526互联

pytorch图像变换和增强

发布时间 2023-11-03 21:39:24作者: 贝壳里的星海

pytorch图像变换和增强

目录

总览

# 使用数据增强技术可以增加数据集中图像的多样性，从而提高模型的性能和泛化能力。
1.尺寸变换
transforms.Resize()  		 		#尺寸变换
transforms.Normalize()       		#标准化
transforms.Pad()             		#边界填充

2.色彩和色域					 
transforms.Grayscale()		   		#转灰度图	
transforms.RandomGrayscale()   		#依概率p转为灰度图
transforms.ColorJitter()      		#随机修改亮度对比度和饱和度

3.裁剪
transforms.CenterCrop(size)       	#中心裁剪
transforms.RandomCrop(size)      	#随机裁剪
transforms.RandomResizedCrop()   	#随机大小、长宽比裁剪
transforms.FiveCrop()               #上下左右中心裁剪,裁剪图像的四个角和中心
transforms.TenCrop()            	#上下左右中心裁剪后翻转,5张图像
  

4.翻转和旋转
transforms.RandomHorizontalFlip(p=0.5)     #依概率p水平翻转
transforms.RandomVerticalFlip(p=0.5)       #依概率p垂直翻转
transforms.RandomRotation(degrees, resample=False, expand=False, center=None)  #随机旋转
	#degrees：旋转角度，当为一个数a时，在（-a，a）之间随机旋转
	#resample：重采样方法
	#expand：旋转时是否保持图片完整，只针对中心旋转
	#center：设置旋转中心点

5.随机遮挡
transforms.RandomErasing            #对图像进行随机遮挡


6.图像变换
transforms.LinearTransformation()   #线性变换
transforms.RandomAffine()           #随机仿射变换
transforms.RandomPerspective()      #随机透视变换
transforms.GaussianBlur()		    #高斯滤波器进行图像模糊
transforms.RandomInvert()           #随机地插入给定图像的颜色
transforms.RandomEqualize()			#直方图均衡化


7.格式变换
transforms.ToPILImage(mode=None)     #图像转换为 PIL图像 
transforms.ToTensor()				 #转换为 torch.tensor

8.数据选择
transforms.RandomChoice(transforms列表)          #从给定的一系列transforms中选一个进行操作
transforms.RandomApply(transforms列表, p=0.5)    #给一个transform加上概率，依概率进行选择操作
transforms.RandomOrder(transforms列表)           #将transforms中的操作随机打乱。

调整大小

from PIL import Image
from pathlib import Path
import matplotlib.pyplot as plt
import numpy as np
import sys
import torch
import numpy as np
import torchvision.transforms as T

plt.rcParams["savefig.bbox"] = 'tight'
orig_img = Image.open(Path('assets/images/1.jpg'))
torch.manual_seed(0) # 设置 CPU 生成随机数的 种子 ，方便下次复现实验结果
print(np.asarray(orig_img).shape) #(800, 800, 3)

#图像大小的调整
resized_imgs128 = T.Resize(size=128)(orig_img)

resized_imgs256 = T.Resize(size=256)(orig_img)
# plt.figure('resize:128*128')

ax1 = plt.subplot(1,3,1)
ax1.set_title('original')
ax1.imshow(orig_img)

ax2 = plt.subplot(1,3,2)
ax2.set_title('resize:128*128')
ax2.imshow(resized_imgs128)

ax3 = plt.subplot(1,3,3)
ax3.set_title('resize:256*256')
ax3.imshow(resized_imgs256)

plt.show()
img

灰度变换

from pathlib import Path
from PIL import Image
import numpy as np
import matplotlib.pyplot as plt
import torch
import torchvision.transforms as T

orig_img = Image.open(Path('assets/images/1.jpg'))
gray_img = T.Grayscale()(orig_img)
# plt.figure('resize:128*128')
ax1 = plt.subplot(121)
ax1.set_title('original')
ax1.imshow(orig_img)

ax2 = plt.subplot(122)
ax2.set_title('gray')
ax2.imshow(gray_img,cmap='gray')
img

