From 8a530d9d4870a9294b6b49e2d6ddcb53a98d678e Mon Sep 17 00:00:00 2001
From: 2ndbeam <2ndbeam@disroot.org>
Date: Mon, 25 Aug 2025 15:15:51 +0300
Subject: [PATCH] mercator

---
 .idea/deploymentTargetSelector.xml            |  4 +-
 .../com/mirenkov/ktheightmap/MainActivity.kt  |  2 +-
 .../com/mirenkov/ktheightmap/MapCanvas.kt     | 51 ++++++++++--------
 .../mirenkov/ktheightmap/SphereMercator.kt    | 52 +++++++++++++++++++
 4 files changed, 84 insertions(+), 25 deletions(-)
 create mode 100644 app/src/main/java/com/mirenkov/ktheightmap/SphereMercator.kt

diff --git a/.idea/deploymentTargetSelector.xml b/.idea/deploymentTargetSelector.xml
index de71baa..338e0e6 100644
--- a/.idea/deploymentTargetSelector.xml
+++ b/.idea/deploymentTargetSelector.xml
@@ -4,10 +4,10 @@
     <selectionStates>
       <SelectionState runConfigName="app">
         <option name="selectionMode" value="DROPDOWN" />
-        <DropdownSelection timestamp="2025-08-08T10:50:02.571721922Z">
+        <DropdownSelection timestamp="2025-08-21T11:17:37.943341883Z">
           <Target type="DEFAULT_BOOT">
             <handle>
-              <DeviceId pluginId="LocalEmulator" identifier="path=/home/secondbeam/.android/avd/Pixel_3.avd" />
+              <DeviceId pluginId="PhysicalDevice" identifier="serial=96DX21GPR" />
             </handle>
           </Target>
         </DropdownSelection>
diff --git a/app/src/main/java/com/mirenkov/ktheightmap/MainActivity.kt b/app/src/main/java/com/mirenkov/ktheightmap/MainActivity.kt
index e861aae..081c344 100644
--- a/app/src/main/java/com/mirenkov/ktheightmap/MainActivity.kt
+++ b/app/src/main/java/com/mirenkov/ktheightmap/MainActivity.kt
@@ -100,7 +100,7 @@ fun Main(vm: TileViewModel = viewModel()) {
                 Slider(
                     value = sliderValue.floatValue,
                     onValueChange = { sliderValue.floatValue = it },
-                    valueRange = 1F..14F,
+                    valueRange = 2F..14F,
                     modifier = Modifier.align(Alignment.CenterStart)
                 )
             }
diff --git a/app/src/main/java/com/mirenkov/ktheightmap/MapCanvas.kt b/app/src/main/java/com/mirenkov/ktheightmap/MapCanvas.kt
index 9e73d6d..e780240 100644
--- a/app/src/main/java/com/mirenkov/ktheightmap/MapCanvas.kt
+++ b/app/src/main/java/com/mirenkov/ktheightmap/MapCanvas.kt
@@ -5,8 +5,10 @@ import androidx.compose.foundation.gestures.detectDragGestures
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.MutableFloatState
+import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableFloatStateOf
 import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.geometry.Size
@@ -22,6 +24,7 @@ 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.sqrt
 
 @Composable
 fun MapCanvas(
@@ -31,15 +34,15 @@ fun MapCanvas(
     tileContainer: TileContainer,
     modifier: Modifier = Modifier
 ) {
-    val offsetX = rememberSaveable { mutableFloatStateOf(-TILE_SIZE) }
-    val offsetY = rememberSaveable { mutableFloatStateOf(-TILE_SIZE) }
+    var offsetX by rememberSaveable { mutableFloatStateOf(-TILE_SIZE) }
+    var offsetY by rememberSaveable { mutableFloatStateOf(-TILE_SIZE) }
     val textMeasurer = rememberTextMeasurer()
     Canvas(
         modifier = modifier.fillMaxSize()
             .pointerInput(Unit) {
                 detectDragGestures { _, distance ->
-                    offsetX.floatValue -= distance.x
-                    offsetY.floatValue -= distance.y
+                    offsetX -= distance.x
+                    offsetY -= distance.y
                 }
             }
     ) {
@@ -53,24 +56,24 @@ fun MapCanvas(
 
         if (levelDiff < 0) {
             repeat (levelDiff.absoluteValue) {
-                offsetX.floatValue -= size.width / 2F + TILE_SIZE
-                offsetY.floatValue -= size.height / 2F + TILE_SIZE
-                offsetX.floatValue /= 2F
-                offsetY.floatValue /= 2F
+                offsetX -= size.width / 2F + TILE_SIZE
+                offsetY -= size.height / 2F + TILE_SIZE
+                offsetX /= 2F
+                offsetY /= 2F
             }
         } else if (levelDiff > 0) {
             repeat (levelDiff) {
-                offsetX.floatValue *= 2F
-                offsetY.floatValue *= 2F
-                offsetX.floatValue += size.width / 2F + TILE_SIZE
-                offsetY.floatValue += size.height / 2F + TILE_SIZE
+                offsetX *= 2F
+                offsetY *= 2F
+                offsetX += size.width / 2F + TILE_SIZE
+                offsetY += size.height / 2F + TILE_SIZE
             }
         }
-        val tileOffsetX = (offsetX.floatValue / TILE_SIZE).toInt()
-        val tileOffsetY = (offsetY.floatValue / TILE_SIZE).toInt()
+        val tileOffsetX = (offsetX / TILE_SIZE).toInt()
+        val tileOffsetY = (offsetY / TILE_SIZE).toInt()
 
