Moar federation

src/main/java/org/operaton/fitpub/service/ActivityImageService.java

@@ -150,11 +150,16 @@ public class ActivityImageService {
         int trackWidth = (int) (width * 0.6);
         int trackHeight = height;
 
-        // The OSM tile renderer already scales the image to fit trackWidth x trackHeight
-        // So we can use simple linear mapping from geographic bounds to pixel coordinates
-        double scaleX = trackWidth / (bounds.maxLon - bounds.minLon);
-        double scaleY = trackHeight / (bounds.maxLat - bounds.minLat);
-        double scale = Math.min(scaleX, scaleY);
+        // Convert bounds to Web Mercator normalized coordinates (0-1)
+        // This matches the projection used by OSM tiles
+        double minX = longitudeToWebMercatorX(bounds.minLon);
+        double maxX = longitudeToWebMercatorX(bounds.maxLon);
+        double minY = latitudeToWebMercatorY(bounds.maxLat); // Note: maxLat -> minY (inverted)
+        double maxY = latitudeToWebMercatorY(bounds.minLat); // Note: minLat -> maxY (inverted)
+
+        // Calculate scale to map Web Mercator coordinates to pixels
+        double scaleX = trackWidth / (maxX - minX);
+        double scaleY = trackHeight / (maxY - minY);
 
         // Draw track segments with privacy fade
         g2d.setStroke(new BasicStroke(4.0f, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND));
@@ -172,12 +177,17 @@ public class ActivityImageService {
             Double lon2 = getDouble(point2, "longitude");
 
             if (lat1 != null && lon1 != null && lat2 != null && lon2 != null) {
-                // Convert geographic coordinates to pixel coordinates
-                // The OSM renderer already handles the projection, so we use linear mapping
-                double x1 = (lon1 - bounds.minLon) * scale;
-                double y1 = trackHeight - (lat1 - bounds.minLat) * scale;
-                double x2 = (lon2 - bounds.minLon) * scale;
-                double y2 = trackHeight - (lat2 - bounds.minLat) * scale;
+                // Convert lat/lon to Web Mercator coordinates (same projection as OSM tiles)
+                double mercatorX1 = longitudeToWebMercatorX(lon1);
+                double mercatorY1 = latitudeToWebMercatorY(lat1);
+                double mercatorX2 = longitudeToWebMercatorX(lon2);
+                double mercatorY2 = latitudeToWebMercatorY(lat2);
+
+                // Map Web Mercator coordinates to pixel coordinates
+                double x1 = (mercatorX1 - minX) * scaleX;
+                double y1 = (mercatorY1 - minY) * scaleY;
+                double x2 = (mercatorX2 - minX) * scaleX;
+                double y2 = (mercatorY2 - minY) * scaleY;
 
                 // Calculate opacity based on distance from start/end
                 double distanceFromStart = cumulativeDistances[i];
@@ -434,6 +444,24 @@ public class ActivityImageService {
         return new TrackBounds(minLat, maxLat, minLon, maxLon);
     }
 
+    /**
+     * Convert longitude to Web Mercator X coordinate (normalized 0-1).
+     * This must match the projection used by OsmTileRenderer.
+     */
+    private double longitudeToWebMercatorX(double lon) {
+        return (lon + 180.0) / 360.0;
+    }
+
+    /**
+     * Convert latitude to Web Mercator Y coordinate (normalized 0-1).
+     * This must match the projection used by OsmTileRenderer.
+     * Uses the same logarithmic transformation as OSM tiles.
+     */
+    private double latitudeToWebMercatorY(double lat) {
+        return (1.0 - Math.log(Math.tan(Math.toRadians(lat)) +
+                1.0 / Math.cos(Math.toRadians(lat))) / Math.PI) / 2.0;
+    }
+
     /**
      * Helper class to store track geographic bounds.
      */