标准化

标准化可以加快基于神经网络结构的模型的计算速度，加快学习速度。

  • 从每个输入通道中减去通道平均值
  • 将其除以通道标准差。
from pathlib import Path
from PIL import Image
import numpy as np
import matplotlib.pyplot as plt
import torch
import torchvision.transforms as T

orig_img = Image.open(Path('assets/images/1.jpg'))
normalized_img = T.Normalize(mean=(0.5, 0.5, 0.5), std=(0.5, 0.5, 0.5))(T.ToTensor()(orig_img))
normalized_img = [T.ToPILImage()(normalized_img)]
# plt.figure('resize:128*128')
ax1 = plt.subplot(121)
ax1.set_title('original')
ax1.imshow(orig_img)

ax2 = plt.subplot(122)
ax2.set_title('normalize')
ax2.imshow(normalized_img[0])

plt.show()
img

水平垂直翻转

from PIL import Image
from pathlib import Path
import matplotlib.pyplot as plt
import numpy as np
import sys
import torch
import numpy as np
import torchvision.transforms as T


plt.rcParams["savefig.bbox"] = 'tight'
orig_img = Image.open(Path('assets/images/1.jpg'))

HorizontalFlip_VerticalFlip_img = [T.RandomHorizontalFlip(p=1)(orig_img),
                      T.RandomVerticalFlip(p=1)(orig_img)
                      ]

plt.figure('resize:128*128')
ax1 = plt.subplot(131)
ax1.set_title('original')
ax1.imshow(orig_img)

ax2 = plt.subplot(132)
ax2.set_title('HorizontalFlip')
ax2.imshow(np.array(HorizontalFlip_VerticalFlip_img[0]))


ax3 = plt.subplot(133)
ax3.set_title('VerticalFlip')
ax3.imshow(np.array(HorizontalFlip_VerticalFlip_img[1]))

plt.show()
img

随机旋转

from pathlib import Path
from PIL import Image
import numpy as np
import matplotlib.pyplot as plt
import torchvision.transforms as T

# 设计角度旋转图像
plt.rcParams["savefig.bbox"] = 'tight'
orig_img = Image.open(Path('assets/images/1.jpg'))

rotated_imgs = [T.RandomRotation(degrees=90)(orig_img)]    # (min, max)
print(rotated_imgs)
ax1 = plt.subplot(121)
ax1.set_title('original')
ax1.imshow(orig_img)

ax2 = plt.subplot(122)
ax2.set_title('90°')
ax2.imshow(np.array(rotated_imgs[0]))
plt.show()
img

中心裁剪

from PIL import Image
from pathlib import Path
import matplotlib.pyplot as plt
import numpy as np
import sys
import torch
import numpy as np
import torchvision.transforms as T

# 剪切图像的中心区域
plt.rcParams["savefig.bbox"] = 'tight'
orig_img = Image.open(Path('assets/images/1.jpg'))

center_crops = [T.CenterCrop(size=size)(orig_img) for size in (256,128)]

plt.figure('resize:128*128')
ax1 = plt.subplot(131)
ax1.set_title('original')
ax1.imshow(orig_img)

ax2 = plt.subplot(132)
ax2.set_title('256*256°')
ax2.imshow(np.array(center_crops[0]))

ax3 = plt.subplot(133)
ax3.set_title('128*128')
ax3.imshow(np.array(center_crops[1]))

plt.show()
img

随机裁剪

from PIL import Image
from pathlib import Path
import matplotlib.pyplot as plt
import numpy as np
import sys
import torch
import numpy as np
import torchvision.transforms as T

# 随机剪切图像的某一部分
plt.rcParams["savefig.bbox"] = 'tight'
orig_img = Image.open(Path('assets/images/1.jpg'))

random_crops = [T.RandomCrop(size=size)(orig_img) for size in (400,300)]

plt.figure('resize:128*128')
ax1 = plt.subplot(131)
ax1.set_title('original')
ax1.imshow(orig_img)

ax2 = plt.subplot(132)
ax2.set_title('400*400')
ax2.imshow(np.array(random_crops[0]))

ax3 = plt.subplot(133)
ax3.set_title('300*300')
ax3.imshow(np.array(random_crops[1]))

plt.show()
img

亮度对比度饱和度

from PIL import Image
from pathlib import Path
import matplotlib.pyplot as plt
import numpy as np
import sys
import torch
import numpy as np
import torchvision.transforms as T


plt.rcParams["savefig.bbox"] = 'tight'
orig_img = Image.open(Path('assets/images/1.jpg'))
# random_crops = [T.RandomCrop(size=size)(orig_img) for size in (832,704, 256)]
colorjitter_img = [T.ColorJitter(brightness=(2,2), contrast=(0.5,0.5), saturation=(0.5,0.5))(orig_img)]

plt.figure('resize:128*128')
ax1 = plt.subplot(121)
ax1.set_title('original')
ax1.imshow(orig_img)
ax2 = plt.subplot(122)
ax2.set_title('colorjitter_img')
ax2.imshow(np.array(colorjitter_img[0]))
plt.show()
img

