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| import numpy as np | |
| import torch | |
| 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] # noqa: E126 | |
| 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] # noqa: E126 | |
| out_img = _convert_output_type_range(out_img, img_type) | |
| 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(f'The img type should be np.float32 or np.uint8, 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(f'The dst_type should be np.float32 or np.uint8, but got {dst_type}') | |
| if dst_type == np.uint8: | |
| img = img.round() | |
| else: | |
| img /= 255. | |
| return img.astype(dst_type) | |
| def rgb2ycbcr_pt(img, y_only=False): | |
| """Convert RGB images to YCbCr images (PyTorch version). | |
| 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. | |
| Args: | |
| img (Tensor): Images with shape (n, 3, h, w), the range [0, 1], float, RGB format. | |
| y_only (bool): Whether to only return Y channel. Default: False. | |
| Returns: | |
| (Tensor): converted images with the shape (n, 3/1, h, w), the range [0, 1], float. | |
| """ | |
| if y_only: | |
| weight = torch.tensor([[65.481], [128.553], [24.966]]).to(img) | |
| out_img = torch.matmul(img.permute(0, 2, 3, 1), weight).permute(0, 3, 1, 2) + 16.0 | |
| else: | |
| weight = torch.tensor([[65.481, -37.797, 112.0], [128.553, -74.203, -93.786], [24.966, 112.0, -18.214]]).to(img) | |
| bias = torch.tensor([16, 128, 128]).view(1, 3, 1, 1).to(img) | |
| out_img = torch.matmul(img.permute(0, 2, 3, 1), weight).permute(0, 3, 1, 2) + bias | |
| out_img = out_img / 255. | |
| return out_img | |