How to use image semantic segmentation technology in Python?

With the continuous development of artificial intelligence technology, image semantic segmentation technology has become a popular research direction in the field of image analysis. In image semantic segmentation, we segment different areas in an image and classify each area to achieve a comprehensive understanding of the image.

Python is a well-known programming language. Its powerful data analysis and data visualization capabilities make it the first choice in the field of artificial intelligence technology research. This article will introduce how to use image semantic segmentation technology in Python.

1. Pre-knowledge

Before learning how to use image semantic segmentation technology in Python, you need to have some knowledge about deep learning and convolutional neural network (CNN). and basic knowledge of image processing. If you are an experienced Python developer but have no experience with deep learning and CNN models, it is recommended that you learn some related knowledge first.

2. Preparation

In order to use image semantic segmentation technology, we need some pre-trained models. There are many popular deep learning frameworks, such as Keras, PyTorch, and TensorFlow, which provide pre-trained models for developers to use.

In this article, we will use the TensorFlow framework and its global image semantic segmentation model - DeepLab-v3, as well as a Python library that can be used to process images - the Pillow library.

We can install the libraries we need to use through the following command:

pip install tensorflow==2.4.0
pip install Pillow

3. Use the DeepLab-v3 network for image semantic segmentation

DeepLab-v3 is an efficient Deep convolutional neural network model for image semantic segmentation. It has a series of advanced technologies, including Dilated Convolution, multi-scale data aggregation and Conditional Random Field (CRF).

The Pillow library provides some convenient tools for processing and reading image files. Next, we will use the Image class from the Pillow library to read an image file. The code looks like this:

from PIL import Image
im = Image.open('example.jpg')

Here we can replace example.jpg with our own image file name.

By using the DeepLab-v3 model and the image we read in, we can get a detailed image semantic segmentation result. In order to use the pre-trained DeepLab-v3 model, we need to download the model weight file. It can be found on the official TensorFlow model page.

# 导入预训练的 DeepLab-v3+ 模型
from tensorflow.keras.models import Model
from tensorflow.keras.layers import Input
from tensorflow.keras.applications import MobileNetV2
from tensorflow.keras.layers import Conv2DTranspose, Concatenate, Activation, MaxPooling2D, Conv2D, BatchNormalization, Dropout 

def create_model(num_classes):
    # 加载 MobileNetV2 预训练模型
    base_model = MobileNetV2(input_shape=(256, 256, 3), include_top=False, weights='imagenet')

    # 获取对应层输出的张量
    low_level_features = base_model.get_layer('block_1_expand_relu').output
    x = base_model.get_layer('out_relu').output

    # 通过使用反卷积尺寸进行上采样和空洞卷积，构建 DeepLab-v3+ 系统，并针对特定的数据集来训练其分类器
    x = Conv2D(256, (1, 1), activation='relu', padding='same', name='concat_projection')(x)
    x = Dropout(0.3)(x)
    x = Conv2DTranspose(128, (3, 3), strides=(2, 2), padding='same', name='decoder_conv0')(x)
    x = BatchNormalization(name='decoder_bn0')(x)
    x = Activation('relu', name='decoder_relu0')(x)
    x = Concatenate(name='decoder_concat0')([x, low_level_features])
    x = Conv2D(128, (1, 1), padding='same', name='decoder_conv1')(x)
    x = Dropout(0.3)(x)
    x = Conv2DTranspose(64, (3, 3), strides=(2, 2), padding='same', name='decoder_conv2')(x)
    x = BatchNormalization(name='decoder_bn2')(x)
    x = Activation('relu', name='decoder_relu2')(x)
    x = Conv2D(num_classes, (1, 1), padding='same', name='decoder_conv3')(x)
    x = Activation('softmax', name='softmax')(x)

    # 创建 Keras 模型，并返回它
    model = Model(inputs=base_model.input, outputs=x)

    return model

Now that we have successfully loaded the model, we can start semantic segmentation of the image. The code is as follows:

import numpy as np
import urllib.request

# 读取图像
urllib.request.urlretrieve('https://www.tensorflow.org/images/surf.jpg', 'image.jpg')
image = Image.open('image.jpg')
image_array = np.array(image)

# 加载训练好的模型
model = create_model(num_classes=21)
model.load_weights('deeplabv3_xception_tf_dim_ordering_tf_kernels.h5')
print('模型加载成功。')

# 将输入图像调整为模型所需形状，并进行语义分割
input_tensor = tf.convert_to_tensor(np.expand_dims(image_array, 0))
output_tensor = model(input_tensor)

# 显示语义分割结果
import matplotlib.pyplot as plt

parsed_results = output_tensor.numpy().squeeze()
parsed_results = np.argmax(parsed_results, axis=2)
plt.imshow(parsed_results)
plt.show()

After running this code, you will get a neural network output with a color distribution similar to the example shown.

4. Summary

In this article, we introduced how to use image semantic segmentation technology in Python and successfully loaded the pre-trained DeepLab-v3 model. Of course, the example used here is just one of the methods, and different research directions require different processing methods. If you're interested, delve into this area and use these techniques in your own projects.

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