Did you make any progress on this, @awezmm? I'm looking to do the same thing as you, with Resnet-18, too, and I got stuck at the same point as you so Googled & found your question here!
So far I've followed the (adapted for resnet) instructions of this tutorial:
So for resnet that'd be:
pretrainedFolder = fullfile(tempdir,'pretrainedNetwork');
pretrainedNetwork = fullfile(pretrainedFolder,'deeplabv3plusResnet18CamVid.mat');
data = load(pretrainedNetwork);
net = data.net;
layers = net.Layers
This shows me all 101 layers for resnet. For me, personally, I'd like to classify 2 things (background or object) so I've edited the final layer to give me 2 things, but I'm pretty sure I need to do more layers and unsure which ones:
layers(101) = pixelClassificationLayer;
& now I'm stuck! I'll comment r.e. letting you know any progress I've made... I'm going to look into the structure of resnet more, now, to get a better understanding of what I need to change and how...