How to convert a 16 bit to an 8 bit image in OpenCV?

问题:

I have a 16bit grayscale image and I want to convert it to a 8bit grayscale image in OpenCV for python to use it with various functions (like findContours etc.). Is it possible to do it in python or I have to switch to C++?

回答1:

You can use numpy conversion methods as an OpenCV mat is a numpy array.

This works:

img8 = (img16/256).astype('uint8')

回答2:

You can do this in Python using NumPy by mapping the image trough a lookup table.

import numpy as np   def map_uint16_to_uint8(img, lower_bound=None, upper_bound=None):     '''     Map a 16-bit image trough a lookup table to convert it to 8-bit.      Parameters     ----------     img: numpy.ndarray[np.uint16]         image that should be mapped     lower_bound: int, optional         lower bound of the range that should be mapped to ``[0, 255]``,         value must be in the range ``[0, 65535]`` and smaller than `upper_bound`         (defaults to ``numpy.min(img)``)     upper_bound: int, optional        upper bound of the range that should be mapped to ``[0, 255]``,        value must be in the range ``[0, 65535]`` and larger than `lower_bound`        (defaults to ``numpy.max(img)``)      Returns     -------     numpy.ndarray[uint8]     '''     if not(0 <= lower_bound < 2**16) and lower_bound is not None:         raise ValueError(             '"lower_bound" must be in the range [0, 65535]')     if not(0 <= upper_bound < 2**16) and upper_bound is not None:         raise ValueError(             '"upper_bound" must be in the range [0, 65535]')     if lower_bound is None:         lower_bound = np.min(img)     if upper_bound is None:         upper_bound = np.max(img)     if lower_bound >= upper_bound:         raise ValueError(             '"lower_bound" must be smaller than "upper_bound"')     lut = np.concatenate([         np.zeros(lower_bound, dtype=np.uint16),         np.linspace(0, 255, upper_bound - lower_bound).astype(np.uint16),         np.ones(2**16 - upper_bound, dtype=np.uint16) * 255     ])     return lut[img].astype(np.uint8)   # Let's generate an example image (normally you would load the 16-bit image: cv2.imread(filename, cv2.IMREAD_UNCHANGED)) img = (np.random.random((100, 100)) * 2**16).astype(np.uint16)  # Convert it to 8-bit map_uint16_to_uint8(img)

回答3:

For converting from 16 bit to 8 bit using python openCV:

import numpy as np import cv2 imagePath = "--"  img_8bit = cv2.imread(imagePath).astype(np.uint8)

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文章来源: How to convert a 16 bit to an 8 bit image in OpenCV?