import cv2 import numpy as np from basicsr.metrics.metric_util import reorder_image, to_y_channel from basicsr.utils.registry import METRIC_REGISTRY @METRIC_REGISTRY.register() def calculate_psnr(img1, img2, crop_border, input_order='HWC', test_y_channel=False): """Calculate PSNR (Peak Signal-to-Noise Ratio). Ref: https://en.wikipedia.org/wiki/Peak_signal-to-noise_ratio Args: img1 (ndarray): Images with range [0, 255]. img2 (ndarray): Images with range [0, 255]. crop_border (int): Cropped pixels in each edge of an image. These pixels are not involved in the PSNR calculation. input_order (str): Whether the input order is 'HWC' or 'CHW'. Default: 'HWC'. test_y_channel (bool): Test on Y channel of YCbCr. Default: False. Returns: float: psnr result. """ assert img1.shape == img2.shape, (f'Image shapes are differnet: {img1.shape}, {img2.shape}.') if input_order not in ['HWC', 'CHW']: raise ValueError(f'Wrong input_order {input_order}. Supported input_orders are ' '"HWC" and "CHW"') img1 = reorder_image(img1, input_order=input_order) img2 = reorder_image(img2, input_order=input_order) img1 = img1.astype(np.float64) img2 = img2.astype(np.float64) if crop_border != 0: img1 = img1[crop_border:-crop_border, crop_border:-crop_border, ...] img2 = img2[crop_border:-crop_border, crop_border:-crop_border, ...] if test_y_channel: img1 = to_y_channel(img1) img2 = to_y_channel(img2) mse = np.mean((img1 - img2)**2) if mse == 0: return float('inf') return 20. * np.log10(255. / np.sqrt(mse)) def _ssim(img1, img2): """Calculate SSIM (structural similarity) for one channel images. It is called by func:`calculate_ssim`. Args: img1 (ndarray): Images with range [0, 255] with order 'HWC'. img2 (ndarray): Images with range [0, 255] with order 'HWC'. Returns: float: ssim result. """ C1 = (0.01 * 255)**2 C2 = (0.03 * 255)**2 img1 = img1.astype(np.float64) img2 = img2.astype(np.float64) kernel = cv2.getGaussianKernel(11, 1.5) window = np.outer(kernel, kernel.transpose()) mu1 = cv2.filter2D(img1, -1, window)[5:-5, 5:-5] mu2 = cv2.filter2D(img2, -1, window)[5:-5, 5:-5] mu1_sq = mu1**2 mu2_sq = mu2**2 mu1_mu2 = mu1 * mu2 sigma1_sq = cv2.filter2D(img1**2, -1, window)[5:-5, 5:-5] - mu1_sq sigma2_sq = cv2.filter2D(img2**2, -1, window)[5:-5, 5:-5] - mu2_sq sigma12 = cv2.filter2D(img1 * img2, -1, window)[5:-5, 5:-5] - mu1_mu2 ssim_map = ((2 * mu1_mu2 + C1) * (2 * sigma12 + C2)) / ((mu1_sq + mu2_sq + C1) * (sigma1_sq + sigma2_sq + C2)) return ssim_map.mean() @METRIC_REGISTRY.register() def calculate_ssim(img1, img2, crop_border, input_order='HWC', test_y_channel=False): """Calculate SSIM (structural similarity). Ref: Image quality assessment: From error visibility to structural similarity The results are the same as that of the official released MATLAB code in https://ece.uwaterloo.ca/~z70wang/research/ssim/. For three-channel images, SSIM is calculated for each channel and then averaged. Args: img1 (ndarray): Images with range [0, 255]. img2 (ndarray): Images with range [0, 255]. crop_border (int): Cropped pixels in each edge of an image. These pixels are not involved in the SSIM calculation. input_order (str): Whether the input order is 'HWC' or 'CHW'. Default: 'HWC'. test_y_channel (bool): Test on Y channel of YCbCr. Default: False. Returns: float: ssim result. """ assert img1.shape == img2.shape, (f'Image shapes are differnet: {img1.shape}, {img2.shape}.') if input_order not in ['HWC', 'CHW']: raise ValueError(f'Wrong input_order {input_order}. Supported input_orders are ' '"HWC" and "CHW"') img1 = reorder_image(img1, input_order=input_order) img2 = reorder_image(img2, input_order=input_order) img1 = img1.astype(np.float64) img2 = img2.astype(np.float64) if crop_border != 0: img1 = img1[crop_border:-crop_border, crop_border:-crop_border, ...] img2 = img2[crop_border:-crop_border, crop_border:-crop_border, ...] if test_y_channel: img1 = to_y_channel(img1) img2 = to_y_channel(img2) ssims = [] for i in range(img1.shape[2]): ssims.append(_ssim(img1[..., i], img2[..., i])) return np.array(ssims).mean()