In the previous blog, we did two things. First, we create a dataset and second we split this into training and test. In this blog, we will learn how to convert this dataset into TFRecord format for training.
Before creating TFRecord file, we just need to do one more step. In the last blog, we have generated XML files using LabelImg. To get labels for training and test dataset, we need to convert these XML files into CSV format. To do this we will use the following code which has been taken from this repository.
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import os import glob import pandas as pd import xml.etree.ElementTree as ET def xml_to_csv(path): xml_list = [] for xml_file in glob.glob(path + '/*.xml'): tree = ET.parse(xml_file) root = tree.getroot() for member in root.findall('object'): value = (root.find('filename').text, int(root.find('size')[0].text), int(root.find('size')[1].text), member[0].text, int(member[4][0].text), int(member[4][1].text), int(member[4][2].text), int(member[4][3].text) ) xml_list.append(value) column_name = ['filename', 'width', 'height', 'class', 'xmin', 'ymin', 'xmax', 'ymax'] xml_df = pd.DataFrame(xml_list, columns=column_name) return xml_df def main(): for directory in ['train','test']: image_path = os.path.join(os.getcwd(), 'images/{}'.format(directory)) xml_df = xml_to_csv(image_path) xml_df.to_csv('data/{}_labels.csv'.format(directory), index=None) print('Successfully converted xml to csv.') main() |
In the above main function, you should specify your XML files path for both train and test folder. The generated CSV files will contain columns as filename, width, and height of images, output label of images and coordinates of the annotated rectangular box as shown in the figure below
Once you have your train and test images with labels in CSV format, let’s convert data in TFRecord format.
A TFRecord file store your data as a sequence of binary strings. It has many advantages over normal data formats. To do this we will use the following code which has been taken from this repository. According to your requirement, you need to change the condition for labels
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""" Usage: # From tensorflow/models/ # Create train data: python generate_tfrecord.py --csv_input=data/train_labels.csv --output_path=train.record # Create test data: python generate_tfrecord.py --csv_input=data/test_labels.csv --output_path=test.record """ from __future__ import division from __future__ import print_function from __future__ import absolute_import import os import io import pandas as pd import tensorflow as tf from PIL import Image from object_detection.utils import dataset_util from collections import namedtuple, OrderedDict flags = tf.app.flags flags.DEFINE_string('csv_input', '', 'Path to the CSV input') flags.DEFINE_string('output_path', '', 'Path to output TFRecord') flags.DEFINE_string('image_dir', '', 'Path to images') FLAGS = flags.FLAGS # TO-DO replace this with label map def class_text_to_int(row_label): if row_label == 'up': return 1 elif row_label == 'down': return 2 elif row_label == 'left': return 3 elif row_label == 'right': return 4 else: None def split(df, group): data = namedtuple('data', ['filename', 'object']) gb = df.groupby(group) return [data(filename, gb.get_group(x)) for filename, x in zip(gb.groups.keys(), gb.groups)] def create_tf_example(group, path): with tf.gfile.GFile(os.path.join(path, '{}'.format(group.filename)), 'rb') as fid: encoded_jpg = fid.read() encoded_jpg_io = io.BytesIO(encoded_jpg) image = Image.open(encoded_jpg_io) width, height = image.size filename = group.filename.encode('utf8') image_format = b'jpg' xmins = [] xmaxs = [] ymins = [] ymaxs = [] classes_text = [] classes = [] for index, row in group.object.iterrows(): xmins.append(row['xmin'] / width) xmaxs.append(row['xmax'] / width) ymins.append(row['ymin'] / height) ymaxs.append(row['ymax'] / height) classes_text.append(row['class'].encode('utf8')) classes.append(class_text_to_int(row['class'])) tf_example = tf.train.Example(features=tf.train.Features(feature={ 'image/height': dataset_util.int64_feature(height), 'image/width': dataset_util.int64_feature(width), 'image/filename': dataset_util.bytes_feature(filename), 'image/source_id': dataset_util.bytes_feature(filename), 'image/encoded': dataset_util.bytes_feature(encoded_jpg), 'image/format': dataset_util.bytes_feature(image_format), 'image/object/bbox/xmin': dataset_util.float_list_feature(xmins), 'image/object/bbox/xmax': dataset_util.float_list_feature(xmaxs), 'image/object/bbox/ymin': dataset_util.float_list_feature(ymins), 'image/object/bbox/ymax': dataset_util.float_list_feature(ymaxs), 'image/object/class/text': dataset_util.bytes_list_feature(classes_text), 'image/object/class/label': dataset_util.int64_list_feature(classes), })) return tf_example def main(_): writer = tf.python_io.TFRecordWriter(FLAGS.output_path) path = os.path.join(FLAGS.image_dir) examples = pd.read_csv(FLAGS.csv_input) grouped = split(examples, 'filename') for group in grouped: tf_example = create_tf_example(group, path) writer.write(tf_example.SerializeToString()) writer.close() output_path = os.path.join(os.getcwd(), FLAGS.output_path) print('Successfully created the TFRecords: {}'.format(output_path)) if __name__ == '__main__': tf.app.run() |
Save this code in a file named generate_tfrecord.py. Now in order to use this code, first we need to clone tensorflow object detection API. For that do the following:
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git clone https://github.com/tensorflow/models.git |
Then we need to do the following steps to avoid getting error of protoc:
- Go to this release link and download
protobuf according to your operating system. - Extract the downloaded file and go to bin folder inside it.
- Copy protoc.exe file and put in models -> research -> object_detection -> protos folder.
- In protos folder run the following command for .proto files.
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protoc string_int_label_map.proto --python_out=. |
After cloning this repository, copy generate_tfrecord.py inside models -> research folder and run the following command.
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python generate_tfrecord.py --csv_input=data/train_labels.csv --output_path=train.record --image_dir data/train python generate_tfrecord.py --csv_input=data/test_labels.csv --output_path=train.record --image_dir data/test |
Above commands will generate two files named train.record and test.record which will be used for training of model.
This is all for generating TFRecord file, in the next blog we will perform training and testing of object detection model.
Next Blog: Snake Game Using Tensorflow Object Detection API – Part III
Hope you enjoy reading.
If you have any doubt/suggestion please feel free to ask and I will do my best to help or improve myself. Good-bye until next time.