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| # Copyright (c) OpenMMLab. All rights reserved. | |
| import cv2 | |
| import numpy as np | |
| def imconvert(img, src, dst): | |
| """Convert an image from the src colorspace to dst colorspace. | |
| Args: | |
| img (ndarray): The input image. | |
| src (str): The source colorspace, e.g., 'rgb', 'hsv'. | |
| dst (str): The destination colorspace, e.g., 'rgb', 'hsv'. | |
| Returns: | |
| ndarray: The converted image. | |
| """ | |
| code = getattr(cv2, f'COLOR_{src.upper()}2{dst.upper()}') | |
| out_img = cv2.cvtColor(img, code) | |
| return out_img | |
| 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 | |
| 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 | |
| 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 | |
| def gray2rgb(img): | |
| """Convert a grayscale image to RGB image. | |
| Args: | |
| img (ndarray): The input image. | |
| Returns: | |
| ndarray: The converted RGB image. | |
| """ | |
| img = img[..., None] if img.ndim == 2 else img | |
| out_img = cv2.cvtColor(img, cv2.COLOR_GRAY2RGB) | |
| return out_img | |
| def _convert_input_type_range(img): | |
| """Convert the type and range of the input image. | |
| It converts the input image to np.float32 type and range of [0, 1]. | |
| It is mainly used for pre-processing the input image in colorspace | |
| conversion functions such as rgb2ycbcr and ycbcr2rgb. | |
| Args: | |
| img (ndarray): The input image. It accepts: | |
| 1. np.uint8 type with range [0, 255]; | |
| 2. np.float32 type with range [0, 1]. | |
| Returns: | |
| (ndarray): The converted image with type of np.float32 and range of | |
| [0, 1]. | |
| """ | |
| img_type = img.dtype | |
| img = img.astype(np.float32) | |
| if img_type == np.float32: | |
| pass | |
| elif img_type == np.uint8: | |
| img /= 255. | |
| else: | |
| raise TypeError('The img type should be np.float32 or np.uint8, ' | |
| f'but got {img_type}') | |
| return img | |
| def _convert_output_type_range(img, dst_type): | |
| """Convert the type and range of the image according to dst_type. | |
| It converts the image to desired type and range. If `dst_type` is np.uint8, | |
| images will be converted to np.uint8 type with range [0, 255]. If | |
| `dst_type` is np.float32, it converts the image to np.float32 type with | |
| range [0, 1]. | |
| It is mainly used for post-processing images in colorspace conversion | |
| functions such as rgb2ycbcr and ycbcr2rgb. | |
| Args: | |
| img (ndarray): The image to be converted with np.float32 type and | |
| range [0, 255]. | |
| dst_type (np.uint8 | np.float32): If dst_type is np.uint8, it | |
| converts the image to np.uint8 type with range [0, 255]. If | |
| dst_type is np.float32, it converts the image to np.float32 type | |
| with range [0, 1]. | |
| Returns: | |
| (ndarray): The converted image with desired type and range. | |
| """ | |
| if dst_type not in (np.uint8, np.float32): | |
| raise TypeError('The dst_type should be np.float32 or np.uint8, ' | |
| f'but got {dst_type}') | |
| if dst_type == np.uint8: | |
| img = img.round() | |
| else: | |
| img /= 255. | |
| return img.astype(dst_type) | |
| def rgb2ycbcr(img, y_only=False): | |
| """Convert a RGB image to YCbCr image. | |
| This function produces the same results as Matlab's `rgb2ycbcr` function. | |
| It implements the ITU-R BT.601 conversion for standard-definition | |
| television. See more details in | |
| https://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.601_conversion. | |
| It differs from a similar function in cv2.cvtColor: `RGB <-> YCrCb`. | |
| In OpenCV, it implements a JPEG conversion. See more details in | |
| https://en.wikipedia.org/wiki/YCbCr#JPEG_conversion. | |
| Args: | |
| img (ndarray): The input image. It accepts: | |
| 1. np.uint8 type with range [0, 255]; | |
| 2. np.float32 type with range [0, 1]. | |
| y_only (bool): Whether to only return Y channel. Default: False. | |
| Returns: | |
| ndarray: The converted YCbCr image. The output image has the same type | |
| and range as input image. | |
| """ | |
| img_type = img.dtype | |
| img = _convert_input_type_range(img) | |
| if y_only: | |
| out_img = np.dot(img, [65.481, 128.553, 24.966]) + 16.0 | |
| else: | |
| out_img = np.matmul( | |
