Aspect Ratio

Another important component of resolution is aspect ratio, or the ratio of the pixel’s width to the pixel’s height. Not all images are square. In 640 x 480, 800 x 600, and 1,024 x 768 mode, the aspect ratio is 1:1 or 1, meaning the pixels are perfectly square.

In 320 x 200 mode, the aspect ratio is 1.21:1 or .82, meaning the pixels are higher than they are wide. If you create an image in 320 x 200 mode and display it in 640 x 480 mode, it will appear slightly squashed, since the pixels are about 20% shorter. See Figures 3.11 and 3.12 and notice the distortion in the image.

Figure 3.11 Here is an image created at 320 x 200 dots per inch.

Figure 3.12 Here is the same image displayed in 640 x 480 mode.