加载大图片到内存

 [HD1]//获取手机的屏幕的窗体大小

       WindowManager windowManager = (WindowManager) getSystemService(WINDOW_SERVICE);

       Display display = windowManager.getDefaultDisplay();

       windowHeight = display.getHeight();

       windowWidth = display.getWidth();

 [HD2]//图片解析配置的类

       Options options = new Options();

       //不会真的进行图片解析,只是获取到图片的头信息:宽X高日期等

       options.inJustDecodeBounds =true;

       //设置图片解析类的目标文件

       BitmapFactory.decodeFile("/sdcard/x.jpg", options);

       //获取图片的高X宽

       int imageHeight = options.outHeight;

       int imageWidth = options.outWidth;

       System.out.println("图片的高:" + imageHeight + "图片的宽:" + imageWidth);

 [HD3]//使用图片的宽高和屏幕的宽高进行计算,算出比例

       int scaleX = imageWidth /windowWidth;

       int scaleY = imageHeight /windowHeight;

       //缺省的比例

       int scale = 1;

       if (scaleX > scaleY & scaleY >= 1) {

           scale = scaleX;

       }

       if (scaleY > scaleX & scaleX >= 1) {

           scale = scaleY;

       }

 [HD4]   // 设置图片解析器真的去解析图片

       options.inJustDecodeBounds =false;

       //设置解析的采样率,设置的值是缩放比例1/scale

       options.inSampleSize = scale;

       //再次获取图片位图,并设置采样率

       Bitmap bitmap = BitmapFactory.decodeFile("/sdcard/x.jpg", options);

       iv.setImageBitmap(bitmap);