Pictures getting automatically cropped

When I try to open certain pictures, either through preview, photo, or anything else, it is cutting out parts of the pictures. Looking at the icon in my finder window the picture looks completely normal with all parts there. However when I actually open it, suddenly parts gets cropped off (and I have never edited/cropped it or anything before to make it do this). I tried copying the picture and pasting in word to see if the rest of the picture would show up there, but it still doesn't. The weird thing is that the image size shows that the rest of the picture should still be there, but the bottom half is still just blank space. I don't know how to fix this or prevent it from happening again.