Add marker colors and update Example03Markers

Author: afarber

examples/Example03Markers/src/main/kotlin/de/afarber/openmapview/example03markers/MainActivity.kt

@@ -18,6 +18,7 @@ import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.viewinterop.AndroidView
+import de.afarber.openmapview.BitmapDescriptorFactory
 import de.afarber.openmapview.LatLng
 import de.afarber.openmapview.Marker
 import de.afarber.openmapview.OpenMapView
@@ -53,12 +54,13 @@ fun MapViewScreen() {
                 setCenter(LatLng(51.4661, 7.2491))
                 setZoom(14.0)
 
-                // Add several markers around Bochum
+                // Add several markers around Bochum with different colors
                 addMarker(
                     Marker(
                         position = LatLng(51.4661, 7.2491),
                         title = "Bochum City Center",
                         snippet = "Welcome to Bochum!",
+                        icon = BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED),
                     ),
                 )
 
@@ -67,6 +69,7 @@ fun MapViewScreen() {
                         position = LatLng(51.4700, 7.2550),
                         title = "North Location",
                         snippet = "A place north of center",
+                        icon = BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_BLUE),
                     ),
                 )
 
@@ -75,6 +78,7 @@ fun MapViewScreen() {
                         position = LatLng(51.4620, 7.2430),
                         title = "South Location",
                         snippet = "A place south of center",
+                        icon = BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_GREEN),
                     ),
                 )
 
@@ -83,6 +87,7 @@ fun MapViewScreen() {
                         position = LatLng(51.4680, 7.2380),
                         title = "West Location",
                         snippet = "A place west of center",
+                        icon = BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_ORANGE),
                     ),
                 )
 
@@ -91,6 +96,7 @@ fun MapViewScreen() {
                         position = LatLng(51.4640, 7.2600),
                         title = "East Location",
                         snippet = "A place east of center",
+                        icon = BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA),
                     ),
                 )
 

openmapview/src/main/kotlin/de/afarber/openmapview/BitmapDescriptorFactory.kt

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2025 Alexander Farber
+ * SPDX-License-Identifier: MIT
+ *
+ * This file is part of the OpenMapView project (https://github.com/afarber/OpenMapView)
+ */
+
+package de.afarber.openmapview
+
+import android.graphics.Bitmap
+
+/**
+ * Factory for creating marker icons, compatible with Google Maps API.
+ *
+ * Provides predefined color constants and methods to generate colored marker icons.
+ * Colors are specified using HSV hue values (0-360 degrees on the color wheel).
+ */
+object BitmapDescriptorFactory {
+    /**
+     * HUE constants matching Google Maps BitmapDescriptorFactory.
+     * Values represent degrees on the HSV color wheel.
+     */
+    const val HUE_RED = 0f
+    const val HUE_ORANGE = 30f
+    const val HUE_YELLOW = 60f
+    const val HUE_GREEN = 120f
+    const val HUE_CYAN = 180f
+    const val HUE_AZURE = 210f
+    const val HUE_BLUE = 240f
+    const val HUE_VIOLET = 270f
+    const val HUE_MAGENTA = 300f
+    const val HUE_ROSE = 330f
+
+    /**
+     * Creates a marker icon with the specified hue.
+     *
+     * @param hue The hue value (0-360) on the color wheel. Defaults to red (0).
+     *            0=red, 120=green, 240=blue, etc.
+     * @return A bitmap of the colored marker icon
+     */
+    fun defaultMarker(hue: Float = HUE_RED): Bitmap = MarkerIconFactory.getDefaultIcon(hue)
+}

openmapview/src/main/kotlin/de/afarber/openmapview/MarkerIconFactory.kt

@@ -14,34 +14,64 @@ import android.graphics.Paint
 import android.graphics.Path
 
 /**
- * Factory for creating default marker icons.
+ * Factory for creating default marker icons with customizable colors.
  */
 internal object MarkerIconFactory {
     private const val DEFAULT_WIDTH = 48
     private const val DEFAULT_HEIGHT = 72
-    private var cachedDefaultIcon: Bitmap? = null
+    private const val MAX_CACHE_SIZE = 10
+
+    // LRU cache for colored marker icons (hue -> bitmap)
+    private val iconCache = LinkedHashMap<Float, Bitmap>(MAX_CACHE_SIZE + 1, 0.75f, true)
 
     /**
-     * Creates or returns a cached default marker icon.
-     * The icon is a red teardrop shape with a white circle in the center.
+     * Creates or returns a cached marker icon with the specified hue.
+     *
+     * @param hue The hue value (0-360) on the HSV color wheel. Defaults to 0 (red).
+     * @return A bitmap of the colored marker icon
      */
-    fun getDefaultIcon(): Bitmap {
-        cachedDefaultIcon?.let { return it }
+    fun getDefaultIcon(hue: Float = 0f): Bitmap {
+        // Normalize hue to 0-360 range
+        val normalizedHue = hue % 360f
+
+        // Return cached icon if available
+        iconCache[normalizedHue]?.let { return it }
+
+        // Create new icon
+        val bitmap = createMarkerIcon(normalizedHue)
+
+        // Add to cache with LRU eviction
+        if (iconCache.size >= MAX_CACHE_SIZE) {
+            val firstKey = iconCache.keys.first()
+            iconCache.remove(firstKey)?.recycle()
+        }
+        iconCache[normalizedHue] = bitmap
+
+        return bitmap
+    }
 
+    /**
+     * Creates a marker icon bitmap with the specified hue.
+     */
+    private fun createMarkerIcon(hue: Float): Bitmap {
         val bitmap = Bitmap.createBitmap(DEFAULT_WIDTH, DEFAULT_HEIGHT, Bitmap.Config.ARGB_8888)
         val canvas = Canvas(bitmap)
 
+        // Convert HSV to RGB
+        val mainColor = Color.HSVToColor(floatArrayOf(hue, 1.0f, 1.0f))
+        val borderColor = Color.HSVToColor(floatArrayOf(hue, 1.0f, 0.6f)) // Darker border
+
         val markerPaint =
             Paint().apply {
                 style = Paint.Style.FILL
-                color = Color.RED
+                color = mainColor
                 isAntiAlias = true
             }
 
         val borderPaint =
             Paint().apply {
                 style = Paint.Style.STROKE
-                color = Color.parseColor("#8B0000") // Dark red
+                color = borderColor
                 strokeWidth = 3f
                 isAntiAlias = true
             }
@@ -75,15 +105,14 @@ internal object MarkerIconFactory {
         // Draw white center circle
         canvas.drawCircle(centerX, circleRadius + 2f, circleRadius * 0.4f, centerPaint)
 
-        cachedDefaultIcon = bitmap
         return bitmap
     }
 
     /**
-     * Clears the cached default icon to free memory.
+     * Clears all cached icons to free memory.
      */
     fun clearCache() {
-        cachedDefaultIcon?.recycle()
-        cachedDefaultIcon = null
+        iconCache.values.forEach { it.recycle() }
+        iconCache.clear()
     }
 }