fix: show generated HTML charts on Win7 Chrome

Rewrite oklch/color-mix and space-separated rgb before iframe preview so pie and bar fills are not dropped on Chrome 109.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend-web/scripts/check-chrome109-css.mjs

@@ -36,6 +36,11 @@ const requiredLegacyFallbacks = [
     pattern: /htmlLabels:\s*false[\s\S]*secure:\s*\[[\s\S]*"htmlLabels"/,
     description: "Sandbox flowcharts must use native SVG labels in legacy browsers",
   },
+  {
+    file: "src/core/utils/legacy-html-preview.ts",
+    pattern: /export function downlevelModernColors[\s\S]*function injectLegacyChartShim/,
+    description: "Generated HTML charts must downlevel modern CSS colors for Chrome 109",
+  },
 ];
 
 for (const file of cssFiles) {

frontend-web/src/components/html-preview-frame.tsx

@@ -1,6 +1,6 @@
 import { useEffect, useState } from "react";
 
-import { injectInPageAnchorHandler } from "@/core/utils/markdown";
+import { prepareGeneratedHtml } from "@/core/utils/legacy-html-preview";
 
 /**
  * Sandboxed preview of a generated HTML document.
@@ -26,7 +26,7 @@ export function HtmlPreviewFrame({
   const [url, setUrl] = useState<string>();
 
   useEffect(() => {
-    const blob = new Blob([injectInPageAnchorHandler(html ?? "")], {
+    const blob = new Blob([prepareGeneratedHtml(html ?? "")], {
       type: "text/html;charset=utf-8",
     });
     const objectUrl = URL.createObjectURL(blob);

frontend-web/src/components/workspace/artifacts/artifact-file-detail.tsx

@@ -97,9 +97,9 @@ import {
   openMermaidSvgInNewTab,
   renderMermaidToSvg,
 } from "@/core/utils/mermaid";
+import { prepareGeneratedHtml } from "@/core/utils/legacy-html-preview";
 import {
   createMarkdownAnchorResolver,
-  injectInPageAnchorHandler,
   isInPageAnchor,
   scrollToInPageAnchor,
 } from "@/core/utils/markdown";
@@ -1422,7 +1422,9 @@ export function ArtifactFileDetail({
       toast.error("文件内容为空，暂时无法在新窗口打开");
       return;
     }
-    const blob = new Blob([source], { type: "text/html;charset=utf-8" });
+    const blob = new Blob([prepareGeneratedHtml(source)], {
+      type: "text/html;charset=utf-8",
+    });
     const url = URL.createObjectURL(blob);
     window.open(url, "_blank", "noopener,noreferrer");
     window.setTimeout(() => URL.revokeObjectURL(url), 60_000);
@@ -2084,7 +2086,7 @@ export function ArtifactFilePreview({
     // <meta charset> 就会中文乱码。与下方下载/新窗口打开的 blobType 保持一致。
     // Intercept in-page anchor clicks so they scroll within the iframe instead
     // of navigating the sandboxed blob: document (which blanks the frame).
-    const blob = new Blob([injectInPageAnchorHandler(content ?? "")], {
+    const blob = new Blob([prepareGeneratedHtml(content ?? "")], {
       type: "text/html;charset=utf-8",
     });
     const url = URL.createObjectURL(blob);

