public class test01

{

    private static int DPI = 300;

    public static void main(String[] args)

    {

        String path = "E:\\002.jpg";

        File file = new File(path);

        handleDpi(file, DPI, DPI);

    }

    /**

     * 改变图片DPI

     * @param file

     * @param xDensity 水平分辨率

     * @param yDensity 垂直分辨率

     */

    public static void handleDpi(File file, int xDensity, int yDensity)

    {

        FileOutputStream fileOutputStream = null;

        try

        {

            BufferedImage image = ImageIO.read(file);

            fileOutputStream = new FileOutputStream(file);

            JPEGImageEncoder jpegEncoder = JPEGCodec.createJPEGEncoder(fileOutputStream);

            JPEGEncodeParam jpegEncodeParam = jpegEncoder.getDefaultJPEGEncodeParam(image);

            jpegEncodeParam.setDensityUnit(JPEGEncodeParam.DENSITY_UNIT_DOTS_INCH);

            jpegEncoder.setJPEGEncodeParam(jpegEncodeParam);

            jpegEncodeParam.setQuality(0.75f, false);

            jpegEncodeParam.setXDensity(xDensity);

            jpegEncodeParam.setYDensity(yDensity);

            jpegEncoder.encode(image, jpegEncodeParam);

            image.flush();

        }

        catch (Exception e)

        {

            e.printStackTrace();

        }

        finally

        {

            //关流

            try

            {

                if(fileOutputStream!=null)

                {

                    fileOutputStream.close();

                }

            }

            catch (Exception e)

            {

                e.printStackTrace();

            }

        }

    }

}