IMAGE COMPRESSION



Introduction:
· Concept of image compression;
· Data compression is the technique that is used to reduce larger data files into smaller file size.
· Images compression is the action of reducing the size of image by increasing its firmness or compactness as with the aim of reducing the space.

·Historical background of image compression.
The historical background of image compression started to become a challenge when digital images were supposed to be transferred from one point to another. In digital image data it is important to reduce the amount of information by using a sparse representation of the image. This is to be done in a very systematic way so as at least to main its quality as not deform its original shape and quality.
The performance of any image compression scheme depends on its ability to capture characteristics features of such image, such as sharp edges and fine textures, while reducing the number of parameters used for its modeling.


· Importance of image compression.
(i). Makes transfer of images through network faster.
(ii).Maximizes space for storage of data images.
(ii). Saves space in storage devices.
(iii). It saves time for image downloaded

· Types of image compression are categorized into:
o Lossless – Compression technique that retains all its original data, such as there is no loss of data after being compression. The size of the file is a bit larger in size if compared to lossy technique and also have better image quality compared to lossy technique.
oLossy – Compression technique in which there is a permanently loss of data after being compressed. Data image can not be decoded to original format and have the same quality. In this technique the fill can have smaller size compared to Lossless technique, also the quality of picture has slightly lower quality compared to lossless.

· There many images format, these are some of image format that are widely used:-
o TIFF (Tagged Image File Format).
o JPEG (Joint Photographic Experts Group).
o GIF (Graphical Interchange Format).
o PNG (Portable network graphics).
o BMP (Bitmap).
o PSD (PhotoShop Document).

· There are many types of images such as:-
DCT is the technique for converting signal into elementary frequency components.
(a). DCT- based image compression relies on two techniques to reduce the required
data to represent the image. These are:-
o Quantization-The process of reducing the numbers of possible value of a quantity thereby reducing the number of bit needed to represent it.
o Entropy coding-Is the technique for representing the quantized data as compactly as possible.

· Tools for image compression.
The tools that can be used in image compression vary from free source to proprietary. Such tools includes;- GIMP free source software, Adobe Photoshop and JPG-seizer.

· Important tips when compressing image:
· In compressing an image, start from the original image since compression from compressed image leads to poor image quality.
· Do not save to the new format if you think you need to still proceed in compressing and image.

· Advantages of image compression includes:-
o To Reduce the data storage requirements
o To Reduce the time for images downloaded
o For E-mail attachment
o For use in Web pages
o In Photo sharing websites

· Disadvantages of image compression.
o Reduce reliability of image records
o Reduction of information or bits
o Time consuming.
o Disruption of data properties

Conclusion;.
The image compression is very important in IT technology regardless of few discussed disadvantages that is having.