frontend-web/src/core/utils/legacy-html-preview.test.ts

@@ -0,0 +1,48 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import { downlevelModernColors, prepareGeneratedHtml } from "./legacy-html-preview";
+
+test("rewrites oklch chart fills to comma rgb", () => {
+  const html = `<svg><path fill="oklch(0.7 0.15 40)"/></svg>`;
+  const out = downlevelModernColors(html);
+  assert.match(out, /fill="rgb\(\d+, \d+, \d+\)"/);
+  assert.doesNotMatch(out, /oklch\(/);
+});
+
+test("rewrites space-separated rgb and hsl used by pie slices", () => {
+  const html = `.slice{fill:rgb(255 99 71 / 80%);stroke:hsl(220 90% 56%)}`;
+  const out = downlevelModernColors(html);
+  assert.match(out, /rgba\(255, 99, 71, 0\.8\)/);
+  assert.match(out, /rgb\(\d+, \d+, \d+\)/);
+  assert.doesNotMatch(out, /rgb\(255 99 71/);
+  assert.doesNotMatch(out, /hsl\(220 90%/);
+});
+
+test("rewrites color-mix after nested oklch is converted", () => {
+  const html = `background:color-mix(in srgb, oklch(0.63 0.2 27) 40%, #ffffff);`;
+  const out = downlevelModernColors(html);
+  assert.match(out, /rgb\(\d+, \d+, \d+\)/);
+  assert.doesNotMatch(out, /color-mix\(|oklch\(/);
+});
+
+test("turns Tailwind-style rgb channels on custom props into comma form", () => {
+  const html = `:root{--c: 37 99 235;} .bar{background:rgb(var(--c) / 50%)}`;
+  const out = downlevelModernColors(html);
+  assert.match(out, /--c: 37, 99, 235;/);
+  assert.match(out, /rgba\(var\(--c\), 0\.5\)/);
+});
+
+test("leaves already-legacy rgb() alone", () => {
+  const html = `<rect fill="rgb(16, 185, 129)"/>`;
+  assert.equal(downlevelModernColors(html), html);
+});
+
+test("prepareGeneratedHtml injects the ES5 chart size shim and anchor handler", () => {
+  const html = `<!doctype html><html><body><svg viewBox="0 0 100 80"></svg></body></html>`;
+  const out = prepareGeneratedHtml(html);
+  assert.match(out, /data-df-legacy-charts="1"/);
+  assert.match(out, /getElementsByTagName\("svg"\)/);
+  assert.match(out, /getElementsByTagName\("canvas"\)/);
+  assert.doesNotMatch(out, /\?\.|=>|`/);
+});

