HTML Colour Codes Hexadecimal How do they work

HTML Colour Codes (Hexadecimal) How do they work?

Introduction • Artists using paint say that the primary colours are?

Introduction • Red • Blue • Yellow http: //shutha. org/sites/default/files//uploads/3_Courses/3_ Digital_Imaging/07 -02 b. png

Introduction • Do you get white when you mix all the colours? • How then do you mix white?

Introduction • You can’t, white is the paper, or the absence of paint. • This is known as the subtractive mixing process, it uses pigment instead of light. – Subtractive = Starts at white and colour is added.

Introduction • What colour does the computer monitor display when it is off? Black. Why?

Introduction • Because there are no active pixels, the absence of light is black. • When it is turned on, each pixel shows in either: • Red • Green • Blue http: //shutha. org/sites/default/files//upload s/3_Courses/3_Digital_Imaging/0701 b. png

Introduction • When these are all on at the same time, the screen appear white. • When they show in different combinations, you get all the other colours. • This is known as the additive mixing process, because it uses light to add colours together. – Additive = Starts at black and colour is added. http: //shutha. org/sites/default/files//upload s/3_Courses/3_Digital_Imaging/0701 b. png

Introduction • As printing is like “painting” you would expect that a printer would do what artists do and use: – Red – Blue – Yellow • But the answer is actually not as simple as this!

Introduction • Artists are actually thinking in “real life colours” which are not colours in their pure form. • For example: a fire engine may be red, but it is never a pure red.

Introduction • We have evolved on a planet awash with blue light and as a result evolution has given us eyes that are only half as sensitive to blue as they are to red and green to help compensate. • This 40% Red, 40% Green, but only 20% Blue sensitivity in the cones at the back of the eye results in us seeing blue as a dark colour.

Introduction • We just can not produce blue dyes, inks and paints that are of a strong enough colour to compete with the extra sensitivity we have to red and green. • For some reason we also have a stronger reaction to green than to red. • The combination of RGB makes white, but of the three, green is the brightest, followed by red, and blue being the darkest.

Introduction • So printers use Cyan, Magenta, Yellow and black (CMYK). • Magenta is formed with red and blue, and as more cones in the eye are used we see it as a lighter colour than red or blue. • Cyan is formed with green and blue and for the same reason it too is a lighter colour. • Yellow is formed with red and green and since this involves most of the cones in the eye it is therefore the lightest colour of all, with the exception of white. • In theory, mixing equal amounts of all three pigments should produce black when all three are applied in sufficient density, but in practice they tend to produce muddy brown colours. So to save ink and decrease drying times, a fourth pigment, black is often used

Introduction • To summarise computers use a mixture of the following colours to form any other colour: – Red – Green – Blue http: //shutha. org/sites/default/files//upload s/3_Courses/3_Digital_Imaging/0701 b. png

Playtime - Colour Mixer • IGCSE – Web Site Authoring – Colour Mixer » http: //www. mathsisfun. com/hexadecimal-colors. html

Hexadecimal Colour Names • http: //www. mathsisfun. com/numbers/hexa decimal-color-names. html • You can try them in Dream. Weaver, when you have the chance.

Plenary • Show us your favourite colour and explain how much: – Red – Green – Blue • it has.