Worked like a charm =) Thanks!
I resorted at some point to transform it back to a PIL Image which was not the prettiest way, here it is anyway x.x
from PIL import Image
import torchvision.transforms
import torchvision.transforms.functional as TF
rgb_img = TF.to_tensor(rgb_img) # rescale it 0<..<1
rgb_img = rgb_img.type(torch.uint8).squeeze(0)
#rgb_img = rgb_img.type(torch.FloatTensor)
img = torchvision.transforms.ToPILImage()(rgb_img)
im = Image.fromarray(img)
img.save("metamorphosis.jpeg")