Utils API

LUT

Lookup Table(LUT) is an array that replaces complex operations by indexing, and converts input data into a more ideal output format, thereby saving a lot of processing time. Especially in the interactive interface, the fluency of the interaction directly determines the user’s experience.

For the processing of medical images(always with a three-dimensional format), the image window adjustment and image format conversion are completed efficiently by establishing of LUT, which provide a guarantee for the smoothness of the interaction of the GUI controls.

Mapping function

Medical images usually have a high dynamic range (for example, the dynamic range of CT is generally -1024~1024), and the image display can be completed through the mapping function. According to DICOM , three mapping functions are defined: LINEAR、LINEAR_EXACT、SIGMOID(MedCV usesLINEARby default). Each function is related to dual variables of window level and window width, please refer to the code for details.

LUT building

medcv.utils.generate_lut_array(image, width, center, y_min=0, y_max=255, dtype=np.uint8, invert=False, mode=medcv.LINEAR_MODE)

This function generates the LUT array based on the incoming image data, and the return value is: offset and lut_array, please refer to the code for details.

Parameter

  • image (np.ndarray): medical image array, support 2-dim and 3-dim

  • width (int): window width for medical image

  • center (int): window center(level) for medical image

  • y_min (number): minimum value corresponding to the mapping function, the default is 0

  • y_max (number): maximum value corresponding to the mapping function, the default is 255

  • dtype: lut_array data type, default is np.uint8

  • invert (bool): reverse mapping mode, default is False

  • mode：mapping function selection, the options are:LINEAR、LINEAR_EXACT and SIGMOID, default is LINEAR

Warning

window width parameter must be set to be greater than or equal to 1

Argument validate

medcv.utils.expected_type(*type_args, **type_kwargs)

Based on the Python closure and decorator, combined with the inspect library signature method, the inspection and verification of the function parameter types are elegantly and concisely completed, please refer to the code for details.