frontend-web/src/core/utils/legacy-html-preview.ts

@@ -0,0 +1,491 @@
+/**
+ * Prepare generated HTML so pie/bar/line charts still paint on Chrome 100–109
+ * (the Win7-era baseline this app targets).
+ *
+ * Model-written pages often copy modern design tokens: `oklch()`, `color-mix()`,
+ * and space-separated `rgb(r g b / a)`. Those declarations are ignored on
+ * Chrome 109, so SVG/CSS/canvas fills become transparent and the chart looks
+ * blank even though the markup is there. This rewrite happens in the parent
+ * before the blob iframe loads; the injected shim is ES5.
+ */
+
+import { injectInPageAnchorHandler } from "./markdown";
+
+const MAX_PASSES = 12;
+
+export function prepareGeneratedHtml(html: string): string {
+  return injectInPageAnchorHandler(injectLegacyChartShim(downlevelModernColors(html ?? "")));
+}
+
+export function downlevelModernColors(html: string): string {
+  let current = rewriteSpaceSeparatedCustomProps(html);
+  current = rewriteVarAlphaRgb(current);
+  let previous = "";
+  for (let pass = 0; pass < MAX_PASSES && current !== previous; pass += 1) {
+    previous = current;
+    current = replaceFunctionCalls(current, "oklch", convertOklch);
+    current = replaceFunctionCalls(current, "oklab", convertOklab);
+    current = replaceFunctionCalls(current, "lch", convertLch);
+    current = replaceFunctionCalls(current, "lab", convertLab);
+    current = replaceFunctionCalls(current, "rgba", convertModernRgb);
+    current = replaceFunctionCalls(current, "rgb", convertModernRgb);
+    current = replaceFunctionCalls(current, "hsla", convertModernHsl);
+    current = replaceFunctionCalls(current, "hsl", convertModernHsl);
+    current = replaceFunctionCalls(current, "color-mix", convertColorMix);
+  }
+  return current;
+}
+
+function injectLegacyChartShim(html: string): string {
+  if (html.includes("data-df-legacy-charts")) return html;
+  const script = `<script data-df-legacy-charts="1">(function(){
+  function viewBox(svg){
+    var vb=svg.getAttribute("viewBox")||svg.getAttribute("viewbox");
+    if(!vb)return null;
+    var p=vb.replace(/,/g," ").replace(/^\\s+|\\s+$/g,"").split(/\\s+/);
+    if(p.length<4)return null;
+    var w=parseFloat(p[2]), h=parseFloat(p[3]);
+    if(!(w>0&&h>0))return null;
+    return {w:w,h:h};
+  }
+  function fixSvg(svg){
+    var box=svg.getBoundingClientRect();
+    if(box.height>=8&&box.width>=8)return;
+    var vb=viewBox(svg);
+    if(!vb)return;
+    if(!svg.getAttribute("width"))svg.setAttribute("width",String(vb.w));
+    if(!svg.getAttribute("height"))svg.setAttribute("height",String(vb.h));
+    svg.style.maxWidth="100%";
+    svg.style.height="auto";
+    svg.style.display="block";
+  }
+  function fixCanvas(c){
+    var box=c.getBoundingClientRect();
+    var parent=c.parentElement;
+    var pw=parent?parent.clientWidth:0;
+    var ph=parent?parent.clientHeight:0;
+    if(c.width<8||box.width<8){
+      c.width=Math.max(pw,320);
+      c.style.width="100%";
+    }
+    if(c.height<8||box.height<8){
+      c.height=Math.max(ph,220);
+      c.style.height=c.height+"px";
+    }
+  }
+  function run(){
+    var svgs=document.getElementsByTagName("svg");
+    for(var i=0;i<svgs.length;i++)fixSvg(svgs[i]);
+    var canvases=document.getElementsByTagName("canvas");
+    for(var j=0;j<canvases.length;j++)fixCanvas(canvases[j]);
+  }
+  if(document.readyState==="complete"||document.readyState==="interactive"){
+    setTimeout(run,0);
+    setTimeout(run,400);
+  }else if(document.addEventListener){
+    document.addEventListener("DOMContentLoaded",function(){
+      run();
+      setTimeout(run,400);
+    });
+  }
+  if(window.addEventListener)window.addEventListener("load",function(){setTimeout(run,50);});
+})();</script>`;
+  if (/<\/body>/i.test(html)) {
+    return html.replace(/<\/body>/i, `${script}</body>`);
+  }
+  return html + script;
+}
+
+function rewriteSpaceSeparatedCustomProps(html: string): string {
+  return html.replace(
+    /(--[\w-]+)\s*:\s*(\d{1,3})\s+(\d{1,3})\s+(\d{1,3})\s*;/g,
+    "$1: $2, $3, $4;",
+  );
+}
+
+function rewriteVarAlphaRgb(html: string): string {
+  return html.replace(
+    /\brgba?\(\s*var\((--[\w-]+)\)\s*\/\s*([^)]+?)\)/gi,
+    (_, name: string, alpha: string) => `rgba(var(${name}), ${normalizeAlpha(alpha.trim())})`,
+  );
+}
+
+function replaceFunctionCalls(
