本文实例讲述了Android开发之使用ExifInterface获取拍照后的图片属性。分享给大家供大家参考，具体如下：
ExifInterface exif = new ExifInterface(file.getPath()); String widthStr = exif.getAttribute(ExifInterface.TAG_IMAGE_WIDTH); String heightStr = exif.getAttribute(ExifInterface.TAG_IMAGE_LENGTH); ......
/*
* Copyright (C) 2007 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 android.media;
import java.io.IOException;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.TimeZone;
/**
* This is a class for reading and writing Exif tags in a JPEG file.
*/
public class ExifInterface {
// The Exif tag names
/** Type is int. */
public static final String TAG_ORIENTATION = "Orientation";
/** Type is String. */
public static final String TAG_DATETIME = "DateTime";
/** Type is String. */
public static final String TAG_MAKE = "Make";
/** Type is String. */
public static final String TAG_MODEL = "Model";
/** Type is int. */
public static final String TAG_FLASH = "Flash";
/** Type is int. */
public static final String TAG_IMAGE_WIDTH = "ImageWidth";
/** Type is int. */
public static final String TAG_IMAGE_LENGTH = "ImageLength";
/** String. Format is "num1/denom1,num2/denom2,num3/denom3". */
public static final String TAG_GPS_LATITUDE = "GPSLatitude";
/** String. Format is "num1/denom1,num2/denom2,num3/denom3". */
public static final String TAG_GPS_LONGITUDE = "GPSLongitude";
/** Type is String. */
public static final String TAG_GPS_LATITUDE_REF = "GPSLatitudeRef";
/** Type is String. */
public static final String TAG_GPS_LONGITUDE_REF = "GPSLongitudeRef";
/** Type is String. */
public static final String TAG_GPS_TIMESTAMP = "GPSTimeStamp";
/** Type is String. */
public static final String TAG_GPS_DATESTAMP = "GPSDateStamp";
/** Type is int. */
public static final String TAG_WHITE_BALANCE = "WhiteBalance";
/** Type is rational. */
public static final String TAG_FOCAL_LENGTH = "FocalLength";
/** Type is String. Name of GPS processing method used for location finding. */
public static final String TAG_GPS_PROCESSING_METHOD = "GPSProcessingMethod";
// Constants used for the Orientation Exif tag.
public static final int ORIENTATION_UNDEFINED = 0;
public static final int ORIENTATION_NORMAL = 1;
public static final int ORIENTATION_FLIP_HORIZONTAL = 2; // left right reversed mirror
public static final int ORIENTATION_ROTATE_180 = 3;
public static final int ORIENTATION_FLIP_VERTICAL = 4; // upside down mirror
public static final int ORIENTATION_TRANSPOSE = 5; // flipped about top-left <--> bottom-right axis
public static final int ORIENTATION_ROTATE_90 = 6; // rotate 90 cw to right it
public static final int ORIENTATION_TRANSVERSE = 7; // flipped about top-right <--> bottom-left axis
public static final int ORIENTATION_ROTATE_270 = 8; // rotate 270 to right it
// Constants used for white balance
public static final int WHITEBALANCE_AUTO = 0;
public static final int WHITEBALANCE_MANUAL = 1;
private static SimpleDateFormat sFormatter;
static {
System.loadLibrary("exif");
sFormatter = new SimpleDateFormat("yyyy:MM:dd HH:mm:ss");
sFormatter.setTimeZone(TimeZone.getTimeZone("UTC"));
}
private String mFilename;
private HashMap<String, String> mAttributes;
private boolean mHasThumbnail;
// Because the underlying implementation (jhead) uses static variables,
// there can only be one user at a time for the native functions (and
// they cannot keep state in the native code across function calls). We
// use sLock to serialize the accesses.
private static Object sLock = new Object();
/**
* Reads Exif tags from the specified JPEG file.
*/
public ExifInterface(String filename) throws IOException {
mFilename = filename;
loadAttributes();
}
/**
* Returns the value of the specified tag or {@code null} if there
* is no such tag in the JPEG file.
*
* @param tag the name of the tag.
