补充:transform.invert 预处理逆操作
from PIL import Image
from torchvision import transforms
import torch
import numpy as np
def transform_invert(img_, transform_train):
"""
将data 进行反transfrom操作
:param img_: tensor
:param transform_train: torchvision.transforms
:return: PIL image
"""
if 'Normalize' in str(transform_train):
# 分析transforms里的Normalize
norm_transform = list(filter(lambda x: isinstance(x, transforms.Normalize), transform_train.transforms))
mean = torch.tensor(norm_transform[0].mean, dtype=img_.dtype, device=img_.device)
std = torch.tensor(norm_transform[0].std, dtype=img_.dtype, device=img_.device)
img_.mul_(std[:, None, None]).add_(mean[:, None, None]) # 广播三个维度 乘标准差 加均值
img_ = img_.transpose(0, 2).transpose(0, 1) # C*H*W --> H*W*C
# 如果有ToTensor,那么之前数值就会被压缩至0-1之间。现在需要反变换回来,也就是乘255
if 'ToTensor' in str(transform_train):
img_ = np.array(img_) * 255
# 先将np的元素转换为uint8数据类型,然后转换为PIL.Image类型
if img_.shape[2] == 3: # 若通道数为3 需要转为RGB类型
img_ = Image.fromarray(img_.astype('uint8')).convert('RGB')
elif img_.shape[2] == 1: # 若通道数为1 需要压缩张量的维度至2D
img_ = Image.fromarray(img_.astype('uint8').squeeze())
else:
raise Exception("Invalid img shape, expected 1 or 3 in axis 2, but got {}!".format(img_.shape[2]))
return img_
if __name__ == '__main__':
img = Image.open(r"./test.jpg").convert('RGB')
img_transform = transforms.Compose([transforms.ToTensor()])
img_tensor = img_transform(img)
# img_tensor.unsqueeze_(dim=0) # C*H*W to B*C*H*W
print(img_tensor)
print(img_tensor.shape)
img = transform_invert(img_tensor, img_transform) # input: shape=[c h w]
img.show()
![](https://img.laitimes.com/img/__Qf2AjLwojIjJCLyojI0JCLiAnYldHL0FWby9mZvwFN4ETMfdHLkVGepZ2XtxSZ6l2clJ3LcV2Zh1Wa9M3clN2byBXLzN3btgHL9s2RkBnVHFmb1clWvB3MaVnRtp1XlBXe0xCMy81dvRWYoNHLwEzX5xCMx8FesU2cfdGLwMzX0xiRGZkRGZ0Xy9GbvNGLpZTY1EmMZVDUSFTU4VFRR9Fd4VGdsQTMfVmepNHLrJXYtJXZ0F2dvwVZnFWbp1zczV2YvJHctM3cv1Ce-cmbw5SOzYzMxYmNmBDZzMGO0MWNzYzXzITNyUDM5IzLcBTMyIDMy8CXn9Gbi9CXzV2Zh1WavwVbvNmLvR3YxUjLyM3Lc9CX6MHc0RHaiojIsJye.png)
一 放射变换:RandomAffine
功能:对图像进行仿射变换,仿射变换是二维的线性变换,由五种基本原子变换构成,分别是旋转、平移、缩放、错切和翻转
主要参数说明:
- degrees:旋转角度设置
-
translate:平移区间设置,如(a, b), a设置宽(width) ,b设置高(height)
图像在宽维度平移的区间为
-img_width * a < dx < img_width *a
- scale:缩放比例(以面积为单位)(范围:0-1)
- fill_color: 填充颜色设置
-
shear:错切角度设置,有水平错切和垂直错切
若为a,则仅在x轴错切,错切角度在(-a, a)之间
若为(a, b), 则a设置x轴角度,b设置y的角度
若为(a,b, c, d),则a, b设置x轴角度,c, d设置y轴角度
- resample:重采样方式,有NEAREST BILINEAR、 BICUBIC
1.旋转
from PIL import Image
from torchvision import transforms
from utils import transform_invert
if __name__ == '__main__':
# 1.读取图像
img = Image.open(r"./cat.png").convert('RGB')
# 2.确定预处理方式
img_transform = transforms.Compose([## transforms.Resize((300,300)), # 重置大小为300*300
transforms.RandomAffine(degrees=60), # 仿射变换
transforms.ToTensor() # 转Tensor型变量
])
# 3.进行预处理
img_tensor = img_transform(img)
# 4.逆Transform变换
img = transform_invert(img_tensor, img_transform) # input: shape=[c h w]
# 5.进行预处理效果展示
img.show()
2.平移
from PIL import Image
from torchvision import transforms
from utils import transform_invert
if __name__ == '__main__':
# 1.读取图像
img = Image.open(r"./cat.png").convert('RGB')
# 2.确定预处理方式
img_transform = transforms.Compose([## transforms.Resize((300,300)), # 重置大小为300*300
transforms.RandomAffine(degrees=0,translate=(0.2,0.2),fillcolor=(0,0,255)), # 仿射变换
transforms.ToTensor() # 转Tensor型变量
])
# 3.进行预处理
img_tensor = img_transform(img)
# 4.逆Transform变换
img = transform_invert(img_tensor, img_transform) # input: shape=[c h w]
# 5.进行预处理效果展示
img.show()
translate=(0.2:宽的平移范围,0.2:高的平移范围)
3.缩放
from PIL import Image
from torchvision import transforms
from utils import transform_invert
if __name__ == '__main__':
# 1.读取图像
img = Image.open(r"./cat.png").convert('RGB')
# 2.确定预处理方式
img_transform = transforms.Compose([## transforms.Resize((300,300)), # 重置大小为300*300
transforms.RandomAffine(degrees=0,scale=(0.2,1),fillcolor=(0,0,255)), # 仿射变换
transforms.ToTensor() # 转Tensor型变量
])
# 3.进行预处理
img_tensor = img_transform(img)
# 4.逆Transform变换
img = transform_invert(img_tensor, img_transform) # input: shape=[c h w]
# 5.进行预处理效果展示
img.show()
4.错切
from PIL import Image
from torchvision import transforms
from utils import transform_invert
if __name__ == '__main__':
# 1.读取图像
img = Image.open(r"./cat.png").convert('RGB')
# 2.确定预处理方式
img_transform = transforms.Compose([## transforms.Resize((300,300)), # 重置大小为300*300
transforms.RandomAffine(degrees=0,shear=(0,0,0,55),fillcolor=(0,0,255)), # 仿射变换
transforms.ToTensor() # 转Tensor型变量
])
# 3.进行预处理
img_tensor = img_transform(img)
# 4.逆Transform变换
img = transform_invert(img_tensor, img_transform) # input: shape=[c h w]
# 5.进行预处理效果展示
img.show()