Raster Image
Raster images are all digital and are made from pixels in a
grid formation, which are known as bitmaps, you will find these types of images
anywhere on your computer, for example the images from the internet including
your own images that you have imported to your computer.
Bitmaps can be in
either a compressed or uncompressed format, for example the JPG (a JPEG image)
is a compressed format, which was compressed by using lossy compression. This
means that the lossy compression removes certain information from the file,
that isn't visible or changes the view of the image you are saving.
A JPEG
(Joint Photographic Experts Group) does this so that you can change the amount
of loss of information and the file size you want to make your image, and can
maintain a high quality image at any size you wish to save it as.
There are
other file extensions such as, BMP, which can be both lossy and lossless
compressed, and GIF (Graphical Interchange File) uses lossless compression as a
format so that all the information before compression is kept afterwards,
making sure you keeping all of the original file. This is used mainly on the
internet so that whilst it’s being stored the size of the file gets smaller,
then when used it returns to its original file size and format. More examples
of file extensions are, PNG (Potable Network Graphic), TIFF (Tagged Image File
Format), and PSD (Adobe Photoshop Document.)
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