Graphical Images

Bitmap vs Vector

There are two main types of graphic file formats, one being Bitmap and the other being Vector.

Bitmap is where the images are created by tiny blocks of colour being built up to trick us into thinking we're seeing an image. If you zoom into the image, you can see the blocks clearly. The blocks are called picture elements; or as they're commonly known, pixels. The more pixels used, the higher the quality because they will use the colour most appropriate for that section so it's close to the original message. The image below shows a zoomed in version of a bitmap image. You can see the pixels.


http://www.webwasp.co.uk/define/bitmap/

The advantage of bitmap images is that it's easy to create so you don't need to be talented to do it. You can just take a photo, scan it onto the computer and that's bitmap done.
It's free because you don't need a specific software to do it on which is helpful to all those who have a tight money budget.
The pixels can be re-coloured so say if you have an image where someone's eyes have gone red, you can change that pixel so it is black.
The disadvantage is that the image loses so much quality if you enlarge the image because the pixels will be shown.
You also need to use a high resolution for a smooth appearance of the image.


Vector is where the images are made up from mathematical equations instead of pixels. They are made up of objects like co-ordinates, curves and lines. These equations include start and end points so the image knows where each part of the image goes. This means that each part is a different layer which allows you to edit them individually so you can move things around without moving other parts of the image.
The advantage of vector images is that it doesn't lose quality when you resize the images because it doesn't have pixels reducing the quality.
You can re-edit parts of the image because of the layers so you can remove or edit unwanted parts (as shown below).

Source from http://esdev.net/raven-free-online-vector-editor/#.Um1Z83C-2So

The disadvantage of vector images is that parts of the image can disappear if you resize it because they are all individual.
If you enlarge the image it may show off errors in the image (like gaps in lines).
You can't take a photo using vector unless using a type of software that can convert it into one.
It's usually used for graphics so it's time consuming and you need talent to be able to create the individual parts of the images.


When comparing bitmap and vector you can see that they have differences. Bitmap used pixels whereas vector uses equations.
Vector allows you to edit individual sections where bitmap doesn't.
Vector has better quality images than bitmap.
Vector takes up less memory and storage space than bitmap does.
Bitmap is easier than vector because it doesn't require you to use software.

Lossy and Lossless Images

When images are being compressed so they are a smaller file size, they are done by either lossy or lossless compression. Both of these compression techniques are used to reduce the file size by removing parts of the data. However, lossy compression permanently discards this data whereas lossless compression doesn't (it removes the data until the file is re-opened). An example of a image file that is lossy is '.JPEG' and an image file that is lossless is '.GIF'. More detail of lossy and lossless compression is on another post.
As you can see from the image below, lossless would be the best compression technique to use if you want to maintain the quality of an image. The lossy image is much more blurred than the lossless because it has completely removed some parts of the data. However, if you want a file that is small, lossy would be better because it doesn't take up as much storage space due to fewer sections of the image.

Colour Models

Colour models are used in create the colours in graphics. It's much easier to choose a model that will suit the graphic so you don't use unwanted colours. For example, you could use a Grey-scale Model for a grey image so you don't have to go through all the colours.

The most common colour models used are RGB and CMYK. RGB stands for 'Red, Green, Blue' and CMYK stands for 'Cyan, Magenta, Yellow, Black'. They work together as RGB is the primary colour model and CMYK is the secondary colour model because when the RGB colours are mixed they create some of the CYMK colours (as shown below).

Source from http://dba.med.sc.edu/price/irf/Adobe_tg/models/rgbcmy.html

RGB is used for screens like TV or projectors due to the colours creating the secondary colours when exposed to light. The colours apart from RGB are only seen because of the illusion we get from the light; they're not actually there. This is why CMYK is used; to actually show these colours.
CMYK is used for printing so RGB colour models have to be converted into CMYK in order for it to print off the colours that are on the monitor.

When comparing the two, we can see some differences.
RGB creates more colours than CMYK due to the lights.
Colours like blue look much better in RBG than in CMYK because it's brighter.
Colours like red look much better in CYMK because it will be darker.
The disadvantage of these two models is the fact that some colours like green will look flat and not bright when converting RGB into CYMK.

Dots per Inch

Dots per inch (DPI) are the individual dots on an image per inch. It measures the resolution of an image because it shows how well it has been displayed. The fewer the dots, the lower the quality will be on a large screen because the dots will have to cover a bigger section of the display (as shown below).

Source from http://www.fmedda.com/en/article/dpi_ppi

The higher the amount of dots, the better the quality and colours of the image because it covers every single spot. The disadvantage of this is that it uses up a lot of ink and can make the printer very slow.