Android开发之使用ExifInterface获取拍照后的图片属性

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);
}

更多关于android开发相关内容感兴趣的读者可查看本站专题：《android开发入门与进阶教程》及《android图形与图像处理技巧总结》

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