*/
public String getAttribute(String tag) {
return mAttributes.get(tag);
}
/**
* Returns the integer value of the specified tag. If there is no such tag
* in the JPEG file or the value cannot be parsed as integer, return
* <var>defaultValue</var>.
*
* @param tag the name of the tag.
* @param defaultValue the value to return if the tag is not available.
*/
public int getAttributeInt(String tag, int defaultValue) {
String value = mAttributes.get(tag);
if (value == null) return defaultValue;
try {
return Integer.valueOf(value);
} catch (NumberFormatException ex) {
return defaultValue;
}
}
/**
* Returns the double value of the specified rational tag. If there is no
* such tag in the JPEG file or the value cannot be parsed as double, return
* <var>defaultValue</var>.
*
* @param tag the name of the tag.
* @param defaultValue the value to return if the tag is not available.
*/
public double getAttributeDouble(String tag, double defaultValue) {
String value = mAttributes.get(tag);
if (value == null) return defaultValue;
try {
int index = value.indexOf("/");
if (index == -1) return defaultValue;
double denom = Double.parseDouble(value.substring(index + 1));
if (denom == 0) return defaultValue;
double num = Double.parseDouble(value.substring(0, index));
return num / denom;
} catch (NumberFormatException ex) {
return defaultValue;
}
}
/**
* Set the value of the specified tag.
*
* @param tag the name of the tag.
* @param value the value of the tag.
*/
public void setAttribute(String tag, String value) {
mAttributes.put(tag, value);
}
/**
* Initialize mAttributes with the attributes from the file mFilename.
*
* mAttributes is a HashMap which stores the Exif attributes of the file.
* The key is the standard tag name and the value is the tag's value: e.g.
* Model -> Nikon. Numeric values are stored as strings.
*
* This function also initialize mHasThumbnail to indicate whether the
* file has a thumbnail inside.
*/
private void loadAttributes() throws IOException {
// format of string passed from native C code:
// "attrCnt attr1=valueLen value1attr2=value2Len value2..."
// example:
// "4 attrPtr ImageLength=4 1024Model=6 FooImageWidth=4 1280Make=3 FOO"
mAttributes = new HashMap<String, String>();
String attrStr;
synchronized (sLock) {
attrStr = getAttributesNative(mFilename);
}
// get count
int ptr = attrStr.indexOf(' ');
int count = Integer.parseInt(attrStr.substring(0, ptr));
// skip past the space between item count and the rest of the attributes
++ptr;
for (int i = 0; i < count; i++) {
// extract the attribute name
int equalPos = attrStr.indexOf('=', ptr);
String attrName = attrStr.substring(ptr, equalPos);
ptr = equalPos + 1; // skip past =
// extract the attribute value length
int lenPos = attrStr.indexOf(' ', ptr);
int attrLen = Integer.parseInt(attrStr.substring(ptr, lenPos));
ptr = lenPos + 1; // skip pas the space
// extract the attribute value
String attrValue = attrStr.substring(ptr, ptr + attrLen);
ptr += attrLen;
if (attrName.equals("hasThumbnail")) {
mHasThumbnail = attrValue.equalsIgnoreCase("true");
} else {
mAttributes.put(attrName, attrValue);
}
}
}
/**
* Save the tag data into the JPEG file. This is expensive because it involves
* copying all the JPG data from one file to another and deleting the old file
* and renaming the other. It's best to use {@link #setAttribute(String,String)}
* to set all attributes to write and make a single call rather than multiple
* calls for each attribute.
*/
public void saveAttributes() throws IOException {
// format of string passed to native C code:
// "attrCnt attr1=valueLen value1attr2=value2Len value2..."
// example:
// "4 attrPtr ImageLength=4 1024Model=6 FooImageWidth=4 1280Make=3 FOO"
StringBuilder sb = new StringBuilder();
int size = mAttributes.size();
if (mAttributes.containsKey("hasThumbnail")) {
--size;
}
sb.append(size + " ");
for (Map.Entry<String, String> iter : mAttributes.entrySet()) {
String key = iter.getKey();
if (key.equals("hasThumbnail")) {
// this is a fake attribute not saved as an exif tag
continue;
}
String val = iter.getValue();
sb.append(key + "=");
sb.append(val.length() + " ");
sb.append(val);
}
String s = sb.toString();
synchronized (sLock) {
saveAttributesNative(mFilename, s);
commitChangesNative(mFilename);
}
}
/**
* Returns true if the JPEG file has a thumbnail.
