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JPEG has been known as an image format that can be seen to be commonly used in representing Images. This format has been known to have compressed and lossy image data. This characteristic enables images to be saved with minimum file size besides maintaining a reasonable and good image quality. Taking less size than other image formats has been the main reason for different devices to use this image format. This image format can also save images with high quality by using lossless compression.
JPEG
Full form of JPEG is Joint Photographic Experts Group. JPEG is mainly an image format that can be seen to be widely used in almost all kinds of devices. The JPEG name came from a committee that has created a unique standard for images which was published in 1992. Based on its full form, the “Joint” part was developed in 1986 with standards like CCITT SGVIII and ISO TC97. JPEG has also been known as a still image coding standard. Development of JPEG standards has concluded after examining different transform coding techniques. After examining all these transform coding techniques, Discrete Cosine Transform (DCT) technique is selected as it has been seen to be the most efficient compression technique among all. JPEG has also been seen to be one subgroup of “IEC/ ISO Joint Technical Committee 1, Subcommittee 29, Working Group 1” and has also been seen to be titled as “Coding of Still Pictures”. The JPEG standard was first approved in September 1992 as Recommendation T.81 of ITU-T and was approved in 1994 as 10918-1 of IEC/ ISO.
JPEG standards have been seen to specify codec of an image. Codec of an image has been seen to define the compression process of that specific image which depicts how an image has been compressed in a byte stream and then can be decompressed back to that image. EXIF and JFIF standards have been seen to define image formats which have been seen to be commonly used which can be helpful in interchanging JPEG compressed images. JPEG standards have been seen to be formally composed of different IEC/ ISO 10918 standards which consist of different parts. Part 1 of this standard contains guidelines and requirements; Part 2 has been useful in testing software compliance to Part 1. Part 3 of this standard has been seen to include different extensions which can be helpful to improve Part 1 of this standard. This Part has also been seen to include “Still Picture Interchange File Format (SPIFF)”. Part 4 of IEC/ ISO 10918 standard has been seen to govern registration of SPIFF tags, SPIFF profiles, SPIFF colour spaces, SPIFF compression, APPn markers and JPEG profiles. It has also been seen to govern registration of different authorities (REGAUT) which are registering different methods or parameters to extend JPEG. Part 5 of this standard has been seen to consist of interchangeable format of JPEG (JFIF) which has been seen to be a popular format encoded by JPEG. Last Part of this standard has been seen to be specifying a group of features and applications for different printing systems.
Compression Technique of JPEG
JPEG has been seen to be using Lossy compression technique which has been known as a data compression process that reduces size of that respective file by eliminating arbitrary data available in that file. Using this technique has been proven to be useful in reducing file size of a JPEG image however; image quality can be seen to degrade equally. Arbitrary data which can be seen to be removed in this compression technique has been seen to be depending on the compression algorithm. This has caused data within a file to change after compression technique has been used; however, data loss cannot be noticed even when resolution of that particular image has been reduced. Lossy compression has been seen to be noticeable in cases when a file has been modified and resaved multiple times. If an image that has been modified and resaved multiple times and one which has not been modified or resaved multiple times are compared, data loss can be noticeable. This happens due to use of lossy compression each time that respective image has been modified and resaved.
Lossy compression has been seen to use different techniques in removing arbitrary data. These techniques include Color Reduction, Fractal Compression, Chroma Subsampling, Vector Quantization and Transform Coding. These techniques of lossy compression techniques have been useful in reducing file size of a JPEG image in order to send that file with more ease.
Conclusion
This article has concluded on JPEG, which is a widely used image format. A brief background of JPEG standard has been concluded here. Different features of JPEG have been concluded in this article. Different standards on which JPEG standard has been established have also been concluded in this article. Compression technique used in this standard has been concluded here. Some Frequently Asked Questions with their respective answers have been concluded in this article. This article has been done in order to provide a proper understanding of JPEG standards.
