# Copyright (c) Open-MMLab. All rights reserved.
import cv2
import numpy as np
[docs]def solarize(img, thr=128):
"""Solarize an image (invert all pixel values above a threshold)
Args:
img (ndarray): Image to be solarized.
thr (int): Threshold for solarizing (0 - 255).
Returns:
ndarray: The solarized image.
"""
img = np.where(img < thr, img, 255 - img)
return img
[docs]def posterize(img, bits):
"""Posterize an image (reduce the number of bits for each color channel)
Args:
img (ndarray): Image to be posterized.
bits (int): Number of bits (1 to 8) to use for posterizing.
Returns:
ndarray: The posterized image.
"""
shift = 8 - bits
img = np.left_shift(np.right_shift(img, shift), shift)
return img
[docs]def iminvert(img):
"""Invert (negate) an image
Args:
img (ndarray): Image to be inverted.
Returns:
ndarray: The inverted image.
"""
return np.full_like(img, 255) - img
[docs]def bgr2gray(img, keepdim=False):
"""Convert a BGR image to grayscale image.
Args:
img (ndarray): The input image.
keepdim (bool): If False (by default), then return the grayscale image
with 2 dims, otherwise 3 dims.
Returns:
ndarray: The converted grayscale image.
"""
out_img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
if keepdim:
out_img = out_img[..., None]
return out_img
[docs]def rgb2gray(img, keepdim=False):
"""Convert a RGB image to grayscale image.
Args:
img (ndarray): The input image.
keepdim (bool): If False (by default), then return the grayscale image
with 2 dims, otherwise 3 dims.
Returns:
ndarray: The converted grayscale image.
"""
out_img = cv2.cvtColor(img, cv2.COLOR_RGB2GRAY)
if keepdim:
out_img = out_img[..., None]
return out_img
[docs]def gray2bgr(img):
"""Convert a grayscale image to BGR image.
Args:
img (ndarray): The input image.
Returns:
ndarray: The converted BGR image.
"""
img = img[..., None] if img.ndim == 2 else img
out_img = cv2.cvtColor(img, cv2.COLOR_GRAY2BGR)
return out_img
[docs]def gray2rgb(img):
"""Convert a grayscale image to RGB image.
Args:
img (ndarray): The input image.
Returns:
ndarray: The converted BGR image.
"""
img = img[..., None] if img.ndim == 2 else img
out_img = cv2.cvtColor(img, cv2.COLOR_GRAY2RGB)
return out_img
def convert_color_factory(src, dst):
code = getattr(cv2, 'COLOR_{}2{}'.format(src.upper(), dst.upper()))
def convert_color(img):
out_img = cv2.cvtColor(img, code)
return out_img
convert_color.__doc__ = """Convert a {0} image to {1} image.
Args:
img (ndarray or str): The input image.
Returns:
ndarray: The converted {1} image.
""".format(src.upper(), dst.upper())
return convert_color
bgr2rgb = convert_color_factory('bgr', 'rgb')
rgb2bgr = convert_color_factory('rgb', 'bgr')
bgr2hsv = convert_color_factory('bgr', 'hsv')
hsv2bgr = convert_color_factory('hsv', 'bgr')
bgr2hls = convert_color_factory('bgr', 'hls')
hls2bgr = convert_color_factory('hls', 'bgr')