This applet shows how an image can be scaled in 2 dimensions in three steps. It provides magnified views of individual pixels as well as a schematic illustration of how individual pixels contribute to a weighted average used to generate the color value of a single pixel in the scaled image.
The Three Step Scaling applet series was developed for use in an undergraduate computer graphics programming course and is appropriate chiefly for computer science students and anyone programming 2D graphics. It can also help non-programmers better understand commercial 2D software packages.
Click anywhere on the image on the left to magnify a small area of pixels to be examined. Click on individual pixels in the generated images to see how they are derived from the other generated images. The schematic diagram in the upper right-hand corner provides a view of how individual pixels are weighted to produce the final result. Other images can be selected through the menubar, as well as the size of the area being magnified. Note that, while at some times it may seem like a pixel should contribute to the resulting weighted average, the pixel center is not actually located under the filter and so does not, in fact, make any contribution.