- Interlacing (bitmaps)
Interlacing is a method of encoding a
bitmap image such that a person who has partially received it sees a degraded copy of the entire image. When communicating over a slow communications link, this is often preferable to seeing a perfectly clear copy of one part of the image, as it helps the viewer decide more quickly whether to abort or continue the transmission.Interlacing is supported by the following formats:
*GIF stores the lines in the order 0, 8, 16, ..., 4, 12, ..., 2, 6, 10, 14, ..., 1, 3, 5, 7, 9, ....
* PNG uses theAdam7 algorithm
*JPEG andJPEG 2000
* PGFInterlacing is also known as "progressive" encoding, because the image becomes progressively clearer as it is received. Note that this terminology has nothing to do with
interlace d andprogressive scan CRTsDubious|date=March 2008.For example: Interlaced GIF is a GIF image that seems to arrive on your display like an image coming through a slowly-opening
Venetian blind . A fuzzy outline of an image is gradually replaced by seven successive waves of bit streams that fill in the missing lines until the image arrives at its full resolution.External links
* [http://nuwen.net/png.html Comparison of GIF and PNG interlacing]
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