COSC1078 Introduction to Information Technology Lecture 4 Images

1. Intro to IT James Harland james.harland@rmit.edu.au COSC1078 Introduction to Information TechnologyLecture 4Images

2. Intro to IT Introduction to IT 1 Introduction 2 Images 3Audio 4Video WebLearn Test 1 5 Computer Fundamentals Assignment 1 6 Computer Fundamentals 7Computer Fundamentals 8 Operating Systems WebLearn Test 1 9 Operating Systems Assignment 2 10 Internet 11Internet Security WebLearn Test 3 12Future of IT Assignment 3, Peer and Self Assessment

3. Intro to IT Overview • Questions? • Images • Assignment 1 • Lab classes • Questions?

4. Intro to IT Introduction James Harland • Email:james.harland@rmit.edu.au • 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?

5. Representing Colours 01010100001010101010100110100010101001101001010010100011100010101010100101111001001010… R Pixel G B Lecture 4: Images Intro to IT

6. Representing Colours • There are various different schemes for representing colours • RGB • CMYK • HSB • HSL • CIE XYZ 01010100001… Lecture 4: Images Intro to IT

7. 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 Lecture 4: Images Intro to IT

8. 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 Lecture 4: Images Intro to IT

9. RGB 8 bits per channel Lecture 4: Images Intro to IT

10. CMYK • Based on 4 colours • Subtractive – more colours means less light Cyan Magenta Yellow blacK + yellow + cyan + magenta Lecture 4: Images Intro to IT

11. 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 Lecture 4: Images Intro to IT

12. Representing Colours • There are various different schemes for representing colours • RGB • CMYK • HSB • HSL • CIE XYZ 01010100001… Lecture 4: Images Intro to IT

13. 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 Lecture 4: Images Intro to IT

14. 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) Lecture 4: Images Intro to IT

15. 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 Lecture 4: Images Intro to IT

16. Intro to IT 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)

17. 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 Lecture 4: Images Intro to IT

18. Intro to IT 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!