CamVid like Mask

Newbie alert
I want to make camvid like dataset for a problem. I am getting transparent images of those “objects” and mixing it other backgrounds , so that I can try with Unet or Tiramansu to do segmentation. Is it possible to can create mask from transparent images programmatically than manually annotating ?
Any code will be helpful.
Also ,any recommendation on the architecture will be great,

Thanks in advance

You should be able to load the image with the alpha channel and make the mask be 1 where alpha is not 0. Fastai does not support tiramisu out of the box so would recomment unet.