Images
From JumbaWiki
There are many different image file formats, designed for different purposes. This article discusses the most common image types found on the web.
Contents |
Common web image formats
JPEG
JPEG is an efficient lossy image file format, particularly suitable for photographic images. JPEG stands for Joint Photographic Experts Group, the name of the committee who created the standard. JPEG files usually have the extension .jpg, though .jpeg, .jpe, .jfif and .jif are also used.
GIF
GIF (Graphics Interchange Format) is a lossless indexed colour image file format that can include frames and timing (animation). It is restricted to a maximum of 256 'indexed' colors, so is best for line drawings and other textual or iconic graphics with large areas of a single colour.
PNG
PNG (Portable Network Graphics) is a lossless image file format that can contain a 24-bit alpha channel for transparency/translucency. PNG was developed as a replacement for the GIF format, and often produces better quality images and smaller file sizes than GIF. However PNG does not support animation. PNG also reproduces good quality photographic images, but their file size is much larger than the lossy JPEG format.
Transparency / translucency
- or this info could be under GIF, PNG headings
Raster images, such as GIF and PNG files, can be made with transparency, so that the background behind such images is visible. This is useful when an image is resting on top of a background that might be another image, or a colour which is not constant (e.g. themes). There are two types of transparency - by setting a transparent colour, or a transparent alpha channel. The first type is often referred to as pixel transparency (each pixel is transparent YES/NO - supported by GIF) and second type is often called alpha transparency (each pixel has a degree of transparency - allows blending - supported by PNG). JPEG images do not support transparency.
Using images on your site
Resizing
Thumbnails
See also
- Indexed colour
- Animation
- List of file formats
- Lossy, Lossless
- Transparency
- How to create an icon file (ico)