-        val strippedOffsetX = offsetX.floatValue % TILE_SIZE
-        val strippedOffsetY = offsetY.floatValue % TILE_SIZE
+        val strippedOffsetX = offsetX % TILE_SIZE
+        val strippedOffsetY = offsetY % TILE_SIZE
 
         val offset = Offset(strippedOffsetX, strippedOffsetY)
 
@@ -89,19 +92,20 @@ fun MapCanvas(
                 val localOffsetY = TILE_SIZE * (cellY - 1)
 
                 val bitmap = tiles.find { it.x == tileX && it.y == tileY && it.level == level }?.toBitmap()
+                val totalOffset = Offset(localOffsetX, localOffsetY) - offset
 
                 bitmap?.let {
                     val imageBitmap = bitmap.asImageBitmap()
                     drawImage(
                         image = imageBitmap,
-                        topLeft = Offset(localOffsetX, localOffsetY) - offset
+                        topLeft = totalOffset
                     )
                 }
-                /*
+
                 drawRect(
                     color = gridColor,
                     size = Size(TILE_SIZE, TILE_SIZE),
-                    topLeft = Offset(localOffsetX, localOffsetY) - offset,
+                    topLeft = totalOffset,
                     style = Stroke(width = 4F)
                 )
 
@@ -110,14 +114,17 @@ fun MapCanvas(
                     text = buildAnnotatedString {
                         withStyle(ParagraphStyle(textAlign = TextAlign.Center)) {
                             withStyle(SpanStyle(color = gridColor)) {
-                                append("x:%d, y:%d".format(tileX, tileY))
+                                val mapSize = (1 shl (level - 1)).toDouble()
+                                val mappedY = (tileY.toDouble() - (mapSize / 2.0))
+                                val mercX = SphereMercator.sx2lon((tileX * TILE_SIZE).toDouble(), level) - 180.0
+                                val mercY = -SphereMercator.sy2lat(mappedY * TILE_SIZE, level - 1)
+                                append("%.6f, %.6f,\n%d, %d".format(mercX, mercY, tileX, tileY))
                             }
                         }
                     },
-                    topLeft = Offset(localOffsetX, localOffsetY) - offset,
+                    topLeft = totalOffset,
                     size = Size(TILE_SIZE, TILE_SIZE)
                 )
-                */
             }
         }
     }
diff --git a/app/src/main/java/com/mirenkov/ktheightmap/SphereMercator.kt b/app/src/main/java/com/mirenkov/ktheightmap/SphereMercator.kt
new file mode 100644
index 0000000..8ffa410
--- /dev/null
+++ b/app/src/main/java/com/mirenkov/ktheightmap/SphereMercator.kt
@@ -0,0 +1,52 @@
+package com.mirenkov.ktheightmap
+
+import java.lang.Math.toRadians
+import java.lang.Math.toDegrees
+import kotlin.math.atan
+import kotlin.math.exp
+import kotlin.math.ln
+import kotlin.math.tan
+import kotlin.math.PI
+
+class SphereMercator {
+    companion object {
+        const val RADIUS = 6378137
+        const val METERS_PER_PIXEL = 156543.0339
+
+        fun x2lon(x: Double): Double {
+            return toDegrees(x / RADIUS)
+        }
+
+        fun y2lat(y: Double): Double {
+            return toDegrees(atan(exp(y / RADIUS / 2)) * 2 - PI / 2)
+        }
+
+        fun lon2x(longitude: Double): Double {
+            return toRadians(longitude) * RADIUS
+        }
+
+        fun lat2y(latitude: Double): Double {
+            return ln(tan(PI / 4 + toRadians(latitude) / 2)) * RADIUS
+        }
+
+        fun scaledMetersPerPixel(level: Int): Double {
+            return METERS_PER_PIXEL / ( 1 shl (level - 1) )
+        }
+
+        fun sx2lon(x: Double, level: Int): Double {
+            return x2lon(x * scaledMetersPerPixel(level))
+        }
+
+        fun sy2lat(y: Double, level: Int): Double {
+            return y2lat( y * scaledMetersPerPixel(level))
+        }
+
+        fun lon2sx(longitude: Double, level: Int) : Double {
+            return lon2x(longitude) / scaledMetersPerPixel(level)
+        }
+
+        fun lat2sy(latitude: Double, level: Int): Double {
+            return lat2y(latitude) / scaledMetersPerPixel(level)
+        }
+    }
+}
\ No newline at end of file