getWriteMetadata

   private static IIOMetadata getWriteMD(ImageWriter writer, ImageWriteParam param)
        throws IIOInvalidTreeException {

        ImageTypeSpecifier typeSpecifier = ImageTypeSpecifier.createFromBufferedImageType(BufferedImage.TYPE_INT_RGB);
        IIOMetadata metadata = writer.getDefaultImageMetadata(typeSpecifier, param);
        if (metadata.isReadOnly() || !metadata.isStandardMetadataFormatSupported()) {
            return null;
        }

        TIFFDirectory dir = TIFFDirectory.createFromMetadata(metadata);

        BaselineTIFFTagSet base = BaselineTIFFTagSet.getInstance();
        // getting the tags
        TIFFTag resUnit = base.getTag(BaselineTIFFTagSet.TAG_RESOLUTION_UNIT);
        TIFFTag tagXRes = base.getTag(BaselineTIFFTagSet.TAG_X_RESOLUTION);
        TIFFTag tagYRes = base.getTag(BaselineTIFFTagSet.TAG_Y_RESOLUTION);
        TIFFTag photoInterp = base.getTag(BaselineTIFFTagSet.TAG_PHOTOMETRIC_INTERPRETATION);

        // (300 x 300 DPI)
        TIFFField fieldXRes = new TIFFField(tagXRes, TIFFTag.TIFF_RATIONAL, 1, new long[][] {{300, 1}});
        TIFFField fieldYRes = new TIFFField(tagYRes, TIFFTag.TIFF_RATIONAL, 1, new long[][] {{300, 1}});
        TIFFField fieldResUnit = new TIFFField(resUnit,BaselineTIFFTagSet.RESOLUTION_UNIT_INCH);

        // doesn't work
        dir.removeTIFFField(photoInterp.getNumber());
        TIFFField fieldPhotoInter = new TIFFField(photoInterp, BaselineTIFFTagSet.PHOTOMETRIC_INTERPRETATION_RGB);

        // writing to tiffdir
        dir.addTIFFField(fieldXRes);
        dir.addTIFFField(fieldYRes);
        dir.addTIFFField(fieldResUnit);
        dir.addTIFFField(fieldPhotoInter);

        return dir.getAsMetadata();
    }