*/
public boolean hasThumbnail() {
return mHasThumbnail;
}
/**
* Returns the thumbnail inside the JPEG file, or {@code null} if there is no thumbnail.
* The returned data is in JPEG format and can be decoded using
* {@link android.graphics.BitmapFactory#decodeByteArray(byte[],int,int)}
*/
public byte[] getThumbnail() {
synchronized (sLock) {
return getThumbnailNative(mFilename);
}
}
/**
* Stores the latitude and longitude value in a float array. The first element is
* the latitude, and the second element is the longitude. Returns false if the
* Exif tags are not available.
*/
public boolean getLatLong(float output[]) {
String latValue = mAttributes.get(ExifInterface.TAG_GPS_LATITUDE);
String latRef = mAttributes.get(ExifInterface.TAG_GPS_LATITUDE_REF);
String lngValue = mAttributes.get(ExifInterface.TAG_GPS_LONGITUDE);
String lngRef = mAttributes.get(ExifInterface.TAG_GPS_LONGITUDE_REF);
if (latValue != null && latRef != null && lngValue != null && lngRef != null) {
output[0] = convertRationalLatLonToFloat(latValue, latRef);
output[1] = convertRationalLatLonToFloat(lngValue, lngRef);
return true;
} else {
return false;
}
}
/**
* Returns number of milliseconds since Jan. 1, 1970, midnight.
* Returns -1 if the date time information if not available.
* @hide
*/
public long getDateTime() {
String dateTimeString = mAttributes.get(TAG_DATETIME);
if (dateTimeString == null) return -1;
ParsePosition pos = new ParsePosition(0);
try {
Date datetime = sFormatter.parse(dateTimeString, pos);
if (datetime == null) return -1;
return datetime.getTime();
} catch (IllegalArgumentException ex) {
return -1;
}
}
/**
* Returns number of milliseconds since Jan. 1, 1970, midnight UTC.
* Returns -1 if the date time information if not available.
* @hide
*/
public long getGpsDateTime() {
String date = mAttributes.get(TAG_GPS_DATESTAMP);
String time = mAttributes.get(TAG_GPS_TIMESTAMP);
if (date == null || time == null) return -1;
String dateTimeString = date + ' ' + time;
if (dateTimeString == null) return -1;
ParsePosition pos = new ParsePosition(0);
try {
Date datetime = sFormatter.parse(dateTimeString, pos);
if (datetime == null) return -1;
return datetime.getTime();
} catch (IllegalArgumentException ex) {
return -1;
}
}
private static float convertRationalLatLonToFloat(
String rationalString, String ref) {
try {
String [] parts = rationalString.split(",");
String [] pair;
pair = parts[0].split("/");
int degrees = (int) (Float.parseFloat(pair[0].trim())
/ Float.parseFloat(pair[1].trim()));
pair = parts[1].split("/");
int minutes = (int) ((Float.parseFloat(pair[0].trim())
/ Float.parseFloat(pair[1].trim())));
pair = parts[2].split("/");
float seconds = Float.parseFloat(pair[0].trim())
/ Float.parseFloat(pair[1].trim());
float result = degrees + (minutes / 60F) + (seconds / (60F * 60F));
if ((ref.equals("S") || ref.equals("W"))) {
return -result;
}
return result;
} catch (RuntimeException ex) {
// if for whatever reason we can't parse the lat long then return
// null
return 0f;
}
}
private native boolean appendThumbnailNative(String fileName,
String thumbnailFileName);
private native void saveAttributesNative(String fileName,
String compressedAttributes);
private native String getAttributesNative(String fileName);
private native void commitChangesNative(String fileName);
private native byte[] getThumbnailNative(String fileName);
}
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