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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.camera;
     18 
     19 import android.util.Log;
     20 
     21 public class Exif {
     22     private static final String TAG = "CameraExif";
     23 
     24     // Returns the degrees in clockwise. Values are 0, 90, 180, or 270.
     25     public static int getOrientation(byte[] jpeg) {
     26         if (jpeg == null) {
     27             return 0;
     28         }
     29 
     30         int offset = 0;
     31         int length = 0;
     32 
     33         // ISO/IEC 10918-1:1993(E)
     34         while (offset + 3 < jpeg.length && (jpeg[offset++] & 0xFF) == 0xFF) {
     35             int marker = jpeg[offset] & 0xFF;
     36 
     37             // Check if the marker is a padding.
     38             if (marker == 0xFF) {
     39                 continue;
     40             }
     41             offset++;
     42 
     43             // Check if the marker is SOI or TEM.
     44             if (marker == 0xD8 || marker == 0x01) {
     45                 continue;
     46             }
     47             // Check if the marker is EOI or SOS.
     48             if (marker == 0xD9 || marker == 0xDA) {
     49                 break;
     50             }
     51 
     52             // Get the length and check if it is reasonable.
     53             length = pack(jpeg, offset, 2, false);
     54             if (length < 2 || offset + length > jpeg.length) {
     55                 Log.e(TAG, "Invalid length");
     56                 return 0;
     57             }
     58 
     59             // Break if the marker is EXIF in APP1.
     60             if (marker == 0xE1 && length >= 8 &&
     61                     pack(jpeg, offset + 2, 4, false) == 0x45786966 &&
     62                     pack(jpeg, offset + 6, 2, false) == 0) {
     63                 offset += 8;
     64                 length -= 8;
     65                 break;
     66             }
     67 
     68             // Skip other markers.
     69             offset += length;
     70             length = 0;
     71         }
     72 
     73         // JEITA CP-3451 Exif Version 2.2
     74         if (length > 8) {
     75             // Identify the byte order.
     76             int tag = pack(jpeg, offset, 4, false);
     77             if (tag != 0x49492A00 && tag != 0x4D4D002A) {
     78                 Log.e(TAG, "Invalid byte order");
     79                 return 0;
     80             }
     81             boolean littleEndian = (tag == 0x49492A00);
     82 
     83             // Get the offset and check if it is reasonable.
     84             int count = pack(jpeg, offset + 4, 4, littleEndian) + 2;
     85             if (count < 10 || count > length) {
     86                 Log.e(TAG, "Invalid offset");
     87                 return 0;
     88             }
     89             offset += count;
     90             length -= count;
     91 
     92             // Get the count and go through all the elements.
     93             count = pack(jpeg, offset - 2, 2, littleEndian);
     94             while (count-- > 0 && length >= 12) {
     95                 // Get the tag and check if it is orientation.
     96                 tag = pack(jpeg, offset, 2, littleEndian);
     97                 if (tag == 0x0112) {
     98                     // We do not really care about type and count, do we?
     99                     int orientation = pack(jpeg, offset + 8, 2, littleEndian);
    100                     switch (orientation) {
    101                         case 1:
    102                             return 0;
    103                         case 3:
    104                             return 180;
    105                         case 6:
    106                             return 90;
    107                         case 8:
    108                             return 270;
    109                     }
    110                     Log.i(TAG, "Unsupported orientation");
    111                     return 0;
    112                 }
    113                 offset += 12;
    114                 length -= 12;
    115             }
    116         }
    117 
    118         Log.i(TAG, "Orientation not found");
    119         return 0;
    120     }
    121 
    122     private static int pack(byte[] bytes, int offset, int length,
    123             boolean littleEndian) {
    124         int step = 1;
    125         if (littleEndian) {
    126             offset += length - 1;
    127             step = -1;
    128         }
    129 
    130         int value = 0;
    131         while (length-- > 0) {
    132             value = (value << 8) | (bytes[offset] & 0xFF);
    133             offset += step;
    134         }
    135         return value;
    136     }
    137 }
    138