+  source: string,
+  name: string,
+  replace: (args: string) => string | null,
+): string {
+  const lower = source.toLowerCase();
+  const token = `${name.toLowerCase()}(`;
+  let output = "";
+  let cursor = 0;
+  while (cursor < source.length) {
+    const index = lower.indexOf(token, cursor);
+    if (index < 0) {
+      output += source.slice(cursor);
+      break;
+    }
+    const before = index === 0 ? "" : source[index - 1]!;
+    if (index > 0 && /[A-Za-z0-9_-]/.test(before)) {
+      output += source.slice(cursor, index + 1);
+      cursor = index + 1;
+      continue;
+    }
+    const open = index + name.length;
+    const close = matchClosingParen(source, open);
+    if (close < 0) {
+      output += source.slice(cursor);
+      break;
+    }
+    const args = source.slice(open + 1, close);
+    const next = replace(args);
+    output += source.slice(cursor, index) + (next ?? source.slice(index, close + 1));
+    cursor = close + 1;
+  }
+  return output;
+}
+
+function matchClosingParen(source: string, openIndex: number): number {
+  let depth = 0;
+  let quote: string | null = null;
+  for (let i = openIndex; i < source.length; i += 1) {
+    const char = source[i]!;
+    if (quote) {
+      if (char === "\\") {
+        i += 1;
+        continue;
+      }
+      if (char === quote) quote = null;
+      continue;
+    }
+    if (char === '"' || char === "'") {
+      quote = char;
+      continue;
+    }
+    if (char === "(") depth += 1;
+    else if (char === ")") {
+      depth -= 1;
+      if (depth === 0) return i;
+    }
+  }
+  return -1;
+}
+
+function convertOklch(args: string): string | null {
+  if (/\bfrom\b/i.test(args)) return null;
+  const { values, alpha } = splitSlashAlpha(args);
+  if (values.length < 3) return null;
+  const L = parseLightness(values[0]!);
+  const C = parseNumber(values[1]!);
+  const H = parseHue(values[2]!);
+  if (L == null || C == null || H == null) return null;
+  const [a, b] = polarToLab(C, H);
+  return formatRgba(oklabToSrgb(L, a, b), alpha);
+}
+
+function convertOklab(args: string): string | null {
+  if (/\bfrom\b/i.test(args)) return null;
+  const { values, alpha } = splitSlashAlpha(args);
+  if (values.length < 3) return null;
+  const L = parseLightness(values[0]!);
+  const a = parseNumber(values[1]!);
+  const b = parseNumber(values[2]!);
+  if (L == null || a == null || b == null) return null;
+  return formatRgba(oklabToSrgb(L, a, b), alpha);
+}
+
+function convertLch(args: string): string | null {
+  if (/\bfrom\b/i.test(args)) return null;
+  const { values, alpha } = splitSlashAlpha(args);
+  if (values.length < 3) return null;
+  const L = parsePercentOrNumber(values[0]!, 100);
+  const C = parseNumber(values[1]!);
+  const H = parseHue(values[2]!);
+  if (L == null || C == null || H == null) return null;
+  const [a, b] = polarToLab(C, H);
+  return formatRgba(labToSrgb(L, a, b), alpha);
+}
+
+function convertLab(args: string): string | null {
+  if (/\bfrom\b/i.test(args)) return null;
+  const { values, alpha } = splitSlashAlpha(args);
+  if (values.length < 3) return null;
+  const L = parsePercentOrNumber(values[0]!, 100);
+  const a = parseNumber(values[1]!);
+  const b = parseNumber(values[2]!);
+  if (L == null || a == null || b == null) return null;
+  return formatRgba(labToSrgb(L, a, b), alpha);
+}
+
+function convertColorMix(args: string): string | null {
+  const parts = splitTopLevel(args, ",");
+  if (parts.length < 2) return null;
+  const colorParts = parts.slice(1);
+  const left = parseMixStop(colorParts[0] ?? "");
+  const right = parseMixStop(colorParts[1] ?? "transparent");
+  if (!left.color && !right.color) return null;
+  const leftPct = left.percent ?? (right.percent == null ? 50 : 100 - right.percent);
+  const rightPct = right.percent ?? 100 - leftPct;
+  const sum = leftPct + rightPct || 1;
+  const leftRgb = resolveMixColor(left.color) ?? [0, 0, 0, 0];
+  const rightRgb = resolveMixColor(right.color) ?? [0, 0, 0, 0];
+  const t = rightPct / sum;
+  return formatRgba(
+    [
+      leftRgb[0] + (rightRgb[0] - leftRgb[0]) * t,
+      leftRgb[1] + (rightRgb[1] - leftRgb[1]) * t,
+      leftRgb[2] + (rightRgb[2] - leftRgb[2]) * t,
+    ],
+    leftRgb[3] + (rightRgb[3] - leftRgb[3]) * t,
+  );
+}
+
+function convertModernRgb(args: string): string | null {
