Graphics for the web: GIF Format
| Category: Internet Tips | Date: 2002-06-24 |
The GIF (Graphics Interchange Format) format was invented in 1987 by Compuserve to allow images to be displayed. This format allows for 256 colors (which was a lot at the time), compression, interlacing and animation. It is a very powerful format, suitable for many different types of images.
Due to the limited number of colors, GIF is primarily useful in images with a distinct separation of colors. A cartoon, for example, is ideal for the GIF format.
When you save an image in GIF format, you have the option to specify how many colors will be saved. By doing this you can decrease the size of an image even further. All of the tools which are available to optimize GIF images work by reducing the number of colors to the bare minimum. This can produce astounding results in the size of the finished file.
Unlike JPEG, GIF uses a non-lossy compression algorithm. This means that images do not loose bits when they are decompressed. In order to accomplish this, GIF uses a proprietary encoding/decoding scheme called LZW (Lempel Zev Welch). LZW is an excellent compression algorithm which typically results in very small files (in comparison to fully expanded BMP files).
This compression method is actually the cause of a bit of controversy. As it turns out, LZW is owned by UniSys, and over the past few years they have made some attempts to collect licensing fees for products which save in the GIF format. These attempts have had mixed results, and has caused the development of a new non-proprietary standard called PNG.
You may indicate that a color in a GIF image is transparent, meaning whatever is below the image will show through.
The GIF89a standard included animation, which basically allows multiple images to be included in a single GIF file. In that image you can specify the timing that the frames are shown and whether or not the animation stops or loops forever.
Interlacing is a cool feature which allows graphics to be "faded in". Initially a very low quality image is displayed, and bits are slowly added as the entire image is received. GIF supports this feature, which is useful for displaying very large images quickly.
An interesting albeit little known fact about GIF images is that they can include comments, which take up space and make the graphic larger. There are a number of products which will remove these comments. I found that the freeware program called GIFclean is simple to use and works well.
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Richard Lowe Jr. is the webmaster of Internet Tips And Secrets. This website includes over 1,000 free articles to improve your internet profits, enjoyment and knowledge.
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Due to the limited number of colors, GIF is primarily useful in images with a distinct separation of colors. A cartoon, for example, is ideal for the GIF format.
When you save an image in GIF format, you have the option to specify how many colors will be saved. By doing this you can decrease the size of an image even further. All of the tools which are available to optimize GIF images work by reducing the number of colors to the bare minimum. This can produce astounding results in the size of the finished file.
Unlike JPEG, GIF uses a non-lossy compression algorithm. This means that images do not loose bits when they are decompressed. In order to accomplish this, GIF uses a proprietary encoding/decoding scheme called LZW (Lempel Zev Welch). LZW is an excellent compression algorithm which typically results in very small files (in comparison to fully expanded BMP files).
This compression method is actually the cause of a bit of controversy. As it turns out, LZW is owned by UniSys, and over the past few years they have made some attempts to collect licensing fees for products which save in the GIF format. These attempts have had mixed results, and has caused the development of a new non-proprietary standard called PNG.
You may indicate that a color in a GIF image is transparent, meaning whatever is below the image will show through.
The GIF89a standard included animation, which basically allows multiple images to be included in a single GIF file. In that image you can specify the timing that the frames are shown and whether or not the animation stops or loops forever.
Interlacing is a cool feature which allows graphics to be "faded in". Initially a very low quality image is displayed, and bits are slowly added as the entire image is received. GIF supports this feature, which is useful for displaying very large images quickly.
An interesting albeit little known fact about GIF images is that they can include comments, which take up space and make the graphic larger. There are a number of products which will remove these comments. I found that the freeware program called GIFclean is simple to use and works well.
About the Author
Richard Lowe Jr. is the webmaster of Internet Tips And Secrets. This website includes over 1,000 free articles to improve your internet profits, enjoyment and knowledge.
Web Site Address: http://www.internet-tips.net
Weekly newsletter: http://www.internet-tips.net/joinlist.htm
Daily Tips: internet-tips@GetResponse.com
Claudia Arevalo-Lowe is the webmistress of Internet Tips And Secrets and Surviving Asthma. Visit her site at http://survivingasthma.com
List of articles available for reprint: article-list@internet-tips.net
email - articles@internet-tips.net
url - http://www.internet-tips.net
articles@internet-tips.net
http://www.internet-tips.net
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