java获取图片dpi

以下是Java获取图片dpi的代码示例：

import org.apache.commons.imaging.ImageReadException;import org.apache.commons.imaging.Imaging;
import org.apache.commons.imaging.common.ImageMetadata;
import org.apache.commons.imaging.common.RationalNumber;
import org.apache.commons.imaging.formats.jpeg.JpegImageMetadata;
import org.apache.commons.imaging.formats.tiff.TiffImageMetadata;
import org.apache.commons.imaging.formats.tiff.constants.TiffTagConstants;
import org.apache.commons.imaging.formats.tiff.fieldtypes.FieldType;
import org.apache.commons.imaging.formats.tiff.taginfos.TagInfo;

import java.io.File;
import java.io.IOException;

public class GetImageDpi {
    public static void main(String[] args) throws IOException, ImageReadException {
        File file = new File("test.jpg");
        ImageMetadata metadata = Imaging.getMetadata(file);
        if (metadata instanceof JpegImageMetadata) {
            JpegImageMetadata jpegMetadata = (JpegImageMetadata) metadata;
            TiffImageMetadata exif = jpegMetadata.getExif();
            if (exif != null) {
                TagInfo tagInfo = TiffTagConstants.TIFF_TAG_XRESOLUTION;
                FieldType fieldType = tagInfo.getDataType().getFieldType();
                RationalNumber rationalNumber = exif.getRational(tagInfo);
                if (rationalNumber != null) {
                    int dpi = rationalNumber.intValue();
                    System.out.println("DPI: " + dpi);
                }
            }
        }
    }
}