+  if (args.includes("var(") || /\bfrom\b/i.test(args)) return null;
+  if (args.includes(",") && !args.includes("/")) return null;
+  const { values, alpha } = splitSlashAlpha(args);
+  if (values.length < 3) return null;
+  const r = parseRgbChannel(values[0]!);
+  const g = parseRgbChannel(values[1]!);
+  const b = parseRgbChannel(values[2]!);
+  if (r == null || g == null || b == null) return null;
+  return formatRgba([r, g, b], alpha);
+}
+
+function convertModernHsl(args: string): string | null {
+  if (args.includes("var(") || /\bfrom\b/i.test(args)) return null;
+  if (args.includes(",") && !args.includes("/")) return null;
+  const { values, alpha } = splitSlashAlpha(args);
+  if (values.length < 3) return null;
+  const h = parseHue(values[0]!);
+  const s = parsePercentOrNumber(values[1]!, 1);
+  const l = parsePercentOrNumber(values[2]!, 1);
+  if (h == null || s == null || l == null) return null;
+  return formatRgba(hslToSrgb(h, s, l), alpha);
+}
+
+function parseMixStop(raw: string): { color: string; percent: number | null } {
+  const trimmed = raw.trim();
+  const match = trimmed.match(/^(.*?)(?:\s+(-?[\d.]+%))?\s*$/);
+  const color = (match?.[1] ?? trimmed).trim();
+  const percent = match?.[2] ? Number.parseFloat(match[2]) : null;
+  return { color, percent: Number.isFinite(percent) ? percent : null };
+}
+
+function resolveMixColor(value: string): [number, number, number, number] | null {
+  const text = value.trim();
+  if (!text || /^var\(/i.test(text)) return null;
+  if (/^transparent$/i.test(text)) return [0, 0, 0, 0];
+  const hex = parseHex(text);
+  if (hex) return hex;
+  const rgbMatch = text.match(/^rgba?\((.+)\)$/i);
+  if (rgbMatch) {
+    const converted = convertModernRgb(rgbMatch[1]!) ?? (/,\s*/.test(rgbMatch[1]!) ? `rgba(${rgbMatch[1]})` : null);
+    if (converted) {
+      const inner = converted.match(/^rgba?\((.+)\)$/i);
+      if (inner) {
+        const bits = inner[1]!.split(",").map((part) => Number.parseFloat(part.trim()));
+        if (bits.length >= 3 && bits.every((n) => Number.isFinite(n))) {
+          return [bits[0]!, bits[1]!, bits[2]!, bits[3] ?? 1];
+        }
+      }
+    }
+  }
+  return NAMED[text.toLowerCase()] ?? null;
+}
+
+function splitSlashAlpha(args: string): { values: string[]; alpha: number } {
+  const pieces = splitTopLevel(args, "/");
+  const values = tokenizeCssList(pieces[0] ?? "");
+  const alpha = pieces.length > 1 ? normalizeAlpha(pieces[1]!.trim()) : 1;
+  return { values, alpha };
+}
+
+function splitTopLevel(source: string, separator: string): string[] {
+  const parts: string[] = [];
+  let current = "";
+  let depth = 0;
+  let quote: string | null = null;
+  for (let i = 0; i < source.length; i += 1) {
+    const char = source[i]!;
+    if (quote) {
+      current += char;
+      if (char === "\\" && i + 1 < source.length) {
+        current += source[i + 1];
+        i += 1;
+      } else if (char === quote) {
+        quote = null;
+      }
+      continue;
+    }
+    if (char === '"' || char === "'") {
+      quote = char;
+      current += char;
+      continue;
+    }
+    if (char === "(") depth += 1;
+    if (char === ")") depth -= 1;
+    if (depth === 0 && char === separator) {
+      parts.push(current);
+      current = "";
+      continue;
+    }
+    current += char;
+  }
+  if (current.trim()) parts.push(current);
+  return parts;
+}
+
+function tokenizeCssList(source: string): string[] {
+  return source
+    .trim()
+    .split(/[\s,]+/)
+    .map((part) => part.trim())
+    .filter(Boolean);
+}
+
+function parseLightness(raw: string): number | null {
+  const value = parseNumber(raw);
+  if (value == null) return null;
+  if (/%$/.test(raw.trim()) || value > 1) return clamp(value / 100, 0, 1);
+  return clamp(value, 0, 1);
+}
+
+function parsePercentOrNumber(raw: string, percentBase: number): number | null {
+  const value = parseNumber(raw);
+  if (value == null) return null;
+  if (/%$/.test(raw.trim())) return value / 100 * (percentBase === 100 ? 100 : 1);
+  if (percentBase === 100 && value <= 1) return value * 100;
+  return value;
+}
+
+function parseRgbChannel(raw: string): number | null {
+  const value = parseNumber(raw);
+  if (value == null) return null;
+  if (/%$/.test(raw.trim())) return clamp(value * 2.55, 0, 255);
+  if (value >= 0 && value <= 1 && /0?\.\d+/.test(raw.trim())) return clamp(value * 255, 0, 255);
