Write dpi metadata to a jpeg image in Java

Question

I am trying to programatically set the dpi metadata of an jpeg image in Java. The source of the image is a scanner, so I get the horizontal/vertical resolution from TWAIN, along with the image raw data. I'd like to save this info for better print results.

Here's the code I have so far. It saves the raw image (byteArray) to a JPEG file, but it ignores the X/Ydensity information I specify via IIOMetadata. Any advice what I'm doing wrong?

Any other solution (third-party library, etc) would be welcome too.

import java.awt.image.BufferedImage;
import java.awt.image.WritableRaster;
import java.io.File;

import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageTypeSpecifier;
import javax.imageio.metadata.IIOMetadata;
import javax.imageio.plugins.jpeg.JPEGImageWriteParam;
import javax.imageio.stream.ImageOutputStream    

import org.w3c.dom.Element;    
import com.sun.imageio.plugins.jpeg.JPEGImageWriter;

public boolean saveJpeg(int[] byteArray, int width, int height, int dpi, String file)
{
 BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

 WritableRaster wr = bufferedImage.getRaster();
 wr.setPixels(0, 0, width, height, byteArray);

 try
 {   
  // Image writer 
  JPEGImageWriter imageWriter = (JPEGImageWriter) ImageIO.getImageWritersBySuffix("jpeg").next();
  ImageOutputStream ios = ImageIO.createImageOutputStream(new File(file));
  imageWriter.setOutput(ios);

  // Compression
  JPEGImageWriteParam jpegParams = (JPEGImageWriteParam) imageWriter.getDefaultWriteParam();
  jpegParams.setCompressionMode(JPEGImageWriteParam.MODE_EXPLICIT);
  jpegParams.setCompressionQuality(0.85f);

  // Metadata (dpi)
  IIOMetadata data = imageWriter.getDefaultImageMetadata(new ImageTypeSpecifier(bufferedImage), jpegParams);
  Element tree = (Element)data.getAsTree("javax_imageio_jpeg_image_1.0");
  Element jfif = (Element)tree.getElementsByTagName("app0JFIF").item(0);
  jfif.setAttribute("Xdensity", Integer.toString(dpi));
  jfif.setAttribute("Ydensity", Integer.toString(dpi));
  jfif.setAttribute("resUnits", "1"); // density is dots per inch   

        // Write and clean up
  imageWriter.write(data, new IIOImage(bufferedImage, null, null), jpegParams);
  ios.close();
  imageWriter.dispose();
 }
 catch (Exception e)
 {
    return false;
 }

 return true;
}

Thanks!

Answer 1

I would seem this could be a bug.

I found this post from a few google searches

Apparently there are alot more that point to a bug as well.

The post above talks about using JMagick as a third party work around.

Answer 2

Some issues that were not considered here:

1) The tree is not directly mapped to the IOMetaData. To apply data from tree, add following call after setting the densities and raster parameters:

data.setFromTree("javax_imageio_jpeg_image_1.0", tree);

2) don't use the meta data as first parameter in the write call. See JPEGImageWriter#write(IIOMetaData, IIOImage, ImageWriteParam). If streamMetaData is not NULL, a warning (WARNING_STREAM_METADATA_IGNORED) will be generated.

3) set the meta data as IOMetadata of the IOImage. These meta data are used by JPEGImageWriter. The correct write call then is

imageWriter.write(null, new IIOImage(F_scaledImg, null, data), jpegParams);

Answer 3

I am getting a null return value on imageWriter.getDefaultImageMetadata.

Any thoughts?

Answer 4

Today, one year later, your explanations are very usefull to me !!! Thanks a lot !!