android 按比例获取SD卡缩略图

                 BitmapFactory.Options options = new BitmapFactory.Options();  
                   options.inJustDecodeBounds = true;  
                     
                   //获取这个图片的宽和高  
                   Bitmap bitmap = BitmapFactory.decodeFile(Environment.getExternalStorageDirectory().getAbsolutePath()+ "/darunfa/temp.jpg",options);//此时返回bm为空  
                   options.inJustDecodeBounds =false;  
                   //计算缩放比  
                   int be = (int)(options.outWidth / (float)600);  
                   if(be <= 0)  
                        be = 1;  
                   options.inSampleSize = be;  
                   //重新读入图片，注意这次要把options.inJustDecodeBounds设为false哦  
                   bitmap = BitmapFactory.decodeFile(Environment.getExternalStorageDirectory().getAbsolutePath()+ "/darunfa/temp.jpg",options);  
                   int w = bitmap.getWidth();  
                   int h = bitmap.getHeight();  
                   System.out.println(w+" "+h);  
                   imageView.setImageBitmap(bitmap);
                   
                   File file2= new File(Environment.getExternalStorageDirectory().getAbsolutePath()+ "/darunfa/aaaa.jpg");  
                   try {  
                    FileOutputStream out = new FileOutputStream(file2);  
                    if(bitmap.compress(Bitmap.CompressFormat.JPEG, 90, out)){  
                        out.flush();  
                        out.close();  
                    }  
                } catch (Exception e) {  
                    // TODO: handle exception  
                }