293 lines
11 KiB
PHP
293 lines
11 KiB
PHP
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<?php
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/**
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* 头像主色 —— 给「人」一个稳定的识别色。
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*
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* 由来（用户 2026-10-01 的第 2 条反馈）：观影人标签一律是灰底，十几个人排在一起
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* 分不清谁是谁。既然每个人都有头像，就从头像里算出一种主色当背景色；
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* 没有头像（或头像是纯灰）的人，按姓名算一个**稳定的**颜色兜底 ——
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* 同一个人在任何页面、任何时候看到的颜色都一样。
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*
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* 三条刻意的设计：
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* · **算一次、存库（persons.avatar_color），不要每次渲染都算**。
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* 头像在 OSS 上，每渲染一个标签就下载一次原图 = 页面上 20 个人就是 20 次外网请求。
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* 只在「上传/换头像」的那一刻算，之后就是读一列 CHAR(7) —— 成本趋零。
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* · **主色不等于背景色**。头像是深色时主色也深，直接当背景会变成黑底黑字。
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* 这里一律输出两个派生色：`bg()` 是"往白里兑"的浅色底（保证深色字读得清），
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* `fg()` 是"往黑里压"的深色字（保证在浅底上够对比）。主色本身只作为**身份色**存库。
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* · **灰片回退到姓名色**。证件照、黑白老照片算不出色相（饱和度极低），
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* 硬取会得到一个飘忽不定的"最深的那个灰"，每次换图颜色就跳一次 ——
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* 不如干脆交给姓名哈希，稳定且可预期。
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*/
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declare(strict_types=1);
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namespace App;
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final class AvatarColor
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{
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/** 判定「这像素算不算有颜色」的色度门槛（max-min）。低于它当成灰。 */
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private const CHROMA_MIN = 18;
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/**
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* 从一张 GD 图像里取主色，返回 '#rrggbb'。
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* 取不到（纯灰/纯白/图坏）返回 '' —— 调用方再决定回退。
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*
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* 做法：缩到 64×64 采样 → 按色相分 36 个桶（每桶 10°）→ 以「色度 × 像素数」加权
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* 选最重的桶 → 桶内按色度加权平均 RGB。比"整图取平均"稳得多：
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* 整图平均会被大面积的背景（白墙）拖成一片灰，而这里白墙根本进不了桶。
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*/
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public static function fromGd($im): string
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{
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if (!$im) {
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return '';
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}
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$w = imagesx($im);
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$h = imagesy($im);
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if ($w < 1 || $h < 1) {
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return '';
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}
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// 先缩到 64×64：采样点数固定，一张 4000×3000 的原图也不会算很久
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$small = $im;
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if ($w > 64 || $h > 64) {
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$scale = min(64 / $w, 64 / $h);
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$sw = max(1, (int)round($w * $scale));
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$sh = max(1, (int)round($h * $scale));
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$tmp = imagecreatetruecolor($sw, $sh);
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if (!$tmp) {
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return '';
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}
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imagecopyresampled($tmp, $im, 0, 0, 0, 0, $sw, $sh, $w, $h);
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$small = $tmp;
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$w = $sw;
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$h = $sh;
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}
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$buckets = []; // hue桶 => [sumR, sumG, sumB, weight]
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for ($y = 0; $y < $h; $y++) {
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for ($x = 0; $x < $w; $x++) {
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$rgb = imagecolorat($small, $x, $y);
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$r = ($rgb >> 16) & 0xFF;
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$g = ($rgb >> 8) & 0xFF;
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$b = $rgb & 0xFF;
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$mx = max($r, $g, $b);
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$mn = min($r, $g, $b);
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$chroma = $mx - $mn;
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if ($chroma < self::CHROMA_MIN) {
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continue; // 灰/白/黑：不参与
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}
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if ($mx > 246 || $mn < 12) {
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continue; // 死白 / 死黑：多半是背景或阴影
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}
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$hue = self::hueOf($r, $g, $b, $mx, $mn, $chroma);
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$bucket = (int)floor($hue / 10);
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if ($bucket >= 36) {
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$bucket = 35;
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}
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// 权重 = 色度（越鲜艳越能代表这张图）× 一个"别太暗也别太亮"的系数
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$weight = $chroma * (1 - abs(($mx + $mn) / 510 - 0.5));
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if (!isset($buckets[$bucket])) {
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$buckets[$bucket] = [0, 0, 0, 0.0];
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}
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$buckets[$bucket][0] += $r * $weight;
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$buckets[$bucket][1] += $g * $weight;
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$buckets[$bucket][2] += $b * $weight;
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$buckets[$bucket][3] += $weight;
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}
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}
