PhotoPlus X2 User Guide - Serif

Image formats for the web
Making Images for the Web 165
PhotoPlus can import and export most types of graphics file which you’re likely to
encounter. In order to "publish" PhotoPlus Picture (SPP) files, you will have to
export them into one of the widely used formats.
One of the main uses for PhotoPlus is to produce graphics for use on the web. For
pictures and animations, the two prevalent formats are .GIF (for both) and .JPG
(just for photos). A newer format, .PNG, affords excellent compression and
variable transparency but older browsers may not support it.
“Performance” may seem like an odd aspect of graphic design, but it’s actually one
of the key factors in designing for the Web. Among other things, it means load
time: how long it takes for your photo to display completely in a Web browser. In
practice, it’s hard to measure. Things like connection bandwidth and server speed
all play a part, although less so with the rollout of high-speed home broadband
services continuing apace.
The PhotoPlus Export Optimizer (see p. 193) will greatly help you in reducing file
sizes as far as possible while maintaining image quality.
.GIF format
The .GIF (Graphics Interchange Format) file format is universally supported in
Web browsers for both static and animated Web graphics. It's a lossless format
(there's no image degradation) with excellent compression but a limitation of 256
colours. Use it for non-photographic images with sharp edges and geometrics—for
example buttons, bursts, decorative elements, and text graphics. It's suitable for
greyscale photos as well.
The .GIF format supports "binary" transparency. That is, any portion of the image
may be either fully opaque or fully transparent. Typically, GIFs use transparency to
eliminate the box-shaped frame around the graphic that would otherwise be
present. Thus elements with rounded edges, such as characters or shapes, preserve
their contours over any background colour or pattern.