// Google Mercator BBOX for northern Washington State (roughly)
CoordinateReferenceSystem webMerc = CRS.decode("EPSG:3785");
ReferencedEnvelope outBounds = new ReferencedEnvelope(-1.4045034049133E7, -1.2937920131607E7, 5916835.1504419, 6386464.2521607, webMerc);
PointStackerProcess psp = new PointStackerProcess();
SimpleFeatureCollection result = psp.execute(fc, 100, // cellSize
null, // normalize
null, // preserve location
outBounds, // outputBBOX
1810, // outputWidth
768, // outputHeight