What are Interlaced Images?
| Interlaced Images |
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Images that are displayed progressively as they download. Interlaced images appear to come into focus gradually in contrast to images that are not interlaced, which are drawn from top down as they download. To interlace an image is to specify how the image is loaded onto a website. Graphics are loaded one of two ways, interlaced (every other line the first time, then the other lines the second time) or non-interlaced (first line, then second line, then third line). The interlaced graphics appear on the net as the complete image first in low resolution, gradually improving until the entire image is loaded and displayed. Non-interlacing images appear in bands from top to bottom. Interlacing images is useful when trying to increase the apparent speed of image loading. When an interlaced format is used, the image first appears slightly fuzzy and then clears. This makes the image appear to load faster and increases the professional look of a website. When you use an interlaced graphic you get a pretty good idea of the picture content before it is completely drawn. Remember though that interlaced formats are usually larger than non-interlacing image files. The necessity of interlacing images is decreasing as as connections to the internet become faster. When using a cable modem or a dsl link, it is often impossible for surfers to notice the difference between an interlacing and non-interlacing graphic. However, this is a nice thing to do when building a website to be accessible to those with lower bandwidths. Most commonly gif 87a and 89a formats are interlaced. JPG's are smaller files designed for photographs. They load fairly quickly without interlacing and can be cleaner looking than gif files. There are several reasons why you would want to use a transparent image. The first being a graphical need to have an image blend with it's background as opposed to showing up as an ugly coloured square. A transparent image allows the background pattern to show through. The use of transparent images can reduce the "halo" or "glowing" effect sometime witnessed on websites. A transparent image is visually cleaner. |
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