高斯模糊

from PIL import Image
from pathlib import Path
import matplotlib.pyplot as plt
import numpy as np
import sys
import torch
import numpy as np
import torchvision.transforms as T

# 使用高斯核对图像进行模糊变换
plt.rcParams["savefig.bbox"] = 'tight'
orig_img = Image.open(Path('image/2.png'))

blurred_imgs = [T.GaussianBlur(kernel_size=(3, 3), sigma=sigma)(orig_img) for sigma in (5,11)]

plt.figure('resize:128*128')
ax1 = plt.subplot(131)
ax1.set_title('original')
ax1.imshow(orig_img)

ax2 = plt.subplot(132)
ax2.set_title('sigma=5')
ax2.imshow(np.array(blurred_imgs[0]))

ax3 = plt.subplot(133)
ax3.set_title('sigma=11')
ax3.imshow(np.array(blurred_imgs[1]))

plt.show()
img

高斯噪声

from PIL import Image
from pathlib import Path
import matplotlib.pyplot as plt
import numpy as np
import sys
import torch
import numpy as np
import torchvision.transforms as T

# 向图像中加入高斯噪声。通过设置噪声因子，噪声因子越高，图像的噪声越大。
plt.rcParams["savefig.bbox"] = 'tight'
orig_img = Image.open(Path('image/2.png'))


def add_noise(inputs, noise_factor=0.3):
    noisy = inputs + torch.randn_like(inputs) * noise_factor
    noisy = torch.clip(noisy, 0., 1.)
    return noisy


noise_imgs = [add_noise(T.ToTensor()(orig_img), noise_factor) for noise_factor in (0.3, 0.6)]
noise_imgs = [T.ToPILImage()(noise_img) for noise_img in noise_imgs]

plt.figure('resize:128*128')
ax1 = plt.subplot(131)
ax1.set_title('original')
ax1.imshow(orig_img)

ax2 = plt.subplot(132)
ax2.set_title('noise_factor=0.3')
ax2.imshow(np.array(noise_imgs[0]))

ax3 = plt.subplot(133)
ax3.set_title('noise_factor=0.6')
ax3.imshow(np.array(noise_imgs[1]))

plt.show()
img

随机块

from PIL import Image
from pathlib import Path
import matplotlib.pyplot as plt
import numpy as np

# 正方形补丁随机应用在图像中。这些补丁的数量越多，神经网络解决问题的难度就越大。
plt.rcParams["savefig.bbox"] = 'tight'
orig_img = Image.open(Path('assets/images/1.jpg'))


def add_random_boxes(img,n_k,size=64):
    h,w = size,size
    img = np.asarray(img).copy()
    img_size = img.shape[1]
    boxes = []
    for k in range(n_k):
        y,x = np.random.randint(0,img_size-w,(2,))
        img[y:y+h,x:x+w] = 0
        boxes.append((x,y,h,w))
    img = Image.fromarray(img.astype('uint8'), 'RGB')
    return img

blocks_imgs = [add_random_boxes(orig_img,n_k=10)]

plt.figure('resize:128*128')
ax1 = plt.subplot(131)
ax1.set_title('original')
ax1.imshow(orig_img)

ax2 = plt.subplot(132)
ax2.set_title('10 black boxes')
ax2.imshow(np.array(blocks_imgs[0]))


plt.show()
img

中心区域

from PIL import Image
from pathlib import Path
import matplotlib.pyplot as plt
import numpy as np

# 和随机块类似，只不过在图像的中心加入补丁
plt.rcParams["savefig.bbox"] = 'tight'
orig_img = Image.open(Path('assets/images/1.jpg'))


def add_central_region(img, size=32):
    h, w = size, size
    img = np.asarray(img).copy()
    img_size = img.shape[1]
    img[int(img_size / 2 - h):int(img_size / 2 + h), int(img_size / 2 - w):int(img_size / 2 + w)] = 0
    img = Image.fromarray(img.astype('uint8'), 'RGB')
    return img


central_imgs = [add_central_region(orig_img, size=128)]


plt.figure('resize:128*128')
ax1 = plt.subplot(131)
ax1.set_title('original')
ax1.imshow(orig_img)

ax2 = plt.subplot(132)
ax2.set_title('add_central_region')
ax2.imshow(np.array(central_imgs[0]))


plt.show()
img

参考资料

https://blog.csdn.net/maizousidemao/article/details/109413113

https://zhuanlan.zhihu.com/p/559887437

https://juejin.cn/post/6996500482273312804