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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     public static int getOrientation(byte[] jpeg) {
     25         if (jpeg == null) {
     26             return 0;
     27         }
     28 
     29         int offset = 0;
     30         int length = 0;
     31 
     32         // ISO/IEC 10918-1:1993(E)
     33         while (offset + 3 < jpeg.length && (jpeg[offset++] & 0xFF) == 0xFF) {
     34             int marker = jpeg[offset] & 0xFF;
     35 
     36             // Check if the marker is a padding.
     37             if (marker == 0xFF) {
     38                 continue;
     39             }
     40             offset++;
     41 
     42             // Check if the marker is SOI or TEM.
     43             if (marker == 0xD8 || marker == 0x01) {
     44                 continue;
     45             }
     46             // Check if the marker is EOI or SOS.
     47             if (marker == 0xD9 || marker == 0xDA) {
     48                 break;
     49             }
     50 
     51             // Get the length and check if it is reasonable.
     52             length = pack(jpeg, offset, 2, false);
     53             if (length < 2 || offset + length > jpeg.length) {
     54                 Log.e(TAG, "Invalid length");
     55                 return 0;
     56             }
     57 
     58             // Break if the marker is EXIF in APP1.
     59             if (marker == 0xE1 && length >= 8 &&
     60                     pack(jpeg, offset + 2, 4, false) == 0x45786966 &&
     61                     pack(jpeg, offset + 6, 2, false) == 0) {
     62                 offset += 8;
     63                 length -= 8;
     64                 break;
     65             }
     66 
     67             // Skip other markers.
     68             offset += length;
     69             length = 0;
     70         }
     71 
     72         // JEITA CP-3451 Exif Version 2.2
     73         if (length > 8) {
     74             // Identify the byte order.
     75             int tag = pack(jpeg, offset, 4, false);
     76             if (tag != 0x49492A00 && tag != 0x4D4D002A) {
     77                 Log.e(TAG, "Invalid byte order");
     78                 return 0;
     79             }
     80             boolean littleEndian = (tag == 0x49492A00);
     81 
     82             // Get the offset and check if it is reasonable.
     83             int count = pack(jpeg, offset + 4, 4, littleEndian) + 2;
     84             if (count < 10 || count > length) {
     85                 Log.e(TAG, "Invalid offset");
     86                 return 0;
     87             }
     88             offset += count;
     89             length -= count;
     90 
     91             // Get the count and go through all the elements.
     92             count = pack(jpeg, offset - 2, 2, littleEndian);
     93             while (count-- > 0 && length >= 12) {
     94                 // Get the tag and check if it is orientation.
     95                 tag = pack(jpeg, offset, 2, littleEndian);
     96                 if (tag == 0x0112) {
     97                     // We do not really care about type and count, do we?
     98                     int orientation = pack(jpeg, offset + 8, 2, littleEndian);
     99                     switch (orientation) {
    100                         case 1:
    101                             return 0;
    102                         case 3:
    103                             return 180;
    104                         case 6:
    105                             return 90;
    106                         case 8:
    107                             return 270;
    108                     }
    109                     Log.i(TAG, "Unsupported orientation");
    110                     return 0;
    111                 }
    112                 offset += 12;
    113                 length -= 12;
    114             }
    115         }
    116 
    117         Log.i(TAG, "Orientation not found");
    118         return 0;
    119     }
    120 
    121     private static int pack(byte[] bytes, int offset, int length,
    122             boolean littleEndian) {
    123         int step = 1;
    124         if (littleEndian) {
    125             offset += length - 1;
    126             step = -1;
    127         }
    128 
    129         int value = 0;
    130         while (length-- > 0) {
    131             value = (value << 8) | (bytes[offset] & 0xFF);
    132             offset += step;
    133         }
    134         return value;
    135     }
    136 }
    137