This is true only if the source image is smaller than the destination image. In the article, the source image is shown as the same size as the destination, and includes a large white border that can be clipped without the inner image being affected.
In the event that the destination buffer is much larger than the source, that additional computation is trivial (it's the same calculation that's already being done for each and every pixel). As it only needs to be additionally done on the corners, not per-pixel, the additional time spent should be quite minimal.
The shearing method in the article is genuinely clever and totally cool, but I just can't shake the feeling that even on 1980s hardware, this method would be better. On modern hardware, there's no question, it's still used to this day. Nowhere near as cool, though.
In the event that the destination buffer is much larger than the source, that additional computation is trivial (it's the same calculation that's already being done for each and every pixel). As it only needs to be additionally done on the corners, not per-pixel, the additional time spent should be quite minimal.
The shearing method in the article is genuinely clever and totally cool, but I just can't shake the feeling that even on 1980s hardware, this method would be better. On modern hardware, there's no question, it's still used to this day. Nowhere near as cool, though.