+  return clamp(value, 0, 255);
+}
+
+function parseHue(raw: string): number | null {
+  const text = raw.trim().toLowerCase();
+  const value = parseNumber(text);
+  if (value == null) return null;
+  if (text.endsWith("rad")) return (value * 180) / Math.PI;
+  if (text.endsWith("turn")) return value * 360;
+  return value;
+}
+
+function parseNumber(raw: string): number | null {
+  const value = Number.parseFloat(raw.trim().replace(/deg|rad|turn|%/gi, ""));
+  return Number.isFinite(value) ? value : null;
+}
+
+function normalizeAlpha(raw: string): number {
+  const value = parseNumber(raw);
+  if (value == null) return 1;
+  if (/%$/.test(raw.trim()) || value > 1) return clamp(value / 100, 0, 1);
+  return clamp(value, 0, 1);
+}
+
+function parseHex(value: string): [number, number, number, number] | null {
+  const hex = value.trim();
+  const short = /^#([\da-f]{3})$/i.exec(hex);
+  if (short) {
+    const [r, g, b] = short[1]!.split("").map((ch) => Number.parseInt(ch + ch, 16));
+    return [r!, g!, b!, 1];
+  }
+  const long = /^#([\da-f]{6})([\da-f]{2})?$/i.exec(hex);
+  if (!long) return null;
+  const n = Number.parseInt(long[1]!, 16);
+  const alpha = long[2] ? Number.parseInt(long[2], 16) / 255 : 1;
+  return [(n >> 16) & 255, (n >> 8) & 255, n & 255, alpha];
+}
+
+function polarToLab(c: number, hueDeg: number): [number, number] {
+  const hue = (hueDeg * Math.PI) / 180;
+  return [c * Math.cos(hue), c * Math.sin(hue)];
+}
+
+function oklabToSrgb(L: number, a: number, b: number): [number, number, number] {
+  const l_ = L + 0.3963377774 * a + 0.2158037573 * b;
+  const m_ = L - 0.1055613458 * a - 0.0638541728 * b;
+  const s_ = L - 0.0894841775 * a - 1.291485548 * b;
+  const l = l_ * l_ * l_;
+  const m = m_ * m_ * m_;
+  const s = s_ * s_ * s_;
+  return linearToSrgb([
+    4.0767416621 * l - 3.3077115913 * m + 0.2309699292 * s,
+    -1.2684380046 * l + 2.6097574011 * m - 0.3413193965 * s,
+    -0.0041960863 * l - 0.7034186147 * m + 1.707614701 * s,
+  ]);
+}
+
+function labToSrgb(L: number, a: number, b: number): [number, number, number] {
+  const y = (L + 16) / 116;
+  const x = a / 500 + y;
+  const z = y - b / 200;
+  const xn = 0.95047;
+  const yn = 1;
+  const zn = 1.08883;
+  const [X, Y, Z] = [xn * labFn(x), yn * labFn(y), zn * labFn(z)];
+  return linearToSrgb([
+    3.2404542 * X - 1.5371385 * Y - 0.4985314 * Z,
+    -0.969266 * X + 1.8760108 * Y + 0.041556 * Z,
+    0.0556434 * X - 0.2040259 * Y + 1.0572252 * Z,
+  ]);
+}
+
+function labFn(t: number): number {
+  const d = 6 / 29;
+  return t > d ? t * t * t : 3 * d * d * (t - 4 / 29);
+}
+
+function hslToSrgb(h: number, s: number, l: number): [number, number, number] {
+  const sat = clamp(s, 0, 1);
+  const light = clamp(l, 0, 1);
+  const c = (1 - Math.abs(2 * light - 1)) * sat;
+  const hp = (((h % 360) + 360) % 360) / 60;
+  const x = c * (1 - Math.abs((hp % 2) - 1));
+  let r = 0;
+  let g = 0;
+  let b = 0;
+  if (hp >= 0 && hp < 1) [r, g, b] = [c, x, 0];
+  else if (hp < 2) [r, g, b] = [x, c, 0];
+  else if (hp < 3) [r, g, b] = [0, c, x];
+  else if (hp < 4) [r, g, b] = [0, x, c];
+  else if (hp < 5) [r, g, b] = [x, 0, c];
+  else [r, g, b] = [c, 0, x];
+  const m = light - c / 2;
+  return [(r + m) * 255, (g + m) * 255, (b + m) * 255];
+}
+
+function linearToSrgb(channels: [number, number, number]): [number, number, number] {
+  return channels.map((channel) => {
+    const c = clamp(channel, 0, 1);
+    const gamma = c <= 0.0031308 ? 12.92 * c : 1.055 * c ** (1 / 2.4) - 0.055;
+    return gamma * 255;
+  }) as [number, number, number];
+}
+
+function formatRgba(rgb: [number, number, number], alpha: number): string {
+  const r = Math.round(clamp(rgb[0], 0, 255));
+  const g = Math.round(clamp(rgb[1], 0, 255));
+  const b = Math.round(clamp(rgb[2], 0, 255));
+  const a = clamp(alpha, 0, 1);
+  if (a >= 0.999) return `rgb(${r}, ${g}, ${b})`;
+  return `rgba(${r}, ${g}, ${b}, ${Number(a.toFixed(3))})`;
+}
+
+function clamp(value: number, min: number, max: number): number {
+  return Math.min(max, Math.max(min, value));
+}
+
+const NAMED: Record<string, [number, number, number, number]> = {
+  black: [0, 0, 0, 1],
+  white: [255, 255, 255, 1],
+  red: [255, 0, 0, 1],
+  green: [0, 128, 0, 1],
+  blue: [0, 0, 255, 1],
+  transparent: [0, 0, 0, 0],
+};