Images for the Web

The two most used image formats on the Web are GIF and JPEG. There is also the PNG format. These format sometimes have sub-formats (GIF87, GIF89a, Progressive JPEG and so on).

GIF is a bitmap image format on 256 colors with sequence-compressed representation, which generates small size of image files for illustrations and icons, which usually has homogeneous coloring. It supports interlaced image, transparence and animation (multi-image).

JPEG - Joint Photographic Experts Group is a 24-bit (true-color, 16M colors) image format, represented using compression with loss. This usually produces reduced files for photos and complex images. The compression rate can be configured: the greater the compression, the smaller the resulting file, but also greater is the quality loss related to the original image.

Another format, PNG - Portable Network Graphics, is a great promise, specially now that Netscape and Microsoft Internet Explorer browsers support this image format. PNG files usually are smaller than the corresponding GIF and have better quality than JPEG, besides PNG is a widely more flexible format. And there's also a very importat point: the compression algorithms used in the PNG format are public domain, in opposition to the GIF format, which compression method is patented.

GIFs & LZW Patent

Animated GIFs

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