3d/scripts/gen-preview.cjs

const { fromFile } = require('geotiff')
const sharp = require('sharp')
const fs = require('fs')
const path = require('path')

async function main() {
  const tiffPath = path.resolve(__dirname, '../de99928f1689454084d1af33ec3cc155.tif')
  const outPath = path.resolve(__dirname, '../public/de99928f-preview.png')

  if (!fs.existsSync(tiffPath)) {
    console.error('TIFF not found:', tiffPath)
    process.exit(1)
  }

  console.log('Reading TIFF...')
  const tiff = await fromFile(tiffPath)
  const image = await tiff.getImage()
  const w = image.getWidth()
  const h = image.getHeight()
  console.log('TIFF size:', w, 'x', h)

  // 控制生成纹理尺寸：原图 14997x19876 太大，浏览器加载 123MB PNG 容易失败。
  // 4096 宽按原比例缩放后约 5425 高，文件体积降到 1/4 左右，仍然足够清晰。
  const targetW = 4096
  const targetH = Math.round(targetW * h / w)
  console.log('Target size:', targetW, 'x', targetH)

  console.log('Reading rasters at target size...')
  const data = await image.readRasters({ width: targetW, height: targetH, samples: [0, 1, 2] })
  const r = data[0]
  const g = data[1]
  const b = data[2]

  console.log('Building RGBA with alpha mask...')
  const rgba = Buffer.alloc(targetW * targetH * 4)
  let blackCount = 0
  for (let i = 0; i < targetW * targetH; i++) {
    const isBlack = r[i] < 10 && g[i] < 10 && b[i] < 10
    rgba[i * 4] = r[i]
    rgba[i * 4 + 1] = g[i]
    rgba[i * 4 + 2] = b[i]
    rgba[i * 4 + 3] = isBlack ? 0 : 255
    if (isBlack) blackCount++
  }

  console.log('Black pixels masked:', blackCount)

  await sharp(rgba, { raw: { width: targetW, height: targetH, channels: 4 } })
    .png({ compressionLevel: 9, adaptiveFiltering: true })
    .toFile(outPath)

  console.log('Saved:', outPath)
}

main().catch(e => {
  console.error(e)
  process.exit(1)
})