This is Words and Buttons Online — a collection of interactive #tutorials, #demos, and #quizzes about #mathematics, #algorithms and #programming. Image interpolation is guessing pixels between pixels. You can go without, but then when you upscale your image or do any other image transformation, you'll see square pixels. Here is the image to play with. The thing is interactive, you can control the frame with your mouse or your fingers. And here are the square pixels. You can make the picture nice...