Scaling is also known as Resize. Sometimes, Resample is even called scaling, which is not entirely unreasonable. Image scaling refers to the computer graphics process which increase or decrease the size of a digital image. As a matter of fact, an image can be easily scaled by an image viewer or editing software. In addition, an image can also be scaled automatically by a program, which can greatly help the image to fit into an area of different size without efforts. People can make use of a lot of methods in order to reduce an image. However, the most popular way adopted by people is a type of sampling called undersampling, which can help to maintain the original quality. It is more complicated to enlarge an image as there is larger area to be filled with more pixels.
Generally speaking, scaling is a non-trivial process which involves a trade-off between efficiency, smoothness and sharpness. With bitmap graphics, the pixels forming the image will become more and more visible when the size of the image is being reduced or enlarged, which can make the image seem “soft” if the pixels are averaged or jagged.
In effect, scaling will not change the image pixels in any way. To be honest, scaling will only change the single number of dpi (ppi), a number simply stored separately in the image file in an arbitrary way. The only equipment makes use of it is the printer. What’s more, it only changes the size the image will print on paper. The images on the computer screen will not be influence by the number at all. Actually, the camera can never know how people want to print the image, and thus just makes up a number. As a result, people are supposed to fix the number before printing anything.