1/*
2 * Copyright (C) 2013 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
17package com.android.bitmap.util;
18
19import android.util.Log;
20
21import java.io.ByteArrayInputStream;
22import java.io.InputStream;
23
24/**
25 * TODO
26 * Exif and InputStreamBuffer were pulled in from frameworks/ex/photo, and should be part of a
27 * separate library that is used by both this and chips.
28 */
29public class Exif {
30    private static final String TAG = Exif.class.getSimpleName();
31
32    /**
33     * Returns the degrees in clockwise. Values are 0, 90, 180, or 270.
34     * @param inputStream The input stream will not be closed for you.
35     * @param byteSize Recommended parameter declaring the length of the input stream. If you
36     *                 pass in -1, we will have to read more from the input stream.
37     * @return 0, 90, 180, or 270.
38     */
39    public static int getOrientation(final InputStream inputStream, final long byteSize) {
40        if (inputStream == null) {
41            return 0;
42        }
43
44        /*
45          Looking at this algorithm, we never look ahead more than 8 bytes. As long as we call
46          advanceTo() at the end of every loop, we should never have to reallocate a larger buffer.
47
48          Also, the most we ever read backwards is 4 bytes. pack() reads backwards if the encoding
49          is in little endian format. These following two lines potentially reads 4 bytes backwards:
50
51          int tag = pack(jpeg, offset, 4, false);
52          count = pack(jpeg, offset - 2, 2, littleEndian);
53
54          To be safe, we will always advance to some index-4, so we'll need 4 more for the +8
55          look ahead, which makes it a +12 look ahead total. Use 16 just in case my analysis is off.
56
57          This means we only need to allocate a single 16 byte buffer.
58
59          Note: If you do not pass in byteSize parameter, a single large allocation will occur.
60          For a 1MB image, I see one 30KB allocation. This is due to the line containing:
61
62          has(jpeg, byteSize, offset + length - 1)
63
64          where length is a variable int (around 30KB above) read from the EXIF headers.
65
66          This is still much better than allocating a 1MB byte[] which we were doing before.
67         */
68
69        final int lookAhead = 16;
70        final int readBackwards = 4;
71        final InputStreamBuffer jpeg = new InputStreamBuffer(inputStream, lookAhead, false);
72
73        int offset = 0;
74        int length = 0;
75
76        if (has(jpeg, byteSize, 1)) {
77            // JPEG image files begin with FF D8. Only JPEG images have EXIF data.
78            final boolean possibleJpegFormat = jpeg.get(0) == (byte) 0xFF
79                    && jpeg.get(1) == (byte) 0xD8;
80            if (!possibleJpegFormat) {
81                return 0;
82            }
83        }
84
85        // ISO/IEC 10918-1:1993(E)
86        while (has(jpeg, byteSize, offset + 3) && (jpeg.get(offset++) & 0xFF) == 0xFF) {
87            final int marker = jpeg.get(offset) & 0xFF;
88
89            // Check if the marker is a padding.
90            if (marker == 0xFF) {
91                continue;
92            }
93            offset++;
94
95            // Check if the marker is SOI or TEM.
96            if (marker == 0xD8 || marker == 0x01) {
97                continue;
98            }
99            // Check if the marker is EOI or SOS.
100            if (marker == 0xD9 || marker == 0xDA) {
101                // Loop ends.
102                jpeg.advanceTo(offset - readBackwards);
103                break;
104            }
105
106            // Get the length and check if it is reasonable.
107            length = pack(jpeg, offset, 2, false);
108            if (length < 2 || !has(jpeg, byteSize, offset + length - 1)) {
109                Log.e(TAG, "Invalid length");
110                return 0;
111            }
112
113            // Break if the marker is EXIF in APP1.
114            if (marker == 0xE1 && length >= 8 &&
115                    pack(jpeg, offset + 2, 4, false) == 0x45786966 &&
116                    pack(jpeg, offset + 6, 2, false) == 0) {
117                offset += 8;
118                length -= 8;
119                // Loop ends.
120                jpeg.advanceTo(offset - readBackwards);
121                break;
122            }
123
124            // Skip other markers.
125            offset += length;
126            length = 0;
127
128            // Loop ends.
129            jpeg.advanceTo(offset - readBackwards);
130        }
131
132        // JEITA CP-3451 Exif Version 2.2
133        if (length > 8) {
134            // Identify the byte order.
135            int tag = pack(jpeg, offset, 4, false);
136            if (tag != 0x49492A00 && tag != 0x4D4D002A) {
137                Log.e(TAG, "Invalid byte order");
138                return 0;
139            }
140            final boolean littleEndian = (tag == 0x49492A00);
141
142            // Get the offset and check if it is reasonable.
143            int count = pack(jpeg, offset + 4, 4, littleEndian) + 2;
144            if (count < 10 || count > length) {
145                Log.e(TAG, "Invalid offset");
146                return 0;
147            }
148            offset += count;
149            length -= count;
150
151            // Offset has changed significantly.
152            jpeg.advanceTo(offset - readBackwards);
153
154            // Get the count and go through all the elements.
155            count = pack(jpeg, offset - 2, 2, littleEndian);
156
157            while (count-- > 0 && length >= 12) {
158                // Get the tag and check if it is orientation.
159                tag = pack(jpeg, offset, 2, littleEndian);
160                if (tag == 0x0112) {
161                    // We do not really care about type and count, do we?
162                    final int orientation = pack(jpeg, offset + 8, 2, littleEndian);
163                    switch (orientation) {
164                        case 1:
165                            return 0;
166                        case 3:
167                            return 180;
168                        case 6:
169                            return 90;
170                        case 8:
171                            return 270;
172                    }
173                    Log.i(TAG, "Unsupported orientation");
174                    return 0;
175                }
176                offset += 12;
177                length -= 12;
178
179                // Loop ends.
180                jpeg.advanceTo(offset - readBackwards);
181            }
182        }
183
184        return 0;
185    }
186
187    private static int pack(final InputStreamBuffer bytes, int offset, int length,
188            final boolean littleEndian) {
189        int step = 1;
190        if (littleEndian) {
191            offset += length - 1;
192            step = -1;
193        }
194
195        int value = 0;
196        while (length-- > 0) {
197            value = (value << 8) | (bytes.get(offset) & 0xFF);
198            offset += step;
199        }
200        return value;
201    }
202
203    private static boolean has(final InputStreamBuffer jpeg, final long byteSize, final int index) {
204        if (byteSize >= 0) {
205            return index < byteSize;
206        } else {
207            // For large values of index, this will cause the internal buffer to resize.
208            return jpeg.has(index);
209        }
210    }
211
212    @Deprecated
213    public static int getOrientation(final byte[] jpeg) {
214        return getOrientation(new ByteArrayInputStream(jpeg), jpeg.length);
215    }
216}