In the previous article we learn some advantages of PNG images, but they were not all. Here are some other positive aspects of PNG format.
The way the images show up on the monitor screen of the viewer is also of great importance. JPEG accomplishes this with a top to bottom progressive display while PNG can use an interlacing scheme. If a PNG is not interlaced it is viewed progressively. PNG interlacing (formally known as Adam 7) begins by only reading a small percentage of all the data and filling in the empty spaces with an interpolated color value. The GIF format can also be interlaced, but the quality is not nearly as good, or fast as a PNG as GIF interlacing is only one-dimensional.
There are also some drawbacks of using the PNG images. They are as follows:
Although the PNG images support alpha channels but the unfortunate thing with alpha in PNG’s is that browser support is way behind the times, although slowly catching up. IE6 doesn’t support alpha-channels. Once a new version of IE comes out with this vital support, you should see the effect springing up on trendy designers’ sites across the web.
The PNG images also do not support animation. PNG can be made into multi-image files through the MNGextension of the format, but browser support is patchy for this format. Therefore the web designer has to stick with GIFs for creating animations.
As we have discussed earlier GIF images use LZW algorithm for compression but the PNG images do not use this technique. Therefore these image format becomes truly free. Not that you ever would have paid for your individual .gif images, but you no longer have to lead the guilty life of an intellectual property thief.
Because of the lack of patent and licensing issues, PNG has become the most attractive option of image format for website developers and Internet standards stalwarts who demand open standards. Because software developers do not have to negotiate a license to use LZW compression, they can charge a lower price for their software. And because open-source and free-software authors try to avoid promoting any software patents, the default image format for most free software projects is PNG.