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if ($small !== $im) {
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imagedestroy($small);
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}
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if (!$buckets) {
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return '';
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}
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// 取权重最大的桶
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$best = null;
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$bestW = -1.0;
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foreach ($buckets as $b) {
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if ($b[3] > $bestW) {
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$bestW = $b[3];
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$best = $b;
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}
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}
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if ($best === null || $best[3] <= 0) {
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return '';
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}
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return sprintf('#%02X%02X%02X',
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(int)round($best[0] / $best[3]),
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(int)round($best[1] / $best[3]),
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(int)round($best[2] / $best[3]));
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}
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/** 从图片二进制里取主色（OSS/本地都行）；失败返回 '' */
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public static function fromBinary(string $bin): string
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{
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if ($bin === '') {
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return '';
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}
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$im = @imagecreatefromstring($bin);
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if ($im === false) {
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return '';
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}
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$hex = self::fromGd($im);
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imagedestroy($im);
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return $hex;
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}
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/**
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* 姓名兜底色：同样的人永远同一个颜色。
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*
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* 色相由姓名的 md5 决定（36 个色相里挑一个），饱和度与亮度**写死**在好看的区间内
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* —— 不用哈希去碰 S/L，那样会随机出刺眼的荧光色或看不清的深色。
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*/
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public static function fromName(string $name): string
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{
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$name = trim($name);
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$seed = $name === '' ? '?' : $name;
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// ⚠️ 色相取 **0.1° 精度**（3600 档）而不是 360 档：派生出来的底色只保留色相
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// （S/L 都被 bg()/fg() 拉到固定区间），所以两个人要能区分，只能靠色相。
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// 360 档时十几个人里就撞色（实测：7 个名字里有两组落到同一个色）。
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// 干脆用 md5 的整个 32 位当连续色相，不再分档。
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$hue = hexdec(substr(md5($seed), 0, 8)) / 4294967296.0;
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return self::hslToHex($hue, 0.55, 0.45);
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}
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/**
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* 一个人的展示色：库里算过就用库里的，没算过按姓名兜底。
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* 页面上一律走这里 —— 不许各自 `$p['avatar_color'] ?: '#888'`。
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*/
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public static function for(?array $p): string
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{
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if (!$p) {
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return self::fromName('');
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}
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$c = self::normalize($p['avatar_color'] ?? null);
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if ($c !== '') {
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return $c;
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}
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return self::fromName((string)($p['name'] ?? ''));
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}
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/** 规整成 '#rrggbb'；认不出来返回 '' */
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public static function normalize($hex): string
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{
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$hex = strtolower(trim((string)$hex));
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if ($hex === '') {
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return '';
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}
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if ($hex[0] === '#') {
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$hex = substr($hex, 1);
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}
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if (preg_match('/^[0-9a-f]{3}$/', $hex)) {
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$hex = $hex[0] . $hex[0] . $hex[1] . $hex[1] . $hex[2] . $hex[2];
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}
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if (!preg_match('/^[0-9a-f]{6}$/', $hex)) {
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return '';
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}
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return '#' . $hex;
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}
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/**
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* 背景色：把主色往白里兑。
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*
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* 兑完统一到 L≈0.90、S≈0.55 —— 不管头像是深蓝还是亮黄，
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* 出来的都是"淡淡的那种蓝/黄"，深色字压在上面都读得清，
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* 同时彼此之间又能一眼区分（这正是用户要的效果）。
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*/
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public static function bg(?string $hex): string
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{
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[$h, $s] = self::hsl(self::normalize($hex) ?: self::fromName(''));
