deeplabv3plusLayers

Create DeepLab v3+ convolutional neural network for semantic image segmentation

Syntax

layerGraph = deeplabv3plusLayers(imageSize,numClasses,network)

layerGraph = deeplabv3plusLayers(___,'DownsamplingFactor',value)

Description

layerGraph = deeplabv3plusLayers(imageSize,numClasses,network) returns a DeepLab v3+ layer with the specified base network, number of classes, and image size.

layerGraph = deeplabv3plusLayers(___,'DownsamplingFactor',value) additionally sets the downsampling factor (output stride) [1] to either 8 or 16. The downsampling factor sets the amount the encoder section of DeepLav v3+ downsamples the input image.

Examples

Create DeepLab v3+ Network Based on ResNet-18

Create a DeepLab v3+ network based on ResNet-18.

imageSize = [480 640 3];
numClasses = 5;
network = 'resnet18';
lgraph = deeplabv3plusLayers(imageSize,numClasses,network, ...
             'DownsamplingFactor',16);

Display the network.

analyzeNetwork(lgraph)

Train DeepLab v3+ Network

Load the triangle data set images using an image datastore. The datastore contains 200 grayscale images of random triangles. Each image is 32-by-32.

dataSetDir = fullfile(toolboxdir('vision'),'visiondata','triangleImages');
imageDir = fullfile(dataSetDir,'trainingImages');
imds = imageDatastore(imageDir);

Load the triangle data set pixel labels using a pixel label datastore.

labelDir = fullfile(dataSetDir, 'trainingLabels');
classNames = ["triangle","background"];
labelIDs   = [255 0];
pxds = pixelLabelDatastore(labelDir,classNames,labelIDs);

Create a DeepLab v3+ network.

imageSize = [256 256];
numClasses = numel(classNames);
lgraph = deeplabv3plusLayers(imageSize,numClasses,'resnet18');

Combine image and pixel label data for training. Set the image output size to the input size of the network to automatically resize images during training.

pximds = pixelLabelImageDatastore(imds,pxds,'OutputSize',imageSize,...
    'ColorPreprocessing','gray2rgb');

Specify training options. Lower the mini-batch size to reduce memory usage.

opts = trainingOptions('sgdm',...
    'MiniBatchSize',8,...
    'MaxEpochs',3);

Train the network.

net = trainNetwork(pximds,lgraph,opts);

Training on single CPU.
|========================================================================================|
|  Epoch  |  Iteration  |  Time Elapsed  |  Mini-batch  |  Mini-batch  |  Base Learning  |
|         |             |   (hh:mm:ss)   |   Accuracy   |     Loss     |      Rate       |
|========================================================================================|
|       1 |           1 |       00:00:08 |       57.31% |       0.7145 |          0.0100 |
|       2 |          50 |       00:06:05 |       99.23% |       0.0198 |          0.0100 |
|       3 |          75 |       00:09:05 |       99.12% |       0.0214 |          0.0100 |
|========================================================================================|

Read a test image.

I = imread('triangleTest.jpg');

Resize the test image by a factor equal to the input image size divided by 32 so that the triangles in the test image are roughly equal to the size of the triangles during training.

I = imresize(I,'Scale',imageSize./32);

Segment the image.

C = semanticseg(I,net);

Display the results.

B = labeloverlay(I,C);
figure
imshow(B)

Input Arguments

imageSize — Network input image size

2-element vector | 3-element vector

Network input image size, specified as a:

• 2-element vector in the format [height, width].

• 3-element vector in the format [height, width, 3]. The third element, 3, corresponds to RGB.

numClasses — Number of classes

integer greater than 1

Number of classes for network to classify, specified as an integer greater than 1.

network — Base network

'resnet18' | 'resnet50' | | 'mobilenetv2' | 'xception' | 'inceptionresnetv2'

Base network, specified as resnet18 (Deep Learning Toolbox), resnet50 (Deep Learning Toolbox), mobilenetv2 (Deep Learning Toolbox), xception (Deep Learning Toolbox), or inceptionresnetv2 (Deep Learning Toolbox). You must install the corresponding network add-on.

Output Arguments

layerGraph — DeepLab v3+ network

layer graph

DeepLab v3+ network, returned as a convolutional neural network for semantic image segmentation. The network uses encoder-decoder architecture, dilated convolutions, and skip connections to segment images. You must use the trainNetwork (Deep Learning Toolbox) function (requires Deep Learning Toolbox™) to train the network before you can use the network for semantic segmentation.

Algorithms

• When you use either the xception (Deep Learning Toolbox) or mobilenetv2 (Deep Learning Toolbox) base networks to create a DeepLab v3+ network, depth separable convolutions are used in the atrous spatial pyramid pooling (ASPP) and decoder subnetworks. For all other base networks, convolution layers are used.

• This implementation of DeepLab v3+ does not include a global average pooling layer in the ASPP.

References

[1] Chen, L., Y. Zhu, G. Papandreou, F. Schroff, and H. Adam. "Encoder-Decoder with Atrous Separable Convolution for Semantic Image Segmentation." Computer Vision — ECCV 2018, 833-851. Munic, Germany: ECCV, 2018.

Extended Capabilities

GPU Code Generation

Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Usage notes and limitations:

For code generation, you must first create a DeepLab v3+ network by using the deeplabv3plusLayers function. Then, use the trainNetwork function on the resulting lgraph object to train the network for segmentation. Once the network is trained and evaluated, you can generate code for the deep learning network object using GPU Coder™.