Add abstraction for coordinate projections

maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/MapFeature.kt

@@ -27,7 +27,8 @@ public interface DraggableMapFeature : MapFeature {
 public fun Iterable<MapFeature>.computeBoundingBox(zoom: Double): GmcRectangle? =
     mapNotNull { it.getBoundingBox(zoom) }.wrapAll()
 
-internal fun Pair<Double, Double>.toCoordinates() = GeodeticMapCoordinates.ofDegrees(first, second)
+internal fun Pair<Number, Number>.toCoordinates() =
+    GeodeticMapCoordinates.ofDegrees(first.toDouble(), second.toDouble())
 
 internal val defaultZoomRange = 1..18
 
@@ -76,7 +77,7 @@ public class MapCircleFeature(
 ) : DraggableMapFeature {
     override fun getBoundingBox(zoom: Double): GmcRectangle {
         val scale = WebMercatorProjection.scaleFactor(zoom)
-        return GmcRectangle.square(center, (size/scale).radians, (size/scale).radians)
+        return GmcRectangle.square(center, (size / scale).radians, (size / scale).radians)
     }
 
     override fun withCoordinates(newCoordinates: GeodeticMapCoordinates): MapFeature =
@@ -91,7 +92,7 @@ public class MapRectangleFeature(
 ) : DraggableMapFeature {
     override fun getBoundingBox(zoom: Double): GmcRectangle {
         val scale = WebMercatorProjection.scaleFactor(zoom)
-        return GmcRectangle.square(center, (size.height.value/scale).radians, (size.width.value/scale).radians)
+        return GmcRectangle.square(center, (size.height.value / scale).radians, (size.width.value / scale).radians)
     }
 
     override fun withCoordinates(newCoordinates: GeodeticMapCoordinates): MapFeature =
@@ -134,11 +135,11 @@ public class MapVectorImageFeature(
     public val painter: Painter,
     public val size: DpSize,
     override val zoomRange: IntRange = defaultZoomRange,
-) : DraggableMapFeature{
+) : DraggableMapFeature {
     override fun getBoundingBox(zoom: Double): GmcRectangle = GmcRectangle(position, position)
 
     override fun withCoordinates(newCoordinates: GeodeticMapCoordinates): MapFeature =
-        MapVectorImageFeature(newCoordinates,painter, size, zoomRange)
+        MapVectorImageFeature(newCoordinates, painter, size, zoomRange)
 }
 
 @Composable
@@ -166,7 +167,7 @@ public class MapTextFeature(
     override val zoomRange: IntRange = defaultZoomRange,
     public val color: Color,
     public val fontConfig: MapTextFeatureFont.() -> Unit,
-) : DraggableMapFeature{
+) : DraggableMapFeature {
     override fun getBoundingBox(zoom: Double): GmcRectangle = GmcRectangle(position, position)
 
     override fun withCoordinates(newCoordinates: GeodeticMapCoordinates): MapFeature =

maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/MapFeatureBuilder.kt

@@ -171,6 +171,16 @@ public fun MapFeatureBuilder.points(
     id: FeatureId? = null,
 ): FeatureId = addFeature(id, MapPointsFeature(points, zoomRange, stroke, color, pointMode))
 
+@JvmName("pointsFromPairs")
+public fun MapFeatureBuilder.points(
+    points: List<Pair<Double, Double>>,
+    zoomRange: IntRange = defaultZoomRange,
+    stroke: Float = 2f,
+    color: Color = Color.Red,
+    pointMode: PointMode = PointMode.Points,
+    id: FeatureId? = null,
+): FeatureId = addFeature(id, MapPointsFeature(points.map { it.toCoordinates() }, zoomRange, stroke, color, pointMode))
+
 @Composable
 public fun MapFeatureBuilder.image(
     position: Pair<Double, Double>,

maps-kt-core/src/commonMain/kotlin/center/sciprog/maps/coordinates/MercatorProjection.kt

@@ -10,7 +10,16 @@ import kotlin.math.atan
 import kotlin.math.ln
 import kotlin.math.sinh
 
-public data class MercatorCoordinates(val x: Distance, val y: Distance)
+public data class ProjectionCoordinates(val x: Distance, val y: Distance)
+
+/**
+ * @param T the type of projection coordinates
+ */
+public interface MapProjection<T: Any>{
+    public fun toGeodetic(pc: T): GeodeticMapCoordinates
+    public fun toProjection(gmc: GeodeticMapCoordinates): T
+}
+
 
 /**
  * @param baseLongitude the longitude offset in radians
@@ -21,18 +30,18 @@ public open class MercatorProjection(
     public val baseLongitude: Angle = Angle.zero,
     protected val radius: Distance = DEFAULT_EARTH_RADIUS,
     private val correctedRadius: ((GeodeticMapCoordinates) -> Distance)? = null,
-) {
+): MapProjection<ProjectionCoordinates> {
 
-    public fun toGeodetic(mc: MercatorCoordinates): GeodeticMapCoordinates {
+    override fun toGeodetic(pc: ProjectionCoordinates): GeodeticMapCoordinates {
         val res = GeodeticMapCoordinates.ofRadians(
-            atan(sinh(mc.y / radius)),
+            atan(sinh(pc.y / radius)),
-            baseLongitude.radians.value + (mc.x / radius),
+            baseLongitude.radians.value + (pc.x / radius),
         )
         return if (correctedRadius != null) {
             val r = correctedRadius.invoke(res)
             GeodeticMapCoordinates.ofRadians(
-                atan(sinh(mc.y / r)),
+                atan(sinh(pc.y / r)),
-                baseLongitude.radians.value + mc.x / r,
+                baseLongitude.radians.value + pc.x / r,
             )
         } else {
             res
@@ -42,10 +51,10 @@ public open class MercatorProjection(
     /**
      * https://en.wikipedia.org/wiki/Web_Mercator_projection#Formulas
      */
-    public fun toMercator(gmc: GeodeticMapCoordinates): MercatorCoordinates {
+    override fun toProjection(gmc: GeodeticMapCoordinates): ProjectionCoordinates {
         require(abs(gmc.latitude) <= MAXIMUM_LATITUDE) { "Latitude exceeds the maximum latitude for mercator coordinates" }
         val r: Distance = correctedRadius?.invoke(gmc) ?: radius
-        return MercatorCoordinates(
+        return ProjectionCoordinates(
             x = r * (gmc.longitude - baseLongitude).radians.value,
             y = r * ln(tan(pi / 4 + gmc.latitude / 2))
         )