pytorch做标准化利用transforms.normalize(mean_vals,std_vals),其中常用数据集的均值方差有:
if 'coco' in args.dataset: mean_vals = [0.471,0.448,0.408] std_vals = [0.234,0.239,0.242]elif 'imagenet' in args.dataset: mean_vals = [0.485,0.456,0.406] std_vals = [0.229,0.224,0.225]
计算自己数据集图像像素的均值方差:
import numpy as npimport cv2import random# calculate means and stdtrain_txt_path = './train_val_List.txt'CNum = 10000 # 挑选多少图片进行计算img_h,img_w = 32,32imgs = np.zeros([img_w,img_h,3,1])means,stdevs = [],[]with open(train_txt_path,'r') as f: lines = f.readlines() random.shuffle(lines) # shuffle,随机挑选图片 for i in tqdm_notebook(range(CNum)): img_path = os.path.join('./train',lines[i].rstrip().split()[0]) img = cv2.imread(img_path) img = cv2.resize(img,(img_h,img_w)) img = img[:,:,np.newaxis] imgs = np.concatenate((imgs,img),axis=3)# print(i)imgs = imgs.astype(np.float32)/255.for i in tqdm_notebook(range(3)): pixels = imgs[:,i,:].ravel() # 拉成一行 means.append(np.mean(pixels)) stdevs.append(np.std(pixels))# cv2 读取的图像格式为BGR,PIL/Skimage读取到的都是RGB不用转means.reverse() # BGR --> RGBstdevs.reverse()print("normMean = {}".format(means))print("normStd = {}".format(stdevs))print('transforms.normalize(normMean = {},normStd = {})'.format(means,stdevs))
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