Line-enhancing filtering
========================

This example demonstrates line-enhancing filtering according to :ref:`Frangi <frangifilter>`.

When using the :ref:`frangifilter <frangifilter>` command, the scaling of the output values
depends on the pixel data type of the input image.
The results of the Frangi filtering are always in the range :math:`[0, 1]`.
In order to be able to express the results in an image of integer pixel data type,
the Frangi filter values are scaled to range :math:`[0, M]`, where :math:`M` is the maximum value
that can be expressed with the pixel data type.

If the image is of floating point pixel data type, the values are not scaled.


::

	def linefilters():
		"""
		Calculates Frangi line-enhancing filter.
		"""

		# Read image
		img = pi.read(input_file())

		# Frangi filter, 16-bit result
		frangi_16bit = pi.newlike(img, ImageDataType.UINT16)
		pi.frangifilter(img, frangi_16bit, 3.0)
		pi.writeraw(frangi_16bit, output_file('frangi_16bit'))


		# Frangi filter, 32-bit result. Notice different scaling in the output, compared to the 16-bit version.
		frangi_32bit = pi.newlike(img, ImageDataType.FLOAT32)
		pi.convert(img, ImageDataType.FLOAT32)
		pi.frangifilter(img, frangi_32bit, 3.0)
		pi.writeraw(frangi_32bit, output_file('frangi_32bit'))
		
		
		
.. figure:: figures/t1-head_slice.png
   :scale: 100 %
   :alt: Input image

   One slice of the input image.


.. figure:: figures/frangi.png
   :scale: 100 %
   :alt: Result of Frangi filtering.

   Result of line-enhancing Frangi filter.