在不删除其 EXIF 数据的情况下操作图像

使用imageIO,我通常会遇到转换图像文件的问题,并且在覆盖它之后,它会丢失所有EXIF数据。有没有办法在不首先提取,缓存,然后重置它的情况下保留它?


答案 1

ImageIO本身确实具有此功能,但您需要使用ImageReader而不是ImageIO.read

ImageReader reader = ImageIO.getImageReadersBySuffix("jpg").next();

(您可能还想检查是否存在这样的读取器)。然后,您需要设置输入:

reader.setInput(ImageIO.createImageInputStream(your_imput_stream));

现在,您可以保存元数据:

IIOMetadata metadata = reader.getImageMetadata(0); 
                            // As far as I understand you should provide 
                            // index as tiff images could have multiple pages

然后阅读图像:

BufferedImage bi = reader.read(0);

如果要保存新图像,则应使用 ImageWriter:

// I'm writing to byte array in memory, but you may use any other stream
ByteArrayOutputStream os = new ByteArrayOutputStream(255);
ImageOutputStream ios = ImageIO.createImageOutputStream(os);

Iterator<ImageWriter> iter = ImageIO.getImageWritersByFormatName("jpeg");
ImageWriter writer = iter.next();
writer.setOutput(ios);

//You may want also to alter jpeg quality
ImageWriteParam iwParam = writer.getDefaultWriteParam();
iwParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
iwParam.setCompressionQuality(.95f);

//Note: we're using metadata we've already saved.
writer.write(null, new IIOImage(bi, null, metadata), iwParam);
writer.dispose();

//ImageIO.write(bi, "jpg", ios); <- This was initially in the code but actually it was only adding image again at the end of the file.

由于这是老话题,我想这个答案有点太晚了,但可能会帮助其他人,因为这个话题仍然很可笑。


答案 2

这是我使用ImageIOImgscalrApache commons-imaging组合的解决方案。遗憾的是,(2016年5月)没有一个库将读取图像与其元数据相结合,这使得这可能在内存使用方面相当过分;欢迎改进。

import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import javax.imageio.ImageIO;
import org.apache.commons.imaging.ImageReadException;
import org.apache.commons.imaging.ImageWriteException;
import org.apache.commons.imaging.Imaging;
import org.apache.commons.imaging.common.IImageMetadata;
import org.apache.commons.imaging.formats.jpeg.JpegImageMetadata;
import org.apache.commons.imaging.formats.jpeg.exif.ExifRewriter;
import org.apache.commons.imaging.formats.tiff.TiffImageMetadata;
import org.apache.commons.io.IOUtils;
import org.imgscalr.Scalr;


public class ImageData {

    private byte[] imageData;


    public ImageData(InputStream instream) throws IOException {
        imageData  = IOUtils.toByteArray(instream);
        instream.close();
    }


    public synchronized void resize(int maxDimension) throws IOException, ImageReadException, ImageWriteException {
        // Resize the image if necessary
        BufferedImage image = readImage(imageData);
        if (image.getWidth() > maxDimension || image.getHeight() > maxDimension) {

            // Save existing metadata, if any
            TiffImageMetadata metadata = readExifMetadata(imageData);
            imageData = null; // allow immediate GC

            // resize 
            image = Scalr.resize(image, maxDimension);

            // rewrite resized image as byte[]
            byte[] resizedData = writeJPEG(image);
            image = null; // allow immediate GC 

            // Re-code resizedData + metadata to imageData 
            if (metadata != null) {
                this.imageData = writeExifMetadata(metadata, resizedData);
            } else {
                this.imageData = resizedData;
            }
        }
    }

    private TiffImageMetadata readExifMetadata(byte[] jpegData) throws ImageReadException, IOException {
        IImageMetadata imageMetadata = Imaging.getMetadata(jpegData);
        if (imageMetadata == null) {
            return null;
        }
        JpegImageMetadata jpegMetadata = (JpegImageMetadata)imageMetadata;
        TiffImageMetadata exif = jpegMetadata.getExif();
        if (exif == null) {
            return null;
        }
        return exif;
    }


    private byte[] writeExifMetadata(TiffImageMetadata metadata, byte[] jpegData) 
                                throws ImageReadException, ImageWriteException, IOException {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        new ExifRewriter().updateExifMetadataLossless(jpegData, out, metadata.getOutputSet());
        out.close();
        return out.toByteArray();
    }


    private BufferedImage readImage(byte[] data) throws IOException {
        return ImageIO.read(new ByteArrayInputStream(data));
    }

    private byte[] writeJPEG(BufferedImage image) throws IOException {
        ByteArrayOutputStream jpegOut = new ByteArrayOutputStream();
        ImageIO.write(image, "JPEG", jpegOut);
        jpegOut.close();
        return jpegOut.toByteArray();
    }

    public synchronized void writeJPEG(OutputStream outstream) throws IOException {
        IOUtils.write(imageData,  outstream);

    }

    public synchronized byte[] getJPEGData() {
        return imageData;
    }

}

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