Images on the Web

JPEGs
A .jpg or .jpeg image (Joint Photographics Experts Group) is a heavily compressed raster image (10:1), created using lossy compression. .jpg images are commonly used on the web for images with a large range of colours, such as photographs and artwork.
This is an example of a .jpg image.




GIFs
A .gif image (Graphics Interchange Format) is a raster image format that supports 8 bit colour (256 colours), compressed using the lossless LZW format. .gif is suitable for use with logos or graphics, simple images with areas of a single colour.
This is an example of a .gif image.



Bitmaps
A bitmap image is an image made of a spatially mapped array of bits or pixels. Bitmaps normally contain 1 bit per pixel. .jpg, .gif, .tiff and .png are all compressed formats of bitmap images. Bitmap images are used for the full resolution (un-compressed) display of images by software and operating systems.
This is an example of a bitmap image.

Resolution
The ideal resolution for images on the Internet is 72 dpi.