COSC1078 Introduction to Information Technology Lecture 4 Images

Lecture 4: Images Intro to IT

COSC1078 Introduction to Information Technology

Lecture 4

ImagesJames Harland

[email protected]


Introduction to IT

1 Introduction

2 Images

3 Audio

4 Video WebLearn Test 1

5 Computer Fundamentals Assignment 1

6 Computer Fundamentals

7 Computer Fundamentals

8 Operating Systems WebLearn Test 1

9 Operating Systems Assignment 2

10 Internet

11 Internet Security WebLearn Test 3

12 Future of IT Assignment 3, Peer and Self Assessment


Overview

Questions?

Images

Assignment 1

Lab classes

Questions?


Introduction

James Harland• Email: [email protected]• URL: www.cs.rmit.edu.au/~jah• Phone: 9925 2045• Office: 14.8.13 (Building 14, level 8, room 13)• Consultation: Wed 1.30-2.30, Thu 11.30-12.30

What colour is my office door? Carpet? Chair?


Representing Colours

01010100001010101010100110100010101001101001010010100011100010101010100101111001001010…

PixelR

GB



There are various different schemes for representing colours

RGB CMYK HSB HSL CIE XYZ

01010100001…


RGB

Human eye uses red, green, blue sensors Additive --- more colours means lighter colour

+

+

+

yellow

cyan

magenta

+ +Other colours by varying amounts of R, G, B


RGB

Often represented as (#R, #G, #B) where #R, #G, #B in range 0, 1, …, 255 (ie 28 -1)

This means 8 bits per channel, or bit depth 24

Gives 2563 = 16,777,216 colours overall

Note that RGB is a scheme, not a particular set of numbers


RGB 8 bits per channel

Colour #R #G #B

White 255 255 255

Black 0 0 0

Red 255 0 0

Green 0 255 0

Blue 0 0 255

Yellow 255 255 0

Cyan 0 255 255

Magenta 255 0 255

“Light orange”

255 166 38

??? 142 223 177


CMYK

Based on 4 colours Subtractive – more colours means less light

YellowCyan Magenta blacK

+

+

+

yellow

cyan

magenta


CMYK Why Black? Why not CMY?

Used mainly in printing (“4-colour print”) In practice, doesn’t look “black” “There is no colour with more shades than black”Too much ink to make black soaks the paper too much Text is traditionally black (and lots more text than pictures in colour) Black ink is cheaper than coloured

+ +



There are various different schemes for representing colours

RGB CMYK HSB HSL CIE XYZ

01010100001…


HSB (or HSV)

How do humans describe colour?“rich dark green”

Hue: basic colour (red, green, blue, yellow, …)Saturation: amount of colour (intensity, purity)Brightness: light or dark or in-between …

Can be thought of as a cone or cylinder or hexacone


HSB and HSV and HSL

Hue is represented on a circle, and hence as a bearing (like on a compass)

Saturation and Brightness/Value are percentages

HSL is similar, except that 100% luminance is always white (just as 0% brightness is black)


CIE XYZ

Standard derived from work in 1931 to identify all colours visible to humans Colours divided into brightness and chromacity Humans can see more colours than a typical monitor can display RGB produces more colours than CMYK


Assignment 1

Use GIMP (or a similar tool) to perform some manipulations on an image

Address two issues in relation to this

Lab classes 2 and 3 will be based around GIMP

Main emphasis is on process, not result!

Will be released (on the Learning Hub) by Wednesday 10th March (later today)


Lab Classes

Start in week 2 (this week)

Work on practical exercises and sometimes assignment materials

Lab assists present to help and an answer questions

Details will be in the Learning Hub


Conclusion

Go to laboratory classes (and tutorials) this week!

Lab notes in the Learning Hubub

Check details in Course Guide

Start reading (notes, problems, report topic)

GET THE BOOK!

Documents

COSC1078 Introduction to Information Technology Lecture 4 Images