Hello Image Segmentation

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A very basic introduction to using segmentation models with OpenVINO™.

In this tutorial, a pre-trained road-segmentation-adas-0001 model from the Open Model Zoo is used. ADAS stands for Advanced Driver Assistance Services. The model recognizes four classes: background, road, curb and mark.

Imports

import cv2
import matplotlib.pyplot as plt
import numpy as np
import sys
from openvino.runtime import Core

sys.path.append("../utils")
from notebook_utils import segmentation_map_to_image

Load the Model

ie = Core()

model = ie.read_model(model="model/road-segmentation-adas-0001.xml")
compiled_model = ie.compile_model(model=model, device_name="CPU")

input_layer_ir = compiled_model.input(0)
output_layer_ir = compiled_model.output(0)

Load an Image

A sample image from the Mapillary Vistas dataset is provided.

# The segmentation network expects images in BGR format.
image = cv2.imread("data/empty_road_mapillary.jpg")

rgb_image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
image_h, image_w, _ = image.shape

# N,C,H,W = batch size, number of channels, height, width.
N, C, H, W = input_layer_ir.shape

# OpenCV resize expects the destination size as (width, height).
resized_image = cv2.resize(image, (W, H))

# Reshape to the network input shape.
input_image = np.expand_dims(
    resized_image.transpose(2, 0, 1), 0
)
plt.imshow(rgb_image)
<matplotlib.image.AxesImage at 0x7f8989602910>
../_images/003-hello-segmentation-with-output_6_1.png

Do Inference

# Run the inference.
result = compiled_model([input_image])[output_layer_ir]

# Prepare data for visualization.
segmentation_mask = np.argmax(result, axis=1)
plt.imshow(segmentation_mask.transpose(1, 2, 0))
<matplotlib.image.AxesImage at 0x7f8948ea21f0>
../_images/003-hello-segmentation-with-output_8_1.png

Prepare Data for Visualization

# Define colormap, each color represents a class.
colormap = np.array([[68, 1, 84], [48, 103, 141], [53, 183, 120], [199, 216, 52]])

# Define the transparency of the segmentation mask on the photo.
alpha = 0.3

# Use function from notebook_utils.py to transform mask to an RGB image.
mask = segmentation_map_to_image(segmentation_mask, colormap)
resized_mask = cv2.resize(mask, (image_w, image_h))

# Create an image with mask.
image_with_mask = cv2.addWeighted(resized_mask, alpha, rgb_image, 1 - alpha, 0)

Visualize data

# Define titles with images.
data = {"Base Photo": rgb_image, "Segmentation": mask, "Masked Photo": image_with_mask}

# Create a subplot to visualize images.
fig, axs = plt.subplots(1, len(data.items()), figsize=(15, 10))

# Fill the subplot.
for ax, (name, image) in zip(axs, data.items()):
    ax.axis('off')
    ax.set_title(name)
    ax.imshow(image)

# Display an image.
plt.show(fig)
../_images/003-hello-segmentation-with-output_12_0.png