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/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.gallery3d.data;
import android.util.Log;
import java.io.IOException;
import java.io.InputStream;
public class Exif {
private static final String TAG = "CameraExif";
public static int getOrientation(InputStream is) {
if (is == null) {
return 0;
}
byte[] buf = new byte[8];
int length = 0;
// ISO/IEC 10918-1:1993(E)
while (read(is, buf, 2) && (buf[0] & 0xFF) == 0xFF) {
int marker = buf[1] & 0xFF;
// Check if the marker is a padding.
if (marker == 0xFF) {
continue;
}
// Check if the marker is SOI or TEM.
if (marker == 0xD8 || marker == 0x01) {
continue;
}
// Check if the marker is EOI or SOS.
if (marker == 0xD9 || marker == 0xDA) {
return 0;
}
// Get the length and check if it is reasonable.
if (!read(is, buf, 2)) {
return 0;
}
length = pack(buf, 0, 2, false);
if (length < 2) {
Log.e(TAG, "Invalid length");
return 0;
}
length -= 2;
// Break if the marker is EXIF in APP1.
if (marker == 0xE1 && length >= 6) {
if (!read(is, buf, 6)) return 0;
length -= 6;
if (pack(buf, 0, 4, false) == 0x45786966 &&
pack(buf, 4, 2, false) == 0) {
break;
}
}
// Skip other markers.
try {
is.skip(length);
} catch (IOException ex) {
return 0;
}
length = 0;
}
// JEITA CP-3451 Exif Version 2.2
if (length > 8) {
int offset = 0;
byte[] jpeg = new byte[length];
if (!read(is, jpeg, length)) {
return 0;
}
// Identify the byte order.
int tag = pack(jpeg, offset, 4, false);
if (tag != 0x49492A00 && tag != 0x4D4D002A) {
Log.e(TAG, "Invalid byte order");
return 0;
}
boolean littleEndian = (tag == 0x49492A00);
// Get the offset and check if it is reasonable.
int count = pack(jpeg, offset + 4, 4, littleEndian) + 2;
if (count < 10 || count > length) {
Log.e(TAG, "Invalid offset");
return 0;
}
offset += count;
length -= count;
// Get the count and go through all the elements.
count = pack(jpeg, offset - 2, 2, littleEndian);
while (count-- > 0 && length >= 12) {
// Get the tag and check if it is orientation.
tag = pack(jpeg, offset, 2, littleEndian);
if (tag == 0x0112) {
// We do not really care about type and count, do we?
int orientation = pack(jpeg, offset + 8, 2, littleEndian);
switch (orientation) {
case 1:
return 0;
case 3:
return 180;
case 6:
return 90;
case 8:
return 270;
}
Log.i(TAG, "Unsupported orientation");
return 0;
}
offset += 12;
length -= 12;
}
}
Log.i(TAG, "Orientation not found");
return 0;
}
private static int pack(byte[] bytes, int offset, int length,
boolean littleEndian) {
int step = 1;
if (littleEndian) {
offset += length - 1;
step = -1;
}
int value = 0;
while (length-- > 0) {
value = (value << 8) | (bytes[offset] & 0xFF);
offset += step;
}
return value;
}
private static boolean read(InputStream is, byte[] buf, int length) {
try {
return is.read(buf, 0, length) == length;
} catch (IOException ex) {
return false;
}
}
}
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