Android：上传图片而不会丢失Exif数据

Question

在我们的应用程序中，用户多年来一直使用（大约）以下代码上传数百万个图像：

BitmapFactory.Options bmOptions = new BitmapFactory.Options();
bmOptions.inJustDecodeBounds = true;
BitmapFactory.decodeFile(postFilePath, bmOptions);
Bitmap roughBitmap = BitmapFactory.decodeFile(postFilePath, bmOptions);

ByteArrayOutputStream stream = new ByteArrayOutputStream();

roughBitmap.compress(Bitmap.CompressFormat.JPEG, 70, stream);
InputStream fis = new ByteArrayInputStream(stream.toByteArray());

int fileSize = stream.toByteArray().length;
conn.setRequestProperty("Content-Length", Integer.toString(fileSize));
conn.setFixedLengthStreamingMode(fileSize);

...

if (fis != null) {
    byte[] buf = new byte[10240];

    int read;

    while ((read = fis.read(buf)) > 0) {
        os.write(buf, 0, read);
        totalBytesRead += read;
        if (uploadProgressListener != null) {
            try {
                uploadProgressListener.onBytesUploaded(read);
            } catch (Exception e) {
                Log.e(e);
            }
        }
    }

    fis.close();
}

最近，我们看到有必要保留Exif上传图像的数据。问题是压缩位图时图像Exif数据丢失。我想到了ExifInterface用于从原始文件中提取此数据的方法：

ExifInterface oldExif = new ExifInterface(postFilePath);
String value = oldExif.getAttribute(ExifInterface.TAG_DATETIME);

..，然后将其添加到InputStream fis，然后继续上传文件。问题是ExifInterface 无法将Exif数据保存到InputStream。

将Exif数据上传到服务器后如何保留在图像中？

它不是重复的： 只是为了更深入地阐明，我尝试duplicate question通过以下方法使用建议的方法：

public static void copyExif(String originalPath, InputStream newStream) throws IOException {

    String[] attributes = new String[]
            {
                    ExifInterface.TAG_DATETIME,
                    ExifInterface.TAG_DATETIME_DIGITIZED,
                    ExifInterface.TAG_EXPOSURE_TIME,
                    ExifInterface.TAG_FLASH,
                    ExifInterface.TAG_FOCAL_LENGTH,
                    ExifInterface.TAG_GPS_ALTITUDE,
                    ExifInterface.TAG_GPS_ALTITUDE_REF,
                    ExifInterface.TAG_GPS_DATESTAMP,
                    ExifInterface.TAG_GPS_LATITUDE,
                    ExifInterface.TAG_GPS_LATITUDE_REF,
                    ExifInterface.TAG_GPS_LONGITUDE,
                    ExifInterface.TAG_GPS_LONGITUDE_REF,
                    ExifInterface.TAG_GPS_PROCESSING_METHOD,
                    ExifInterface.TAG_GPS_TIMESTAMP,
                    ExifInterface.TAG_MAKE,
                    ExifInterface.TAG_MODEL,
                    ExifInterface.TAG_ORIENTATION,
                    ExifInterface.TAG_SUBSEC_TIME,
                    ExifInterface.TAG_WHITE_BALANCE
            };

    ExifInterface oldExif = new ExifInterface(originalPath);
    ExifInterface newExif = new ExifInterface(newStream);

    if (attributes.length > 0) {
        for (int i = 0; i < attributes.length; i++) {
            String value = oldExif.getAttribute(attributes[i]);
            if (value != null)
                newExif.setAttribute(attributes[i], value);
        }
        newExif.saveAttributes();
    }
}

..但在java.io.IOException: ExifInterface does not support saving attributes for the current input.之后出现异常，newExif.saveAttributes();因为我试图将属性保存到InputStream。我还能怎么做？

Answer 1

我的解决方案：

正如@amuttsch和@CommonsWare建议的那样，我：

1. 将缩放/压缩的位图保存到临时文件
2. 将exif从原始文件复制到临时文件
3. 将临时文件转换为字节数组并发送给上载

..然后我发现服务器在生成图像变体:-P时再次剥离了Exif，但这是服务器人员正在努力纠正的另一个故事。

主要代码：

...
// Copy original Exif to scaledBitmap
String tempFilePath = getTempFilePath(postFilePath);
try {
    FileOutputStream out = new FileOutputStream(tempFilePath);
    scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 70, out);
    copyExif(postFilePath, tempFilePath);
} catch (Exception e) {
    e.printStackTrace();
}

// Get stream from temp (exif loaded) file
File tempFile = new File(tempFilePath);
byte[] byteFile = readFile(tempFile);
fis = new ByteArrayInputStream(byteFile);

// Remove the temp file
boolean deleted = tempFile.delete();

// Finalize
int fileSize = byteFile.length;
conn.setRequestProperty("Content-Length", Integer.toString(fileSize));
conn.setFixedLengthStreamingMode(fileSize);
...

getTempFilePath（）：

private String getTempFilePath(String filename) {
    String temp = "_temp";
    int dot = filename.lastIndexOf(".");
    String ext = filename.substring(dot + 1);

    if (dot == -1 || !ext.matches("\\w+")) {
        filename += temp;
    } else {
        filename = filename.substring(0, dot) + temp + "." + ext;
    }

    return filename;
}

copyExif（）：

public static void copyExif(String originalPath, String newPath) throws IOException {

    String[] attributes = new String[]
            {
                    ExifInterface.TAG_DATETIME,
                    ExifInterface.TAG_DATETIME_DIGITIZED,
                    ExifInterface.TAG_EXPOSURE_TIME,
                    ExifInterface.TAG_FLASH,
                    ExifInterface.TAG_FOCAL_LENGTH,
                    ExifInterface.TAG_GPS_ALTITUDE,
                    ExifInterface.TAG_GPS_ALTITUDE_REF,
                    ExifInterface.TAG_GPS_DATESTAMP,
                    ExifInterface.TAG_GPS_LATITUDE,
                    ExifInterface.TAG_GPS_LATITUDE_REF,
                    ExifInterface.TAG_GPS_LONGITUDE,
                    ExifInterface.TAG_GPS_LONGITUDE_REF,
                    ExifInterface.TAG_GPS_PROCESSING_METHOD,
                    ExifInterface.TAG_GPS_TIMESTAMP,
                    ExifInterface.TAG_MAKE,
                    ExifInterface.TAG_MODEL,
                    ExifInterface.TAG_ORIENTATION,
                    ExifInterface.TAG_SUBSEC_TIME,
                    ExifInterface.TAG_WHITE_BALANCE
            };

    ExifInterface oldExif = new ExifInterface(originalPath);
    ExifInterface newExif = new ExifInterface(newPath);

    if (attributes.length > 0) {
        for (int i = 0; i < attributes.length; i++) {
            String value = oldExif.getAttribute(attributes[i]);
            if (value != null)
                newExif.setAttribute(attributes[i], value);
        }
        newExif.saveAttributes();
    }
}

readFile（）：

public static byte[] readFile(File file) throws IOException {
    // Open file
    RandomAccessFile f = new RandomAccessFile(file, "r");
    try {
        // Get and check length
        long longlength = f.length();
        int length = (int) longlength;
        if (length != longlength)
            throw new IOException("File size >= 2 GB");
        // Read file and return data
        byte[] data = new byte[length];
        f.readFully(data);
        return data;
    } finally {
        f.close();
    }
}