Not sure I understand what you mean by "resize". Lets say, for the simplicity sake, your original is 2400 x 3600 px and you crop it, keeping the same aspect ratio, to, say, 2000 x 3000... obviously, when you crop, you are changing the size, by definition. Are you saying you want to have the same file size, i.e., 2400 x 3600, even after cropping? If that is the case, you would need to uprez (resample) after cropping.