从图像字节中检索创建日期

Question

我将图像作为Base64编码的字符串存储在数据库中。我想读取这个字符串，把它解码成一个字节数组，然后显示它。到目前一切尚好。

现在，我还想显示有关此图像的其他信息。我真的很在乎这张照片是什么时候拍的。

我尝试过几种方法。当文件系统中存在图像时，没有问题。但是，当我读取编码的字符串，将其解码为字节时，就会出现一个问题。

我使用了metadata-extractor库。

    <dependency>
        <groupId>com.drewnoakes</groupId>
        <artifactId>metadata-extractor</artifactId>
        <version>2.9.0</version>
    </dependency>



 public void processData(String data) {
    if (data == null || data.isEmpty()) {
        return;
    }
    byte[] base64Decoded = DatatypeConverter.parseBase64Binary(data);
    read(base64Decoded );
    //displayImage();
    //displayImageInfo();
}




public void read(byte [] data) {
    try {
        InputStream inputStream = new ByteArrayInputStream(data);
        BufferedImage image = ImageIO.read(inputStream);
        retrieveImageInfo();

        Metadata metadata = ImageMetadataReader.readMetadata(inputStream);
        retrieveAdditiaonlInfo2(metadata);
    } catch (Exception e) {
        //throw new RuntimeException("Failed to read the image from bytes.", e);
    }
}

private void retrieveImageInfo() {
    imageWidth = (long) image.getWidth();
    imageHeight = (long) image.getHeight();
    imageSize = (long) data.length;

}

private void retrieveAdditiaonlInfo2(Metadata metadata) {
    for (Directory directory : metadata.getDirectories()) {
        for (Tag tag : directory.getTags()) {
            System.out.format("[%s] - %s = %s", directory.getName(), tag.getTagName(), tag.getDescription());
            System.out.println();
        }
        if (directory.hasErrors()) {
            for (String error : directory.getErrors()) {
                System.err.format("ERROR: %s", error);
                System.err.println();
            }
        }
    }
}

对于从文件中读取的图像来说，这很好。但对我们的数据库来说，它不起作用。上面写着，

导致: java.io.IOException:流结束之前，文件的神奇数字可以确定。在com.drew.imaging.FileTypeDetector.detectFileType(FileTypeDetector.java:97)

​

​

Answer 1

经过研究和调试，我发现了这个。BufferedInputStream是必需的！

        File imageFile = new File(filename);
        Path path = imageFile.toPath();
        byte[] data = Files.readAllBytes(path);

        String str = DatatypeConverter.printBase64Binary(data);
        //Store encoded data.
        //Retrieve encoded string from the database.
        byte [] data2 = DatatypeConverter.parseBase64Binary(str);

        InputStream inputStream = new ByteArrayInputStream(data2);
        BufferedInputStream bis = new BufferedInputStream(inputStream);
        Metadata metadata = ImageMetadataReader.readMetadata(bis);

所以起作用了！

有一点，并不是所有的图像都包含元数据(我需要日期-时间)。以下是两个元数据示例。

[JPEG] - Compression Type = Baseline
[JPEG] - Data Precision = 8 bits
[JPEG] - Image Height = 758 pixels
[JPEG] - Image Width = 1024 pixels
[JPEG] - Number of Components = 3
[JPEG] - Component 1 = Y component: Quantization table 0, Sampling factors 2 horiz/2 vert
[JPEG] - Component 2 = Cb component: Quantization table 1, Sampling factors 1 horiz/1 vert
[JPEG] - Component 3 = Cr component: Quantization table 1, Sampling factors 1 horiz/1 vert
[JFIF] - Version = 1.1
[JFIF] - Resolution Units = none
[JFIF] - X Resolution = 1 dot
[JFIF] - Y Resolution = 1 dot
[JFIF] - Thumbnail Width Pixels = 0
[JFIF] - Thumbnail Height Pixels = 0

[JPEG] - Compression Type = Baseline
[JPEG] - Data Precision = 8 bits
[JPEG] - Image Height = 3104 pixels
[JPEG] - Image Width = 4192 pixels
[JPEG] - Number of Components = 3
[JPEG] - Component 1 = Y component: Quantization table 0, Sampling factors 2 horiz/1 vert
[JPEG] - Component 2 = Cb component: Quantization table 1, Sampling factors 1 horiz/1 vert
[JPEG] - Component 3 = Cr component: Quantization table 1, Sampling factors 1 horiz/1 vert
[Exif IFD0] - Software = Flyme
[Exif IFD0] - Orientation = Top, left side (Horizontal / normal)
[Exif IFD0] - Unknown tag (0x0224) = 1
[Exif IFD0] - Unknown tag (0x0225) = 
[Exif IFD0] - Date/Time = 2016:04:13 10:20:08
[Exif IFD0] - Model = m1 note                        
[Exif IFD0] - Unknown tag (0x0222) = 0
[Exif IFD0] - Unknown tag (0x0223) = 0
[Exif IFD0] - Unknown tag (0x0220) = 0
[Exif IFD0] - Unknown tag (0x0221) = 0
[Exif IFD0] - Y Resolution = 72 dots per inch
[Exif IFD0] - X Resolution = 72 dots per inch
[Exif IFD0] - YCbCr Positioning = Datum point
[Exif IFD0] - Resolution Unit = Inch
[Exif IFD0] - Image Description =                                
[Exif IFD0] - Make = Meizu                          
[GPS] - GPS Img Direction = 49 degrees
[GPS] - GPS Img Direction Ref = Magnetic direction
[Exif SubIFD] - Date/Time Digitized = 2016:04:13 10:20:08
[Exif SubIFD] - Color Space = sRGB
[Exif SubIFD] - Date/Time Original = 2016:04:13 10:20:08
[Exif SubIFD] - FlashPix Version = 1.00
[Exif SubIFD] - Metering Mode = Center weighted average
[Exif SubIFD] - Exposure Bias Value = 0 EV
[Exif SubIFD] - Exif Image Height = 3104 pixels
[Exif SubIFD] - Exif Version = 2.20
[Exif SubIFD] - Exif Image Width = 4192 pixels
[Exif SubIFD] - Focal Length = 3.8 mm
[Exif SubIFD] - Digital Zoom Ratio = 1
[Exif SubIFD] - White Balance = (Other)
[Exif SubIFD] - Scene Capture Type = Standard
[Exif SubIFD] - Flash = Flash did not fire
[Exif SubIFD] - White Balance Mode = Auto white balance
[Exif SubIFD] - Exposure Mode = Auto exposure
[Exif SubIFD] - Exposure Time = 79999/1000000 sec
[Exif SubIFD] - ISO Speed Ratings = 810
[Exif SubIFD] - Components Configuration = YCbCr
[Exif SubIFD] - F-Number = f/2.2
[Exif SubIFD] - Exposure Program = Unknown (0)
[Interoperability] - Interoperability Index = Recommended Exif Interoperability Rules (ExifR98)
[Interoperability] - Interoperability Version = 1.00
[Exif Thumbnail] - Orientation = Top, left side (Horizontal / normal)
[Exif Thumbnail] - Compression = JPEG (old-style)
[Exif Thumbnail] - Thumbnail Offset = 962 bytes
[Exif Thumbnail] - YCbCr Positioning = Datum point
[Exif Thumbnail] - Thumbnail Length = 0 bytes
[Exif Thumbnail] - Y Resolution = 72 dots per inch
[Exif Thumbnail] - Resolution Unit = Inch
[Exif Thumbnail] - X Resolution = 72 dots per inch