图片按比例缩放

 private Bitmap getSmallerBitmap(Bitmap bitmap) {        if (bitmap != null) {            Matrix matrix = new Matrix();            matrix.postScale(bitMapRatio, bitMapRatio); //长和宽放大缩小的比例            Bitmap resizeBmp = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);            return resizeBmp;        }        return null;    }