What term refers to the mathematical ratio of a pixel's width to its height in a digital image?

The term that refers to the mathematical ratio of a pixel's width to its height in a digital image is known as pixel aspect ratio. This concept is crucial in digital imaging as it defines how pixels are shaped in relation to each other. In many digital formats, especially in video and animation, understanding pixel aspect ratio is essential because it influences the final visual appearance of the images when displayed on screens.

For instance, in standard displays, pixels are often square, leading to a 1:1 pixel aspect ratio, meaning the width and height are equal. However, in other cases, particularly with non-square pixels used in certain video formats, the pixel aspect ratio can vary, affecting how the image is rendered. This clarity helps in achieving the correct visual alignment and quality when editing or compositing images in filmmaking and animation.

Other choices like pixel density refer to the number of pixels packed into a specific area (often related to resolution but different from the shape of the pixels), image resolution measures the total number of pixels in an image (such as width by height, but not the individual pixel shape), and aspect ratio generally refers to the ratio of width to height of the entire image or screen, rather than that of an individual pixel.