const rgb of [...colourCases, ...greyCases]) { const g = rebuild(rgb, {}, b); for (let i = 0; i < 3; i++) close(g.clamped[i], rgb[i], `the base path is not the identity at zero, base ${b}`); } // THE EXPOSURE KNOB, the same move on a different input. Behind it: -2..+2 EV in // half stops, on the frame and inside a gradient mask. // A grey is the knob it always was — a stop on a neutral is a stop on its light, // and nothing else: this is the number the old linear per-channel multiply put // there, so no exposure a user has dialled in moves. for (const g of [0.05, 0.1, 0.5, 0.7, 0.9, 0.97]) for (const ev of [-2, -1, -0.5, 0.5, 1, 2]) close( exposureMove([g, g, g], ev)[0], linToSrgb(Math.min(1, srgbToLin(g) * 2 ** ev)), `the exposure is no longer a stop on a grey: ${g} at ${ev} EV`, ); // ...and zero stops is the identity on a COLOUR too, exactly — the knob has to be // able to leave the frame alone. for (const rgb of [...colourCases, ...greyCases]) for (let i = 0; i < 3; i++) close(exposureMove(rgb, 0)[i], rgb[i], 'the exposure move is not the identity at 0 EV'); // Hue cannot move, at any stop, on any colour: this is the whole fix. The old // pass multiplied the three channels by the same number in LINEAR light and then // clipped them by three different amounts, and the hue went with them — 29.2° on // the skin tone at +1 EV, 33.3° at +2 EV (scratchpad exp-variant.mjs), against // 0.00° here. for (const rgb of colourCases) for (const ev of [-2, -1, -0.5, 0, 0.5, 1, 2]) { const out = exposureMove(rgb, ev); const dh = hueOf(out) - hueOf(rgb); assert.ok(Number.isNaN(dh) || Math.abs(dh) < 1e-9, `the exposure moved the hue ${dh}° on ${rgb} at ${ev} EV`); assert.ok(out.every((c) => c >= -1e-12 && c <= 1 + 1e-12), `the exposure left the cube on ${rgb} at ${ev} EV`); } // A pixel already on the ceiling: the channel that used to clip lands exactly ON // the ceiling and the other two follow it down at the one shared scale, so the // pixel gives up saturation rather than having the three clip by three different // amounts — which is where the old pass lost the hue. const blown = exposureMove([1, 0.6, 0.2], 5); assert.ok(blown.every((c) => c >= -1e-12 && c <= 1 + 1e-12), 'the exposure overshot the ceiling'); close(blown[0], 1, 'the channel that hit the ceiling stopped short of it'); assert.ok(blown[1] > 0.9 && blown[2] > 0.85, 'the pixel collapsed to white instead of keeping its colour'); assert.ok(Math.abs(hueOf(blown) - hueOf([1, 0.6, 0.2])) < 1e-9, 'the pixel lost its hue at the ceiling'); // ...and a pixel the move really does drive to 1.0 (an exposure past the head of // the ramp) is white, in all three channels at once. const white = exposureMove([0.98, 0.98, 0.98], 5); for (let i = 0; i < 3; i++) close(white[i], 1, 'a blown pixel stopped short of white'); // Darkening is the mirror: the light comes down, and a colour with no room below // gives up saturation and arrives neutral, not negative. const crushed = exposureMove([0.02, 0.01, 0.005], -5); assert.ok(crushed.every((c) => c >= -1e-12 && c <= 1 + 1e-12), 'the exposure went outside the cube on the way down'); assert.ok(crushed[0] >= crushed[1] && crushed[1] >= crushed[2], 'the exposure inverted the channel order on the way down'); // Black has no light to move: every stop leaves it where it is, and none of them // divides by zero on the way. for (const ev of [-5, -1, 0, 1, 5]) assert.equal(exposureMove([0, 0, 0], ev)[0], 0, `black moved at ${ev} EV`); // THE PASS ITSELF, compiled and run. Everything above is a twin, and a twin is // only as good as its reading of the source; nothing else compiles EXPOSURE_SKSL, // so a wrapper whose uniform stopped matching its own main would only show up in // the app. Four pixels through the real shader, against the twin. const exposureSrc = EXPOSURE_SKSL; assert.match(exposureSrc, /uniform float ev;/, 'the exposure pass no longer takes its stops'); assert.match(exposureSrc, /return vec4\(exposureMove\(clamp\(c\.rgb, 0\.0, 1\.0\), ev\), c\.a\);/, 'the pass stopped calling exposureMove'); const { default: CanvasKitInit } = await import('canvaskit-wasm/bin/full/canvaskit.js'); const ck = await CanvasKitInit({ locateFile: () => fileURLToPath(new URL('../node_modules/canvaskit-wasm/bin/full/canvaskit.wasm', import.meta.url)), }); const effect = ck.RuntimeEffect.Make(exposureSrc); assert.ok(effect, 'EXPOSURE_SKSL does not compile — the whole frame loses its exposure'); const throughPass = (rgb, ev) => { const surface = ck.MakeSurface(4, 4); const paint = new ck.Paint(); paint.setColor(ck.Color(...rgb)); surface.getCanvas().drawPaint(paint); const child = surface.makeImageSnapshot().makeShaderOptions( ck.TileMode.Clamp, ck.TileMode.Clamp, ck.FilterMode.Linear, ck.MipmapMode.None, ); const shaderPaint = new ck.Paint(); shaderPaint.setShader(effect.makeShaderWithChildren([ev], [child])); const out = ck.MakeSurface(4, 4); out.getCanvas().drawRect(ck.XYWHRect(0, 0, 4, 4), shaderPaint); const px = out.getCanvas().readPixels(0, 1, { width: 4, height: 1, colorType: ck.ColorType.RGBA_8888, alphaType: ck.AlphaType.Unpremul, colorSpace: ck.ColorSpace.SRGB, }); return [px[0], px[1], px[2]]; }; for (const [rgb, ev] of [[[128, 128, 128], 1], [[230, 150, 50], 1], [[230, 150, 50], 2], [[20, 10, 5], -2]]) { const want = exposureMove(rgb.map((v) => v / 255), ev).map((v) => Math.round(v * 255)); const got = throughPass(rgb, ev); assert.ok( got.every((v, i) => Math.abs(v - want[i]) <= 1), `the pass and its twin disagree on ${rgb} at ${ev} EV: ${got} against ${want}`, ); } console.log('highlight-knee-check ok');