【发布时间】：2021-04-04 23:50:06
【问题描述】：
我正在尝试在 LandCoverNet 数据集上训练一个 Unit 模型，该数据集是一个卫星图像数据集，其中包含输入图像和相应的土地覆盖类型掩码。 我创建了一个自定义数据集来获取我的图像和蒙版：
# Create custom dataset that accepts 4 channels images
from torch.utils.data import Dataset, DataLoader, sampler
from pathlib import Path
from PIL import Image
import matplotlib.pyplot as plt
import os
import numpy as np
import rasterio as rio
from torchvision import transforms, datasets, models
# We have two dir: inputs(folder for each image) and tatgets
class LandCoverNetDataset(BaseDataset):
CLASSES = ['otherland', 'cropland', 'pastureland', 'bare soil', 'openwater', 'forestland']
def __init__(self, inputs_dir, targets_dir,
classes = None,
augmentation=None ,
preprocessing = False,
pytorch=True):
super().__init__()
self.samples = []
self.pytorch = pytorch
self.augmentation = augmentation
self.preprocessing = preprocessing
# Convert str names to class values on masks
self.class_value = [self.CLASSES.index(cls.lower()) for cls in classes]
# Create dictionary for images and targets
for sub_dir in os.listdir(inputs_dir):
files = {}
files = {
'img_bands' : os.path.join(inputs_dir, sub_dir),
'target' : os.path.join(targets_dir, sub_dir[:13] + "_LC_10m.png")
}
self.samples.append(files)
def __len__(self):
return len(self.samples)
def normalize(self, band):
'''Notmalize a numpy array to have values between 0 and 1'''
band_min, band_max = band.min(), band.max()
np.seterr(divide='ignore', invalid='ignore')
normalized_band = ((band - band_min)/(band_max - band_min))
#Remove any nan value and subtitute by zero
where_are_NaNs = isnan(normalized_band)
normalized_band[where_are_NaNs] = 0
return normalized_band
def open_as_array(self, idx, include_ndvi = False):
'''
Merge the 4 bands into one image and normalize the bands
'''
# List indivisual bands in each image folder
# Stack them togather
list_bands = []
for img_file in os.listdir(self.samples[idx]['img_bands']):
# Get the ndvi band
if 'NDVI' in img_file:
ndvi_band = os.path.join(self.samples[idx]['img_bands'], img_file)
else:
# Get the rgb bands
band = rio.open(os.path.join(self.samples[idx]['img_bands'], img_file)).read(1)
if self.preprocessing:
# preprocess the bands before stacking them (only rgb)
band = self.normalize(band)
list_bands.append(band)
# Stack the bands
raw_rgb = np.stack(list_bands, axis=2).astype('float32')
if include_ndvi:
# Include the NDVI band in the input images
ndvi = np.expand_dims(rio.open(ndvi_band).read(1).astype('float32'), 2)
raw_rgb = np.concatenate([raw_rgb, ndvi], axis=2)
if self.augmentation:
transformed = self.augmentation(image = raw_rgb)
raw_rgb = transformed["image"]
if self.preprocessing:
# transpose to tensor shape
raw_rgb = raw_rgb.transpose((2,0,1)).astype('float32')
return raw_rgb
def open_mask(self, idx):
# Extract certain classes from mask
mask = cv2.imread(self.samples[idx]['target'], 0)
masks = [(mask == v) for v in self.class_value]
mask = np.stack(masks, axis=-1).astype('long')
if self.augmentation:
transformed = self.augmentation(image = mask)
mask = transformed["image"]
if self.preprocessing:
# preprocess the mask
mask = self.normalize(mask)
# transpose to tensor shape
mask = mask.transpose((2, 0, 1)).astype('long')
