This is an example how to read the image width tag.
ImageIO does not support tiffs by default.
You need to download jai_imageio.jar and put it in your build path.
You can find it here:
https://jai-imageio.dev.java.net/binary-builds.html
ImageInputStream is = ImageIO.createImageInputStream(new File("d:/tiffs/test/test.tif"));
ImageReader reader = (ImageReader) ImageIO.getImageReaders(is).next();
reader.setInput(is, true);
TIFFImageMetadata metadata = (TIFFImageMetadata) reader.getImageMetadata(0);
TIFFField field = metadata.getTIFFField(BaselineTIFFTagSet.TAG_IMAGE_WIDTH);
int imageWidth = field.getAsInt(0);