2. In the mathematical concept, it is explained as follows: the original image is the image in a set, and the mapping consists of two sets. From one set to the other set through corresponding rules, the elements involved in the operation with corresponding rules are the original image, and the corresponding result of the operation is the image.
3. Note: Each picture has the original picture. This explanation is hard to understand. Let's take an example: let's set two sets A and B and the corresponding relation R between their elements. If every element in A to R has a unique element correspondence, then the correspondence R is called the mapping from A to B, where A is called the original image and B is called the image.