mask = mask[0, :, :]
return mask
def __getitem__(self, idx):
x = torch.tensor(self.open_as_array(idx, include_ndvi=True), dtype=torch.float)
y = torch.tensor(self.open_mask(idx), dtype=torch.long)
return x, y
def open_as_pil(self, idx):
arr = 256*self.open_as_array(idx)
return Image.fromarray(arr.astype(np.uint8), 'RGB')
def __repr__(self):
s = 'Dataset class with {} files'.format(self.__len__())
return s
这里的输入是 4 个波段。 这是输入/目标的第一批的形状
torch.Size([16, 4, 224, 224])
torch.Size([16, 224, 224])
我正在使用来自 segmentation-models-pytorch 库的模型，下面是我为我的案例定制它的方法：
ENCODER = 'se_resnext50_32x4d'
ENCODER_WEIGHTS = 'imagenet'
ACTIVATION = 'softmax2d'
DEVICE = 'cuda'
model = smp.FPN(ENCODER, classes=len(CLASSES), activation=ACTIVATION)
# Replace the model.conv1 to accept 4 channels
# first: copy the layer's weights
weight = model.encoder.layer0.conv1.weight.clone()
model.encoder.layer0.conv1 = nn.Conv2d(4, 64,kernel_size=(7, 7), stride=(2, 2), padding=(3, 3), bias=False)
with torch.no_grad():
model.encoder.layer0.conv1.weight[:, :3] = weight
model.encoder.layer0.conv1.weight[:, 3] = model.encoder.layer0.conv1.weight[:, 0]
loss = smp.utils.losses.NLLLoss()
metrics = [
smp.utils.metrics.IoU(threshold=0.5),
]
optimizer = torch.optim.SGD([
dict(params=model.parameters(), lr=0.001, weight_decay=1e-8, momentum=0.9),
])
# create epoch runners
# it is a simple loop of iterating over dataloader`s samples
train_epoch = smp.utils.train.TrainEpoch(
model,
loss=loss,
metrics=metrics,
optimizer=optimizer,
device=DEVICE,
verbose=True,
)
valid_epoch = smp.utils.train.ValidEpoch(
model,
loss=loss,
metrics=metrics,
device=DEVICE,
verbose=True,
)
这是我的训练循环
# train model for 40 epochs
max_score = 0
for i in range(0, 40):
print('\nEpoch: {}'.format(i))
train_logs = train_epoch.run(train_loader)
valid_logs = valid_epoch.run(valid_loader)
# do something (save model, change lr, etc.)
if max_score < valid_logs['iou_score']:
max_score = valid_logs['iou_score']
torch.save(model, './best_model.pth')
print('Model saved!')
if i == 25:
optimizer.param_groups[0]['lr'] = 1e-5
print('Decrease decoder learning rate to 1e-5!')
一开始，目标形状是[16, 6, 224, 224] 但我有错误发现this thread应该是[batch_size, height, width] 这就是我在 Dataset 类中添加这一行的原因： mask = mask[0, :, :] 让课程的数量变暗，在这里事情让我感到困惑，因为我模型的输出是 torch.Size([10, 6, 224, 224])。
这是完整的错误信息：
Epoch: 0
train: 0%| | 0/157 [00:00<?, ?it/s]
---------------------------------------------------------------------------
RuntimeError Traceback (most recent call last)
<ipython-input-215-2ae39e205dee> in <module>()
7
8 print('\nEpoch: {}'.format(i))
----> 9 train_logs = train_epoch.run(train_loader)
10 valid_logs = valid_epoch.run(valid_loader)
11
3 frames
/usr/local/lib/python3.6/dist-packages/segmentation_models_pytorch/utils/functional.py in iou(pr, gt, eps, threshold, ignore_channels)
32 pr, gt = _take_channels(pr, gt, ignore_channels=ignore_channels)
33
---> 34 intersection = torch.sum(gt * pr)
35 union = torch.sum(gt) + torch.sum(pr) - intersection + eps
36 return (intersection + eps) / union
RuntimeError: The size of tensor a (16) must match the size of tensor b (6) at non-singleton dimension 1
谢谢！
【问题讨论】：
标签： python deep-learning pytorch image-segmentation multiclass-classification