Image Interlacing
Interlacing is a techniques that allows an image to progressively display itself in a browser as it downloads. The image will appear in stages over the period of downloading time. This action makes your pages more accessible to users with slower Internet connections.
Stander image formats are read from top to bottom. The top of a non interlaced image will appear after the browser has read 50 percent of the image. The bottom half will render some time later.
A non-interlaced image can remain invisible or incomplete for some time to a user who is downloading the image across a slow connection.
By contrast, an interlaced image appears to fade in as it renders in browser because it is interpreted differently. An interlaced image is repeatedly scanned from left to right. The first pass will render roughly 13 percent of the entire image. The second pass delivers 25 percent, and then continues in 25 percent increments until the image renders completely. During this precess, the full image will at first appear fuzzy, but will continuously sharpen.
The only web-ready image file formats that support interlacing are GIF and PNG. Both GIF formats, 87a and 89a, support interlacing. You can create an interlaced image by configuring an image file in a graphics-editing application and saving it as a compatible file type.
Tags: image interlacing
