Which format to use?

There are two common graphic formats used on the internet - .jpg and .gif. Another - .png - is becoming popular but has yet to dent the market enough to use unless there is, for some odd reason, no choice.

In most instances, photos should be saved in .jpg (it stands for Joint Photographic Experts Group) format. It provides greatest compression with the least quality loss.

The .gif (Graphical Image Format) format is more versatile, and is best suited for drawn (by hand or computer) graphics and type. It is also the format that best takes advantage of anti-aliasing (to eliminate the "jaggies"), transparency (where the background is eliminated), multi-graphic animations, and dithering (the mixing of dots to form colors other than cyan, magenta, yellow, and black that you would normally see).

.GIF format comes in two compression levels, 87a and 89a. Only in 89a can users get transparency and animations.

The afore-mentioned .png format was created when it looked as though people would have to pay royalties for using .gif images. That goal has apparently subsided and, after all, as the commercial says, "Shouldn't the internet be free for everyone?"

The short answer is "Yes." The longer answer is "Yes" if the graphic is in .gif format, but not if it is in .jpg format.

The reason for that is because the content of .jpgs is such that it doesn't produce the jaggies. It might seem that way if the subject of the photo has a bad complexion, but the photo itself will not.

Because drawings are made of pixels on the screen, even a straight line if angled will have a stair step look (that's the jaggies) and for best appearance needs to be anti-aliased.

That can be done within the graphic program used in most cases, and it will make the graphics appear smoother and more like a real picture.

Should graphics be dithered?

Dithering occurs when other colors are used to blend those in a graphic and create a smoother transition of color. Dithered graphics will be larger because they do not compress as much as those not dithered.

Using .jpgs, the practice of dithering is essentially useless because there is no pixel by pixel control. In .gifs, however, it can improve the graphic's display.

Dithering is a valuable tool to use to create gradient colors and flat color areas.

Should graphics be interlaced?

This will help graphics appear more quickly on the page, but they won't look all that good at first. It involves the display to expose lines of the graphic as it loads.

This is intended mostly for .gifs, because there is a progressive .jpg format that actually ends smaller than a normal .jpg.

Using interlaced .gifs means the designer is making a choice between faster load times or better first appearance. That is up to the individual designer.

Can I use transparent images?

Transparent images are one of the fun things for a designer to use on the internet. Photos in .gif and .png format can be transparent, but .jpg images cannot.

Transparent .gifs are also great to use as animations. In that way, the user can have the animation appear on the background of choice.

There are several graphic programs that designers can use to make transparencies, and some HTML editors even have that ability as part of their features.

Using transparent images eliminates the square look that web sites often have, because even though the image is square or rectangle, the viewer only sees the image and not the box surrounding it.

Should filters be used?

While they can change the storage size of a file, they definitely can and, in many cases, should be used. There is a virtual cottage industry in producing filters, most frequently for Photoshop.

It is those filters that allow designers to provide special effects that can help make a photo more interesting, not to mention improve the look of a web site.

In some cases, filters help maintain a theme of a site; others help the viewer focus on what is important in the graphic.

Some filters enable users to play with the gamma of a graphic, the contrast, and many other components.

Processing and Using Photos for the Internet
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