In　this　paper,　we　present　an　improved　electrostatics-based　analytical　method　for　fixed-outline　floorplanning,　which　incorporates　module　rotation　and　sizing　driven　by　wirelength.　To　accurately　compute　the　density　function　after　module　rotation,　we　propose　a　novel　density　calculation　algorithm　based　on　line　drawing　and　polygon　clipping　algorithms　commonly　used　in　computer　graphics.　By　using　this　algorithm,　we　are　able　to　accurately　compute　the　density　function　after　module　rotation　without　adding　any　complexity.　Moreover,　we　propose　a　module　legalization　algorithm　by　adding　module　sizing　and　module　rotation　after　the　existing　constraint　graph　adjustment　step.　Furthermore,　we　adopt　a　linear　programming　to　minimize　wirelength　to　improve　the　quality　of　the　results.　Experimental　results　demonstrate　that　our　floorplanning　algorithm　achieves　at　least　5.9%　and　11%　reduction　in　half-perimeter　wirelength　on　the　HB+　and　ami49_x　benchmarks,　respectively,　compared　to　state-of-the-art　floorplanners.