Major Image File Formats Widely Used to Display Images on the Internet

When we see a digital photo, clipart, logos, or animation, that's visual representation of image data that are rasterized to pixels (picture elements) when displayed in a vector graphic display. The pixels are ordered as a grid (columns and rows), and each pixel consists of numbers representing magnitudes of brightness and color.

Image file formats differ in some ways, including how they represent image data (as pixels or as vectors), or in their compression technique. There are hundreds of image formats available, but only few that widely used to display images on the internet, as listed and briefly described below:

JPEG is an acronym for Joint Photographic Experts Group. JPEG and its variation/derivative formats is the most common image format used by digital cameras and other photographic image capture devices, as well as storing and transmitting photographic images on the internet, because JPEG favors smooth gradients and softer images.

JPEG commonly used lossy compression, meaning that some original image information is lost and cannot be restored. However, the degree of compression can be adjusted (typically 10:1 compression with little perceptible loss in image quality), allowing a selectable tradeoff between storage size and image quality.

A JPEG image is automatically decompressed when opened. JPEG format supports CMYK, RGB, and Grayscale color modes, but doesn't support alpha channels. 

Unlike GIF format, JPEG retains all color information in an RGB image but compresses file size by selectively discarding data. A higher level of JPEG compression results in lower image quality, and vice versa, a lower level of compression results in better image quality.

GIF is a bitmap image format that was introduced by CompuServe in 1987, compressed using lossless data compression method (LZW-compressed) to minimize file size and electronic transfer time, and commonly used to display indexed-color graphics and images (along with JPEG and PNG formats) in HTML documents over the internet and other online services. GIF format preserves transparency in indexed-color images; however, it does not support alpha channels.

Takes advantage of the format's lossless compression which favors flat areas of uniform color with well defined edges, GIF format are suitable for sharp-edged line art with a limited number of colors, such as logos, small animations, and low-resolution film clips.

GIF is not usually used as a format for digital photography because the format incapable of reproducing a greater range of color as JPEG (general limitation on the GIF image palette only 256 colors).

Controversy over GIF format licensing agreement in 1994 spurred the development of the Portable Network Graphics (PNG) standard; since then all the relevant patents have expired.

PNG is a bitmapped image format developed as a patent-free alternative to GIF. The format is used for lossless compression and for display of images on the World Wide Web. PNG format supports RGB, indexed-color, grayscale, and Bitmap-mode images without alpha channels. It preserves transparency in grayscale and RGB images. The format also supports 24-bit images.

The PNG format is a popular alternative to GIF images since it uses better compression techniques and does not have a limit of 256 colors. PNG gives a much wider range of color depths than GIF, including 24-bit (8 bits per channel) and 48-bit (16 bits per channel) truecolor, allowing for greater color precision, smoother fades. When an alpha channel is added, it is possible to provide color depths up to 64 bits per pixel (before compression).