Information about JPG
|Joint photographic experts group
|The JPEG group
|Files stored in this format are small in size that is why they can be uploaded and downloaded with ease. It takes less time over the internet to upload and download due to smaller size which results in saving of bandwidth. This extension is compressed using a lossy algorithm that is why there can be a reduction in the quality of the photograph. It has the ability to compress the file to one-tenth of its original size. It is widely used in emails and also when images are to be posted on websites. Digital Cameras and other photographic image capture devices widely use this JPG format. The paintings and photos of realistic scenes that have smooth variations of colour can be best illustrated by this format.
|A technique used in JPEG format to compress files is lossy compression which is based on DCT (Discrete Cosine Transform) as it is the most practical Mathematical operation. The DCT actually converts each frame of the video from the spatial domain to a frequency/transform domain. It discards the information of high frequency that has sharp transitions in intensity as well as in colour hue. Furthermore, this standard defines a codec which tells how an image can be encoded into a stream of bytes and decoded back into an image. The files can be compressed in the ratio of 100:1 but that would result in the poor quality of an image. Therefore, to retain the quality of a photo, a file should be compressed till 20:1 ratio not more than that.
Information about GIF
|Raster Image file
|Graphics Interchange Format
|GIF is an image format which is known worldwide and it is used as a second option after JPEG. It offers high portability between OS(Operating Systems) and applications. Each picture can support up to 8 bits per pixel, as a resultant, it enables an image to have a separate palette of up to 256 distinct colours that are taken from the 24-bit RGB colour space. Furthermore, it is commonly used for web graphics, logos with solid colour and also for animated images. These files are saved as ‘animated GIFs' and it displays general animations on websites. Besides this, this format has the capability to blend varied colour backgrounds due to the presence of transparent pixels. It should be noted that pixels should be either fully transparent or opaque so that it doesn’t result in the faded picture.
|GIF is an inadequate format for colour photographs due to palette limitations. It enables an independent palette of up to 256 colors for a solo frame. These files are compressed using a lossless data compression algorithm known as LZW( Lempel-Ziv-Welch) and this algorithm was created by Abraham Lempel, Jacob Ziv and Terry Welch. It removes the unwanted colours that are not in use to compress raster data. The maximum limit which is permitted for colours is 256 and the minimum is 2 (black and white). Apart from this, it has a fixed-length header which gives the version and pixel dimensions are provided by the ‘logical screen' descriptor.