feat: convert mbtiles to a styled map package file (#35)

* feat: convert mbtiles to a styled map package file

* update package-lock

* address PR comments

bin/smp-mbtiles.js

@@ -0,0 +1,21 @@
+#!/usr/bin/env node
+import { Command } from 'commander'
+import { pipeline } from 'stream/promises'
+
+import fromMBTiles from '../lib/from-mbtiles.js'
+
+const program = new Command()
+
+program
+  .description('Convert a MBTiles file to a styled map package file')
+  .option('-o, --output <file>', 'output smp file')
+  .argument('<mbtiles>', 'MBTiles file to convert')
+  .action(async (mbtilesPath, { output }) => {
+    if (output) {
+      await fromMBTiles(mbtilesPath, output)
+    } else {
+      await pipeline(fromMBTiles(mbtilesPath), process.stdout)
+    }
+  })
+
+program.parseAsync(process.argv)

bin/smp.js

@@ -7,5 +7,6 @@ program
   .name('smp')
   .command('download', 'Download a map style to a styled map package file')
   .command('view', 'Preview a styled map package in a web browser')
+  .command('mbtiles', 'Convert a MBTiles file to a styled map package file')
 
 program.parse(process.argv)

lib/from-mbtiles.js

@@ -0,0 +1,83 @@
+import { MBTiles } from 'mbtiles-reader'
+import SMPWriter from 'styled-map-package/writer'
+
+import fs from 'node:fs'
+import { Transform } from 'node:stream'
+import { pipeline } from 'node:stream'
+import { pipeline as pipelinePromise } from 'node:stream/promises'
+
+const SOURCE_ID = 'mbtiles-source'
+
+/**
+ * @overload
+ * @param {string} mbtilesPath
+ * @returns {import('stream').Readable}
+ */
+
+/**
+ * @overload
+ * @param {string} mbtilesPath
+ * @param {string} outputPath
+ * @returns {Promise<void>}
+ */
+
+/**
+ * @param {string} mbtilesPath
+ * @param {string} [outputPath]
+ * @returns {Promise<void> | import('stream').Readable}
+ */
+export default function fromMBTiles(mbtilesPath, outputPath) {
+  const reader = new MBTiles(mbtilesPath)
+  if (reader.metadata.format === 'pbf') {
+    throw new Error('Vector MBTiles are not yet supported')
+  }
+  const style = {
+    version: 8,
+    name: reader.metadata.name,
+    sources: {
+      [SOURCE_ID]: {
+        ...reader.metadata,
+        type: 'raster',
+      },
+    },
+    layers: [
+      {
+        id: 'background',
+        type: 'background',
+        paint: {
+          'background-color': 'white',
+        },
+      },
+      {
+        id: 'raster',
+        type: 'raster',
+        source: SOURCE_ID,
+        paint: {
+          'raster-opacity': 1,
+        },
+      },
+    ],
+  }
+
+  const writer = new SMPWriter(style)
+
+  const returnValue = outputPath
+    ? pipelinePromise(writer.outputStream, fs.createWriteStream(outputPath))
+    : writer.outputStream
+
+  const tileWriteStream = writer.createTileWriteStream()
+
+  const transform = new Transform({
+    objectMode: true,
+    transform({ z, x, y, data, format }, encoding, callback) {
+      callback(null, [data, { z, x, y, format, sourceId: SOURCE_ID }])
+    },
+  })
+
+  pipeline(reader, transform, tileWriteStream, (err) => {
+    if (err) return writer.outputStream.destroy(err)
+    writer.finish()
+  })
+
+  return returnValue
+}

lib/index.js

@@ -8,3 +8,4 @@ export { default as Server } from './server.js'
 export { default as StyleDownloader } from './style-downloader.js'
 export { downloadTiles } from './tile-downloader.js'
 export { default as download } from './download.js'
+export { default as fromMBTiles } from './from-mbtiles.js'