LZW compression is very happy to turn that into a succint representation.Ī smaller, thinner, sexier GIF. If the majority of the frame is transparent, the majority of these rows will just be the transparent pixel repeated over and over again. With LZW, however, those transparent pixels become hugely advantageous over just storing the full frame. If we didn't include LZW, the transparency optimisation trick alluded to above wouldn't make anything smaller.Įach of those transparent pixels has to be recorded in the GIF. These symbols are placed whereever you meet repetitive data.Īnnoyingly enough, LZW compression was also one of the major issues with GIF in the olden days: the patent for it expired in 2003. LZW compresses by creating a dictionary of commonly occurring sequences and replacing them with a shorter symbol. One of the other advantages of GIF is that the images are compressed using the lossless Lempel-Ziv-Welch (LZW) technique. GIF doesn't support semi-transparency (like that fancy young PNG), but it does support binary transparency.īinary transparency is simple: either you see the colour or you don't. One of the colours you can select is transparent. Wouldn't it be nice if you could just paint the difference between this frame and the last? Uncompressed GIF animations store the full frame for each and every image.Īs you might guess, that gets pretty large pretty quickly. Instead, GIF uses an interesting little hack called Transparency Optimisation to optimise animations. GIF didn't have fancy techniques like spatial image compression or temporal motion compensation like these fancy new video formats. Other formats have come and gone, but nothing has replaced the vehicle of the lolcats, our beloved GIF. The lolcats are probably what made it so resilient to change. It has been plagued by lawsuits, poor algorithms, poor defaults, and lolcats.Īctually, to be fair, I shouldn't be dissing the lolcats. It was introduced in 1987 and only supports 256 colours in an image. GIF, if you didn't know, is a most marvelously strange image format. You've pondered this question for the longest time.ĭid I accidentally poke holes in my RAM again? You likely ended up with a horrible, strange looking freeze frame. Have you ever posted an animated GIF to an application or website that didn't like the idea of motion? The Mystery of the Spotty Animated GIF March 21, 2013
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