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, a

Answer 1

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);