City-Lifeline-Cockpit/.scratch/lanhu-cockpit-asset-replacement/research/measure-master.mjs

// 测量两个白母版的 alpha 包围盒、尖端（最低不透明点）、圆帽几何（帽心/帽径）
// 输出将作为 markerAssets.js 的实测依据（规格 10：锚点/内层几何按素材属性登记）
import { readFileSync } from 'node:fs'
import { inflateSync } from 'node:zlib'

function decodePng(path) {
    const buf = readFileSync(path)
    if (buf.readUInt32BE(0) !== 0x89504e47) throw new Error('非 PNG')
    let pos = 8
    const idat = []
    let width = 0, height = 0, bitDepth = 0, colorType = 0, palette = null, trns = null
    while (pos < buf.length) {
        const len = buf.readUInt32BE(pos)
        const type = buf.toString('ascii', pos + 4, pos + 8)
        const data = buf.subarray(pos + 8, pos + 8 + len)
        if (type === 'IHDR') {
            width = data.readUInt32BE(0); height = data.readUInt32BE(4)
            bitDepth = data[8]; colorType = data[9]
        } else if (type === 'PLTE') palette = Buffer.from(data)
        else if (type === 'tRNS') trns = Buffer.from(data)
        else if (type === 'IDAT') idat.push(data)
        else if (type === 'IEND') break
        pos += 12 + len
    }
    const channels = colorType === 6 ? 4 : colorType === 2 ? 3 : 1
    const stride = width * channels
    const raw = inflateSync(Buffer.concat(idat))
    const img = Buffer.alloc(height * stride)
    for (let y = 0; y < height; y++) {
        const filter = raw[y * (stride + 1)]
        const row = raw.subarray(y * (stride + 1) + 1, (y + 1) * (stride + 1))
        const prev = y > 0 ? img.subarray((y - 1) * stride, y * stride) : null
        const out = img.subarray(y * stride, (y + 1) * stride)
        for (let x = 0; x < stride; x++) {
            const a = x >= channels ? out[x - channels] : 0
            const b = prev ? prev[x] : 0
            const c = prev && x >= channels ? prev[x - channels] : 0
            let v = row[x]
            if (filter === 1) v += a
            else if (filter === 2) v += b
            else if (filter === 3) v += (a + b) >> 1
            else if (filter === 4) {
                const p = a + b - c
                const pa = Math.abs(p - a), pb = Math.abs(p - b), pc = Math.abs(p - c)
                v += pa <= pb && pa <= pc ? a : pb <= pc ? b : c
            }
            out[x] = v & 0xff
        }
    }
    // 提取 alpha 通道函数
    const alphaAt = (x, y) => {
        if (colorType === 6) return img[y * stride + x * 4 + 3]
        if (colorType === 2) return 255
        const idx = img[y * stride + x]
        if (trns && idx < trns.length) return trns[idx]
        return 255
    }
    return { width, height, alphaAt }
}

for (const file of ['public/cockpit/assets/icons/T_MarkPoint_WhiteFull.png', 'public/cockpit/assets/icons/T_MarkPoint_White.png']) {
    const { width, height, alphaAt } = decodePng(file)
    let minX = width, maxX = -1, minY = height, maxY = -1
    for (let y = 0; y < height; y++) {
        for (let x = 0; x < width; x++) {
            if (alphaAt(x, y) > 8) {
                if (x < minX) minX = x
                if (x > maxX) maxX = x
                if (y < minY) minY = y
                if (y > maxY) maxY = y
            }
        }
    }
    const bw = maxX - minX + 1
    const bh = maxY - minY + 1
    // 尖端：包围盒底部一行的不透明质心 x
    let tipSum = 0, tipCount = 0
    for (let x = minX; x <= maxX; x++) {
        if (alphaAt(x, maxY) > 8) { tipSum += x; tipCount++ }
    }
    const tipX = tipCount ? tipSum / tipCount : -1
    // 圆帽几何：从顶往下找「宽度最大的行」——实心版即圆帽直径线；镂空版因孔洞偏下，取首次接近 95% 最大宽的行
    let widest = 0, widestY = minY
    let firstNearMaxY = -1
    for (let y = minY; y <= maxY; y++) {
        let cnt = 0
        for (let x = minX; x <= maxX; x++) if (alphaAt(x, y) > 8) cnt++
        if (cnt > widest) { widest = cnt; widestY = y }
        if (firstNearMaxY < 0 && widest > 0 && cnt >= widest * 0.95) firstNearMaxY = y
    }
    const capCY = firstNearMaxY
    const capCX = (() => {
        let s = 0, n = 0
        for (let x = minX; x <= maxX; x++) if (alphaAt(x, capCY) > 8) { s += x; n++ }
        return n ? s / n : -1
    })()
    console.log(`${file.split('/').pop()}:`)
    console.log(`  画布 ${width}x${height} | bbox x${minX}..${maxX} y${minY}..${maxY} (${bw}x${bh})`)
    console.log(`  宽高比 ${ (bh / bw).toFixed(3) }`)
    console.log(`  尖端 x=${tipX.toFixed(1)} (bbox 相对 ${(100 * (tipX - minX) / bw).toFixed(1)}%) y=${maxY}`)
    console.log(`  圆帽线 y=${capCY}（帽心相对高度 ${((capCY - minY) / bh).toFixed(3)}）帽心x=${capCX.toFixed(1)}（bbox 相对 ${(100 * (capCX - minX) / bw).toFixed(1)}%）`)
    console.log(`  锚点(尖端)相对 bbox: x=${((tipX - minX) / bw).toFixed(4)}, y=1.0`)
}