[GitHub] [incubator-sedona] jiayuasu commented on a diff in pull request #612: [SEDONA-108] Write Support for GeoTiff Raster Images

[GitBox <gi...@apache.org>]

jiayuasu commented on code in PR #612:
URL: https://github.com/apache/incubator-sedona/pull/612#discussion_r853400083


##########
sql/src/main/scala/org/apache/spark/sql/sedona_sql/io/GeotiffFileFormat.scala:
##########
@@ -101,4 +126,123 @@ private[spark] class GeotiffFileFormat extends FileFormat with DataSourceRegiste
       }
     }
   }
+
+  private def isValidGeoTiffSchema(options: Map[String, String], dataSchema: StructType): Boolean = {
+    val colImage = options.getOrElse("key_image", "image")
+    val fields = dataSchema.fieldNames
+    if (fields.contains(colImage) ){
+      val schemaFields = dataSchema.fields(dataSchema.fieldIndex(colImage)).dataType.asInstanceOf[StructType]
+      if (schemaFields.fieldNames.length != 6) return false
+    }
+    else {
+      if (fields.length != 6) return false
+    }
+    true
+  }
+
+}
+
+// class for writing geoTiff images
+private class GeotiffFileWriter(savePath: String,
+                                options: Map[String, String],
+                                dataSchema: StructType,
+                                context: TaskAttemptContext) extends OutputWriter {
+
+  // set writing parameters
+  private val DEFAULT_WRITE_PARAMS: GeoTiffWriteParams = new GeoTiffWriteParams()
+  DEFAULT_WRITE_PARAMS.setCompressionMode(ImageWriteParam.MODE_EXPLICIT)
+  DEFAULT_WRITE_PARAMS.setCompressionType("LZW")
+  DEFAULT_WRITE_PARAMS.setCompressionQuality(0.75F)
+  DEFAULT_WRITE_PARAMS.setTilingMode(ImageWriteParam.MODE_EXPLICIT)
+  DEFAULT_WRITE_PARAMS.setTiling(512, 512)
+
+  private val hfs = new Path(savePath).getFileSystem(context.getConfiguration)
+
+  override def write(row: InternalRow): Unit = {
+    // retrieving the metadata of a geotiff image
+    var rowFields: InternalRow = row
+    var schemaFields: StructType = dataSchema
+    val fields = dataSchema.fieldNames
+
+    val colImage = options.getOrElse("key_image", "image")
+    val colOrigin = options.getOrElse("key_origin", "origin")
+    val colBands = options.getOrElse("key_n_bands", "nBands")
+    val colWidth = options.getOrElse("key_width", "width")
+    val colHeight = options.getOrElse("key_height", "height")
+    val colWkt = options.getOrElse("key_wkt", "wkt")
+    val colData = options.getOrElse("key_data", "data")
+
+    if (fields.contains(colImage)) {
+      schemaFields = dataSchema.fields(dataSchema.fieldIndex(colImage)).dataType.asInstanceOf[StructType]
+      rowFields = row.getStruct(dataSchema.fieldIndex(colImage), 6)
+    }
+
+    val tiffOrigin = rowFields.getString(schemaFields.fieldIndex(colOrigin))
+    val tiffBands = rowFields.getInt(schemaFields.fieldIndex(colBands))
+    val tiffWidth = rowFields.getInt(schemaFields.fieldIndex(colWidth))
+    val tiffHeight = rowFields.getInt(schemaFields.fieldIndex(colHeight))
+    val tiffGeometry = rowFields.getString(schemaFields.fieldIndex(colWkt))
+    val tiffData = rowFields.getArray(schemaFields.fieldIndex(colData)).toDoubleArray()
+
+    // create a writable raster object
+    val raster = RasterFactory.createBandedRaster(DataBuffer.TYPE_DOUBLE, tiffWidth, tiffHeight, tiffBands, null)
+
+    // extract the pixels of the geotiff image and write to the writable raster
+    val pixelVal = Array.ofDim[Double](tiffBands)
+    for (i <- 0 until tiffHeight) {
+      for (j <- 0 until tiffWidth) {
+        for (k <- 0 until tiffBands) {
+          pixelVal(k) = tiffData(tiffHeight*tiffWidth*k + i * tiffWidth + j)
+        }
+        raster.setPixel(j, i, pixelVal)
+      }
+    }
+
+    // CRS is always fixed to EPSG:4326
+    val crs = CRS.decode("EPSG:4326", true)

Review Comment:
   This should NOT be always fixed to EPSG:4326. The user will use ST_Transform in their DF to convert coordinates to whatever CRS they like. Then call df.write.save to save GeoTiff. GeoTiff meta data has a place for storing the name of the CRS.



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