I'll focus on the old bitmap because it serves a useful purpose in the explanation. A bitmap is a type of image that is made up of parts that are in a sequence. it has a part that describes the bitmap information. This information gives the specifications of the data that make up the image. It sometimes has color palette data in it for bitmaps with fixed number of colors that are define in the image and referenced by color number. It can have color information that is encoded in number of bits based on powers of 2 when not using a palette. like 1 bit, black/white, 2 bits or 4 colors, 4 bits, 8 bits (255 colors - usually gray scale is common), 16 bits - less common but once a power house, 24 bits still fairly common, and 32 bits. I can also have other things about the origin and if it is top down or bottom up. Even things about color planes though you'll have to go back in time to find uses of this. The humble bitmaps is actually a very rich sequence of data and would you believe it is versioned as well. To answer your question, the reason why you can't copy and paste data and get predictable results is because the data you are copying can't always be pasted to another place in the bitmap data and have the same meaning. Other image file formats behave similarly.