『MXNet』第六彈_數據處理API（待續）
阿新 • • 發佈：2018-05-27
convert lena PE color bus AS array 維度 shuff
一、Gluon數據加載
圖片數據(含標簽)加載函數：gluon.data.vision.ImageFolderDataset
給出ImageFolderDataset類的描述，
Init signature: mxnet.gluon.data.vision.datasets.ImageFolderDataset(root, flag=1, transform=None)
Source:
class ImageFolderDataset(dataset.Dataset):
"""A dataset for loading image files stored in a folder structure like::
root/car/0001.jpg
root/car/xxxa.jpg
root/car/yyyb.jpg
root/bus/123.jpg
root/bus/023.jpg
root/bus/wwww.jpg
Parameters
----------
root : str
Path to root directory.
flag : {0, 1}, default 1 # 控制彩色or灰度
If 0, always convert loaded images to greyscale (1 channel).
If 1, always convert loaded images to colored (3 channels).
transform : callable, default None
A function that takes data and label and transforms them:
::
transform = lambda data, label: (data.astype(np.float32)/255, label)
Attributes
----------
synsets : list # 查看類別，實際就是文件名
List of class names. `synsets[i]` is the name for the integer label `i`
items : list of tuples # 生成的數據
List of all images in (filename, label) pairs.
"""實例：
train_imgs = gluon.data.vision.ImageFolderDataset(
data_dir+‘/hotdog/train‘,
transform=lambda X, y: transform(X, y, train_augs))
test_imgs = gluon.data.vision.ImageFolderDataset(
data_dir+‘/hotdog/test‘,
transform=lambda X, y: transform(X, y, test_augs))
print(train_imgs)
print(train_imgs.synsets)
data = gluon.data.DataLoader(train_imgs, 32, shuffle=True)
<mxnet.gluon.data.vision.datasets.ImageFolderDataset object at 0x7fbed5641c18> [‘hotdog‘, ‘not-hotdog‘]
batch叠代器：gluon.data.DataLoader
具有特殊方法，def __iter__(self)，其實例可以被叠代，也就是每次返回一個batch的數據，在第一維度上切割。
首個定位參數文檔如下：
dataset : Dataset
Source dataset. Note that numpy and mxnet arrays can be directly used
as a Dataset.最後生成的X_batch送入net(X_batch)向前傳播，y_batch送入loss(output,y_batch)計算loss後反向傳播。
二、MXNet數據加載
https://blog.csdn.net/qq_36165459/article/details/78394322
https://blog.csdn.net/u012759136/article/details/50208733#%E4%BA%8C%E4%BB%8E%E5%8E%9F%E7%94%9F%E6%95%B0%E6%8D%AE%E7%94%9F%E6%88%90lst%E6%96%87%E4%BB%B6
『MXNet』第六彈_數據處理API（待續）