App now finally represents feature for which it was named

app/src/main/java/com/mirenkov/ktheightmap/KhmParser.kt

@@ -1,27 +1,61 @@
 package com.mirenkov.ktheightmap
 
+import android.content.Context
 import android.util.Log
 import java.io.DataInputStream
 import java.io.FileInputStream
 
+private data class HeightInfo(
+    val minLon: Float,
+    val minLat: Float,
+    val lonPerValue: Float,
+    val latPerValue: Float,
+    val width: Int,
+    val height: Int
+)
+
 class KhmParser {
     companion object {
-        fun parse(filePath: String) {
-            Log.i(TAG, "start")
-            val dis = DataInputStream(FileInputStream(filePath))
-            with(dis) {
-                Log.i(TAG, "start2")
+        const val HEIGHT_FILE: String = "height.khm"
+        fun load(filePath: String, ctx: Context) {
+            if (ctx.getFileStreamPath(HEIGHT_FILE).exists()) {
+                Log.i(TAG, "height.khm already exists")
+                return
+            }
+
+            val inp = FileInputStream(filePath)
+            ctx.openFileOutput(HEIGHT_FILE, Context.MODE_PRIVATE).use {
+                it.write(inp.readBytes())
+                Log.i(TAG, "Copied %s to height.khm".format(filePath))
+            }
+        }
+
+        private fun getOffset(header: HeightInfo, x: Int, y: Int): Int {
+            Log.i(TAG, "Offset for (%d, %d) = %d".format(x, y, y * header.height + x))
+            return (x * header.width + y) * 2
+        }
+
+        private fun readHeader(dis: DataInputStream): HeightInfo {
+            return with(dis) {
                 val minLon = readFloat()
                 val minLat = readFloat()
-                val lonPerPixel = readFloat()
-                val latPerPixel = readFloat()
-                val rasterWidth = readInt()
-                val rasterHeight = readInt()
-                Log.i(TAG, "mLon: %.6f, mLat: %.6f, pLon: %.6f, pLat: %.6f, w: %d, h: %d".format(
-                    minLon, minLat, lonPerPixel, latPerPixel, rasterWidth, rasterHeight
-                ))
+                val lonPerValue = readFloat()
+                val latPerValue = readFloat()
+                val width = readInt()
+                val height = readInt()
+                Log.i(TAG, "Header: %.6f, %.6f, %.6f, %.6f, %d, %d".format(minLon, minLat, lonPerValue, latPerValue, width, height))
+                HeightInfo( minLon, minLat, lonPerValue, latPerValue, width, height )
             }
-            Log.i(TAG, "end")
+        }
+
+        fun getHeight(lon: Float, lat: Float, ctx: Context): UShort {
+            val dis = DataInputStream(ctx.openFileInput(HEIGHT_FILE))
+            val header = readHeader(dis)
+            val x = ((lon - header.minLon) / header.lonPerValue).toInt()
+            val y = ((lat - header.minLat) / header.latPerValue).toInt()
+            val offset = getOffset(header, x, y)
+            dis.skipBytes(offset)
+            return dis.readUnsignedShort().toUShort()
         }
     }
 }

app/src/main/java/com/mirenkov/ktheightmap/MainActivity.kt

@@ -175,6 +175,7 @@ fun ToolButton(viewModel: TileViewModel) {
 @Suppress("VariableNeverRead", "AssignedValueIsNeverRead")
 @Composable
 fun SetLocationDialog(vm: TileViewModel, dialogShown: MutableState<Boolean>) {
+    val ctx = LocalContext.current
     var showLocationDialog by dialogShown
     if (showLocationDialog) {
         var latitudeText by remember { vm.latitudeText }
@@ -214,6 +215,7 @@ fun SetLocationDialog(vm: TileViewModel, dialogShown: MutableState<Boolean>) {
                 Log.i(TAG, "Y = %.6f".format(SphereMercator.mercateLat(latitude, vm.scale.floatValue.toInt(), -TILE_SIZE.toDouble())))
                 offsetX = SphereMercator.mercateLon(longitude, vm.scale.floatValue.toInt(),  -vm.halvedOffsetX!!.toDouble() - TILE_SIZE).toFloat()
                 offsetY = SphereMercator.mercateLat(latitude, vm.scale.floatValue.toInt(), -vm.halvedOffsetY!!.toDouble() - TILE_SIZE).toFloat()
+                Log.i(TAG, "%d".format(KhmParser.getHeight(longitude.toFloat(), latitude.toFloat(), ctx).toInt()))
             }) {
                     Text("Confirm".uppercase())
                 } },

app/src/main/java/com/mirenkov/ktheightmap/SettingsActivity.kt

@@ -75,6 +75,7 @@ class SettingsActivity : ComponentActivity() {
 fun SettingsMain(vm: TileViewModel, launcher: ActivityResultLauncher<DocumentFilePickerConfig?>) {
     val coroutineScope = rememberCoroutineScope()
     val filePath by remember { SettingsActivity.filePath }
+    val ctx = LocalContext.current
     KtHeightMapTheme {
         Column(Modifier.fillMaxSize()
             .safeDrawingPadding()) {
@@ -100,7 +101,9 @@ fun SettingsMain(vm: TileViewModel, launcher: ActivityResultLauncher<DocumentFil
                 onClick = { coroutineScope.launch { vm.repository.clearTiles() } },
             ) { Text(text = "Clear database") }
             Button(
-                onClick = { filePath?.let { KhmParser.parse(it) } },
+                onClick = { filePath?.let {
+                    KhmParser.load(it, ctx)
+                } },
             ) { Text(text = "Load .khm") }
         }
     }