1. Colour Light and Spectra
Visible light is an electromagnetic wave in the 400 nm nm range.
Most light we see is not one wavelength, it's a combination of many wavelengths.
The range of frequencies is called a spectrum.

2. Colour Human Retina
The eye is like a camera with light sensitive neurons
Each neuron is either a rod or a cone.
Rods are only sensitive to luminance & not sensitive to colour.

3. Colour Cones and Perception
Cones come in 3 types: red, green and blue. Each responds differently to various frequencies of light. The following figure shows the spectral-response functions of the cones and the luminous-efficiency function of the human eye.
The colour signal to the brain comes from the response of the 3 cones to the spectra being observed.

4. Colour CIE Chromaticity Diagram
In 1931, the CIE defined three standard primaries (X, Y, Z). The Y primary was intentionally chosen to be identical to the luminous-efficiency function of human eyes.
CIE: Commission Internationale de l’Eclairage (International Commission on Illumination)

5. Colour RGB Colour Model for CRT Displays
CRT displays have three phosphors (RGB) which produce a combination of wavelengths when excited with electrons

6. Colour CMY Colour Model
Cyan, Magenta, and Yellow (CMY) are complementary colors of RGB. They can be used as Subtractive Primaries.
CMY model is mostly used in printing devices where the color pigments on the paper absorb certain colors (e.g., no red light reflected from cyan ink).

7. Colour Conversion between RGB & CMY
White is represented as (1, 1, 1) in RGB and (0, 0, 0) in CMY

8. Colour YUV Colour Model in Video
Initially, for PAL analog video, it is now also used in CCIR standard for digital video
Y (luminance) is the CIE Y primary
Y = 0.299R G B
Chrominance is defined as the difference between a colour and a reference white at the same luminance. It can be represented by U and V -- the colour differences.
U = B - Y V = R - Y
If U = V = 0 then black/white image i.e. No chrominance
In actual PAL implementation:
U = (B - Y) V = (R - Y)
Eye is most sensitive to Y. In PAL, 5 (or 5.5) MHz is allocated to Y, MHz to U and V.

9. Colour YUV Composition

10. Colour YCbCr Colour Model in Video
The YCbCr model is closely related to the YUV, it is a scaled and shifted YUV:
Y = 0.299R G B + 16
Cb = R G B + 128
Cr = 0.439R G B + 128
The chrominance values in YCbCr are always in the range of 0 to 255
YCbCr is used in JPEG and MPEG

11. Colour YIQ Colour Model in Video
YIQ is used in NTSC color TV broadcasting, it is downward compatible with B/W TV where only Y is used.
I is the orange-blue axis, Q is the purple-green axis. I and Q axes are scaled and rotated R - Y and B - Y (by 33 degrees clockwise).
I = 0.877(R - Y) cos (B - Y) sin Q = 0.877(R - Y) sin (B - Y) cos 33
Namely,
I = 0.74(R - Y) (B - Y) = 0.596R G B Q = 0.48(R - Y) (B - Y) = 0.212R G B
The YIQ transform:
Eye is most sensitive to Y, next to I, next to Q. In NTSC broadcast TV, MHz is allocated to Y, 1.5 MHz to I, 0.55 MHz to Q.

12. Colour Types of Colour Video Signal
Component video -- each primary is sent as a separate video signal
The primaries can either be RGB or a luminance-chrominance transformation of them (e.g., YIQ, YUV).
Best color reproduction
Requires more bandwidth and good synchronization of the three components
Composite analogue video -- colour (chrominance) and luminance signals are mixed into a single carrier wave. Some interference between the two signals is inevitable.
Composite digital video -- colour (chrominance) and luminance bits are mixed into a single stream.
S-Video (Separated video, e.g., in S-VHS) -- a compromise between component analog video and the composite video. It uses two lines, one for luminance and another for composite chrominance signal.

13. Composite Analogue Video System Diagram

14. Composite Analogue Video Interlacing

15. Composite Analogue Video:Line & Field Syncs of even and odd fields and active Image area

16. Composite Analogue Video Carrier Burst (PAL)

17. Composite Analogue Video Luminance & Colour Video Signal Spectra
The luminance signal is located at nFL where n=0,1,2,3… and FL is the line frequency.
The chrominance signal is inserted between the gaps of the luminance signal at nFL/2 where n is odd integer.

18. Composite Analogue Video Combined Luminance & Chrominance Signals in Spectra
The bandwidth of the luminance signal is 5.5MHz.
The bandwidth of the chrominance signal is 2.0MHz.
The two bandwidths coincide.

