What is PNG image?

by Karthikeyan 2010-01-28 20:09:12

What is PNG?

PNG is an image format that combines the best features of GIF and JPG/JPEG, the traditional and most common image formats used on the World Wide Web. PNG is supported by virtually all major and minor browsers that are in use today.

* JPEG format approximates the original picture, so the quality can be quite low, but it allows the images to be significantly smaller in file size than the equivalent raw image (pixmap or Windows Bitmap). JPEGs do not support Transparency, but images can have up to 16 million colours. Athough the compression technique uses approximation, for natural photographs, JPEG compression usually produces the smallest file size of any of the standard image formats with the approximation being almost undetectable to the naked eye. However, GIF is more traditionally used when pictures contain large areas of the same colour, as the approximation used by JPEG becomes quite noticeable. JPEG does not support multiple image layers to allow animation, but its related format - MPEG - does.
* GIF format reduces the file size of the original image by recognising patterns in the raw image data, effectively making a zipped version of the image. This means the displayed image is identical to the original but requires the image to have a maximum of 256 unique colours. GIF format allows one colour to represent 100% transparency (known as binary transparency). GIF also supports multiple image layers to allow animation.
* PNG format compresses images in a similar way to GIF, but images can have up to 280 thousand billion unique colours (normally, a maximum of 16 million colours are used). PNG also supports binary transparency, as well as full Alpha, meaning that each pixel of the image can also have one of 256 different levels of transparency (or 65 thousand levels if you really want to). PNG format produces files with approximately the same file size as the equivalent GIF image, assuming they have the same number of colours. PNG does not support multiple image layers to allow animation, but its related format - MNG - does.

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