The four axis conventions
Read every convention as a sentence:
HWC— height × width × colourCHW— colour × height × widthNHWC— examples × height × width × colourNCHW— examples × colour × height × width
scikit-image and most image files give you HWC. PyTorch wants NCHW. TensorFlow wants NHWC. None of them is right or wrong; they simply disagree, and you have to know which one you are holding.