File extensions and file compression

File Extention
File extention is the file format of a certain file you save. You do this by putting a .*** at the end of your file name. This changes the type of file it gets saved as. Some examples are .png , .jpeg , .exe , .dmg and .txt. These file types are used for different things and you need to use a specific one depending on what your making it for. Some people use filename extentions to trick people into thinking its a harmless file where infact it contains a virus or malicous software.

File Compression
There are two different types of file compression which are "lossless" and "lossy". These are two ways to compress a file in different ways

Lossless
Lossless compression is a form of compression which you don't lose any information in the process. This has become more and more advanced as technology has. An example of this is when an image has area's of pixels the same colour, the data can be read as 100 blue pixels instead or blue pixel blue pixel.

Lossy
Lossy compression is the opposite to lossless as you lose data and quality whereas in lossless you don't. The benifit to lossy though is that the loss is acceptable. Depending on the file changes the amount of data can be lost with still able to have decent quality. An example of this is in JPEG images it works by rounding off the less important bits. In audio you use speech compression which is used for CD ripping.

Raster and vector images

Raster Images
Raster images are images which when you zoom in you can see each pixel. When you do this you then can get the colour value of each pixel using the red , green and blue scale. You can see it in this picture for example.Raster images usually use jpg , tiff , png ,psd and bmp file formats to save them to.

The problem with raster images is that the resolution is set. You cant scale it to a different size without a loss of quality. This is the complete opposite to vector images as they scale easily. They main use for raster images is photographs and photo-realistic images. Devices such as camera's and scanners produce a raster image since an image editor will work on pixels.


Vector Images
Vector images are mad up of paths and stokes. vector images are good because they keep their quality even if you zoom in. This is because vector images can be scaled to any size without loss of quality since raster are based on pixels and vector images arn't. The file formates vector images use though are normally wmf , psd , fla and ai.

Another advantage about vector images are that no matter what resolution the image is , it will always be the same file size which doesn't really matter any more since there's hard drives with terabytes of space now. For a vector image to be displayed or printed the device has to convert it into raster format before its able to render it.