| img, [[65.481, -37.797, 112.0], [128.553, -74.203, -93.786], | |
| [24.966, 112.0, -18.214]]) + [16, 128, 128] | |
| out_img = _convert_output_type_range(out_img, img_type) | |
| return out_img | |
| def bgr2ycbcr(img, y_only=False): | |
| """Convert a BGR image to YCbCr image. | |
| The bgr version of rgb2ycbcr. | |
| It implements the ITU-R BT.601 conversion for standard-definition | |
| television. See more details in | |
| https://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.601_conversion. | |
| It differs from a similar function in cv2.cvtColor: `BGR <-> YCrCb`. | |
| In OpenCV, it implements a JPEG conversion. See more details in | |
| https://en.wikipedia.org/wiki/YCbCr#JPEG_conversion. | |
| Args: | |
| img (ndarray): The input image. It accepts: | |
| 1. np.uint8 type with range [0, 255]; | |
| 2. np.float32 type with range [0, 1]. | |
| y_only (bool): Whether to only return Y channel. Default: False. | |
| Returns: | |
| ndarray: The converted YCbCr image. The output image has the same type | |
| and range as input image. | |
| """ | |
| img_type = img.dtype | |
| img = _convert_input_type_range(img) | |
| if y_only: | |
| out_img = np.dot(img, [24.966, 128.553, 65.481]) + 16.0 | |
| else: | |
| out_img = np.matmul( | |
| img, [[24.966, 112.0, -18.214], [128.553, -74.203, -93.786], | |
| [65.481, -37.797, 112.0]]) + [16, 128, 128] | |
| out_img = _convert_output_type_range(out_img, img_type) | |
| return out_img | |
| def ycbcr2rgb(img): | |
| """Convert a YCbCr image to RGB image. | |
| This function produces the same results as Matlab's ycbcr2rgb function. | |
| It implements the ITU-R BT.601 conversion for standard-definition | |
| television. See more details in | |
| https://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.601_conversion. | |
| It differs from a similar function in cv2.cvtColor: `YCrCb <-> RGB`. | |
| In OpenCV, it implements a JPEG conversion. See more details in | |
| https://en.wikipedia.org/wiki/YCbCr#JPEG_conversion. | |
| Args: | |
| img (ndarray): The input image. It accepts: | |
| 1. np.uint8 type with range [0, 255]; | |
| 2. np.float32 type with range [0, 1]. | |
| Returns: | |
| ndarray: The converted RGB image. The output image has the same type | |
| and range as input image. | |
| """ | |
| img_type = img.dtype | |
| img = _convert_input_type_range(img) * 255 | |
| out_img = np.matmul(img, [[0.00456621, 0.00456621, 0.00456621], | |
| [0, -0.00153632, 0.00791071], | |
| [0.00625893, -0.00318811, 0]]) * 255.0 + [ | |
| -222.921, 135.576, -276.836 | |
| ] | |
| out_img = _convert_output_type_range(out_img, img_type) | |
| return out_img | |
| def ycbcr2bgr(img): | |
| """Convert a YCbCr image to BGR image. | |
| The bgr version of ycbcr2rgb. | |
| It implements the ITU-R BT.601 conversion for standard-definition | |
| television. See more details in | |
| https://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.601_conversion. | |
| It differs from a similar function in cv2.cvtColor: `YCrCb <-> BGR`. | |
| In OpenCV, it implements a JPEG conversion. See more details in | |
| https://en.wikipedia.org/wiki/YCbCr#JPEG_conversion. | |
| Args: | |
| img (ndarray): The input image. It accepts: | |
| 1. np.uint8 type with range [0, 255]; | |
| 2. np.float32 type with range [0, 1]. | |
| Returns: | |
| ndarray: The converted BGR image. The output image has the same type | |
| and range as input image. | |
| """ | |
| img_type = img.dtype | |
| img = _convert_input_type_range(img) * 255 | |
| out_img = np.matmul(img, [[0.00456621, 0.00456621, 0.00456621], | |
| [0.00791071, -0.00153632, 0], | |
| [0, -0.00318811, 0.00625893]]) * 255.0 + [ | |
| -276.836, 135.576, -222.921 | |
| ] | |
| out_img = _convert_output_type_range(out_img, img_type) | |
| return out_img | |
| def convert_color_factory(src, dst): | |
| code = getattr(cv2, f'COLOR_{src.upper()}2{dst.upper()}') | |
| def convert_color(img): | |
| out_img = cv2.cvtColor(img, code) | |
| return out_img | |
| convert_color.__doc__ = f"""Convert a {src.upper()} image to {dst.upper()} | |
| image. | |
| Args: | |
| img (ndarray or str): The input image. | |
| Returns: | |
| ndarray: The converted {dst.upper()} image. | |
| """ | |
| 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') | |