Pictures in Binary

pictures are converted to a series of squares aka pixels (picture elements)
the pixels are coloured in to create pictures
more pixels = a nicer more defined picture
number of pixels is the resolution of the picture
on printers pixels are called dots. the resolution of a printer is in dpi or dots per inch
When pictures are encoded, they contain a string of numbers that has the colour number, then how many pixels to colour in, then the next pixel colour, how many to fill in.

Header Information

This is information (in binary) that is provided in a standard order at the beginning of a picture.
The computer opens the file, reads the header information and gets ready to draw the picture.
The information at the end of the file is the part that shows how the pixels are encoded and which pixels are coloured in.
Header information includes details about how the file is stored, its dimensions and what colours are needed (maybe in a colour lookup table)

Black and White

Colour

Compressed (aka Block Art)

You have a 20 pixel x 30 pixel picture which has 19 colours. The header information takes 64 bits of space.

(a) Determine how many bits are needed for one pixel.

4 bits will store 16 colours, 5 will store 32. Since we have 19 colours, we will need 5 bits per pixel.

(b) Determine how many pixels.

20 x 30 = 600

number of pixels x bits per pixel = 600 x 5 = 3000

(d) Add on the headerinformation

3000+64=3064 bits