Changed multiple heights parsing

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

@@ -2,10 +2,12 @@ package com.mirenkov.ktheightmap
 
 import android.content.Context
 import android.util.Log
+import java.io.DataInput
 import java.io.DataInputStream
 import java.io.FileInputStream
 import kotlin.math.max
 import kotlin.math.min
+import kotlin.math.sign
 
 private data class HeightInfo(
     val minLon: Float,
@@ -20,6 +22,7 @@ class KhmParser {
     companion object {
         private var header: HeightInfo? = null
         const val HEIGHT_FILE: String = "height.khm"
+
         fun load(filePath: String, ctx: Context) {
             if (ctx.getFileStreamPath(HEIGHT_FILE).exists()) {
                 return
@@ -77,6 +80,42 @@ class KhmParser {
             }
         }
 
+
+        @OptIn(ExperimentalUnsignedTypes::class)
+        fun getHeightsMul(ctx: Context, coords: Array<Pair<Float, Float>>): Pair<UShortArray, Array<Pair<Float, Float>>> {
+            if (coords.isEmpty()) return Pair(ushortArrayOf(), coords)
+            val dis = DataInputStream(ctx.openFileInput(HEIGHT_FILE))
+            dis.use {
+                val header = readHeader(dis)
+
+                val glist: Array<Pair<Pair<Float, Float>, Int>> = Array(coords.size) { i ->
+                    val x = ((coords[i].first - header.minLon) / header.lonPerValue).toInt()
+                    val y = ((coords[i].second - header.minLat) / header.latPerValue).toInt()
+                    val offset = getOffset(header, x, y)
+                    Pair(coords[i], offset)
+                }
+                glist.sortBy {
+                    it.second
+                }
+
+                coords.sortBy { oit ->
+                    glist.find { it.first == oit }!!.second
+                }
+
+                val cutOffsets = IntArray(glist.size)
+                cutOffsets[0] = glist[0].second
+                for (i in 1 until glist.size) {
+                    cutOffsets[i] = glist[i].second - glist[i-1].second - 2
+                    assert(cutOffsets[i] >= 0)
+                }
+
+                return Pair(UShortArray(coords.size) { i ->
+                    dis.skipBytes(cutOffsets[i])
+                    dis.readUnsignedShort().toUShort()
+                }, coords)
+            }
+        }
+
         fun getLonPerValue(): Float {
             return header?.lonPerValue ?: 0F
         }

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

@@ -24,11 +24,11 @@ import androidx.compose.ui.text.rememberTextMeasurer
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.text.withStyle
 import kotlin.math.absoluteValue
-import kotlin.math.ceil
 import kotlin.math.floor
 import kotlin.math.pow
 import kotlin.math.sqrt
 
+@OptIn(ExperimentalUnsignedTypes::class)
 @Composable
 fun MapCanvas(
     viewModel: TileViewModel,
@@ -200,15 +200,20 @@ fun MapCanvas(
                     val lonDiff = lon - pointLon
                     val distance = sqrt((latDiff).pow(2) + (lonDiff).pow(2))
                     val valuesCount = floor(distance / valueDistance).toInt()
-                    for (step in 0 .. valuesCount) {
+                    val array: Array<Pair<Float, Float>> = Array(valuesCount) { step ->
                         val interCoef = 1F - step.toFloat() / valuesCount
-                        val stepLat = lat - latDiff * interCoef
+                        Pair(lon - lonDiff * interCoef, lat - latDiff * interCoef)
-                        val stepLon = lon - lonDiff * interCoef
+                    }
+                    val heightPair = KhmParser.getHeightsMul(ctx, array)
+                    val heights = heightPair.first
+                    val coords = heightPair.second
+                    for (step in 0 until coords.size) {
+                        val stepLat = coords[step].second
+                        val stepLon = coords[step].first
                         val stepOffsetX = SphereMercator.mercateLon(stepLon.toDouble(), level, -TILE_SIZE.toDouble()).toFloat() - offsetX
                         val stepOffsetY = SphereMercator.mercateLat(stepLat.toDouble(), level, -TILE_SIZE.toDouble()).toFloat() - offsetY
-                        val height = KhmParser.getHeight(stepLon, stepLat, ctx)
                         drawRect(
-                            color = if (height > startHeight) Color.Red else Color.Green,
+                            color = if (heights[step] > startHeight) Color.Red else Color.Green,
                             size = Size(8F, 8F),
                             topLeft = Offset(stepOffsetX - 4, stepOffsetY - 4)
                         )