Joint Photographic Experts Group (JPEG) format is commonly used to
display photographs and other continuous-tone images in hypertext markup
language (HTML) documents over the World Wide Web and other online
services. JPEG format supports CMYK, RGB, and Grayscale color modes,
and does not support alpha channels. Unlike GIF format, JPEG retains all
color information in an RGB image but compresses file size by selectively
discarding data.
A JPEG image is automatically decompressed when opened. A higher level
of compression results in lower image quality, and a lower level of
compression results in better image quality. In most cases, the Maximum
quality option produces a result indistinguishable from the original.
JPEG is the preferred file format for photographic images. In addition, the
JPEG format works well with subtle transitions in color, such as watercolors,
pencil or charcoal drawings, etc. The JPEG file format supports 24-bit
images (over 16 million colors).
Here are some other important features of JPEG images:
1. JPEGs use a lossy compression scheme; data is removed from the
image to make the file size smaller when compressed.
2. JPEG images allow for various compression levels, providing for the
adjustment of compression to best display the image without losing too
much of the image quality. Due to the various compression levels, it is
suggested that the original image be saved and used for editing
purposes; don't edit a JPEG image that has been compressed.
3. JPEG images are not interlaced; however, progressive JPEG images
can be interlaced.
4. JPEGs are saved with a .jpeg or .jpg extension.