如何将位置信息写入JPEG图片文件【android】

通过ExifInterface可以将拍照时的一些属性信息写入图片文件里，其中包括经纬度信息。本文介绍一种将经纬度坐标写入JPEG图片文件的方法！

核心代码

    /**
     * 浮点型经纬度值转成度分秒格式
     * 
     * @param coord
     * @return
     */
    public String decimalToDMS(double coord) {
        String output, degrees, minutes, seconds;

        // gets the modulus the coordinate divided by one (MOD1).
        // in other words gets all the numbers after the decimal point.
        // e.g. mod := -79.982195 % 1 == 0.982195
        //
        // next get the integer part of the coord. On other words the whole
        // number part.
        // e.g. intPart := -79

        double mod = coord % 1;
        int intPart = (int) coord;

        // set degrees to the value of intPart
        // e.g. degrees := "-79"

        degrees = String.valueOf(intPart);

        // next times the MOD1 of degrees by 60 so we can find the integer part
        // for minutes.
        // get the MOD1 of the new coord to find the numbers after the decimal
        // point.
        // e.g. coord := 0.982195 * 60 == 58.9317
        // mod := 58.9317 % 1 == 0.9317
        //
        // next get the value of the integer part of the coord.
        // e.g. intPart := 58

        coord = mod * 60;
        mod = coord % 1;
        intPart = (int) coord;
        if (intPart < 0) {
            // Convert number to positive if it's negative.
            intPart *= -1;
        }

        // set minutes to the value of intPart.
        // e.g. minutes = "58"
        minutes = String.valueOf(intPart);

        // do the same again for minutes
        // e.g. coord := 0.9317 * 60 == 55.902
        // e.g. intPart := 55
        coord = mod * 60;
        intPart = (int) coord;
        if (intPart < 0) {
            // Convert number to positive if it's negative.
            intPart *= -1;
        }

        // set seconds to the value of intPart.
        // e.g. seconds = "55"
        seconds = String.valueOf(intPart);

        // I used this format for android but you can change it
        // to return in whatever format you like
        // e.g. output = "-79/1,58/1,56/1"
        output = degrees + "/1," + minutes + "/1," + seconds + "/1";

        // Standard output of D°M′S″
        // output = degrees + "°" + minutes + "'" + seconds + """;

        return output;
    }

    /**
     * 将经纬度信息写入JPEG图片文件里
     * 
     * @param picPath
     *            JPEG图片文件路径
     * @param dLat
     *            纬度
     * @param dLon
     *            经度
     */
    public void writeLatLonIntoJpeg(String picPath, double dLat, double dLon) {
        File file = new File(picPath);
        if (file.exists()) {
            try {
                ExifInterface exif = new ExifInterface(picPath);
                String tagLat = exif
                        .getAttribute(ExifInterface.TAG_GPS_LATITUDE);
                String tagLon = exif
                        .getAttribute(ExifInterface.TAG_GPS_LONGITUDE);
                if (tagLat == null && tagLon == null) // 无经纬度信息
                {
                    exif.setAttribute(ExifInterface.TAG_GPS_LATITUDE,
                            decimalToDMS(dLat));
                    exif.setAttribute(ExifInterface.TAG_GPS_LATITUDE_REF,
                            dLat > 0 ? "N" : "S"); // 区分南北半球
                    exif.setAttribute(ExifInterface.TAG_GPS_LONGITUDE,
                            decimalToDMS(dLon));
                    exif.setAttribute(ExifInterface.TAG_GPS_LONGITUDE_REF,
                            dLon > 0 ? "E" : "W"); // 区分东经西经

                    exif.saveAttributes();
                }
            } catch (Exception e) {

            }
        }
    }

            String strImgPath = getImageCachePath() + File.separator + "1.jpg";

            ExifInterface eif = new ExifInterface(strImgPath);
            String lat = eif.getAttribute(ExifInterface.TAG_GPS_LATITUDE);
            String latRef = eif.getAttribute(ExifInterface.TAG_GPS_LATITUDE_REF);
            String lon = eif.getAttribute(ExifInterface.TAG_GPS_LONGITUDE);
            String lonRef = eif.getAttribute(ExifInterface.TAG_GPS_LONGITUDE_REF);

            System.out.println("Latitude Ref - " + latRef);
            System.out.println("Latitude - " + lat);
            System.out.println("Longitude Ref - " + lonRef);
            System.out.println("Longitude - " + lon);

            if (lat == null && lon == null) // 没有位置信息才写入
            {
                writeLatLonIntoJpeg(strImgPath, 39.23456, 116.123456);
            }

05-22 17:36:24.566: I/System.out(17966): Latitude Ref - null
05-22 17:36:24.566: I/System.out(17966): Latitude - null
05-22 17:36:24.566: I/System.out(17966): Longitude Ref - null
05-22 17:36:24.566: I/System.out(17966): Longitude - null

第二次运行结果

05-22 17:37:11.446: I/System.out(17966): Latitude Ref - N
05-22 17:37:11.446: I/System.out(17966): Latitude - 39/1,14/1,4/1
05-22 17:37:11.446: I/System.out(17966): Longitude Ref - E
05-22 17:37:11.446: I/System.out(17966): Longitude - 116/1,7/1,24/1

参考：

http://blog.csdn.net/henry121212/article/details/17553719

http://blog.csdn.net/caiwenfeng_for_23/article/details/37706617