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$s = $s < 0.18 ? 0.30 : min(0.62, max(0.34, $s));
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return self::hslToHex($h, $s, 0.90);
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}
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/** 文字色：把主色往黑里压，保证在 bg() 上有足够对比 */
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public static function fg(?string $hex): string
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{
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[$h, $s] = self::hsl(self::normalize($hex) ?: self::fromName(''));
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$s = $s < 0.18 ? 0.35 : min(0.75, max(0.40, $s));
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return self::hslToHex($h, $s, 0.30);
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}
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/** 边线色（比 bg 深一档，让浅色标签在白底上仍有轮廓） */
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public static function bd(?string $hex): string
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{
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[$h, $s] = self::hsl(self::normalize($hex) ?: self::fromName(''));
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$s = $s < 0.18 ? 0.35 : min(0.70, max(0.38, $s));
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return self::hslToHex($h, $s, 0.72);
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}
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// ---------------- 颜色空间小工具 ----------------
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/** 0..360 的色相 */
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private static function hueOf(int $r, int $g, int $b, int $mx, int $mn, int $chroma): float
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{
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if ($chroma === 0) {
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return 0.0;
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}
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if ($mx === $r) {
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$h = fmod((($g - $b) / $chroma), 6.0);
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} elseif ($mx === $g) {
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$h = (($b - $r) / $chroma) + 2.0;
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} else {
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$h = (($r - $g) / $chroma) + 4.0;
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}
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$h *= 60.0;
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if ($h < 0) {
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$h += 360.0;
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}
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return $h;
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}
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/** @return array{0:float,1:float,2:float} h(0..1) s(0..1) l(0..1) */
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private static function hsl(string $hex): array
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{
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$hex = ltrim($hex, '#');
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$r = hexdec(substr($hex, 0, 2)) / 255;
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$g = hexdec(substr($hex, 2, 2)) / 255;
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$b = hexdec(substr($hex, 4, 2)) / 255;
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$mx = max($r, $g, $b);
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$mn = min($r, $g, $b);
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$l = ($mx + $mn) / 2;
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$d = $mx - $mn;
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if ($d == 0) {
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return [0.0, 0.0, $l];
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}
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// 分母在 l=0（死黑）/ l=1（死白）时为 0 —— 那时饱和度本来就没有意义，记 0。
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$den = 1 - abs(2 * $l - 1);
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$s = $den > 1e-9 ? $d / $den : 0.0;
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$h = self::hueOf(
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(int)round($r * 255), (int)round($g * 255), (int)round($b * 255),
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(int)round($mx * 255), (int)round($mn * 255), max(1, (int)round($d * 255))
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);
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return [$h / 360.0, $s, $l];
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}
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private static function hslToHex(float $h, float $s, float $l): string
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{
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$h = $h - floor($h);
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if ($s <= 0) {
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$v = (int)round($l * 255);
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return sprintf('#%02X%02X%02X', $v, $v, $v);
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}
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$q = $l < 0.5 ? $l * (1 + $s) : $l + $s - $l * $s;
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$p = 2 * $l - $q;
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$conv = static function (float $t) use ($p, $q): float {
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$t = $t - floor($t);
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if ($t < 1 / 6) {
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return $p + ($q - $p) * 6 * $t;
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}
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if ($t < 1 / 2) {
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return $q;
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}
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if ($t < 2 / 3) {
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return $p + ($q - $p) * (2 / 3 - $t) * 6;
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}
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return $p;
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};
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$r = (int)round($conv($h + 1 / 3) * 255);
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$g = (int)round($conv($h) * 255);
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$b = (int)round($conv($h - 1 / 3) * 255);
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return sprintf('#%02X%02X%02X', max(0, min(255, $r)), max(0, min(255, $g)), max(0, min(255, $b)));
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}
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}
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