Image sprites are used in numerous web apps where multiple images are used. Rather than include each image as a separate image file, it is much more memory and bandwidth-friendly to send them as a single image, so the number of HTTP requests is reduced.
CSS gradients are new types of <image> added in the CSS3 Image Module. Using CSS gradients lets you display smooth transitions between two or more specified colors. This lets you avoid using images for these effects, thereby reducing download time and bandwidth usage. In addition, because the gradient is generated by the browser, objects with gradients look better when zoomed, and you can adjust your layout much more flexibly.
The <image>CSS data type represents a 2D image. There are two kinds of images in CSS: plain static images, often referenced using a URL, and dynamically-generated images like gradients or representations of parts of the tree.
The image-renderingCSS property provides a hint to the browser about the algorithm it should use to scale images. It applies to the element itself as well as any images supplied in other properties for the element. It has no effect on non-scaled images.
The CSS linear-gradient() function creates an <image> which represents a linear gradient of colors. The result of this function is an object of the CSS <gradient> data type. Like any other gradient, a CSS linear gradient is not a CSS <color> but an image with no intrinsic dimensions; that is, it has neither natural or preferred size, nor ratio. Its concrete size will match the size of the element it applies to.
The CSS radial-gradient() function creates an <image> which represents a gradient of colors radiating from an origin, the center of the gradient. The result of this function is an object of the CSS <gradient> data type.
This works similarly to the standard radial gradients as described by radial-gradient(), but it automatically repeats the color stops infinitely in both directions, with their positions shifted by multiples of the difference between the last color stop's position and the first one's position.
The CSS repeating-linear-gradient function creates an <image> consisting of repeating gradients. It works similarly to the basic linear gradients as described by linear-gradient(), and takes the same arguments. However, it automatically repeats the color stops infinitely in both directions. The color stops' positions shift by multiples of the length of a basic linear gradient (the difference between the last color stops' position and the first).