I gave the crop function another try - and have a further suggestion for improvement of the cropping. When crop area includes some empty spaces without input image pixels and crop icon is pressed, the crop rectangle always auto-sizes to exclude the empty space. This is not always desirable, as empty space is likely pre-selected by the user. So if there is an attempt to fine-tune crop selection, previous user input gets overridden by auto-sizing with exclusion of the empty space.
Although auto-sizing is a useful function, it would be nice to be able to bypass it, may be clicking crop with a Shift key?