How can I make transparent and interlaced GIFs for a Web page?
Transparent GIFs are used to eliminate the typical rectangular borders associated with most bitmapped images that appear on a Web page. The creator of a GIF image may set certain pixels within the bitmap to a color desiganted within the image file as “transparent”. When this GIF image is displayed by a Web browser the transparent pixels take on the color of the user’s display. This is identical to the blue screen effect found in chromakeying. GIF89a files are made transparent by the use of graphics file editing software (GIF87a files do not support transparency and must first be converted to the GIF89a format). Such software will set the transparency color flag and the transparent color index value of a Graphics Control Extension block within the GIF89a file. Any pixel set to the specified transparent color index value will take on the background color of the display device when displayed. Interlaced GIFs are used to give the user a idea of that an image looks like before all of the bi