19. Composite Analogue Video: Phase Alternation Line (PAL) Sequential Colour avec Memoire (SECAM)
625 scan lines per frame, 25 frames per second (40 msec/frame)
Aspect ratio 4:3
Interlaced, each frame is divided into 2 fields, lines/field
Uses YUV (YCbCr) color model

20. Composite Analogue Video: North American Telecom Standards Committee (NTSC)
525 scan lines per frame, 30 frames per second
Aspect ratio 4:3
Interlaced, each frame is divided into 2 fields, lines/field
20 lines reserved for control information at the beginning of each field
So a maximum of 485 lines of visible data
Laserdisc and S-VHS have actual resolution of ~420 lines
Ordinary TV -- ~320 lines
Each line takes 63.5 microseconds to scan. Horizontal retrace takes 10 microseconds so the active line time is microseconds.
uses YIQ color model

21. Composite Analogue Video NTSC, SECAM, PAL
Phase Shift Keying is used to carry the two colour signals on 2 phases (0º and 90º) with the same carrier frequency.
For NTSC, (R-Y) is sent on one phase and (B-Y) on the other phase.
For PAL, (R-Y) is sent on one phase and (B-Y) on the other phase. The phases are alternated from one line to another to compensate for phase errors.
For SECAM, (R-Y) is sent on one line and (B-Y) on the other line and both colours used for each line.

22. Composite Digital Video Advantages
Direct random access --> good for nonlinear video editing
No problem for repeated recording
No need for blanking and sync pulse
Almost all digital video uses component video

23. Composite Digital Video Colour Subsampling
4:4:4 --> Colour signal is not subsampled e.g. (Cr0, Cb0, Y0)(Cr1, Cb1, Y1)(Cr2, Cb2, Y2)(Cr3, Cb3, Y3)(Cr4, Cb4, Y4) ...
4:2:2 --> Horizontally subsampled colour signals by a factor of 2. Each pixel is two bytes, e.g., (Cb0, Y0)(Cr0, Y1)(Cb2, Y2)(Cr2, Y3)(Cb4, Y4) ...
4:1:1 --> Horizontally subsampled by a factor of 4
4:2:0 --> Subsampled in both the horizontal and vertical axes by a factor of 2 between pixels.
Note on notation:
4:2:2 for every four luminance pixels in a row there are 2 red and 2 blue)
4:2:0 for every four luminance pixels in a row there are 2 red/blue and 0 blue/red)

24. Composite Digital Video Colour Subsampling

25. Composite Digital Video: CCIR-601 Consultative Committee for International Radio

26. Composite Digital Video: Advanced Digital Television Standard - HDTV (High Definition TV).
The aspect ratio for HDTV is 16:9 as opposed to 4:3 in NTSC, PAL, and SECAM. (A 33% increase in horizontal dimension.)
In the picture rate column, the "I" means interlaced scan, and the "P" means progressive (non-interlaced) scan.
Both NTSC rates and integer rates are supported (i.e., 60.00, 59.94, , 29.97, 24.00, and 23.98).

27. Image Formats Pixels and Images
Pixels -- picture elements in digital images
Image Resolution -- number of pixels in a digital image (Higher resolution always yields better quality.)
Bit-Map -- a representation for the graphic/image data in the same manner as they are stored in video memory.

28. Image Formats Monochrome Images
One of the output-quality issues with most displays and printers is visible dithering in graphics and photos. The problem is that most images need shades of colours or grey, but most printers don't literally produce shades:either a given colour appears or it doesn't. This type of printer is known as a bilevel printer. The most common way around the problem is dithering, which combines dots on the page in a way that fools the eye into seeing shades and colours that aren't really there.
With a monochrome printer, for example, you can map the printer dots onto a grid divided into tiny dithering cells, with some arbitrary number of dots in each cell. You can then treat each dithering cell as a picture element, or pixel, in the image. If a cell has, say, 5 dots across and 5 down, you can print each pixel in any one of 26 values of grey--from "0," or pure white, through 25 increasingly dark shades--by using from 0 to 25 printer dots per pixel.
For colour printers, you do the same thing with each colour. So with 26 possible values each for cyan, yellow, and magenta, you can create 17,576 colours (the total number of possibilities being ). Black doesn't count, because black is not normally combined with other colours in conventional colour printing.
One cost of dithering is that the effective resolution for the printer is based on the number of dithering cells. With dithering cells of 5 dots across and 5 dots down, the effective resolution on a 300-dpi printer is only 60 dpi--300 divided by 5. Another issue is that a block of cells with the same colour can show visible patterns from the dithering, like the squares on a tiled floor. Variations in implementation can make the dithering patterns less visible, but they are always there.
Each pixel is stored as a single bit (0 or 1)
A 640 x 480 monochrome image requires 37.5 KB of storage.
Dithering is often used for displaying monochrome images

29. Image Formats Greyscale Images
Each pixel is usually stored as a byte (value between 0 to 255)
A 640 x 480 grayscale image requires over 300 KB of storage.

