#!/usr/bin/env python
# Copyright 2016-2019 Biomedical Imaging Group Rotterdam, Departments of
# Medical Informatics and Radiology, Erasmus MC, Rotterdam, The Netherlands
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import numpy as np
[docs]def linstretch(i, i_max=255, i_min=0):
'''
Stretch the input image i pixel values from i_min to i_max
'''
rmin = np.min(i.flatten()) # find the min. value of pixel in the image
rmax = np.max(i.flatten()) # find the max. value of pixel in the image
m = (i_max - i_min)/(rmax - rmin) # find the slope of line joining point (0, 255) to (rmin,rmax)
c = i_max - m*rmax # find the intercept of the straight line with the axis
i_stretch = m*i + c # transform the image according to new slope
return i_stretch