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Most images you see on the web are raster (bitmap) images. This means that they are made up of a bunch of little dots called pixels. The JPG and GIF pictures that we will learn about below are also bitmap pictures, in addition to the old BMP (Windows Bitmap), the standard TIFF, and the more recent PNG, etc. This means that the finer you want to make a picture, the more pixels you will need, and the more memory it will take up. This is why small pictures, or low resolution pictures (See the magnified picture below) load quicker, than pictures with a lot more detail.

Macromedia Flash introduced vector graphics for the web which is one of the reasons Flash became popular. Vector images, unlike raster images, are described by formulas and not created by pixels. Since an arc is an arc no matter how much you magnify it, the vector arc will always look round, and smooth. The size of a vector image does not affect the file size, which is why even slow modem computers can download dynamic Flash Animations faster than they can download static bitmap pictures. Notice what happened to the magnified bitmap picture...you start seeing the pixels that make up the picture.

Street Corner (72 dots per inch [dpi])
Street Corner (x 10 magnification)


JPG format is the best choice for Photographic material where every color our eyes can detect is important. The drawbacks for the JPG format are the bigger file size, and no transparent background option.

GIF format is usually used for images that need to be compressed (file size) or for images that do not use many colors like logos and image text. Other advantages of the GIF format include animation applications, and transparent background options.

JPG - Joint Photographic Experts Group
(24 bit True Color: 16.7 million colors)
GIF - Graphics Interchange Format
(Indexed Color: Max. 256 colors)

Bitmap vs. Vector Graphics

Spin vs. Spin

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