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 
getOrientation(byte[] jpeg)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 
pack(byte[] bytes, int offset, int length, boolean littleEndian)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