Tensorflow:从 TFRecords 文件中提取图像和标签 [英] Tensorflow: Extracting image and label from TFRecords file
问题描述
我有一个 TFRecords 文件,其中包含带有标签、名称、大小等的图像.我的目标是将标签和图像提取为一个 numpy 数组.
I have a TFRecords file which contains images with their labels, name, size, etc. My goal is to extract the label and the image as a numpy array.
我执行以下操作来加载文件:
I do the following to load the file:
def extract_fn(data_record):
features = {
# Extract features using the keys set during creation
"image/class/label": tf.FixedLenFeature([], tf.int64),
"image/encoded": tf.VarLenFeature(tf.string),
}
sample = tf.parse_single_example(data_record, features)
#sample = tf.cast(sample["image/encoded"], tf.float32)
return sample
filename = "path\train-00-of-10"
dataset = tf.data.TFRecordDataset(filename)
dataset = dataset.map(extract_fn)
iterator = dataset.make_one_shot_iterator()
next_element = iterator.get_next()
with tf.Session() as sess:
while True:
data_record = sess.run(next_element)
print(data_record)
图像保存为字符串.如何将图像转换为 float32
?我试过 sample = tf.cast(sample["image/encoded"], tf.float32)
这不起作用.我希望 data_record
是一个列表,其中包含作为 numpy-array 的图像和作为 np.int32
数字的标签.我该怎么做?
The image is saved as a string. How can I convert the image to float32
? I tried sample = tf.cast(sample["image/encoded"], tf.float32)
which does not work. I want data_record
to be a list containing the image as a numpy-array and the label as a np.int32
number. How can I do that?
现在 data_record
看起来像这样:
Right now data_record
looks like this:
{'image/encoded': SparseTensorValue(indices=array([[0]]), values=array([b'\xff\xd8\ ... 8G\xff\xd9'], dtype=object), dense_shape=array([1])), 'image/class/label': 394}
我不知道如何处理它.我将不胜感激
I have no idea how I can work with that. I would appreciate any help
编辑
如果我在 extract_fn()
中打印 sample
和 sample['image/encoded']
我得到以下内容:
If I print sample
and sample['image/encoded']
in extract_fn()
I get the following:
print(sample) ={'image/encoded': <tensorflow.python.framework.sparse_tensor.SparseTensor object at 0x7fe41ec15978>, 'image/class/label': <tf.Tensor 'ParseSingleExample/ParseSingleExample:3' shape=(6)>;}
print(sample['image/encoded'] =SparseTensor(indices=Tensor("ParseSingleExample/ParseSingleExample:0", shape=(?, 1), dtype=int64), values=Tensor("ParseSingleExample/ParseSingleExample:1", shape=(?,), dtype=string),dense_shape=Tensor("ParseSingleExample/ParseSingleExample:2", shape=(1,), dtype=int64))
图像似乎是一个稀疏张量,tf.image.decode_image
抛出错误.将图像提取为 tf.float32
张量的正确方法是什么?
It seems that the image is a sparse tensor and tf.image.decode_image
throws an error. What is the right way to extract the image as an tf.float32
tensor?
推荐答案
我相信您将图像存储为 JPEG 或 PNG 或其他一些格式.所以,在阅读时,你必须解码它们:
I believe you store images encoded as JPEG or PNG or some other format. So, when reading, you have to decode them:
def extract_fn(data_record):
features = {
# Extract features using the keys set during creation
"image/class/label": tf.FixedLenFeature([], tf.int64),
"image/encoded": tf.VarLenFeature(tf.string),
}
sample = tf.parse_single_example(data_record, features)
image = tf.image.decode_image(sample['image/encoded'], dtype=tf.float32)
label = sample['image/class/label']
return image, label
...
with tf.Session() as sess:
while True:
image, label = sess.run(next_element)
image = image.reshape(IMAGE_SHAPE)
更新:似乎您将数据作为稀疏张量中的单个单元格值.尝试将其转换回密集并在解码前后进行检查:
Update: It seems you got your data as a single cell value in a sparse Tensor. Try to convert it back to dense and inspect before and after decoding:
def extract_fn(data_record):
features = {
# Extract features using the keys set during creation
"image/class/label": tf.FixedLenFeature([], tf.int64),
"image/encoded": tf.VarLenFeature(tf.string),
}
sample = tf.parse_single_example(data_record, features)
label = sample['image/class/label']
dense = tf.sparse_tensor_to_dense(sample['image/encoded'])
# Comment it if you got an error and inspect just dense:
image = tf.image.decode_image(dense, dtype=tf.float32)
return dense, image, label
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