android 加载大图片时计算图片的缩放比例

	BitmapFactory.decodeStream(in, null, opts);
				int imageHeight = opts.outHeight;
				int imageWidth = opts.outWidth;
				System.out.println("图片宽:"+imageHeight);
				System.out.println("图片高:"+imageWidth);
				 
				//得到手机屏幕的宽高
				WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
				windowWidth = wm.getDefaultDisplay().getHeight();
				windowHeight = wm.getDefaultDisplay().getWidth();
				
				//计算缩放比例
				int scaleX  = imageWidth/windowWidth;
				int scaleY = imageHeight/windowHeight;
				int scale = 1;
				if(scaleX>scaleY && scaleX>1){
					scale = scaleX;
				}
				if(scaleY>scaleX && scaleY>1){
					scale = scaleY;
				}