30. Image Formats 24-bit Colour Images
Each pixel is represented by three bytes (e.g., RGB)
Supports 256 x 256 x 256 possible combined colors (16,777,216)
A 640 x bit color image would require KB of storage
Many 24-bit color images are stored as 32-bit images, the extra byte of data for each pixel is used to store an alpha value representing special effect information

31. Image Formats 8-bit Colour Images
One byte for each pixel
Supports 256 out of the millions colors possible, acceptable color quality
Requires Color Look-Up Tables (LUTs)
A 640 x bit color image requires KB of storage (the same as 8-bit grayscale)

32. Image Format Standard GIF (GIF87a, GIF89a)
Graphics Interchange Format (GIF) devised by the UNISYS Corp. and Compuserve, initially for transmitting graphical images over phone lines via modems
Uses the Lempel-Ziv Welch algorithm (a form of Huffman Coding), modified slightly for image scan line packets (line grouping of pixels)
Limited to only 8-bit (256) color images, suitable for images with few distinctive colors (e.g., graphics drawing)
Supports interlacing
GIF89a supports simple animation (Graphics Control Extension has control over delay time, transparent index, etc. Software such as Coral Draw will allow access and editing of GIF images.)

33. Image Format Standard TIFF
Tagged Image File Format (TIFF), stores many different types of images (e.g., monochrome, grayscale, 8-bit & 24-bit RGB, etc.) --> tagged
Developed by the Aldus Corp. in the 1980's and later supported by Microsoft
TIFF is a lossless format (when not utilizing the new JPEG tag which allows for JPEG compression)

34. Image Format Standard JPEG
A standard for photographic image compression created by the Joint Photographics Experts Group
Takes advantage of limitations in the human vision system to achieve high rates of compression
Lossy compression which allows user to set the desired level of quality/compression

35. Image Format Standard Postscript/Encapsulated
A typesetting language which includes text as well as vector/structured graphics and bit-mapped images
Used in several popular graphics programs (Illustrator, FreeHand)
Does not provide compression, files are often large

36. Video Format Standard Digital Video Disk (DVD)
Uses MPEG-2 operating at “Main Profile at Main Level” and uses CCIR601 with 4:2:0 chrominance sub- sampling.
Supports data rate of 15Mbit/second

37. Video Format Standard Digital Video (DV)
DV is intended for consumer and semi-professional use. There are two versions DVCAM and DVPRO.
DVPRO uses MJPEG with CCIR601 and 4:2:2 chrominance sub-sampling.
DVCAM uses MJPEG with CCIR601 and 4:1:1 chrominance sub-sampling.
Motion JPEG (MJPEG) is JPEG applied to each frame of video

38. System Dependant Image Format: Microsoft Windows: BMP
A system standard graphics file format for Microsoft Windows
Used in PC Paintbrush and other programs
capable of storing 24-bit bitmap images

39. System Dependant Image Format Macintosh: PAINT and PICT
PAINT was originally used in MacPaint program, initially only for 1-bit monochrome images.
PICT-JPEG format is used in MacDraw (a vector based drawing program) for storing structured graphics

40. System Dependant Image Format X-windows: XBM
Primary graphics format for the X Window
Supports 24-bit color bitmap
Many public domain graphic editors, e.g., xv
Used in X Windows for storing icons, pixmaps, backdrops, etc.

41. System Dependant Image Format QuickTime
It comprises of several components:
Photo Compressor: based around JPEG standards and is compatible with most JPEG decoders.
Animation Compressor: based around run-length encoding.
Video Compressor: Proprietary Apple standard based around spatial and temporal redundancy.
Graphics Compressor: Proprietary Apple standard.
Compact Video Compressor: Proprietary Apple standard that compresses video more than Video Compressor.

42. System Dependant Image Format Windows Media
It does not describe a compression technology but the framework for supporting different compression algorithms.
It identifies the compression algorithm from the format/header of the file which contains the compressed data

43. System Dependant Image Format RealMedia
RealMedia is a standard for streaming audio and video on the Internet.
RealVideo is a proprietary standard
RealAudio is a proprietary standard